Post on 04-May-2023
→ → Introduction Introduction → → Precision frontierPrecision frontier→ → Rare decaysRare decays→ → The FutureThe Future→ → Conclusions & OutlookConclusions & Outlook
Top quark propertiesTop quark propertiesand rare decaysand rare decays
Andreas Jung (Purdue University)Andreas Jung (Purdue University)
4747thth SLAC Summer Institute SLAC Summer InstituteAugust 16August 16thth, 2019, 2019
Disclaimer: Impossible tocover wealth of top physics,nor the prospects for future,including new colliders!
Fundamental building blocks:Matter (quarks, leptons)Forces (gauge bosons)
Development “guided” by the idea of
unifying forces, ultimately one force
2Top quark properties and rare decaysA. Jung
The Standard ModelThe Standard Model
Top quark discovery in 1995at Fermilab (CDF & D0)
Higgs discovery in 2012 (ATLAS & CMS)
Unification of weak and electromagnetic forces
Beautiful – but symmetry is broken: photons massless, W/Z massive
→ solution is the Higgs field which breaks EWK symmetry and manifests itself with a new particle: the Higgs boson
3Top quark properties and rare decaysA. Jung
Success of the SMSuccess of the SM
LHC
4Top quark properties and rare decaysA. Jung
The Large Hadron ColliderThe Large Hadron Collider
p p
√s=7/8/13 TeV
Peak luminosities: 8 x 1033 cm-2s-1
~5 / 20 / 160 fb-1 per experiment LHC shutdown is next
27 km circumference
Detectors – comparisonDetectors – comparison
NIM A 634:8-46 (2011)
Huge difference in all aspects of the silicon detector, e.g. No channels and area Consequences for object IDs using silicon
detector, e.g. b-tagging
CMS silicon tracker:
D0 silicon tracker:
7Top quark properties and rare decaysA. Jung
8Top quark properties and rare decaysA. Jung
Proton-proton collision @13 TeVProton-proton collision @13 TeV
9Top quark properties and rare decaysA. Jung
● Top quark physics requires precise b- and c-physics (oh, well: uds-physics)
Particle flow Combines detector
information to ID particles
Jets and missing ET
Gamma & Z-jet balance Pile-up subtraction
Isolated Leptons Dilepton resonances (Z,
upsilon, J/psi)
“b-tagging” of jets Several techniques,
dominated by silicontracker information
Relative b-jet correction:0.998 ± 0.005
CMS-JME-13001
Object ID: CMS as exampleObject ID: CMS as example
10Top quark properties and rare decaysA. Jung
How to extract signalevents ?
Pioneered atTevatron Allowed single top
observation “Wide-spread” use in all
experiments... Overtraining, bias, etc. Not your old-school
event counting technique
Cross sections & “purity”Cross sections & “purity”
11Top quark properties and rare decaysA. Jung
● Kinematic plane, Q vs. x, for production of top quarks and W, Z bosons● Horizontal lines indicate production thresholds
● Measurements of t, W, Z constrain αS and proton structure (PDFs)
● Differential top quark cross sections
Tev
atr
on
@1.
96 T
eV
Heavy Particle ProductionHeavy Particle Production
Top is the heaviest fundamental particlediscovered so far→ mt = 173.34 ± 0.76 GeV
Unique quark:
→ Observe bare quark properties
Large Yukawa coupling to Higgs boson → λt ~ 1 only mt is natural mass
Special role in EW symmetry breaking ?
No fine-tuning if top quark partner exists
[arxiv:1403.4427]
Elementary mass particle spectra:The top quarkThe top quark
12Top quark properties and rare decaysA. Jung
13Top quark properties and rare decaysA. Jung
If we could calculate the Higgs mass: → Large corrections to the Higgs mass from top quark “loops”
(Hierarchy problem)
Higgs mass at ~ 125 GeV!→ New physics can appear in
these loops
The top – Higgs connectionThe top – Higgs connection
The Big Bang Theory
dilepton
lepton+jets
All hadronicBR, bgincrease
Strong interaction: Top pairs
gg fusion
qq: ~15/13%gg: ~85/87%
(~10%, 13 TeV)
(~90%, 13 TeV)
LHC (7/8/13 TeV):
14Top quark properties and rare decaysA. Jung
Top quark introductionTop quark introduction
Top quark decay: t → Wb in ~ 100% of the cases
...to be exact: 99.82%
15Top quark properties and rare decaysA. Jung
The past...The past...Discovery atTevatron: 1995 1000's events
(Tevatron Run II)100,000's events(LHC Run I)
Establish top quark SM First differential
measurements Searches...
