EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-PH-EP/2011-0562011/05/12

CMS-HIN-11-001

Long-range and short-range dihadron angular correlationsin central PbPb collisions at √sNN = 2.76 TeV

The CMS Collaboration∗

Abstract

First measurements of dihadron correlations for charged particles are presented forcentral PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV over abroad range in relative pseudorapidity (∆η) and the full range of relative azimuthalangle (∆φ). The data were collected with the CMS detector, at the LHC. A broadeningof the away-side (∆φ ≈ π) azimuthal correlation is observed at all ∆η, as comparedto the measurements in pp collisions. Furthermore, long-range dihadron correlationsin ∆η are observed for particles with similar φ values. This phenomenon, also knownas the “ridge”, persists up to at least |∆η| = 4. For particles with transverse momenta(pT) of 2–4 GeV/c, the ridge is found to be most prominent when these particles arecorrelated with particles of pT = 2–6 GeV/c, and to be much reduced when paired withparticles of pT = 10–12 GeV/c.

Submitted to the Journal of High Energy Physics

∗See Appendix A for the list of collaboration members

arX

iv:s

ubm

it/02

4651

2 [

nucl

-ex]

12

May

201

1

1

1 IntroductionMeasurements of dihadron azimuthal correlations [1–7] have provided a powerful tool to studythe properties of the strongly interacting medium created in ultrarelativistic nuclear collisions [8–11]. An early indication of strong jet-medium interactions at RHIC was the absence of high-transverse-momentum (high-pT) back-to-back particle pairs in dihadron correlation measure-ments [1] and the corresponding enhancement of low-pT hadrons recoiling from a high-pT lead-ing, or “trigger”, particle [3]. The recent observations of the suppression of high-pT chargedhadrons [12] and of asymmetric energies of reconstructed jets [13, 14] in PbPb collisions at theLarge Hadron Collider (LHC) provide further evidence of jet quenching, suggesting a largeenergy loss for partons traversing the produced medium.

At RHIC, extending dihadron azimuthal correlation measurements to larger relative pseudo-rapidities resulted in the discovery of a ridge-shaped correlation in central AuAu collisionsbetween particles with small relative azimuthal angles (|∆φ| ≈ 0), out to very large relativepseudorapidity (|∆η|) [2, 6]. Although the “ridge” has been qualitatively described by severaldifferent models [15–26], its origin is still not well understood. Some models attribute the ridgeto jet-medium interactions, while others attribute it to the medium itself. The ridge has beenobserved for particles with transverse momenta from several hundred MeV/c to a few GeV/c.However, the character of the ridge for even higher-pT particles, as well as its dependence oncollision energy, is still poorly understood from the RHIC results [2]. Recently, a striking ridgestructure has also been observed in very high multiplicity proton-proton (pp) collisions at acenter-of-mass energy of 7 TeV at the LHC by the Compact Muon Solenoid (CMS) Collabora-tion [27], posing new challenges to the understanding of these long-range correlations.

This paper presents the first measurement of dihadron correlations for charged particles pro-duced in the most central (0–5% centrality) PbPb collisions at a nucleon-nucleon center-of-massenergy (

√sNN ) of 2.76 TeV over a large phase space. The results are presented in terms of the as-

sociated hadron yields as a function of pseudorapidity and azimuthal angle relative to triggerparticles in different transverse momentum intervals. Traditionally, trigger particles have beenutilized to represent the direction of the leading hadron in a jet, and were required to have ahigher momentum than all the other associated particles in the jet [2, 6]. However, as shownin Ref. [27], important information can also be obtained by studying the correlation of hadronpairs from the same pT interval, which is particularly useful when addressing the properties ofthe medium itself. The current analysis employs both approaches. This measurement providesa unique examination of the ridge in the most central PbPb collisions at the highest energiesreached so far in the laboratory over a wide range in transverse momentum (2–12 GeV/c) andup to large relative pseudorapidity (|∆η| ≈ 4), imposing further quantitative constraints on thepossible origin of the ridge.

Details of event readout and analysis for extracting the correlation functions are described inSection 2, the physics results found using the correlations are described in Section 3, and asummary is given in Section 4.

2 Data and AnalysisThe analysis reported in this paper is based on PbPb collisions at

√sNN = 2.76 TeV collected

during the LHC heavy-ion run in November and December 2010 with the CMS detector. Thecentral feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter.Within the field volume are the inner tracker, the crystal electromagnetic calorimeter, and thebrass/scintillator hadron calorimeter. Muons are measured in gas-ionization detectors embed-

2 2 Data and Analysis

ded in the steel return yoke. In addition to the barrel and endcap detectors, CMS has extensiveforward calorimetry. The nearly 4π solid-angle acceptance of the CMS detector is ideally suitedfor studies of both short- and long-range particle correlations. A detailed description of theCMS detector can be found in Ref. [28]. CMS uses a right-handed coordinate system, with theorigin at the nominal interaction point, the x axis pointing to the center of the LHC, the y axispointing up (perpendicular to the LHC plane), and the z axis along the counterclockwise beamdirection. The detector subsystem primarily used for the present analysis is the inner trackerthat reconstructs the trajectories of charged particles with pT > 100 MeV/c, covering the pseu-dorapidity region |η| < 2.5, where η = − ln[tan(θ/2)] and θ is the polar angle relative to thebeam direction. The inner tracker consists of 1440 silicon pixel and 15 148 silicon strip detectormodules immersed in the 3.8 T axial magnetic field of the superconducting solenoid.

The event readout of the CMS detector for PbPb collisions is triggered by coincident signals inforward detectors located on both sides of the nominal collision point. In particular, minimumbias PbPb data are recorded based on coincident signals in the beam scintillator counters (BSC,3.23 < |η| < 4.65) or in the steel/quartz-fiber Cherenkov forward hadron calorimeters (HF,2.9 < |η| < 5.2) from both ends of the detector. In order to suppress events due to noise,cosmic rays, double-firing triggers, and beam backgrounds, the minimum bias trigger used inthis analysis is required to be in coincidence with bunches colliding in the interaction region.The trigger has an acceptance of (97± 3)% for hadronic inelastic PbPb collisions [14].

Events are selected offline by requiring in addition at least three hits in the HF calorimetersat both ends of CMS, with at least 3 GeV of energy in each cluster, and the presence of a re-constructed primary vertex containing at least two tracks. These criteria further reduce back-ground from single-beam interactions (e.g., beam gas and beam halo), cosmic muons, andlarge-impact-parameter, ultra-peripheral collisions that lead to the electromagnetic breakupof one or both of the Pb nuclei [29]. The reconstructed primary vertex is required to be locatedwithin 15 cm of the nominal collision point along the beam axis and within a radius of 0.02 cmrelative to the average vertex position in the transverse plane.

This analysis is based on a data sample of PbPb collisions corresponding to an integrated lumi-nosity of approximately 3.12 µb−1 [30, 31], which contains 24.1 million minimum bias collisionsafter all event selections are applied.

The energy released in the collisions is related to the centrality of heavy-ion interactions, i.e.,the geometrical overlap of the incoming nuclei. In CMS, centrality is classified according topercentiles of the distribution of the energy deposited in the HF calorimeters. The centralityclass used in this analysis corresponds to the 0–5% most central PbPb collisions, a total of1.2 million events. More details on the centrality determination can be found in Refs. [14, 32].

A reconstructed track is considered as a primary-track candidate if the significance of the sepa-ration along the beam axis between the track and the primary vertex, dz/σ(dz), and the signifi-cance of the impact parameter relative to the primary vertex transverse to the beam, dxy/σ(dxy),are each less than 3. In order to remove tracks with potentially poorly reconstructed momen-tum values, the relative uncertainty of the momentum measurement, σ(pT)/pT, is required tobe less than 5.0%. Requiring at least 12 hits on each track helps to reject misidentified tracks.Systematic uncertainties related to the track selections have been evaluated as discussed below.

Trigger particles are defined as all charged particles originating from the primary vertex, with|η| < 2.4 and in a specified ptrig

T range. The number of trigger particles in the event is denotedby Ntrig, which can be more than one per event. Hadron pairs are formed by associating withevery trigger particle the remaining charged particles with |η| < 2.4 and in a specified passoc

T

3

range. The per-trigger-particle associated yield distribution is then defined by:

1Ntrig

d2Npair

d∆ηd∆φ= B(0, 0)× S(∆η, ∆φ)

B(∆η, ∆φ), (1)

where ∆η and ∆φ are the differences in η and φ of the pair, respectively. The signal distribution,S(∆η, ∆φ), is the measured per-trigger-particle distribution of same-event pairs, i.e.,

S(∆η, ∆φ) =1

Ntrig

d2Nsame

d∆ηd∆φ. (2)

The mixed-event background distribution,

B(∆η, ∆φ) =1

Ntrig

d2Nmix

d∆ηd∆φ, (3)

is constructed by pairing the trigger particles in each event with the associated particles from 10different random events, excluding the original event. The symbol Nmix denotes the number ofpairs taken from the mixed event. The background distribution is used to account for randomcombinatorial background and pair-acceptance effects. The normalization factor B(0, 0) is thevalue of B(∆η, ∆φ) at ∆η = 0 and ∆φ = 0 (with a bin width of 0.3 in ∆η and π/16 in ∆φ), repre-senting the mixed-event associated yield for both particles of the pair going in approximatelythe same direction, thus having full pair acceptance. Therefore, the ratio B(0, 0)/B(∆η, ∆φ)is the pair-acceptance correction factor used to derive the corrected per-trigger-particle associ-ated yield distribution. Equation (1) is calculated in 2 cm wide bins of the vertex position (zvtx)along the beam direction and averaged over the range |zvtx| < 15 cm. To maximize the statis-tical precision, the absolute values of ∆η and ∆φ are used to fill one quadrant of the (∆η, ∆φ)histograms, with the other three quadrants filled (only for illustration purposes) by reflection.Therefore, the resulting distributions are symmetric about (∆η, ∆φ) = (0, 0) by construction.

Each reconstructed track is weighted by the inverse of the efficiency factor, εtrk(η, pT), as afunction of the track’s pseudorapidity and transverse momentum. The efficiency weightingfactor accounts for the detector acceptance A(η, pT), the reconstruction efficiency E(η, pT), andthe fraction of misidentified tracks, F(η, pT),

εtrk(η, pT) =AE

1− F. (4)

Studies with simulated Monte Carlo (MC) events show that the combined geometrical accep-tance and reconstruction efficiency for the primary-track reconstruction reaches about 60% forthe 0–5% most central PbPb collisions at pT > 2 GeV/c over the full CMS tracker acceptance(|η| < 2.4) and 65% for |η| < 1.0. The fraction of misidentified tracks is about 1–2% for|η| < 1.0, but increases to 10% at |η| ≈ 2.4. The weighting changes the overall scale butnot the shape of the associated yield distribution, which depends on the ratio of the signal tobackground distributions.

A closure test of the track-weighting procedure is performed on HYDJET [33] (version 1.6)MC events. The efficiency-weighted associated yield distribution from reconstructed tracks isfound to agree with the generator-level correlation function to within 3.3%. In addition, sys-tematic checks of the tracking efficiency, in which simulated MC tracks are embedded into

4 3 Results

data events, give results consistent with pure HYDJET simulations to within 5.0%. The track-ing efficiency also depends on the vertex z position of the event. However, this dependenceis negligible in this analysis, and its effects are taken into account in the systematic uncer-tainty by comparing the efficiency-corrected correlation functions for two different zvtx ranges,|zvtx| < 15 cm and |zvtx| < 5 cm, which are found to differ by less than 2.2%. Additional uncer-tainties due to track quality cuts are examined by loosening or tightening the track selectionsdescribed previously, and the final results are found to be insensitive to the selections to within2.0%. An independent analysis, using a somewhat different but well-established methodol-ogy [34, 35] in constructing the mixed-event background is performed as a cross-check, where10 trigger particles from different events are selected first and combined to form a single event,and then correlated with particles from another event. It yields results within 2.9–3.6% of thedefault values (3.6% for |∆η| < 1 and 2.9% for 2 < |∆η| < 4), with a slight dependence on ∆ηand ∆φ. The other four sources of systematic uncertainty are largely independent of ∆η and∆φ.

Table 1 summarizes the different systematic sources, whose corresponding uncertainties areadded in quadrature becoming the quoted systematic uncertainties of the per-trigger-particleassociated yield.

Table 1: Summary of systematic uncertainties.

Source Systematic uncertainty ofthe per-trigger-particle associated yield (%)

Tracking weighting closure test 3.3Tracking efficiency 5.0Vertex dependence 2.2Track selection dependence 2.0Construction of the mixed-event background 2.9–3.6Total 7.3–7.6

3 ResultsThe measured per-trigger-particle associated yield distribution of charged hadrons as a func-tion of |∆η| and |∆φ| in the 0–5% most central PbPb collisions at

√sNN = 2.76 TeV is shown in

Fig. 1a for trigger particles with 4 < ptrigT < 6 GeV/c and associated particles with 2 < passoc

T <4 GeV/c. To understand the effects of the hot, dense medium produced in the collisions, thisdistribution can be compared to that from a PYTHIA8 MC simulation [36] (version 8.135) of ppcollisions at

√s = 2.76 TeV, shown in Fig. 1b. This transverse momentum range, one of several

studied later in this paper, is chosen for this figure since it illustrates the differences betweencorrelations from PbPb data and PYTHIA8 pp MC events most clearly. The main features of thesimulated pp MC distribution are a narrow jet-fragmentation peak at (∆η, ∆φ) ≈ (0, 0) anda back-to-back jet structure at |∆φ| = π, but extended in ∆η. In the 0–5% most central PbPbcollisions, particle correlations are significantly modified, as shown in Fig. 1a. The away-sidepairs (∆φ ≈ π) exhibit a correlation with similar amplitude compared to PYTHIA8, althoughthe structure in PbPb data is much broader in both ∆φ and ∆η so that it appears almost flat.On the near side (∆φ ≈ 0), besides the common jet-like particle production in both pp andPbPb at (∆η, ∆φ) ≈ (0, 0) due to jet fragmentation, a clear and significant ridge-like structureis observed in PbPb at ∆φ ≈ 0, which extends all the way to the limit of the measurement of

3.1 Associated Yield Distributions versus ∆φ 5

|∆η| = 4.

In relativistic heavy-ion collisions, the anisotropic hydrodynamic expansion of the producedmedium is one possible source of long-range azimuthal correlations, driven by the event-by-event initial anisotropy of the collision zone [7, 37]. For non-central collisions, these correlationsare dominated by the second-order Fourier component of the |∆φ| distribution, usually calledelliptic flow or v2. Measurements of dihadron correlations at RHIC have frequently attemptedto subtract or factorize the elliptic flow contribution based on direct v2 measurements, in orderto reveal other features of particle correlations that may provide insight into the interactionsbetween the jets and the medium. However, recent theoretical developments indicate thatthe interplay between initial-state fluctuations and the subsequent hydrodynamic expansiongives rise to additional Fourier components in the azimuthal particle correlations [25, 26, 38–42]. These components need to be treated on equal footing with the elliptic flow component.In particular for the 0–5% most central PbPb collisions, the elliptic flow contribution to theazimuthal correlations is not expected to be dominant [43]. Therefore, the original unsubtractedcorrelation functions are presented in this paper, containing the full information necessary forthe comparison with theoretical calculations.

η∆-4

-20

24

φ∆0

2

4

φ∆ dη∆d

pair

N2 d

trig

N1 5.8

6.06.26.46.6 φ∆

dη∆d

pair

N2 d

trig

N1

5.8

6.0

6.2

6.4

6.6(a) -1

bµ L dt = 3.1 ∫CMS

= 2.76 TeV, 0-5% centralityNNsPbPb

η∆-4

-20

24

φ∆0

2

4

φ∆ dη∆d

pair

N2 d

trig

N1 0.1

0.20.30.4 φ∆

dη∆d

pair

N2 d

trig

N1

0.1

0.2

0.3

0.4(b) CMS Simulations

= 2.76 TeVsPYTHIA8 pp MC

Figure 1: Two-dimensional (2-D) per-trigger-particle associated yield of charged hadrons as afunction of |∆η| and |∆φ| for 4 < ptrig

T < 6 GeV/c and 2 < passocT < 4 GeV/c from (a) 0–5% most

central PbPb collisions at√

sNN = 2.76 TeV, and (b) PYTHIA8 pp MC simulation at√

s = 2.76 TeV.

3.1 Associated Yield Distributions versus ∆φ

To quantitatively examine the features of short-range and long-range azimuthal correlations,one dimensional (1-D) ∆φ correlation functions are calculated by averaging the 2-D distribu-tions over a limited region in ∆η from ∆ηmin to ∆ηmax:

1Ntrig

dNpair

d∆φ=

1∆ηmax − ∆ηmin

∫ ∆ηmax

∆ηmin

1Ntrig

d2Npair

d∆ηd∆φd∆η. (5)

The results of extracting the 1-D ∆φ correlations for the 0–5% most central PbPb collisions areshown in Figs. 2 and 3. The associated yield per trigger particle in the range of 2 < passoc

T <

4 GeV/c is extracted for five different ptrigT intervals (2–4, 4–6, 6–8, 8–10, and 10–12 GeV/c) and

6 3 Results

two ranges in ∆η. Figure 2 gives the short-range pseudorapidity result, i.e., averaged over theregion |∆η| < 1. Figure 3 shows the same comparison for long-range correlations, i.e., averagedover the region 2 < |∆η| < 4. A comparison to PYTHIA8 pp MC events at

√s = 2.76 TeV is

also shown, with a constant added to match the PbPb results at ∆φ = 1 in order to facilitatethe comparison. In this projection, only the range 0 < ∆φ < π is shown, as the ∆φ correlationfunction is symmetric around ∆φ = 0 by construction.

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

6.0

6.5

7.0 < 4 GeV/cT

trig2 < p

| < 1η∆0 < |

= 2.76 TeV, 0-5%NNsPbPb

= 2.76 TeVsPYTHIA8 pp

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

6.0

6.5

7.0 < 6 GeV/cT

trig4 < p

< 4 GeV/cTassoc2 < p

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

6.0

6.5

7.0

∫ -1bµCMS L dt = 3.1

< 8 GeV/cT

trig6 < p

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

6.0

6.5

7.0 < 10 GeV/cT

trig8 < p

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

6.0

6.5

7.0 < 12 GeV/cT

trig10 < p

Figure 2: Short-range (|∆η| < 1) per-trigger-particle associated yields of charged hadrons asa function of |∆φ| from the 0–5% most central PbPb collisions at

√sNN = 2.76 TeV, requiring

2 < passocT < 4 GeV/c, for five different intervals of ptrig

T . The PYTHIA8 pp MC results (solidhistograms) are also shown, shifted up by a constant value to match the PbPb data at ∆φ = 1for ease of comparison. The error bars are statistical only and are too small to be visible in mostof the panels. The systematic uncertainty of 7.6% for all data points is not shown in the plots.

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

5.8

6.0

6.2

6.4 < 4 GeV/c

T

trig2 < p

| < 4η∆2 < |

= 2.76 TeV, 0-5%NNsPbPb

= 2.76 TeVsPYTHIA8 pp

5-term Fourier fits

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

5.8

6.0

6.2

6.4 < 6 GeV/c

T

trig4 < p

< 4 GeV/cTassoc2 < p

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

5.8

6.0

6.2

6.4

∫ -1bµCMS L dt = 3.1

< 8 GeV/cT

trig6 < p

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

5.8

6.0

6.2

6.4 < 10 GeV/c

T

trig8 < p

|φ∆|0 1 2 3

φ∆d

pair

N2 d tr

igN

1

5.8

6.0

6.2

6.4 < 12 GeV/c

T

trig10 < p

Figure 3: Long-range (2 < |∆η| < 4) per-trigger-particle associated yields of charged hadronsas a function of |∆φ| under the same conditions as in Fig. 2. The systematic uncertainty of 7.3%for all data points is not shown in the plots. Dashed lines show the fits by the first five terms inthe Fourier series, as discussed in Section 3.3.

The panels of Figs. 2 and 3 show a modification of the away-side associated yield for |∆φ| >π/2 in central PbPb collisions that is not present in the PYTHIA8 pp MC simulation. This modi-fication is most pronounced for lower ptrig

T values and is characterized by a similarly broad dis-tribution as seen in lower-energy RHIC measurements, where it was attributed to jet quenchingand related phenomena [3, 5]. The near-side associated yield in PbPb data includes the con-tributions from both the jet-like peak and the ridge structure seen in Fig. 1a. Thus, it is notdirectly comparable to PYTHIA8 pp MC events, where the ridge component is absent. A morequantitative comparison of the jet-like component between PbPb data and PYTHIA8 pp MCevents will be discussed below.

For azimuthal correlations at large values of ∆η (Fig. 3), a clear maximum at ∆φ ≈ 0 is ob-served, which corresponds to the ridge structure seen in the 2-D distribution of Fig. 1a. This

3.2 Integrated Associated Yield 7

feature of the long-range azimuthal correlation function is not present in the PYTHIA8 pp MCsimulation for any ptrig

T bin. In PbPb, the height of the ridge structure decreases as ptrigT increases

(Fig. 3) and has largely vanished for ptrigT ≈ 10–12 GeV/c. The diminishing height of the ridge

with increasing ptrigT was not evident from previous measurements at RHIC in AuAu collisions

presumably because of lack of events at high pT.

3.2 Integrated Associated Yield

The strengths of the jet peak and ridge on the near side, as well as their dependences on ∆η andptrig

T , can be quantified by the integrated associated yields. In the presence of multiple sourcesof correlations, the correlation of interest is commonly estimated using an implementation ofthe zero-yield-at-minimum (ZYAM) method [17]. However, as mentioned previously, the pos-sible contribution of elliptic flow is not taken into account as it is not the dominant effect for themost central PbPb collisions considered here. The ZYAM method is implemented as follows.A second-order polynomial is fitted to the |∆φ| distributions in the region 0.5 < |∆φ| < 1.5.The location of the minimum of the polynomial in this region is denoted as ∆φZYAM. Usingthe position of the minimum, the associated yield is then calculated as the integral of the |∆φ|distribution minus its value at ∆φZYAM between |∆φ| = 0 and ∆φZYAM. The uncertainty on theminimum level obtained by the ZYAM procedure, combined with the uncertainty arising fromthe choice of fit range in |∆φ|, results in an uncertainty on the absolute associated yield that isconstant with a value of 0.012 over all ∆η and ptrig

T bins.

|η∆|0 1 2 3 4

Ass

ocia

ted

Yie

ld

0.0

0.1

0.2

0.3

0.4

= 2.76 TeV, 0-5%NNsPbPb

= 2.76 TeVsPYTHIA8 pp

-1bµ L dt = 3.1 ∫CMS

< 6 GeV/cT

trig4 < p

< 4 GeV/cT

assoc2 < p

Figure 4: Integrated near-side (|∆φ| < ∆φZYAM) associated yield for 4 < ptrigT < 6 GeV/c and

2 < passocT < 4 GeV/c, above the minimum level found by the ZYAM procedure, as a function of

|∆η| for the 0–5% most central PbPb collisions at√

sNN = 2.76 TeV. The error bars correspond tostatistical uncertainties, while the brackets denote the systematic uncertainties. The solid lineshows the prediction from the PYTHIA8 simulation of pp collisions at

√s = 2.76 TeV.

The ZYAM procedure enables the direct extraction of integrated yields of the ∆φ-projecteddistributions in a well-defined manner. Figure 4 shows the resulting near-side associated yield

8 3 Results

(GeV/c)T

trigp5 10

Ass

ocia

ted

Yie

ld

0.0

0.1

0.2

0.3 (a) Jet Region

< 4 GeV/cT

assoc2 < p

= 2.76 TeV, 0-5%NNsPbPb

= 2.76 TeVsPYTHIA8 pp

(GeV/c)T

trigp5 10

Ass

ocia

ted

Yie

ld0.0

0.1

0.2

0.3 (b) Ridge Region

-1bµ L dt = 3.1 ∫CMS

Figure 5: Integrated near-side (|∆φ| < ∆φZYAM) associated yield above the minimum levelfound by the ZYAM procedure for (a) the short-range jet region (|∆η| < 1) and (b) the long-range ridge region (2 < |∆η| < 4), as a function of ptrig

T in the 0–5% most central PbPb collisionsat√

sNN = 2.76 TeV with 2 < passocT < 4 GeV/c. The error bars correspond to statistical uncertain-

ties, while the brackets around the data points denote the systematic uncertainties. The solidline shows the prediction from the PYTHIA8 simulation of pp collisions at

√s = 2.76 TeV.

as a function of |∆η| (in slices of 0.6 units) in both the central PbPb collisions and PYTHIA8 ppMC. The near-side associated yield for PYTHIA8 pp shows a strong peak at |∆η| = 0, whichcorresponds to the expected correlations within jets. This near-side peak diminishes rapidlywith increasing |∆η|. The PbPb data also exhibit a jet-like correlation peak in the yield forsmall |∆η|, but in contrast, the PbPb data clearly show that the ridge extends to the highest|∆η| values measured.