SM top quark ? Multi-differential Precision measurements
16Top quark properties and rare decaysA. Jung
The present...LHC Run IIThe present...LHC Run II
Outline of the talk: (Ultimate) precision frontier
Cross sections, angular correlations, massImplications, any evidence for non-SM contribution
New frontiers: tt+W, tt+Z, tt+H, tt+n-jets
Full Run II provides about~ 120 million tt pairs~ 30 million single top~ 120k ttZ, tZ
New measurements at 2, 5, 8 and 13 TeV – agreement with the SM
Profile log-LH fit by D0:Reduced uncertainties
18Top quark properties and rare decaysA. Jung
σ = 7.26 ± 0.13 (stat.) ± 0.57/0.50 (syst.) pbδσ/σ = 7.6%
The precision frontier: topThe precision frontier: top
Phys. Rev. D 94 092004 (2016)
ATLAS cross section at 13 TeV in eμ channelRelative precision: δσ/σ = 2.4%
ATLAS-CONF-2019-041
σ = 826.4± 3.6 (stat) ± 11.5 (syst) ± 15.7 (lumi) ± 1.9 (beam) pb
CMS 2nd cross section Relative precision: δσ/σ = 13%
σ = 68.9 ± 6.5 (stat.) ± 6.1 (syst.) ± 1.6 (lumi.) pb
PRL 119 (2017) 242001
NEW
First 2D cross section measurement of this type at the LHC Dilepton eμ channel – very good S/B Provide single & double differential cross sections
2D cross sections more sensitive to large x PDFsConstrain PDFs at large x
19Top quark properties and rare decaysA. Jung
CMS-TOP-14-013
Add 2D top quarkcross sections
Differential cross sectionsDifferential cross sections
→ BSM physics at high scales requires initial parton x at > 0.1
Typical theoretical uncertainties are about 2-3% (scale + PDF)
Typical experimental: ~3.7%
20Top quark properties and rare decaysA. Jung
Czakon et al. [arXiv:1705.04105]
Challenges: UncertaintiesChallenges: Uncertainties
21Top quark properties and rare decaysA. Jung
Extract yt by using l+jets differential cross
sections in 3, 4, and 5 jet bins
Relies on Hathor to extract scale factors for Powheg, templates in y
t
Likelihood fit in 55 bins to extract yt:
Extraction of YukawaExtraction of YukawaCMS-PAS-TOP-17-004
Templates of yt:
Extract top quark Yukawa coupling:
Sensitive to yt
p p
t
t
W–
b
W+
bl
nl
q
q'
Top mass (difference)Top width, LifetimeTop Charge
Branching Ratios |Vtb|
Anomalous couplingsRare decays
Spin CorrelationProduction Asymmetries
Spin CorrelationsProduction AsymmetriesPolarization
Production cross sectionsTop kinematicsProduction via resonanceNew particles
W helicity
→ Selection of results, focus on most recent and/or precise results
tt + W, Z, γ
22Top quark properties and rare decaysA. Jung
Top quark physicsTop quark physics
Interference appears at NLO QCD:
→ Only occurs in qq initial state; gg is fwd-bwd symmetric
This is a forward-backward asymmetry at Tevatron No valence anti-quarks at LHC → t more central
SM predictions at NLO (QCD+EWK) → Tevatron: AFB ~ 10 % vs. LHC: AC ~ 1 %
(These are NNLO pQCD predictions, there is also the PMC approach)
Experimentally: Asymmetries based on decay leptons or fully reconstructed top quarks
Positive asymmetry Negative asymmetry
“easier”
“harder”
23Top quark properties and rare decaysA. Jung
Top Quark AsymmetriesTop Quark Asymmetries
Production asymmetry due to NLO interferences
→ Final Tevatron combination agrees with SM (at 1.5 SD)
24Top quark properties and rare decaysA. Jung
Tevatron (2018)
Tevatron Preliminary (2017)
● Inclusive combinations via BLUE● Differential combinations employing
full covariance matrices
Top Quark AsymmetriesTop Quark Asymmetries
CautionTevatron
Phys. Rev. Lett. 120, 042001 (2018)
25Top quark properties and rare decaysA. Jung
CDF observed a 3 SD tension between data and SM theory > 450 GeV D0 observed agreement to SM theory, but also agrees with CDF
Tevatron Preliminary (2017)
Top Quark AsymmetriesTop Quark Asymmetries
Production asymmetry due to NLO interferences
26Top quark properties and rare decaysA. Jung
Measurements at the LHC much harder:
→ LHC results agree with SM (but not yet significant)→ Associated production (ttbar + photon, ttbar + W)
Czakon et al.[arXiv:1711.03945]
Top Quark AsymmetriesTop Quark Asymmetries
Production asymmetry due to NLO interferences
27Top quark properties and rare decaysA. Jung
Measurements at the LHC much harder:
→ LHC results agree with SM (but not yet significant)→ Associated production (ttbar + photon, ttbar + W)
Czakon et al.[arXiv:1711.03945]
Top Quark AsymmetriesTop Quark Asymmetries
ATLAS-CONF-2019-026
Update by ATLAS Used 139\fb of data l+jets decay channel Inclusive and
differential in m(tt)
Different from 0 with > 4 SD, but
No real test of SM
NEW
Ac = 0.006 ± 0.0015 (stat+syst)
Evidence for Ac being non-zero
28Top quark properties and rare decaysA. Jung
Spin correlationsSpin correlations Double-differential cross section allows to access spin correlation and
polarization information in top quark events
Charged lepton is perfect spin analyzer, well reconstructed as well Can probe top quark spin in 3 dimensions Sensitive to BSM physics (more spin corr's =
s-channel dark matter; less spin corr's = new scalars)
Schulze et al.
29Top quark properties and rare decaysA. Jung
Spin correlationsSpin correlations● ATLAS measures dPhi in 1D and as a function of mttbar, B and C as well
as cross correlations● Discrepancy between NLO simulations and data at the 3s level in dPhi at
particle and parton level, also seen in differential in mttbar bins:● f
SM of 1 agrees with NLO SM, observe
Extrapolate from particle to full phase space
ATL-PHYS-PUB-2018-034/
30Top quark properties and rare decaysA. Jung
Spin correlationsSpin correlations Further insights to spin correlations:
NLO effects in decay (modeled by MCFM) similar to Powheg+Pythia8 (noNLO effects in decay)
Discrepancy likely explained by missing higher order correction to top quark kinematics relevant to fiducial phase space
31Top quark properties and rare decaysA. Jung
Spin correlationsSpin correlations CMS employs 13 TeV dilepton data Opening angle maximally sensitive to alignment of top
quark spins Most precise direct measurement via cosj
Systematic: pT and BG modeling
Indirect measurement via dPhi shows about 1s discrepancy to NLO simulations
fSM
= 0.97±0.05
fSM
= 1.10±0.16
NEW
32Top quark properties and rare decaysA. Jung
EFT and SUSY constraintsEFT and SUSY constraints ATLAS employs spin correlation to constrain
SUSY top quark partner, low mass preferred bynaturalness arguments
Signature: Top quark spins more uncorrelatedsince stop is scalar
CMS uses EFT approach for interpretation ofspin density matrix measurement
Stringent constrain on chromomagnetic dipolemoment: -0.07 < CtG/L2 < 0.16 TeV-2
p p
t
t
W–
b
W+
bl
nl
q
q'
Top mass (difference)Top width, LifetimeTop Charge
Branching Ratios |Vtb|
Anomalous couplingsRare decays
Spin CorrelationProduction AsymmetriesSpin CorrelationsProduction AsymmetriesPolarization
Production cross sectionsTop kinematicsProduction via resonanceNew particles
W helicity
→ Selection of results, focus on most recent and/or precise results
tt + W, Z, γ
33Top quark properties and rare decaysA. Jung
Top quark physicsTop quark physics
The low Cross Section FrontierThe low Cross Section Frontier
34Top quark properties and rare decaysA. Jung
Single top cross section as high as tt at 8 TeV – large samples Single top production: Test of EW interactions
35Top quark properties and rare decaysA. Jung
Single Top Quark ProductionSingle Top Quark Production
Nov 2018
t-channel tW-channels-channel
tZ/γq-channel(rare process)
Heavy use of BDT to enhance sensitivity – multiple signal regions CMS measurement of tZq single top production @13 TeV
Observation of tZq36Top quark properties and rare decaysA. Jung
Single top quark productionSingle top quark production
tZ/γq-channel(rare process)
SM NLO prediction: σ = 94.2 ± 3.1 fb