Figure 5 presents the integrated associated yield for the jet region (|∆η| < 1) and the ridgeregion (2 < |∆η| < 4) with 2 < passoc

T < 4 GeV/c, as a function of ptrigT in the 0–5% most

central PbPb collisions. The ridge-region yield is defined as the integral of the near side inlong-range ∆φ azimuthal correlation functions (Fig. 3), while the jet-region yield is determinedby the difference between the short- and long-range near-side integral, as the ridge is foundto be approximately constant in ∆η (Fig. 4). While the jet-region yield shows an increase withptrig

T due to the increasing jet transverse energy, the ridge-region yield is most prominent for2 < ptrig

T < 6 GeV/c and tends to drop to almost zero when ptrigT reaches 10–12 GeV/c. The

bars in Fig. 5 correspond to the statistical uncertainties, while the brackets around the datapoints denote the systematic uncertainties, which are dominated by the tracking performance,as discussed earlier. Results from the PYTHIA8 pp MC simulation, displayed as solid lines inFig. 5, are consistent with zero for all ptrig

T bins in the ridge region and have qualitatively thesame trend with ptrig

T in the jet region as the data. It has been seen from previous studies thatthe ridge is absent in both minimum bias pp data and PYTHIA8 MC simulations. However, thePYTHIA8 program does not fully describe the jet-like correlations observed in pp collisions at

3.3 Fourier Decomposition of ∆φ Distributions 9

√s = 7 TeV [27]. A quantitative comparison of the correlations in PbPb and pp collisions will

therefore be deferred until pp results at√

s = 2.76 TeV become available.

(GeV/c)trigT

p5 10

]-2

[10

nf V

PbP

bas

soc

/Nas

soc

N

-1.0

-0.5

0.0

0.5

1.0

1fV

| < 4η∆2 < |

= 2.76 TeV, 0-5%NNsPbPb = 2.76TeVsPYTHIA8 pp

(GeV/c)trigT

p5 10

]-2

[10

nf V

PbP

bas

soc

/Nas

soc

N

-1.0

-0.5

0.0

0.5

1.0

< 4 GeV/cT

assoc2 < p

2fV

(GeV/c)trigT

p5 10

]-2

[10

nf V

PbP

bas

soc

/Nas

soc

N

-1.0

-0.5

0.0

0.5

1.0

3fV

∫ -1bµCMS L dt = 3.1

(GeV/c)trigT

p5 10

]-2

[10

nf V

PbP

bas

soc

/Nas

soc

N

-1.0

-0.5

0.0

0.5

1.0

4fV

(GeV/c)trigT

p5 10

]-2

[10

nf V

PbP

bas

soc

/Nas

soc

N

-1.0

-0.5

0.0

0.5

1.0

5fV

Figure 6: Fourier coefficients, Vf1 , Vf

2 , Vf3 , Vf

4 , and Vf5 , extracted as functions of ptrig

T for 2 <passoc

T < 4 GeV/c for the 0–5% most central PbPb collisions at√

sNN = 2.76 TeV. The error barsrepresent statistical uncertainties only. The solid lines show the predictions from the PYTHIA8simulation of pp collisions at

√s = 2.76 TeV.

3.3 Fourier Decomposition of ∆φ Distributions

Motivated by recent theoretical developments in understanding the long-range ridge effectin the context of higher-order hydrodynamic flow induced by initial geometric fluctuations,such as the “triangular flow” effect [26, 38–42], an alternative way of quantifying the observedlong-range correlations is investigated in this paper. The 1-D ∆φ-projected distribution for2 < |∆η| < 4 is decomposed in a Fourier series as

1Ntrig

dNpair

d∆φ=

Nassoc

2π

{1 +

∞

∑n=1

2Vfn cos(n∆φ)

}, (6)

where Nassoc represents the total number of hadron pairs per trigger particle for a given |∆η|range and (ptrig

T , passocT ) bin. The 1-D ∆φ projections displayed in Fig. 3 are fitted by the first

five terms in the Fourier series, the resulting fits being shown as the dashed lines in Fig. 3.The data are well described by the fits. Figure 6 presents the first five Fourier coefficientsfrom the fit as functions of ptrig

T for 2 < passocT < 4 GeV/c for the 0–5% most central PbPb

collisions and for the PYTHIA8 pp MC simulation. The PYTHIA8 results are scaled by the ratioof NPYTHIA8

assoc /NPbPbassoc in order to remove the trivial effect of the multiplicity dependence. The error

bars are statistical only, while the systematic uncertainties are found to be negligible becausethe Fourier coefficients characterize the overall shape of the correlation functions, and thus arenot sensitive to the absolute scale. The coefficients from the fit are also found to be largelyindependent of each other (correlation coefficients typical below 5%).

All the Fourier coefficients found from fitting the PbPb data show a similar dependence onptrig

T except for the Vf1 term, which contains an additional negative contribution that grows

toward higher ptrigT . This negative Vf

1 component is consistent with a contribution from mo-mentum conservation or back-to-back dijets [44]. If the observed correlation is purely drivenby the single-particle azimuthal anisotropy arising from the hydrodynamic expansion of themedium [45], the extracted Vf

n components would be related to the flow coefficients vn (i.e.,v2 for anisotropic elliptic flow) via Vf

n ∼ vtrign × vassoc

n , where vtrign and vassoc

n are the flow co-efficients for the trigger and associated particles [26]. The flow coefficients, and especially

10 4 Summary

the higher-order terms, are sensitive to the initial conditions and viscosity of the hot, densemedium [38, 46]. This Fourier analysis serves as an alternative way of quantifying the az-imuthal correlation functions in heavy-ion collisions and potentially provides new insights inunderstanding the origin of the ridge effect in these collisions. Analysis of larger data samplesin terms of ptrig

T and passocT , as well as centrality, would allow a more detailed comparison to

theoretical calculations of hydrodynamics, for which the Fourier components provide a con-cise description of the data.

4 SummaryThe CMS detector at the LHC has been used to measure angular correlations between chargedparticles in ∆η and ∆φ up to |∆η| ≈ 4 and over the full range of ∆φ in the 0–5% most centralPbPb collisions at

√sNN = 2.76 TeV. This is the first study of long-range azimuthal correlations

over a large difference in pseudorapidity in PbPb interactions at the LHC energy. The extracted2-D associated yield distributions show a variety of characteristic features in heavy-ion colli-sions that are not present in minimum bias pp interactions. Short- and long-range azimuthalcorrelations have been studied as a function of the transverse momentum of the trigger parti-cles. The observed long-range ridge-like structure for approximately equal azimuthal angles(∆φ ≈ 0) is most evident in the intermediate transverse momentum range, 2 < ptrig

T < 6 GeV/c,and decreases to almost zero for ptrig

T above 10–12 GeV/c. A qualitatively similar dependenceof the ridge on transverse momentum has also been observed in high-multiplicity pp events,indicating a potentially similar physical origin of the effect. A Fourier decomposition of the1-D ∆φ-projected correlation functions in the ridge region (2 < |∆η| < 4) has been presented.This alternative way of quantifying the correlation data provides valuable information to test awide range of theoretical models, including recent hydrodynamic calculations of higher-orderFourier components. The very broad solid-angle coverage of the CMS detector and the statisti-cal accuracy of the sample analyzed in this paper provide significantly improved observationsof short- and long-range particle correlations over previously available measurements.

AcknowledgmentsWe wish to congratulate our colleagues in the CERN accelerator departments for the excellentperformance of the LHC machine. We thank the technical and administrative staff at CERN andother CMS institutes, and acknowledge support from: FMSR (Austria); FNRS and FWO (Bel-gium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, andNSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sci-ences and NICPB (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3(France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAEand DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithua-nia); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pak-istan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan);MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies(Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE andNSF (USA).

Individuals have received support from the Marie-Curie programme and the European Re-search Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; theAlexander von Humboldt Foundation; the Associazione per lo Sviluppo Scientifico e Tecno-logico del Piemonte (Italy); the Belgian Federal Science Policy Office; the Fonds pour la For-

11

mation a la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschapvoor Innovatie door Wetenschap en Technologie (IWT-Belgium); and the Council of Scienceand Industrial Research, India.

References[1] STAR Collaboration, “Disappearance of back-to-back high pT hadron correlations in

central Au+Au collisions at√

sNN = 200-GeV”, Phys. Rev. Lett. 90 (2003) 082302,arXiv:nucl-ex/0210033. doi:10.1103/PhysRevLett.90.082302.

[2] STAR Collaboration, “Long range rapidity correlations and jet production in high energynuclear collisions”, Phys. Rev. C80 (2009) 064912, arXiv:0909.0191.doi:10.1103/PhysRevC.80.064912.

[3] STAR Collaboration, “Distributions of charged hadrons associated with high transversemomentum particles in pp and Au + Au collisions at

√sNN = 200 GeV”, Phys. Rev. Lett.

95 (2005) 152301, arXiv:nucl-ex/0501016.doi:10.1103/PhysRevLett.95.152301.

[4] PHENIX Collaboration, “System size and energy dependence of jet-induced hadron paircorrelation shapes in Cu + Cu and Au + Au collisions at

√sNN = 200 GeV and 62.4 GeV”,

Phys. Rev. Lett. 98 (2007) 232302, arXiv:nucl-ex/0611019.doi:10.1103/PhysRevLett.98.232302.

[5] PHENIX Collaboration, “Dihadron azimuthal correlations in Au+Au collisions at√

sNN= 200 GeV”, Phys. Rev. C78 (2008) 014901, arXiv:0801.4545.doi:10.1103/PhysRevC.78.014901.

[6] PHOBOS Collaboration, “High transverse Momentum Triggered Correlations over aLarge Pseudorapidity Acceptance in Au+Au Collisions at

√sNN = 200 GeV”, Phys. Rev.

Lett. 104 (2010) 062301, arXiv:0903.2811.doi:10.1103/PhysRevLett.104.062301.

[7] PHOBOS Collaboration, “System Size Dependence of Cluster Properties from Two-Particle Angular Correlations in Cu+Cu and Au+Au Collisions at

√sNN = 200 GeV”,

Phys. Rev. C81 (2010) 024904, arXiv:0812.1172.doi:10.1103/PhysRevC.81.024904.

[8] STAR Collaboration, “Experimental and Theoretical Challenges in the Search for theQuark Gluon Plasma: The STAR Collaboration’s Critical Assessment of the Evidencefrom RHIC Collisions”, Nucl. Phys. A757 (2005) 102, arXiv:nucl-ex/0501009.doi:10.1016/j.nuclphysa.2005.03.085.

[9] PHENIX Collaboration, “Formation of Dense Partonic Matter in Relativistic NucleusNucleus Collisions at RHIC: Experimental Evaluation by the PHENIX Collaboration”,Nucl. Phys. A757 (2005) 184, arXiv:nucl-ex/0410003.doi:10.1016/j.nuclphysa.2005.03.086.

[10] PHOBOS Collaboration, “The PHOBOS Perspective on Discoveries at RHIC”, Nucl. Phys.A757 (2005) 28, arXiv:nucl-ex/0410022.doi:10.1016/j.nuclphysa.2005.03.084.

12 4 Summary

[11] BRAHMS Collaboration, “Quark Gluon Plasma an Color Glass Condensate at RHIC? Theperspective from the BRAHMS experiment”, Nucl. Phys. A757 (2005) 1,arXiv:nucl-ex/0410020. doi:10.1016/j.nuclphysa.2005.02.130.

[12] ALICE Collaboration, “Suppression of Charged Particle Production at Large TransverseMomentum in Central Pb–Pb Collisions at

√sNN = 2.76 TeV”, Phys. Lett. B696 (2011) 30,

arXiv:1012.1004. doi:10.1016/j.physletb.2010.12.020.

[13] ATLAS Collaboration, “Observation of a Centrality-Dependent Dijet Asymmetry inLead-Lead Collisions at

√sNN = 2.76 TeV with the ATLAS Detector at the LHC”, Phys.

Rev. Lett. 105 (2010) 252303, arXiv:1011.6182.doi:10.1103/PhysRevLett.105.252303.

[14] CMS Collaboration, “Observation and studies of jet quenching in PbPb collisions atnucleon-nucleon center-of-mass energy = 2.76 TeV”, arXiv:1102.1957.

[15] N. Armesto, C. A. Salgado, and U. A. Wiedemann, “Measuring the collective flow withjets”, Phys. Rev. Lett. 93 (2004) 242301, arXiv:hep-ph/0405301.doi:10.1103/PhysRevLett.93.242301.

[16] A. Majumder, B. Muller, and S. A. Bass, “Longitudinal Broadening of Quenched Jets inTurbulent Color Fields”, Phys. Rev. Lett. 99 (2007) 042301, arXiv:hep-ph/0611135.doi:10.1103/PhysRevLett.99.042301.

[17] C. B. Chiu and R. C. Hwa, “Pedestal and peak structure in jet correlation”, Phys. Rev. C72(2005) 034903, arXiv:nucl-th/0505014. doi:10.1103/PhysRevC.72.034903.

[18] C.-Y. Wong, “The Momentum Kick Model Description of the Near-Side Ridge and JetQuenching”, Phys. Rev. C78 (2008) 064905, arXiv:0806.2154.doi:10.1103/PhysRevC.78.064905.

[19] S. A. Voloshin, “Transverse radial expansion in nuclear collisions and two particlecorrelations”, Phys. Lett. B632 (2006) 490, arXiv:nucl-th/0312065.doi:10.1016/j.physletb.2005.11.024.

[20] P. Romatschke, “Momentum broadening in an anisotropic plasma”, Phys. Rev. C75(2007) 014901, arXiv:hep-ph/0607327. doi:10.1103/PhysRevC.75.014901.

[21] E. V. Shuryak, “On the Origin of the ’Ridge’ phenomenon induced by Jets in Heavy IonCollisions”, Phys. Rev. C76 (2007) 047901, arXiv:0706.3531.doi:10.1103/PhysRevC.76.047901.

[22] A. Dumitru et al., “Glasma flux tubes and the near side ridge phenomenon at RHIC”,Nucl. Phys. A810 (2008) 91, arXiv:0804.3858.doi:10.1016/j.nuclphysa.2008.06.012.

[23] S. Gavin, L. McLerran, and G. Moschelli, “Long Range Correlations and the Soft Ridge inRelativistic Nuclear Collisions”, Phys. Rev. C79 (2009) 051902, arXiv:0806.4718.doi:10.1103/PhysRevC.79.051902.

[24] K. Dusling, D. Fernandez-Fraile, and R. Venugopalan, “Three-particle correlation fromglasma flux tubes”, Nucl. Phys. A828 (2009) 161, arXiv:0902.4435.doi:10.1016/j.nuclphysa.2009.06.017.

13

[25] Y. Hama et al., “Trying to understand the ridge effect in hydrodynamic model”, Nonlin.Phenom. Complex Syst. 12 (2009) 466, arXiv:0911.0811.

[26] B. Alver and G. Roland, “Collision geometry fluctuations and triangular flow inheavy-ion collisions”, Phys. Rev. C81 (2010) 054905, arXiv:1003.0194.doi:10.1103/PhysRevC.81.054905.

[27] CMS Collaboration, “Observation of Long-Range Near-Side Angular Correlations inProton-Proton Collisions at the LHC”, JHEP 09 (2010) 091, arXiv:1009.4122.doi:10.1007/JHEP09(2010)091.

[28] CMS Collaboration, “The CMS Experiment at the CERN LHC”, JINST 03 (2008) S08004.doi:10.1088/1748-0221/3/08/S08004.

[29] O. Djuvsland and J. Nystrand, “Single and Double Photonuclear Excitations in Pb+PbCollisions at the LHC”, arXiv:1011.4908.

[30] CMS Collaboration, “Measurement of CMS Luminosity”, CMS Physics AnalysisSummary CMS-PAS-EWK-10-004 (2010).

[31] CMS Collaboration, “Absolute luminosity normalization”, CMS Detector PerformanceSummary CMS-DP-2011-002 (2011).

[32] CMS Collaboration, “CMS physics technical design report: Addendum on high densityQCD with heavy ions”, J. Phys. G34 (2007) 2307.doi:10.1088/0954-3899/34/11/008.

[33] I. P. Lokhtin and A. M. Snigirev, “A model of jet quenching in ultrarelativistic heavy ioncollisions and high-pT hadron spectra at RHIC”, Eur. Phys. J. C45 (2006) 211,arXiv:hep-ph/0506189. doi:10.1140/epjc/s2005-02426-3.

[34] STAR Collaboration, “Azimuthal di-hadron correlations in d+Au and Au+Au collisionsat√

sNN = 200 GeV from STAR”, Phys. Rev. C82 (2010) 024912, arXiv:1004.2377.doi:10.1103/PhysRevC.82.024912.

[35] V. Chetluru and O. Barannikova, “Jet Studies for 5.5 TeV Pb+Pb Collisions via Di-HadronCorrelations”, Indian Journal of Physics 84 (2011) 1807.doi:10.1007/s12648-010-0177-x.

[36] T. Sjostrand, S. Mrenna, and P. Z. Skands, “A Brief Introduction to PYTHIA 8.1”, Comput.Phys. Commun. 178 (2008) 852, arXiv:0710.3820.doi:10.1016/j.cpc.2008.01.036.

[37] PHOBOS Collaboration, “System Size, Energy, Pseudorapidity, and CentralityDependence of Elliptic Flow”, Phys. Rev. Lett. 98 (2007) 242302,arXiv:nucl-ex/0610037. doi:10.1103/PhysRevLett.98.242302.

[38] B. H. Alver et al., “Triangular flow in hydrodynamics and transport theory”, Phys. Rev.C82 (2010) 034913, arXiv:1007.5469. doi:10.1103/PhysRevC.82.034913.

[39] B. Schenke, S. Jeon, and C. Gale, “Elliptic and triangular flow in event-by-event (3+1)Dviscous hydrodynamics”, Phys. Rev. Lett. 106 (2011) 042301, arXiv:1009.3244.doi:10.1103/PhysRevLett.106.042301.

14 4 Summary

[40] H. Petersen et al., “Triangular flow in event-by-event ideal hydrodynamics in Au+Aucollisions at

√sNN = 200A GeV”, Phys. Rev. C82 (2010) 041901, arXiv:1008.0625.

doi:10.1103/PhysRevC.82.041901.

[41] J. Xu and C. M. Ko, “The effect of triangular flow on di-hadron azimuthal correlations inrelativistic heavy ion collisions”, Phys. Rev. C83 (2011) 021903, arXiv:1011.3750.doi:10.1103/PhysRevC.83.021903.

[42] D. Teaney and L. Yan, “Triangularity and Dipole Asymmetry in Heavy Ion Collisions”,arXiv:1010.1876.

[43] ALICE Collaboration, “Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV”,Phys. Rev. Lett. 105 (2010) 252302, arXiv:1011.3914.doi:10.1103/PhysRevLett.105.252302.

[44] M. Luzum and J.-Y. Ollitrault, “Directed flow at midrapidity in heavy-ion collisions”,Phys. Rev. Lett. 106 (2011) 102301, arXiv:1011.6361.doi:10.1103/PhysRevLett.106.102301.

[45] S. Voloshin and Y. Zhang, “Flow study in relativistic nuclear collisions by Fourierexpansion of Azimuthal particle distributions”, Z. Phys. C70 (1996) 665,arXiv:hep-ph/9407282. doi:10.1007/s002880050141.

[46] P. Staig and E. Shuryak, “The Fate of the Initial State Fluctuations in Heavy IonCollisions. II The Fluctuations and Sounds”, arXiv:1008.3139.

15

A The CMS CollaborationYerevan Physics Institute, Yerevan, ArmeniaS. Chatrchyan, V. Khachatryan, A.M. Sirunyan, A. Tumasyan

Institut fur Hochenergiephysik der OeAW, Wien, AustriaW. Adam, T. Bergauer, M. Dragicevic, J. Ero, C. Fabjan, M. Friedl, R. Fruhwirth, V.M. Ghete,J. Hammer1, S. Hansel, M. Hoch, N. Hormann, J. Hrubec, M. Jeitler, W. Kiesenhofer,M. Krammer, D. Liko, I. Mikulec, M. Pernicka, H. Rohringer, R. Schofbeck, J. Strauss, A. Taurok,F. Teischinger, P. Wagner, W. Waltenberger, G. Walzel, E. Widl, C.-E. Wulz

National Centre for Particle and High Energy Physics, Minsk, BelarusV. Mossolov, N. Shumeiko, J. Suarez Gonzalez

Universiteit Antwerpen, Antwerpen, BelgiumS. Bansal, L. Benucci, E.A. De Wolf, X. Janssen, J. Maes, T. Maes, L. Mucibello, S. Ochesanu,B. Roland, R. Rougny, M. Selvaggi, H. Van Haevermaet, P. Van Mechelen, N. Van Remortel

Vrije Universiteit Brussel, Brussel, BelgiumF. Blekman, S. Blyweert, J. D’Hondt, O. Devroede, R. Gonzalez Suarez, A. Kalogeropoulos,M. Maes, W. Van Doninck, P. Van Mulders, G.P. Van Onsem, I. Villella

Universite Libre de Bruxelles, Bruxelles, BelgiumO. Charaf, B. Clerbaux, G. De Lentdecker, V. Dero, A.P.R. Gay, G.H. Hammad, T. Hreus,P.E. Marage, L. Thomas, C. Vander Velde, P. Vanlaer

Ghent University, Ghent, BelgiumV. Adler, A. Cimmino, S. Costantini, M. Grunewald, B. Klein, J. Lellouch, A. Marinov,J. Mccartin, D. Ryckbosch, F. Thyssen, M. Tytgat, L. Vanelderen, P. Verwilligen, S. Walsh,N. Zaganidis

Universite Catholique de Louvain, Louvain-la-Neuve, BelgiumS. Basegmez, G. Bruno, J. Caudron, L. Ceard, E. Cortina Gil, J. De Favereau De Jeneret,C. Delaere1, D. Favart, A. Giammanco, G. Gregoire, J. Hollar, V. Lemaitre, J. Liao, O. Militaru,S. Ovyn, D. Pagano, A. Pin, K. Piotrzkowski, N. Schul

Universite de Mons, Mons, BelgiumN. Beliy, T. Caebergs, E. Daubie

Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, BrazilG.A. Alves, D. De Jesus Damiao, M.E. Pol, M.H.G. Souza

Universidade do Estado do Rio de Janeiro, Rio de Janeiro, BrazilW. Carvalho, E.M. Da Costa, C. De Oliveira Martins, S. Fonseca De Souza, L. Mundim,H. Nogima, V. Oguri, W.L. Prado Da Silva, A. Santoro, S.M. Silva Do Amaral, A. Sznajder

Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, BrazilC.A. Bernardes2, F.A. Dias, T.R. Fernandez Perez Tomei, E. M. Gregores2, C. Lagana,F. Marinho, P.G. Mercadante2, S.F. Novaes, Sandra S. Padula

Institute for Nuclear Research and Nuclear Energy, Sofia, BulgariaN. Darmenov1, L. Dimitrov, V. Genchev1, P. Iaydjiev1, S. Piperov, M. Rodozov, S. Stoykova,G. Sultanov, V. Tcholakov, R. Trayanov, I. Vankov

16 A The CMS Collaboration

University of Sofia, Sofia, BulgariaA. Dimitrov, R. Hadjiiska, A. Karadzhinova, V. Kozhuharov, L. Litov, M. Mateev, B. Pavlov,P. Petkov

Institute of High Energy Physics, Beijing, ChinaJ.G. Bian, G.M. Chen, H.S. Chen, C.H. Jiang, D. Liang, S. Liang, X. Meng, J. Tao, J. Wang,J. Wang, X. Wang, Z. Wang, H. Xiao, M. Xu, J. Zang, Z. Zhang

State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, ChinaY. Ban, S. Guo, Y. Guo, W. Li, Y. Mao, S.J. Qian, H. Teng, L. Zhang, B. Zhu, W. Zou

Universidad de Los Andes, Bogota, ColombiaA. Cabrera, B. Gomez Moreno, A.A. Ocampo Rios, A.F. Osorio Oliveros, J.C. Sanabria

Technical University of Split, Split, CroatiaN. Godinovic, D. Lelas, K. Lelas, R. Plestina3, D. Polic, I. Puljak

University of Split, Split, CroatiaZ. Antunovic, M. Dzelalija

Institute Rudjer Boskovic, Zagreb, CroatiaV. Brigljevic, S. Duric, K. Kadija, S. Morovic

University of Cyprus, Nicosia, CyprusA. Attikis, M. Galanti, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis

Charles University, Prague, Czech RepublicM. Finger, M. Finger Jr.