Phys. Lett. B 779 (2018)358
Phys. Lett. B 779 (2018)358
σ = 111 ± 13 (stat) ± 10 (syst) pbobs. (exp.) significance: 8.2 (7.7) SD
PRL122(2019)132003
NEW
37Top quark properties and rare decaysA. Jung
FCNC's in top quark sectorFCNC's in top quark sector
[arxiv:1707.01404]
→ Vtb enters in production and decay: σ ~ |Vtb|2, FCNCs highly suppressed but limits start to reach relevant BSM BRsno BSM signal yet NEW
ttH
38Top quark properties and rare decaysA. Jung
ttbar+X: Highlightsttbar+X: Highlightstt+tt
ttZ
CMS-PAS-TOP-18-003
arXiv:1907.11270
ttZ: Most precise measurement, allowed for 1st differential cross sections
ttγ: Not shown, first evidence for ttγby ATLAS
tZq: Discussed before, evidence by ATLASand Observation by CMS
ttH: Observation at CMS and ATLAS tt+tt: Full Run 2 close to evidence at CMS
CMS, PRL 122 (2019) 132003ATLAS, PLB 780 (2018) 557
EPJC 79 (2019) 382
p p
t
t
W–
b
W+
bl
nl
q
q'
Top mass (difference)Top width, LifetimeTop Charge
Branching Ratios |Vtb|
Anomalous couplingsRare decays
Spin CorrelationProduction AsymmetriesSpin CorrelationsProduction AsymmetriesPolarization
Production cross sectionsTop kinematicsProduction via resonanceNew particles
W helicity
→ Selection of results, focus on most recent and/or precise results
tt + W, Z, γ
39Top quark properties and rare decaysA. Jung
Top quark physicsTop quark physics
Self-consistency of SM & stability of the EW vacuum rely on the pole mass Indirect extraction from e.g. cross section, end point, J/psi method
→ top quark pole mass Direct methods e.g. template, matrix element, likelihood, ideogram
→ “MC” mass, close to pole mass Efforts to “calibrate” the “MC” mass to pole mass
→ Estimates: GeV difference to pole mass
The top quark massThe top quark mass
PRL 117, 232001 (2016)
[arXiv:1803.01853]
40Top quark properties and rare decaysA. Jung
[arXiv:1707.08124]
Tools, Complications, ...Tools, Complications, ...
41Top quark properties and rare decaysA. Jung
jet
jet
W boson fully reconstructed:→ In-situ calibration, Constrain
reconstructed mW to m
W
mW
→ Make use of all-hadronic decays of W bosons, serves as in-situ calibration
→ Pile-up complicates reconstruction of objects, needs “compensation”, all do-able but adds to systematic uncertainties
Eur. Phys. J. C (2016) 76:581
Eur. Phys. J. C(2016) 76:581
42Top quark properties and rare decaysA. Jung
Direct measurements combined using BLUE Latest CMS combination, δm
t/m
t = 0.28%
World combination, δmt/m
t = 0.44%
Final D0 combination, δmt/m
t = 0.43%
mtop
= 174.95 ± 0.75 GeV
– consistent among methods/channels
[arXiv:1703.06994]
CMS-PAS-TOP-15-012Top Quark MassTop Quark Mass
NEW
43Top quark properties and rare decaysA. Jung
CMS measurement at 13 TeV, dilepton Use y(tt), M(tt), N(add. jet) Unfolded to parton level & NLO fixed order, 7
PDF sets in simultaneous fit PDF, aS, m
t
Weak correlation of 0.3 aS and m
tpole
mtop
= 170.5 ± 0.7 (fit) ± 0.1 (mod) ± 0.1 (scale) GeVpole
Indirect methods: diff. Indirect methods: diff. ss
δmt/m
t = 0.47% CMS-TOP-18-004
Sensitive to gluonstructure of theproton, xg(x)
Consistent picture in boosted and resolved phase space Parton/Particle level results receive larger/reduced systematic uncertainties CMS 13 TeV all-hadronic combined resolved and boosted analysis
44Top quark properties and rare decaysA. Jung
Boosted RegimeBoosted Regime
CMS-PAG-TOP-16-013
CMS-PAS-TOP-19-005
45Top quark properties and rare decaysA. Jung
Mtop
= 172.6 ± 2.5 (tot) GeV
Boosted RegimeBoosted Regime CMS-PAS-TOP-19-005
Hadronic decay products reconstructed with single jet R = 1.2
Peak position of mjet
sensitive to mt
Detailed understanding of jet substructure observable crucial for boosted topologiesδm
t/m
t = 1.4%
NEW
Relative b-jet correction:0.998 ± 0.005
46Top quark properties and rare decaysA. Jung
Direct methods: Most precise results, δm
t/m
t = 0.28% (!)