Academy of Scientific Research and Technology of the Arab Republic of Egypt, EgyptianNetwork of High Energy Physics, Cairo, EgyptY. Assran4, S. Khalil5, M.A. Mahmoud6

National Institute of Chemical Physics and Biophysics, Tallinn, EstoniaA. Hektor, M. Kadastik, M. Muntel, M. Raidal, L. Rebane

Department of Physics, University of Helsinki, Helsinki, FinlandV. Azzolini, P. Eerola, G. Fedi

Helsinki Institute of Physics, Helsinki, FinlandS. Czellar, J. Harkonen, A. Heikkinen, V. Karimaki, R. Kinnunen, M.J. Kortelainen, T. Lampen,K. Lassila-Perini, S. Lehti, T. Linden, P. Luukka, T. Maenpaa, E. Tuominen, J. Tuominiemi,E. Tuovinen, D. Ungaro, L. Wendland

Lappeenranta University of Technology, Lappeenranta, FinlandK. Banzuzi, A. Korpela, T. Tuuva

Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux,FranceD. Sillou

DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, FranceM. Besancon, S. Choudhury, M. Dejardin, D. Denegri, B. Fabbro, J.L. Faure, F. Ferri, S. Ganjour,F.X. Gentit, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, E. Locci, J. Malcles,M. Marionneau, L. Millischer, J. Rander, A. Rosowsky, I. Shreyber, M. Titov, P. Verrecchia

17

Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, FranceS. Baffioni, F. Beaudette, L. Benhabib, L. Bianchini, M. Bluj7, C. Broutin, P. Busson, C. Charlot,T. Dahms, L. Dobrzynski, S. Elgammal, R. Granier de Cassagnac, M. Haguenauer, P. Mine,C. Mironov, C. Ochando, P. Paganini, D. Sabes, R. Salerno, Y. Sirois, C. Thiebaux, B. Wyslouch8,A. Zabi

Institut Pluridisciplinaire Hubert Curien, Universite de Strasbourg, Universite de HauteAlsace Mulhouse, CNRS/IN2P3, Strasbourg, FranceJ.-L. Agram9, J. Andrea, D. Bloch, D. Bodin, J.-M. Brom, M. Cardaci, E.C. Chabert, C. Collard,E. Conte9, F. Drouhin9, C. Ferro, J.-C. Fontaine9, D. Gele, U. Goerlach, S. Greder, P. Juillot,M. Karim9, A.-C. Le Bihan, Y. Mikami, P. Van Hove

Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique desParticules (IN2P3), Villeurbanne, FranceF. Fassi, D. Mercier

Universite de Lyon, Universite Claude Bernard Lyon 1, CNRS-IN2P3, Institut de PhysiqueNucleaire de Lyon, Villeurbanne, FranceC. Baty, S. Beauceron, N. Beaupere, M. Bedjidian, O. Bondu, G. Boudoul, D. Boumediene,H. Brun, J. Chasserat, R. Chierici, D. Contardo, P. Depasse, H. El Mamouni, J. Fay, S. Gascon,B. Ille, T. Kurca, T. Le Grand, M. Lethuillier, L. Mirabito, S. Perries, V. Sordini, S. Tosi, Y. Tschudi,P. Verdier

Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi,GeorgiaD. Lomidze

RWTH Aachen University, I. Physikalisches Institut, Aachen, GermanyG. Anagnostou, M. Edelhoff, L. Feld, N. Heracleous, O. Hindrichs, R. Jussen, K. Klein, J. Merz,N. Mohr, A. Ostapchuk, A. Perieanu, F. Raupach, J. Sammet, S. Schael, D. Sprenger, H. Weber,M. Weber, B. Wittmer

RWTH Aachen University, III. Physikalisches Institut A, Aachen, GermanyM. Ata, W. Bender, E. Dietz-Laursonn, M. Erdmann, J. Frangenheim, T. Hebbeker,A. Hinzmann, K. Hoepfner, T. Klimkovich, D. Klingebiel, P. Kreuzer, D. Lanske†, C. Magass,M. Merschmeyer, A. Meyer, P. Papacz, H. Pieta, H. Reithler, S.A. Schmitz, L. Sonnenschein,J. Steggemann, D. Teyssier

RWTH Aachen University, III. Physikalisches Institut B, Aachen, GermanyM. Bontenackels, M. Davids, M. Duda, G. Flugge, H. Geenen, M. Giffels, W. Haj Ahmad,D. Heydhausen, T. Kress, Y. Kuessel, A. Linn, A. Nowack, L. Perchalla, O. Pooth, J. Rennefeld,P. Sauerland, A. Stahl, M. Thomas, D. Tornier, M.H. Zoeller

Deutsches Elektronen-Synchrotron, Hamburg, GermanyM. Aldaya Martin, W. Behrenhoff, U. Behrens, M. Bergholz10, A. Bethani, K. Borras, A. Cakir,A. Campbell, E. Castro, D. Dammann, G. Eckerlin, D. Eckstein, A. Flossdorf, G. Flucke,A. Geiser, J. Hauk, H. Jung1, M. Kasemann, I. Katkov11, P. Katsas, C. Kleinwort, H. Kluge,A. Knutsson, M. Kramer, D. Krucker, E. Kuznetsova, W. Lange, W. Lohmann10, R. Mankel,M. Marienfeld, I.-A. Melzer-Pellmann, A.B. Meyer, J. Mnich, A. Mussgiller, J. Olzem, D. Pitzl,A. Raspereza, A. Raval, M. Rosin, R. Schmidt10, T. Schoerner-Sadenius, N. Sen, A. Spiridonov,M. Stein, J. Tomaszewska, R. Walsh, C. Wissing

University of Hamburg, Hamburg, GermanyC. Autermann, V. Blobel, S. Bobrovskyi, J. Draeger, H. Enderle, U. Gebbert, K. Kaschube,

18 A The CMS Collaboration

G. Kaussen, R. Klanner, J. Lange, B. Mura, S. Naumann-Emme, F. Nowak, N. Pietsch, C. Sander,H. Schettler, P. Schleper, M. Schroder, T. Schum, J. Schwandt, H. Stadie, G. Steinbruck,J. Thomsen

Institut fur Experimentelle Kernphysik, Karlsruhe, GermanyC. Barth, J. Bauer, J. Berger, V. Buege, T. Chwalek, W. De Boer, A. Dierlamm, G. Dirkes,M. Feindt, J. Gruschke, C. Hackstein, F. Hartmann, M. Heinrich, H. Held, K.H. Hoffmann,S. Honc, J.R. Komaragiri, T. Kuhr, D. Martschei, S. Mueller, Th. Muller, M. Niegel, O. Oberst,A. Oehler, J. Ott, T. Peiffer, G. Quast, K. Rabbertz, F. Ratnikov, N. Ratnikova, M. Renz, C. Saout,A. Scheurer, P. Schieferdecker, F.-P. Schilling, G. Schott, H.J. Simonis, F.M. Stober, D. Troendle,J. Wagner-Kuhr, T. Weiler, M. Zeise, V. Zhukov11, E.B. Ziebarth

Institute of Nuclear Physics ”Demokritos”, Aghia Paraskevi, GreeceG. Daskalakis, T. Geralis, S. Kesisoglou, A. Kyriakis, D. Loukas, I. Manolakos, A. Markou,C. Markou, C. Mavrommatis, E. Ntomari, E. Petrakou

University of Athens, Athens, GreeceL. Gouskos, T.J. Mertzimekis, A. Panagiotou, E. Stiliaris

University of Ioannina, Ioannina, GreeceI. Evangelou, C. Foudas, P. Kokkas, N. Manthos, I. Papadopoulos, V. Patras, F.A. Triantis

KFKI Research Institute for Particle and Nuclear Physics, Budapest, HungaryA. Aranyi, G. Bencze, L. Boldizsar, C. Hajdu1, P. Hidas, D. Horvath12, A. Kapusi, K. Krajczar13,F. Sikler1, G.I. Veres13, G. Vesztergombi13

Institute of Nuclear Research ATOMKI, Debrecen, HungaryN. Beni, J. Molnar, J. Palinkas, Z. Szillasi, V. Veszpremi

University of Debrecen, Debrecen, HungaryP. Raics, Z.L. Trocsanyi, B. Ujvari

Panjab University, Chandigarh, IndiaS.B. Beri, V. Bhatnagar, N. Dhingra, R. Gupta, M. Jindal, M. Kaur, J.M. Kohli, M.Z. Mehta,N. Nishu, L.K. Saini, A. Sharma, A.P. Singh, J.B. Singh, S.P. Singh

University of Delhi, Delhi, IndiaS. Ahuja, S. Bhattacharya, B.C. Choudhary, B. Gomber, P. Gupta, S. Jain, S. Jain, R. Khurana,A. Kumar, M. Naimuddin, K. Ranjan, R.K. Shivpuri

Bhabha Atomic Research Centre, Mumbai, IndiaR.K. Choudhury, D. Dutta, S. Kailas, V. Kumar, P. Mehta, A.K. Mohanty1, L.M. Pant, P. Shukla

Tata Institute of Fundamental Research - EHEP, Mumbai, IndiaT. Aziz, M. Guchait14, A. Gurtu, M. Maity15, D. Majumder, G. Majumder, K. Mazumdar,G.B. Mohanty, A. Saha, K. Sudhakar, N. Wickramage

Tata Institute of Fundamental Research - HECR, Mumbai, IndiaS. Banerjee, S. Dugad, N.K. Mondal

Institute for Research and Fundamental Sciences (IPM), Tehran, IranH. Arfaei, H. Bakhshiansohi16, S.M. Etesami, A. Fahim16, M. Hashemi, A. Jafari16, M. Khakzad,A. Mohammadi17, M. Mohammadi Najafabadi, S. Paktinat Mehdiabadi, B. Safarzadeh,M. Zeinali18

19

INFN Sezione di Bari a, Universita di Bari b, Politecnico di Bari c, Bari, ItalyM. Abbresciaa,b, L. Barbonea,b, C. Calabriaa ,b, A. Colaleoa, D. Creanzaa,c, N. De Filippisa,c,1,M. De Palmaa ,b, L. Fiorea, G. Iasellia,c, L. Lusitoa ,b, G. Maggia,c, M. Maggia, N. Mannaa ,b,B. Marangellia ,b, S. Mya ,c, S. Nuzzoa,b, N. Pacificoa,b, G.A. Pierroa, A. Pompilia ,b, G. Pugliesea,c,F. Romanoa ,c, G. Rosellia ,b, G. Selvaggia,b, L. Silvestrisa, R. Trentaduea, S. Tupputia ,b, G. Zitoa

INFN Sezione di Bologna a, Universita di Bologna b, Bologna, ItalyG. Abbiendia, A.C. Benvenutia, D. Bonacorsia, S. Braibant-Giacomellia,b, L. Brigliadoria,P. Capiluppia,b, A. Castroa,b, F.R. Cavalloa, M. Cuffiania ,b, G.M. Dallavallea, F. Fabbria,A. Fanfania ,b, D. Fasanellaa, P. Giacomellia, M. Giuntaa, C. Grandia, S. Marcellinia, G. Masettib,M. Meneghellia ,b, A. Montanaria, F.L. Navarriaa ,b, F. Odoricia, A. Perrottaa, F. Primaveraa,A.M. Rossia,b, T. Rovellia ,b, G. Sirolia,b, R. Travaglinia,b

INFN Sezione di Catania a, Universita di Catania b, Catania, ItalyS. Albergoa,b, G. Cappelloa ,b, M. Chiorbolia ,b ,1, S. Costaa,b, A. Tricomia,b, C. Tuvea

INFN Sezione di Firenze a, Universita di Firenze b, Firenze, ItalyG. Barbaglia, V. Ciullia,b, C. Civininia, R. D’Alessandroa ,b, E. Focardia ,b, S. Frosalia ,b, E. Galloa,S. Gonzia,b, P. Lenzia,b, M. Meschinia, S. Paolettia, G. Sguazzonia, A. Tropianoa,1

INFN Laboratori Nazionali di Frascati, Frascati, ItalyL. Benussi, S. Bianco, S. Colafranceschi19, F. Fabbri, D. Piccolo

INFN Sezione di Genova, Genova, ItalyP. Fabbricatore, R. Musenich

INFN Sezione di Milano-Biccoca a, Universita di Milano-Bicocca b, Milano, ItalyA. Benagliaa,b, F. De Guioa ,b ,1, L. Di Matteoa,b, S. Gennai1, A. Ghezzia,b, S. Malvezzia,A. Martellia ,b, A. Massironia,b, D. Menascea, L. Moronia, M. Paganonia,b, D. Pedrinia,S. Ragazzia,b, N. Redaellia, S. Salaa, T. Tabarelli de Fatisa,b

INFN Sezione di Napoli a, Universita di Napoli ”Federico II” b, Napoli, ItalyS. Buontempoa, C.A. Carrillo Montoyaa,1, N. Cavalloa ,20, A. De Cosaa ,b, F. Fabozzia ,20,A.O.M. Iorioa ,1, L. Listaa, M. Merolaa ,b, P. Paoluccia

INFN Sezione di Padova a, Universita di Padova b, Universita di Trento (Trento) c, Padova,ItalyP. Azzia, N. Bacchettaa, P. Bellana,b, M. Bellatoa, M. Biasottoa,21, D. Biselloa,b, A. Brancaa,P. Checchiaa, M. De Mattiaa ,b, T. Dorigoa, F. Gasparinia ,b, F. Gonellaa, A. Gozzelino,M. Gulminia,21, S. Lacapraraa,21, I. Lazzizzeraa ,c, M. Margonia,b, G. Marona ,21,A.T. Meneguzzoa,b, M. Nespoloa ,1, M. Passaseoa, L. Perrozzia ,1, N. Pozzobona ,b, P. Ronchesea ,b,F. Simonettoa ,b, E. Torassaa, M. Tosia,b, A. Triossia, S. Vaninia ,b

INFN Sezione di Pavia a, Universita di Pavia b, Pavia, ItalyP. Baessoa,b, U. Berzanoa, S.P. Rattia,b, C. Riccardia,b, P. Torrea ,b, P. Vituloa,b, C. Viviania,b

INFN Sezione di Perugia a, Universita di Perugia b, Perugia, ItalyM. Biasinia ,b, G.M. Bileia, B. Caponeria,b, L. Fanoa,b, P. Laricciaa,b, A. Lucaronia ,b ,1,G. Mantovania ,b, M. Menichellia, A. Nappia,b, F. Romeoa ,b, A. Santocchiaa ,b, S. Taronia ,b ,1,M. Valdataa,b

INFN Sezione di Pisa a, Universita di Pisa b, Scuola Normale Superiore di Pisa c, Pisa, ItalyP. Azzurria,c, G. Bagliesia, J. Bernardinia,b, T. Boccalia ,1, G. Broccoloa ,c, R. Castaldia,R.T. D’Agnoloa ,c, R. Dell’Orsoa, F. Fioria ,b, L. Foaa,c, A. Giassia, A. Kraana, F. Ligabuea ,c,

20 A The CMS Collaboration

T. Lomtadzea, L. Martinia ,22, A. Messineoa,b, F. Pallaa, G. Segneria, A.T. Serbana, P. Spagnoloa,R. Tenchinia, G. Tonellia ,b ,1, A. Venturia ,1, P.G. Verdinia

INFN Sezione di Roma a, Universita di Roma ”La Sapienza” b, Roma, ItalyL. Baronea ,b, F. Cavallaria, D. Del Rea,b, E. Di Marcoa,b, M. Diemoza, D. Francia ,b, M. Grassia,1,E. Longoa,b, S. Nourbakhsha, G. Organtinia,b, F. Pandolfia,b ,1, R. Paramattia, S. Rahatloua ,b,C. Rovelli1

INFN Sezione di Torino a, Universita di Torino b, Universita del Piemonte Orientale (No-vara) c, Torino, ItalyN. Amapanea,b, R. Arcidiaconoa ,c, S. Argiroa ,b, M. Arneodoa ,c, C. Biinoa, C. Bottaa ,b ,1,N. Cartigliaa, R. Castelloa ,b, M. Costaa ,b, N. Demariaa, A. Grazianoa ,b ,1, C. Mariottia,M. Maronea,b, S. Masellia, E. Migliorea,b, G. Milaa,b, V. Monacoa,b, M. Musicha ,b,M.M. Obertinoa,c, N. Pastronea, M. Pelliccionia,b, A. Romeroa,b, M. Ruspaa,c, R. Sacchia ,b,V. Solaa ,b, A. Solanoa,b, A. Staianoa, A. Vilela Pereiraa

INFN Sezione di Trieste a, Universita di Trieste b, Trieste, ItalyS. Belfortea, F. Cossuttia, G. Della Riccaa,b, B. Gobboa, D. Montaninoa,b, A. Penzoa

Kangwon National University, Chunchon, KoreaS.G. Heo, S.K. Nam

Kyungpook National University, Daegu, KoreaS. Chang, J. Chung, D.H. Kim, G.N. Kim, J.E. Kim, D.J. Kong, H. Park, S.R. Ro, D. Son, D.C. Son,T. Son

Chonnam National University, Institute for Universe and Elementary Particles, Kwangju,KoreaZero Kim, J.Y. Kim, S. Song

Korea University, Seoul, KoreaS. Choi, B. Hong, M.S. Jeong, M. Jo, H. Kim, J.H. Kim, T.J. Kim, K.S. Lee, D.H. Moon, S.K. Park,H.B. Rhee, E. Seo, S. Shin, K.S. Sim

University of Seoul, Seoul, KoreaM. Choi, S. Kang, H. Kim, C. Park, I.C. Park, S. Park, G. Ryu

Sungkyunkwan University, Suwon, KoreaY. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, J. Lee, S. Lee, H. Seo, I. Yu

Vilnius University, Vilnius, LithuaniaM.J. Bilinskas, I. Grigelionis, M. Janulis, D. Martisiute, P. Petrov, T. Sabonis

Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, MexicoH. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-de La Cruz, R. Lopez-Fernandez,R. Magana Villalba, A. Sanchez-Hernandez, L.M. Villasenor-Cendejas

Universidad Iberoamericana, Mexico City, MexicoS. Carrillo Moreno, F. Vazquez Valencia

Benemerita Universidad Autonoma de Puebla, Puebla, MexicoH.A. Salazar Ibarguen

Universidad Autonoma de San Luis Potosı, San Luis Potosı, MexicoE. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos

21

University of Auckland, Auckland, New ZealandD. Krofcheck, J. Tam

University of Canterbury, Christchurch, New ZealandP.H. Butler, R. Doesburg, H. Silverwood

National Centre for Physics, Quaid-I-Azam University, Islamabad, PakistanM. Ahmad, I. Ahmed, M.I. Asghar, H.R. Hoorani, W.A. Khan, T. Khurshid, S. Qazi

Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, PolandG. Brona, M. Cwiok, W. Dominik, K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski

Soltan Institute for Nuclear Studies, Warsaw, PolandT. Frueboes, R. Gokieli, M. Gorski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska,M. Szleper, G. Wrochna, P. Zalewski

Laboratorio de Instrumentacao e Fısica Experimental de Partıculas, Lisboa, PortugalN. Almeida, P. Bargassa, A. David, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro, P. Musella,A. Nayak, P.Q. Ribeiro, J. Seixas, J. Varela

Joint Institute for Nuclear Research, Dubna, RussiaS. Afanasiev, I. Belotelov, P. Bunin, I. Golutvin, A. Kamenev, V. Karjavin, G. Kozlov, A. Lanev,P. Moisenz, V. Palichik, V. Perelygin, S. Shmatov, V. Smirnov, A. Volodko, A. Zarubin

Petersburg Nuclear Physics Institute, Gatchina (St Petersburg), RussiaV. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov,L. Uvarov, S. Vavilov, A. Vorobyev, A. Vorobyev

Institute for Nuclear Research, Moscow, RussiaYu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov, N. Krasnikov, V. Matveev,A. Pashenkov, A. Toropin, S. Troitsky

Institute for Theoretical and Experimental Physics, Moscow, RussiaV. Epshteyn, V. Gavrilov, V. Kaftanov†, M. Kossov1, A. Krokhotin, N. Lychkovskaya, V. Popov,G. Safronov, S. Semenov, V. Stolin, E. Vlasov, A. Zhokin

Moscow State University, Moscow, RussiaE. Boos, A. Ershov, A. Gribushin, O. Kodolova, V. Korotkikh, I. Lokhtin, A. Markina,S. Obraztsov, M. Perfilov, S. Petrushanko, L. Sarycheva, V. Savrin, A. Snigirev, I. Vardanyan

P.N. Lebedev Physical Institute, Moscow, RussiaV. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, S.V. Rusakov, A. Vinogradov

State Research Center of Russian Federation, Institute for High Energy Physics, Protvino,RussiaI. Azhgirey, S. Bitioukov, V. Grishin1, V. Kachanov, D. Konstantinov, A. Korablev, V. Krychkine,V. Petrov, R. Ryutin, S. Slabospitsky, A. Sobol, L. Tourtchanovitch, S. Troshin, N. Tyurin,A. Uzunian, A. Volkov

University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade,SerbiaP. Adzic23, M. Djordjevic, D. Krpic23, J. Milosevic

Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT),Madrid, SpainM. Aguilar-Benitez, J. Alcaraz Maestre, P. Arce, C. Battilana, E. Calvo, M. Cepeda, M. Cerrada,

22 A The CMS Collaboration

M. Chamizo Llatas, N. Colino, B. De La Cruz, A. Delgado Peris, C. Diez Pardos, D. DomınguezVazquez, C. Fernandez Bedoya, J.P. Fernandez Ramos, A. Ferrando, J. Flix, M.C. Fouz,P. Garcia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, G. Merino,J. Puerta Pelayo, I. Redondo, L. Romero, J. Santaolalla, M.S. Soares, C. Willmott

Universidad Autonoma de Madrid, Madrid, SpainC. Albajar, G. Codispoti, J.F. de Troconiz

Universidad de Oviedo, Oviedo, SpainJ. Cuevas, J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, L. Lloret Iglesias,J.M. Vizan Garcia

Instituto de Fısica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, SpainJ.A. Brochero Cifuentes, I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros,M. Felcini24, M. Fernandez, G. Gomez, J. Gonzalez Sanchez, C. Jorda, P. Lobelle Pardo, A. LopezVirto, J. Marco, R. Marco, C. Martinez Rivero, F. Matorras, F.J. Munoz Sanchez, J. PiedraGomez25, T. Rodrigo, A.Y. Rodrıguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, M. SobronSanudo, I. Vila, R. Vilar Cortabitarte

CERN, European Organization for Nuclear Research, Geneva, SwitzerlandD. Abbaneo, E. Auffray, G. Auzinger, P. Baillon, A.H. Ball, D. Barney, A.J. Bell26, D. Benedetti,C. Bernet3, W. Bialas, P. Bloch, A. Bocci, S. Bolognesi, M. Bona, H. Breuker, K. Bunkowski,T. Camporesi, G. Cerminara, J.A. Coarasa Perez, B. Cure, D. D’Enterria, A. De Roeck, S. DiGuida, N. Dupont-Sagorin, A. Elliott-Peisert, B. Frisch, W. Funk, A. Gaddi, G. Georgiou,H. Gerwig, D. Gigi, K. Gill, D. Giordano, F. Glege, R. Gomez-Reino Garrido, M. Gouzevitch,P. Govoni, S. Gowdy, L. Guiducci, M. Hansen, C. Hartl, J. Harvey, J. Hegeman, B. Hegner,H.F. Hoffmann, A. Honma, V. Innocente, P. Janot, K. Kaadze, E. Karavakis, P. Lecoq,C. Lourenco, T. Maki, M. Malberti, L. Malgeri, M. Mannelli, L. Masetti, A. Maurisset, F. Meijers,S. Mersi, E. Meschi, R. Moser, M.U. Mozer, M. Mulders, E. Nesvold1, M. Nguyen, T. Orimoto,L. Orsini, E. Perez, A. Petrilli, A. Pfeiffer, M. Pierini, M. Pimia, D. Piparo, G. Polese, A. Racz,J. Rodrigues Antunes, G. Rolandi27, T. Rommerskirchen, M. Rovere, H. Sakulin, C. Schafer,C. Schwick, I. Segoni, A. Sharma, P. Siegrist, M. Simon, P. Sphicas28, M. Spiropulu29, M. Stoye,M. Tadel, P. Tropea, A. Tsirou, P. Vichoudis, M. Voutilainen, W.D. Zeuner