Does not include theoretical “scheme” uncertainty No single large uncertainty left:
Color reconnection: “off vs. on” yields smalleruncertainty than detailed study
Alternative methods: larger uncertainties but perpendicular
Indirect methods: Relies on theoretical predictions (various choices) Fully corrected data, more complex Larger uncertainties
5% theory, 2% experiment → 0.5% pole mass
Challenges/PerspectivesChallenges/Perspectives
● Employ different decay channels (different systematics, in-situ jet energy scale)● Use direct (classical), direct (alternative), and indirect (based on σ, dX/dσ)
[arXiv:1707.08124]
A very fundamental question: What happens with the SM theory at highest physically allowed scales ? → extrapolate to 1018 GeV
Vacuum meta-stable if Unstable once:
(corresponds to mt ~ 178 GeV)
In classical physics “stable” means minimum of potential energy:
SM vacuum stabilitySM vacuum stability
47Top quark properties and rare decaysA. Jung
Tevatron
CMSATLAS
48Top quark properties and rare decaysA. Jung
Very subjective but illustrative, latest results from LHC & Tevatron – SM true
ttH observation by CMS:
Modified from originalby Degrassi et al.
Caveat: New physics changes the vacuum stability, even if at Planck scale Theoretical uncertainties apply! PRL 117, 232001 (2016)
Most recent combinatons
yt ~ 0.96
point shifted
SM vacuum stabilitySM vacuum stability
[arXiv:1804.03682]
→ SM EW fit closer to the unstable boundary ? Beware of uncertainties...butcould indicate SM is not enough to describe nature
→ Need more data!
SM vacuum stability & EW fitSM vacuum stability & EW fit Latest EW-fit by GFitter
[arXiv:1803.01853]
“Don't panic!” (D. Adams) Lifetime is much much larger than current age of the universe: 1080 – 10320 tUniverse
49Top quark properties and rare decaysA. Jung
x
[arXiv:1707.08124]
EW-ft by GFiter
Worldaverage
E. Branchina et al.
SM Higgspotential
dim 6 & 8 BSMmodifications
With the Higgs discovery the SM can be extrapolated to Planck scale energies “Test” the stability of the electroweak
vacuum, under assumption of no new physics: → meta-stable, life time > O(1080) t
universe
→ but new physics can change that dramatically
SM vacuum stabilitySM vacuum stability
50Top quark properties and rare decaysA. Jung
[arXiv:1707.08124]
Worldaverage
Difficult to project, depends on physics outcome of Run IISM precision tests & BSM scenarios
“Keep running” does not work → Need improved detectors
Future upgrade plansFuture upgrade plans
52Top quark properties and rare decaysA. Jung
p p √s=13 TeV
Unprecedented luminosities at ahadron collider: 5.0 x 1034 cm-2s-1
Expect ~ 3000 fb-1 per experiment Major upgrades of LHC and detectors needed
2035
Pha
se II
upg
rade
s
Future upgrade plansFuture upgrade plans
LHC
Billions of top quarks !