Paul Scherrer Institut, Villigen, SwitzerlandW. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram, H.C. Kaestli,S. Konig, D. Kotlinski, U. Langenegger, F. Meier, D. Renker, T. Rohe, J. Sibille30,A. Starodumov31

Institute for Particle Physics, ETH Zurich, Zurich, SwitzerlandP. Bortignon, L. Caminada32, N. Chanon, Z. Chen, S. Cittolin, G. Dissertori, M. Dittmar,J. Eugster, K. Freudenreich, C. Grab, W. Hintz, P. Lecomte, W. Lustermann, C. Marchica32,P. Martinez Ruiz del Arbol, P. Meridiani, P. Milenovic33, F. Moortgat, C. Nageli32, P. Nef,F. Nessi-Tedaldi, L. Pape, F. Pauss, T. Punz, A. Rizzi, F.J. Ronga, M. Rossini, L. Sala,A.K. Sanchez, M.-C. Sawley, B. Stieger, L. Tauscher†, A. Thea, K. Theofilatos, D. Treille,C. Urscheler, R. Wallny, M. Weber, L. Wehrli, J. Weng

Universitat Zurich, Zurich, SwitzerlandE. Aguilo, C. Amsler, V. Chiochia, S. De Visscher, C. Favaro, M. Ivova Rikova, B. Millan Mejias,P. Otiougova, C. Regenfus, P. Robmann, A. Schmidt, H. Snoek

National Central University, Chung-Li, Taiwan

23

Y.H. Chang, K.H. Chen, S. Dutta, C.M. Kuo, S.W. Li, W. Lin, Z.K. Liu, Y.J. Lu, D. Mekterovic,R. Volpe, J.H. Wu, S.S. Yu

National Taiwan University (NTU), Taipei, TaiwanP. Bartalini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, W.-S. Hou, Y. Hsiung,K.Y. Kao, Y.J. Lei, R.-S. Lu, J.G. Shiu, Y.M. Tzeng, M. Wang

Cukurova University, Adana, TurkeyA. Adiguzel, M.N. Bakirci34, S. Cerci35, C. Dozen, I. Dumanoglu, A. Ekenel, E. Eskut, S. Girgis,G. Gokbulut, I. Hos, E.E. Kangal, A. Kayis Topaksu, G. Onengut, K. Ozdemir, S. Ozturk,A. Polatoz, K. Sogut36, D. Sunar Cerci35, B. Tali35, H. Topakli34, D. Uzun, L.N. Vergili, M. Vergili,S. Yilmaz

Middle East Technical University, Physics Department, Ankara, TurkeyI.V. Akin, T. Aliev, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler, K. Ocalan, A. Ozpineci,M. Serin, R. Sever, U.E. Surat, E. Yildirim, M. Zeyrek

Bogazici University, Istanbul, TurkeyM. Deliomeroglu, D. Demir37, E. Gulmez, B. Isildak, M. Kaya38, O. Kaya38, S. Ozkorucuklu39,N. Sonmez40

National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, UkraineL. Levchuk

University of Bristol, Bristol, United KingdomF. Bostock, J.J. Brooke, T.L. Cheng, E. Clement, D. Cussans, R. Frazier, J. Goldstein, M. Grimes,M. Hansen, D. Hartley, G.P. Heath, H.F. Heath, L. Kreczko, S. Metson, D.M. Newbold41,K. Nirunpong, A. Poll, S. Senkin, V.J. Smith, S. Ward

Rutherford Appleton Laboratory, Didcot, United KingdomL. Basso42, A. Belyaev42, C. Brew, R.M. Brown, B. Camanzi, D.J.A. Cockerill, J.A. Coughlan,K. Harder, S. Harper, J. Jackson, B.W. Kennedy, E. Olaiya, D. Petyt, B.C. Radburn-Smith,C.H. Shepherd-Themistocleous, I.R. Tomalin, W.J. Womersley, S.D. Worm

Imperial College, London, United KingdomR. Bainbridge, G. Ball, J. Ballin, R. Beuselinck, O. Buchmuller, D. Colling, N. Cripps, M. Cutajar,G. Davies, M. Della Negra, W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert, A. Guneratne Bryer,G. Hall, Z. Hatherell, J. Hays, G. Iles, M. Jarvis, G. Karapostoli, L. Lyons, B.C. MacEvoy, A.-M. Magnan, J. Marrouche, B. Mathias, R. Nandi, J. Nash, A. Nikitenko31, A. Papageorgiou,M. Pesaresi, K. Petridis, M. Pioppi43, D.M. Raymond, S. Rogerson, N. Rompotis, A. Rose,M.J. Ryan, C. Seez, P. Sharp, A. Sparrow, A. Tapper, S. Tourneur, M. Vazquez Acosta, T. Virdee,S. Wakefield, N. Wardle, D. Wardrope, T. Whyntie

Brunel University, Uxbridge, United KingdomM. Barrett, M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, D. Leslie, W. Martin,I.D. Reid, L. Teodorescu

Baylor University, Waco, USAK. Hatakeyama, H. Liu

Boston University, Boston, USAT. Bose, E. Carrera Jarrin, C. Fantasia, A. Heister, J. St. John, P. Lawson, D. Lazic, J. Rohlf,D. Sperka, L. Sulak

24 A The CMS Collaboration

Brown University, Providence, USAA. Avetisyan, S. Bhattacharya, J.P. Chou, D. Cutts, A. Ferapontov, U. Heintz, S. Jabeen,G. Kukartsev, G. Landsberg, M. Luk, M. Narain, D. Nguyen, M. Segala, T. Sinthuprasith,T. Speer, K.V. Tsang

University of California, Davis, Davis, USAR. Breedon, M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok, J. Conway, P.T. Cox,J. Dolen, R. Erbacher, E. Friis, W. Ko, A. Kopecky, R. Lander, H. Liu, S. Maruyama, T. Miceli,M. Nikolic, D. Pellett, J. Robles, S. Salur, T. Schwarz, M. Searle, J. Smith, M. Squires, M. Tripathi,R. Vasquez Sierra, C. Veelken

University of California, Los Angeles, Los Angeles, USAV. Andreev, K. Arisaka, D. Cline, R. Cousins, A. Deisher, J. Duris, S. Erhan, C. Farrell, J. Hauser,M. Ignatenko, C. Jarvis, C. Plager, G. Rakness, P. Schlein†, J. Tucker, V. Valuev

University of California, Riverside, Riverside, USAJ. Babb, A. Chandra, R. Clare, J. Ellison, J.W. Gary, F. Giordano, G. Hanson, G.Y. Jeng,S.C. Kao, F. Liu, H. Liu, O.R. Long, A. Luthra, H. Nguyen, B.C. Shen†, R. Stringer, J. Sturdy,S. Sumowidagdo, R. Wilken, S. Wimpenny

University of California, San Diego, La Jolla, USAW. Andrews, J.G. Branson, G.B. Cerati, D. Evans, F. Golf, A. Holzner, R. Kelley, M. Lebourgeois,J. Letts, B. Mangano, S. Padhi, C. Palmer, G. Petrucciani, H. Pi, M. Pieri, R. Ranieri, M. Sani,V. Sharma, S. Simon, E. Sudano, Y. Tu, A. Vartak, S. Wasserbaech44, F. Wurthwein, A. Yagil,J. Yoo

University of California, Santa Barbara, Santa Barbara, USAD. Barge, R. Bellan, C. Campagnari, M. D’Alfonso, T. Danielson, K. Flowers, P. Geffert,J. Incandela, C. Justus, P. Kalavase, S.A. Koay, D. Kovalskyi, V. Krutelyov, S. Lowette, N. Mccoll,V. Pavlunin, F. Rebassoo, J. Ribnik, J. Richman, R. Rossin, D. Stuart, W. To, J.R. Vlimant

California Institute of Technology, Pasadena, USAA. Apresyan, A. Bornheim, J. Bunn, Y. Chen, M. Gataullin, Y. Ma, A. Mott, H.B. Newman,C. Rogan, K. Shin, V. Timciuc, P. Traczyk, J. Veverka, R. Wilkinson, Y. Yang, R.Y. Zhu

Carnegie Mellon University, Pittsburgh, USAB. Akgun, R. Carroll, T. Ferguson, Y. Iiyama, D.W. Jang, S.Y. Jun, Y.F. Liu, M. Paulini, J. Russ,H. Vogel, I. Vorobiev

University of Colorado at Boulder, Boulder, USAJ.P. Cumalat, M.E. Dinardo, B.R. Drell, C.J. Edelmaier, W.T. Ford, A. Gaz, B. Heyburn, E. LuiggiLopez, U. Nauenberg, J.G. Smith, K. Stenson, K.A. Ulmer, S.R. Wagner, S.L. Zang

Cornell University, Ithaca, USAL. Agostino, J. Alexander, D. Cassel, A. Chatterjee, S. Das, N. Eggert, L.K. Gibbons, B. Heltsley,W. Hopkins, A. Khukhunaishvili, B. Kreis, G. Nicolas Kaufman, J.R. Patterson, D. Puigh,A. Ryd, E. Salvati, X. Shi, W. Sun, W.D. Teo, J. Thom, J. Thompson, J. Vaughan, Y. Weng,L. Winstrom, P. Wittich

Fairfield University, Fairfield, USAA. Biselli, G. Cirino, D. Winn

Fermi National Accelerator Laboratory, Batavia, USAS. Abdullin, M. Albrow, J. Anderson, G. Apollinari, M. Atac, J.A. Bakken, S. Banerjee,L.A.T. Bauerdick, A. Beretvas, J. Berryhill, P.C. Bhat, I. Bloch, F. Borcherding, K. Burkett,

25

J.N. Butler, V. Chetluru, H.W.K. Cheung, F. Chlebana, S. Cihangir, W. Cooper, D.P. Eartly,V.D. Elvira, S. Esen, I. Fisk, J. Freeman, Y. Gao, E. Gottschalk, D. Green, K. Gunthoti,O. Gutsche, J. Hanlon, R.M. Harris, J. Hirschauer, B. Hooberman, H. Jensen, M. Johnson,U. Joshi, R. Khatiwada, B. Klima, K. Kousouris, S. Kunori, S. Kwan, C. Leonidopoulos,P. Limon, D. Lincoln, R. Lipton, J. Lykken, K. Maeshima, J.M. Marraffino, D. Mason, P. McBride,T. Miao, K. Mishra, S. Mrenna, Y. Musienko45, C. Newman-Holmes, V. O’Dell, R. Pordes,O. Prokofyev, N. Saoulidou, E. Sexton-Kennedy, S. Sharma, W.J. Spalding, L. Spiegel, P. Tan,L. Taylor, S. Tkaczyk, L. Uplegger, E.W. Vaandering, R. Vidal, J. Whitmore, W. Wu, F. Yang,F. Yumiceva, J.C. Yun

University of Florida, Gainesville, USAD. Acosta, P. Avery, D. Bourilkov, M. Chen, M. De Gruttola, G.P. Di Giovanni, D. Dobur,A. Drozdetskiy, R.D. Field, M. Fisher, Y. Fu, I.K. Furic, J. Gartner, B. Kim, J. Konigsberg,A. Korytov, A. Kropivnitskaya, T. Kypreos, K. Matchev, G. Mitselmakher, L. Muniz, C. Prescott,R. Remington, M. Schmitt, B. Scurlock, P. Sellers, N. Skhirtladze, M. Snowball, D. Wang,J. Yelton, M. Zakaria

Florida International University, Miami, USAC. Ceron, V. Gaultney, L. Kramer, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez, D. Mesa,J.L. Rodriguez