53Top quark properties and rare decaysA. Jung
High-luminosity phase of the LHC Instantaneous luminosities up by factor 5 Collected data up by factor 10
→ Rates of lepton-based trigger are too high
ATLAS+CMS exposed to significantly higher rates, radiation damage, pile-up Tracking information for the trigger system Higher granularity of tracking devices (→ more channels) Radiation-hard devices Reduce amount of “dead” material
78 reconstructed vertices
Future upgrade plansFuture upgrade plans
54Top quark properties and rare decaysA. Jung
Barrel & Forward Pixel Detector: 3D silicon sensor R&D
CMSbeam-pipe
Support structures:Carbon fiber & foam based,Tight tolerances of 100's microns160 kg's of detector
Beam interactionpoint
CMS inner tracker region (half of it)CMS inner tracker region (half of it)● CMS Instrumentation R&D
Current challenge: Remove 35 kW of heat
55Top quark properties and rare decaysA. Jung
Need all avenues to pin down BSM:→ Precision/Energy frontier (e.g. Yukawa)→ Extend reach for searches→ Intensity Frontier
The future...The future...
56Top quark properties and rare decaysA. Jung
HERA shutdown, Tevatron shutdown, but LHC continues!→ We will get about 3 billion tt events→ Allows for multi-dimensional measurements of σ, αS, PDFs
and any properties, associated production as well→ FCNCs and other statistically limited processes improve
160/fb in the can!150 million tt events
Extrapolations to HL-LHC:→ watch out for the bar:
Caveats: Some are“inclusive”...and also, we tendto do (much) better thanprojections, so we can hope toexclude more phase space
The future...FCNC prospectsThe future...FCNC prospects
57Top quark properties and rare decaysA. Jung
private
CERN-LPCC-2018-03
Next 2 years will show what 150 million ttbar events teach us Precision frontier of top quark physics
“Deviations” in the top quark sector, not yet conclusive enough:
→ Spin correlations: 3 – 1 SD→ Forward-backward asymmetry at Tevatron: 1.5 SD→ tt+H observation indicates μ~ 1.2-1.3 SM
Exciting times for top quark physics...stay tuned!
Instrumentation R&D is an absolutely essential ingredient tomake progress in elementary particle physics!
Thank you!
ConclusionsConclusions
58Top quark properties and rare decaysA. Jung
Use differential distributions to extract the well defined top quark pole mass Fixed αS and PDF set, translated into uncertainties
ATLAS: 0.9%; CMS precision at <1%D0 precision (best at Tevatron): ~ 1.5%
With ~5% theory uncertainty and ~2%exp → can reach 0.5% on pole mass
Indirect methodsIndirect methods
ATLAS-CONF-2017-044
D0 conference note 6473
60Top quark physics at the precision frontierA. Jung
61Top quark properties and electroweak measurementsA. Jung
BSM physics in top sector ?BSM physics in top sector ?→ Detailed study of the Wtb vertext to identify any BSM contributions→ Use triple-differential angular decay rates in single t-channel production
→ Data agrees with SMno BSM signal yet
[arxiv:1707.01404]JHEP 07 (2017) 003
→ FCNCs in tZ (ATLAS & CMS) and t →cH(ATLAS) – no BSM signal yet
62Latest news on top quark physicsA. Jung
Expand Lagrangian in orders of 1/L 59 (B and L-conserving) dim-6 operators
This analysis: Simultaneous fit to ttW and ttZ (for now) One operator at a time (clear limitation) Only operators with significant impact on
ttW, ttZ, ttH CL for Wilson coefficients:
SM expected very similar
Effective Field TheoryEffective Field Theory
63Top quark properties: mass, spin correlations, polarizationA. Jung
CMS measurement at 13 TeV, dilepton 12 categories based on N(b-jets), N(light jets) Employ m
lb , p
T, event yield
Simultaneous fit to measure cross sectionand top mass
888 ± 2 (stat.) ± 27 (syst.) ± 20 (theo.) pbExtract MC mass from cross section:
min
mtop
= 172.33 ± 0.14 (stat.) ± 0.66/0.72 (syst.) GeVMC
Dominant systematics: → Jet energy (0.57 GeV)→ MC statistics (0.36 GeV)→ Background (0.28 GeV)
Extract most precise MS mass:
Indirect methods: incl. Indirect methods: incl. ss
δmt/m
t = 0.42%
EPJC 79 (2019) 368
Nuisance fit to constrainsystematics on mt(MC)
64Top quark properties: mass, spin correlations, polarizationA. Jung
Use differential distributions to extract the top quark pole and MS mass ATLAS also measures ratio in ttbar+1 jet events to extract top mass
Partial cancellation of systematic uncertainties
Indirect methods: l+jetsIndirect methods: l+jets
[arXiv:1905:02302]m
top = 171.1 ± 0.4 (stat.) ± 0.9 (syst.) ± 0.5 (theo.) GeVpole
δmt/m
t = 0.65%
Measurements at Tevatron & LHC are complimentary
Variety of models with wideparameter space stillallowed→ W', G, w , j, W
Top quark asymmetriesTop quark asymmetries
65Precision top quark measurements and searches for new physicsA. Jung
CMS: 13 TeV data shows less jets than MCRegime of the parton showers (PS)Already systematically limited, betterunderstanding of signal model needed
Use 8 TeV dilepton channel results to tuneMC parameters, than check description in 8TeV l+jets and in 13 TeV for both channels
Improve high Njets phase spaceh
damp:: control ME/PS matching
αISR
: αS for initial state radiation
66Top quark physics at the precision frontierA. Jung
CMS-PAS-TOP-16-011
PS regime
CMS-PAS-TOP-16-008
Dileptonl+jets
Differential cross section asa function of event variables:
Phys. Rev. D 94 (2016) 052006CMS-PAS-TOP-16-021
Differential cross sectionsDifferential cross sections
Many Run I & Run II top pT measurements at ATLAS/CMS not described by NLO and most MCs – pQCD calculation do a better job
Data is more soft: consistently seen in all decay channels, also at 13 TeV
→ The pT spectra in 8 TeV are described by pQCD NNLO calculations, but→ First indications of a slope wrt NNLO in 13 TeV data, not yet significant
67Top quark physics at the precision frontierA. Jung
EPJC 76 (2016) 128
Differential cross sectionsDifferential cross sections
68Top quark physics at the precision frontierA. Jung
CDF observed a 3 SD tension between data and SM theory > 450 GeV D0 observed agreement to SM theory, but also agrees with CDF Both results used regularized unfolding, but different strategies which
resulted in largely different correlations between bins:
Top Quark AsymmetriesTop Quark Asymmetries
69Top quark physics at the precision frontierA. Jung
CDF observed a 3 SD tension between data and SM theory > 450 GeV D0 observed agreement to SM theory, but also agrees with CDF Final Tevatron combination agrees with SM and takes all correlations
between the experiments properly into account
Top Quark AsymmetriesTop Quark Asymmetries
“Running” of the Higgs quarticself-coupling:
Higgs closely tied to the top:→ Top mass significant impact
Need to keep “mexican-hat” shape
71Top quark physics at the precision frontierA. Jung
SM vacuum stabilitySM vacuum stability
→ Top quark as a window to new physics
SM Vacuum isonly metastable
Degrassi et al.
72Top quark physics at the precision frontierA. Jung
Extraction from production cross sectionnot (yet) competitive with directmeasurements – but getting closer CMS precision at 1%; ATLAS: 1.45%
D0 precision (best at Tevatron): ~ 1.9%
With ~5% theory uncertainty and ~2% exp→ can reach 0.5% on pole mass
CMS [arXiv:1603.02303]
Phys. Rev. D 94 092004 (2016)
Top Quark Mass: poleTop Quark Mass: pole
73Top quark physics at the precision frontierA. Jung
Extraction from production cross section not (yet) competitive with direct measurements – but getting closer
ATLAS: 0.9%; CMS precision at 1%D0 precision (best at Tevatron): ~ 1.5%
With ~5% theory uncertainty and ~2% exp→ can reach 0.5% on pole mass
CMS [arXiv:1603.02303]
Phys. Rev. D 94 092004 (2016)ATLAS-CONF-2017-044
CMS-TOP-16-006
D0 6473
Top Quark Mass: poleTop Quark Mass: pole
p p
t
t
W–
b
W+
bl
nl
q
q'
Top mass (difference)Top width, LifetimeTop Charge
Branching Ratios |Vtb|
Anomalous couplingsRare decays
Spin CorrelationProduction AsymmetriesSpin CorrelationsProduction AsymmetriesPolarization
Production cross sectionsTop kinematicsProduction via resonanceNew particles
W helicity
→ Selection of results, focus on most recent and/or precise results
tt + H, W, Z, γ
74Top quark physics at the precision frontierA. Jung
Top quark physicsTop quark physics
75Latest news on top quark physicsA. Jung
Observation of tt+H a major goal for ATLAS & CMS:→ Correct modeling of associated HF production is crucial→ Theoretical and experimental challenge
Measurements at 8 TeV (ATLAS & CMS) and 13 TeV (CMS)
CMS-TOP-16-010(Subm. to PLB)ttbar+X: heavy flavorsttbar+X: heavy flavors
76Top quark properties and electroweak measurementsA. Jung
Ttbar + X: W, ZTtbar + X: W, Z
σ(ttZ) = 1.00 ± 0.09/0.08(stat.) ± 0.12/0.10(syst.) pbExpected (observed) significance of 4.6 (9.9)
σ(ttW)= 0.80 ± 0.12/0.11(stat.) ± 0.13/0.12(syst.) pbExpected (observed) significance of 4.6 (5.5)
→ Sensitive to FCNC couplings (ttZ) and BSM (ttW and ttZ)→ Results consistent with the SM (NLO prediction)
ATLAS-CONF-2016-003
SM (NLO) σ(ttZ) = 839 ± 93 fb σ(ttW) = 601 ± 55 fb
CMS-TOP-17-005
First 2D cross section measurement of this type at the LHC Dilepton eμ channel – very good S/B Provide single & double differential cross sections
77Latest news on top quark physicsA. Jung
CMS-TOP-14-013
Differential cross sectionsDifferential cross sections
78Latest news on top quark physicsA. Jung
Expand Lagrangian in orders of 1/L 59 (B and L-conserving) dim-6 operators
This analysis: Simultaneous fit to ttW and ttZ (for now) One operator at a time (clear limitation) Only operators with significant impact on
ttW, ttZ, ttH CL for Wilson coefficients:
SM expected very similar
Effective Field TheoryEffective Field Theory
ATLAS (13 TeV) & CMS (8 TeV) measurements on tZq
Rely on NN and BDT to enrich signal Dominant SM production @leading order:
79Top quark properties and electroweak measurementsA. Jung
Single top quark productionSingle top quark productionATLAS-CONF-2017-052
JHEP 07 (2017) 003
σ = 600 ± 170 (stat.) ± 140 (syst.) fb(Expected is 5.4 SD, observed 4.2 SD) 13 TeV
σ = 10 ± 8/7 (tot.) fb(Observed 2.4 SD) 8 TeV
80Latest news on top quark physicsA. Jung
Direct measurementscombined using BLUE
● Takes correlations intoaccount
Latest ATLAS combinationPrecision of 0.4% (!)
Latest CMS combinationPrecision of 0.3% (!)
World averagePrecision of 0.4% (!)
Final D0 combination Precision of 0.4% (!)m
top = 174.95 ± 0.76 GeV D0 note 6485
PRD 93 (2016) 072004
Top Quark MassTop Quark Mass
81Top quark properties and electroweak measurementsA. Jung
Employ the 7 TeV data: low pile up environmentHuge effort to control systematic uncertaintiesHigher pile-up at 8 and 13 TeV challenging
W mass: 1W mass: 1stst LHC measurement LHC measurement
mW
= 80370 ± 7 (stat) ± 11 (exp. syst.) ± 14 (modeling syst.) MeV
δmW/m
W = 0.024%
[arXiv:1701.07240]
CMS: First differential measurement of t-channel top production @13 TeV Muon-channel only employing a BDT discriminator and maximum likelihood fit Correct detector and measure parton level cross section for pT and y
84CMS Top quark resultsA. Jung
Single top quark productionSingle top quark production
Run I & Run II top pT measurements at ATLAS/CMS not described by NLO and most MCs
Data is more soft: consistently seen in all decay channels
Spectra are described by NNLO+NNLLcalculations
85CMS Top quark resultsA. Jung
LHCTopWG
EPJC 76 (2016) 128
Differential cross sectionsDifferential cross sections
TOP-16-021
f0=0.70 f
R=0f
L=0.30 W helicity in SM:
W helicity in top pair l+jets channel CMS also measured W helicity in single top events
Similar precision but orthogonal systematic uncertainties in single top channels
Signal model & template statistics
W helicityW helicity
86CMS Top quark resultsA. Jung
F0 = 0.681 ± 0.012 (stat.) ± 0.023 (syst.)
FL = 0.323 ± 0.008 (stat.) ± 0.014 (syst.)
FR = 0.004 ± 0.005 (stat.) ± 0.014 (syst.)
Most accurate experimental determination
PLB 762 (2016) 512