Florida State University, Tallahassee, USAT. Adams, A. Askew, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyzer, J. Haas,S. Hagopian, V. Hagopian, M. Jenkins, K.F. Johnson, H. Prosper, L. Quertenmont, S. Sekmen,V. Veeraraghavan

Florida Institute of Technology, Melbourne, USAM.M. Baarmand, B. Dorney, S. Guragain, M. Hohlmann, H. Kalakhety, R. Ralich,I. Vodopiyanov

University of Illinois at Chicago (UIC), Chicago, USAM.R. Adams, I.M. Anghel, L. Apanasevich, Y. Bai, V.E. Bazterra, R.R. Betts, J. Callner,R. Cavanaugh, C. Dragoiu, L. Gauthier, C.E. Gerber, S. Hamdan, D.J. Hofman, S. Khalatyan,G.J. Kunde46, F. Lacroix, M. Malek, C. O’Brien, C. Silvestre, A. Smoron, D. Strom, N. Varelas

The University of Iowa, Iowa City, USAU. Akgun, E.A. Albayrak, B. Bilki, W. Clarida, F. Duru, C.K. Lae, E. McCliment, J.-P. Merlo,H. Mermerkaya47, A. Mestvirishvili, A. Moeller, J. Nachtman, C.R. Newsom, E. Norbeck,J. Olson, Y. Onel, F. Ozok, S. Sen, J. Wetzel, T. Yetkin, K. Yi

Johns Hopkins University, Baltimore, USAB.A. Barnett, B. Blumenfeld, A. Bonato, C. Eskew, D. Fehling, G. Giurgiu, A.V. Gritsan, Z.J. Guo,G. Hu, P. Maksimovic, S. Rappoccio, M. Swartz, N.V. Tran, A. Whitbeck

The University of Kansas, Lawrence, USAP. Baringer, A. Bean, G. Benelli, O. Grachov, R.P. Kenny Iii, M. Murray, D. Noonan, S. Sanders,J.S. Wood, V. Zhukova

Kansas State University, Manhattan, USAA.f. Barfuss, T. Bolton, I. Chakaberia, A. Ivanov, S. Khalil, M. Makouski, Y. Maravin, S. Shrestha,I. Svintradze, Z. Wan

Lawrence Livermore National Laboratory, Livermore, USAJ. Gronberg, D. Lange, D. Wright

26 A The CMS Collaboration

University of Maryland, College Park, USAA. Baden, M. Boutemeur, S.C. Eno, D. Ferencek, J.A. Gomez, N.J. Hadley, R.G. Kellogg, M. Kirn,Y. Lu, A.C. Mignerey, K. Rossato, P. Rumerio, F. Santanastasio, A. Skuja, J. Temple, M.B. Tonjes,S.C. Tonwar, E. Twedt

Massachusetts Institute of Technology, Cambridge, USAB. Alver, G. Bauer, J. Bendavid, W. Busza, E. Butz, I.A. Cali, M. Chan, V. Dutta, P. Everaerts,G. Gomez Ceballos, M. Goncharov, K.A. Hahn, P. Harris, Y. Kim, M. Klute, Y.-J. Lee, W. Li,C. Loizides, P.D. Luckey, T. Ma, S. Nahn, C. Paus, D. Ralph, C. Roland, G. Roland, M. Rudolph,G.S.F. Stephans, F. Stockli, K. Sumorok, K. Sung, E.A. Wenger, S. Xie, M. Yang, Y. Yilmaz,A.S. Yoon, M. Zanetti

University of Minnesota, Minneapolis, USAS.I. Cooper, P. Cushman, B. Dahmes, A. De Benedetti, P.R. Dudero, G. Franzoni, J. Haupt,K. Klapoetke, Y. Kubota, J. Mans, V. Rekovic, R. Rusack, M. Sasseville, A. Singovsky

University of Mississippi, University, USAL.M. Cremaldi, R. Godang, R. Kroeger, L. Perera, R. Rahmat, D.A. Sanders, D. Summers

University of Nebraska-Lincoln, Lincoln, USAK. Bloom, S. Bose, J. Butt, D.R. Claes, A. Dominguez, M. Eads, J. Keller, T. Kelly, I. Kravchenko,J. Lazo-Flores, H. Malbouisson, S. Malik, G.R. Snow

State University of New York at Buffalo, Buffalo, USAU. Baur, A. Godshalk, I. Iashvili, S. Jain, A. Kharchilava, A. Kumar, S.P. Shipkowski, K. Smith

Northeastern University, Boston, USAG. Alverson, E. Barberis, D. Baumgartel, O. Boeriu, M. Chasco, S. Reucroft, J. Swain, D. Trocino,D. Wood, J. Zhang

Northwestern University, Evanston, USAA. Anastassov, A. Kubik, N. Odell, R.A. Ofierzynski, B. Pollack, A. Pozdnyakov, M. Schmitt,S. Stoynev, M. Velasco, S. Won

University of Notre Dame, Notre Dame, USAL. Antonelli, D. Berry, M. Hildreth, C. Jessop, D.J. Karmgard, J. Kolb, T. Kolberg, K. Lannon,W. Luo, S. Lynch, N. Marinelli, D.M. Morse, T. Pearson, R. Ruchti, J. Slaunwhite, N. Valls,M. Wayne, J. Ziegler

The Ohio State University, Columbus, USAB. Bylsma, L.S. Durkin, J. Gu, C. Hill, P. Killewald, K. Kotov, T.Y. Ling, M. Rodenburg,G. Williams

Princeton University, Princeton, USAN. Adam, E. Berry, P. Elmer, D. Gerbaudo, V. Halyo, P. Hebda, A. Hunt, J. Jones, E. Laird,D. Lopes Pegna, D. Marlow, T. Medvedeva, M. Mooney, J. Olsen, P. Piroue, X. Quan, H. Saka,D. Stickland, C. Tully, J.S. Werner, A. Zuranski

University of Puerto Rico, Mayaguez, USAJ.G. Acosta, X.T. Huang, A. Lopez, H. Mendez, S. Oliveros, J.E. Ramirez Vargas,A. Zatserklyaniy

Purdue University, West Lafayette, USAE. Alagoz, V.E. Barnes, G. Bolla, L. Borrello, D. Bortoletto, A. Everett, A.F. Garfinkel, L. Gutay,Z. Hu, M. Jones, O. Koybasi, M. Kress, A.T. Laasanen, N. Leonardo, C. Liu, V. Maroussov,

27

P. Merkel, D.H. Miller, N. Neumeister, I. Shipsey, D. Silvers, A. Svyatkovskiy, H.D. Yoo,J. Zablocki, Y. Zheng

Purdue University Calumet, Hammond, USAP. Jindal, N. Parashar

Rice University, Houston, USAC. Boulahouache, V. Cuplov, K.M. Ecklund, F.J.M. Geurts, B.P. Padley, R. Redjimi, J. Roberts,J. Zabel

University of Rochester, Rochester, USAB. Betchart, A. Bodek, Y.S. Chung, R. Covarelli, P. de Barbaro, R. Demina, Y. Eshaq, H. Flacher,A. Garcia-Bellido, P. Goldenzweig, Y. Gotra, J. Han, A. Harel, D.C. Miner, D. Orbaker,G. Petrillo, D. Vishnevskiy, M. Zielinski

The Rockefeller University, New York, USAA. Bhatti, R. Ciesielski, L. Demortier, K. Goulianos, G. Lungu, S. Malik, C. Mesropian, M. Yan

Rutgers, the State University of New Jersey, Piscataway, USAO. Atramentov, A. Barker, D. Duggan, Y. Gershtein, R. Gray, E. Halkiadakis, D. Hidas, D. Hits,A. Lath, S. Panwalkar, R. Patel, A. Richards, K. Rose, S. Schnetzer, S. Somalwar, R. Stone,S. Thomas

University of Tennessee, Knoxville, USAG. Cerizza, M. Hollingsworth, S. Spanier, Z.C. Yang, A. York

Texas A&M University, College Station, USAR. Eusebi, J. Gilmore, A. Gurrola, T. Kamon, V. Khotilovich, R. Montalvo, I. Osipenkov,Y. Pakhotin, J. Pivarski, A. Safonov, S. Sengupta, A. Tatarinov, D. Toback, M. Weinberger

Texas Tech University, Lubbock, USAN. Akchurin, C. Bardak, J. Damgov, C. Jeong, K. Kovitanggoon, S.W. Lee, P. Mane, Y. Roh,A. Sill, I. Volobouev, R. Wigmans, E. Yazgan

Vanderbilt University, Nashville, USAE. Appelt, E. Brownson, D. Engh, C. Florez, W. Gabella, M. Issah, W. Johns, P. Kurt, C. Maguire,A. Melo, P. Sheldon, B. Snook, S. Tuo, J. Velkovska

University of Virginia, Charlottesville, USAM.W. Arenton, M. Balazs, S. Boutle, B. Cox, B. Francis, R. Hirosky, A. Ledovskoy, C. Lin, C. Neu,R. Yohay

Wayne State University, Detroit, USAS. Gollapinni, R. Harr, P.E. Karchin, P. Lamichhane, M. Mattson, C. Milstene, A. Sakharov

University of Wisconsin, Madison, USAM. Anderson, M. Bachtis, J.N. Bellinger, D. Carlsmith, S. Dasu, J. Efron, K. Flood, L. Gray,K.S. Grogg, M. Grothe, R. Hall-Wilton, M. Herndon, A. Herve, P. Klabbers, J. Klukas, A. Lanaro,C. Lazaridis, J. Leonard, R. Loveless, A. Mohapatra, F. Palmonari, D. Reeder, I. Ross, A. Savin,W.H. Smith, J. Swanson, M. Weinberg

†: Deceased1: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland2: Also at Universidade Federal do ABC, Santo Andre, Brazil3: Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France4: Also at Suez Canal University, Suez, Egypt

28 A The CMS Collaboration

5: Also at British University, Cairo, Egypt6: Also at Fayoum University, El-Fayoum, Egypt7: Also at Soltan Institute for Nuclear Studies, Warsaw, Poland8: Also at Massachusetts Institute of Technology, Cambridge, USA9: Also at Universite de Haute-Alsace, Mulhouse, France10: Also at Brandenburg University of Technology, Cottbus, Germany11: Also at Moscow State University, Moscow, Russia12: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary13: Also at Eotvos Lorand University, Budapest, Hungary14: Also at Tata Institute of Fundamental Research - HECR, Mumbai, India15: Also at University of Visva-Bharati, Santiniketan, India16: Also at Sharif University of Technology, Tehran, Iran17: Also at Shiraz University, Shiraz, Iran18: Also at Isfahan University of Technology, Isfahan, Iran19: Also at Facolta Ingegneria Universita di Roma ”La Sapienza”, Roma, Italy20: Also at Universita della Basilicata, Potenza, Italy21: Also at Laboratori Nazionali di Legnaro dell’ INFN, Legnaro, Italy22: Also at Universita degli studi di Siena, Siena, Italy23: Also at Faculty of Physics of University of Belgrade, Belgrade, Serbia24: Also at University of California, Los Angeles, Los Angeles, USA25: Also at University of Florida, Gainesville, USA26: Also at Universite de Geneve, Geneva, Switzerland27: Also at Scuola Normale e Sezione dell’ INFN, Pisa, Italy28: Also at University of Athens, Athens, Greece29: Also at California Institute of Technology, Pasadena, USA30: Also at The University of Kansas, Lawrence, USA31: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia32: Also at Paul Scherrer Institut, Villigen, Switzerland33: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences,Belgrade, Serbia34: Also at Gaziosmanpasa University, Tokat, Turkey35: Also at Adiyaman University, Adiyaman, Turkey36: Also at Mersin University, Mersin, Turkey37: Also at Izmir Institute of Technology, Izmir, Turkey38: Also at Kafkas University, Kars, Turkey39: Also at Suleyman Demirel University, Isparta, Turkey40: Also at Ege University, Izmir, Turkey41: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom42: Also at School of Physics and Astronomy, University of Southampton, Southampton,United Kingdom43: Also at INFN Sezione di Perugia; Universita di Perugia, Perugia, Italy44: Also at Utah Valley University, Orem, USA45: Also at Institute for Nuclear Research, Moscow, Russia46: Also at Los Alamos National Laboratory, Los Alamos, USA47: Also at Erzincan University, Erzincan, Turkey