氏名 Emy Mulyani 学位（専攻分野）博士（理学）学位記番号 ...

氏名 Emy Mulyani

学位（専攻分野）博士（理学）

学位記番号総研大甲第 2030 号

学位授与の日付平成 30 年９月２８日

学位授与の要件高エネルギー加速器科学研究科加速器科学専攻

学位規則第６条第１項該当

学位論文題目 Development of X-Ray Beam Size Monitor for the

SuperKEKB Rings

論文審査委員主査教授三橋利行

教授飛山真理

准教授池田仁美

准教授内藤孝

教授フラナガンジョン

Professor Gary S. Varner

High Energy Physics Group

University of Hawaii

研究員福間均

高エネルギー加速器研究機構

加速器第四研究系

1

Form 3

Summary of Doctoral Thesis Name: Emy Mulyani Title: Development of X-Ray Beam Size Monitor for the SuperKEKB Rings The SuperKEKB facility is the upgrade of KEKB to increase the luminosity 40 times, to 8 × 1035 cm-2 s -1 , with the overarching mission is to search for new physics beyond the standard model of particle physics in the B meson regime. It has two rings, the High Energy Ring (HER) and the Low Energy Ring (LER), for 7 GeV electrons and 4 GeV positrons, respectively.

Beam instrumentation in the accelerator serves as the 'eyes' of the machine operators, requiring the design, construction and operation of instruments to observe particle beams, and also research and development to find new, or improve existing, techniques to fulfill new requirements. Several beam parameters that we need to measure in the accelerator (i.e., SuperKEKB) are beam position (to know the horizontal and vertical positions of the beam throughout the accelerator chamber), beam intensity, and lifetime measurement. Other parameters are beam loss, beam profile (actual shape of the beam, in both transverse and longitudinal planes), and collision rate to measure of how well the beams overlap at the collision point.

There are two different types of synchrotron radiation (SR) monitors for beam profile diagnostics in SuperKEKB: SR interferometers (visible-light monitors, SRM) and x-ray beam size monitors (XRM). The XRM will be used primarily for vertical bunch profile measurements and secondarily for horizontal beam size measurements, and the visible light monitors will be used primarily for horizontal bunch profile measurements, with the possibility of vertical measurements at larger beam sizes for comparison with the XRM measurements.

The principal aim of the XRM is for vertical beam size measurements that eventually have the capability for high-resolution bunch-by-bunch, turn-by-turn measurements for low emittance tuning, collision tuning, and instability measurements. The motivation of the present research was the development of the XRM, consisting of designing the mask patterns, calibrating the XRMs during the commissioning of the SuperKEKB operation, and exploring the image reconstruction technique using uniformly redundant array (URA) coded apertures.

The main principle of the XRM system is to propagate X-rays from the SR source point (bending magnet) through optical elements to the observation plane (detector). They form a diffraction pattern with an array of peaks on the detector depending on the pattern of the optical elements. This pattern is a point response function (PRF),

2

i.e., the expected X-ray intensity distribution at the observation plane for a given X-ray spectrum, beamline geometry, and optical elements, for a point source at a given location in the source plane. We used a Fresnel-Kirchhoff diffraction approximation to estimate the propagation of the X-ray distribution from the SR source to the detector. Figure 1 shows the simplified schematic of the XRM.

Fig. 1: Schematic of the XRM beamline at each of the SuperKEKB rings (not to scale). It consists of a beryllium filter placed upstream of the optics to reduce the heat load and to separate x-ray beamline vacuum from the ring vacuum, three sets of optical elements (a single pinhole and two sets of coded apertures), a beryllium window, and the detector system. For Phase 1 (Phase 2) of SuperKEKB commissioning, a 141 µm-thick YAG:Ce (LuAG:Ce) scintillator with a CCD camera focused on it is used as the imaging system. In the next phase, the scintillator will be supplemented by 128 channels of silicon detector with 2-mm sensing depth and a pixel pitch of 50 μm, for a single-shot measurements.

There are two types of the optical element for the XRM in each ring, a single pinhole and coded apertures (CA). For pinhole imaging, the hole should be as small as possible (within diffraction limits) to provide resolution. However, a small hole often has an insufficient area to collect enough X-rays to produce an interpretable image. The capability of CA becomes useful to overcome the limitation of pinhole imaging and provide better resolution. Because CA offers greater open aperture and photon throughput than a single pinhole, the CA has the capability for better statistical resolution in single-shot measurements. Accordingly, three optics/masks that have been designed and installed at each ring: pinhole, 17 multi-slits, and 12-slits Uniformly Redundant Array (URA).

We simulated the propagation of the X-rays through the optical elements then calculated the statistical resolution for a single-shot measurement by calculating the difference between two images recorded by the detector for various simulated beam sizes, for a given number of photons. The 17 multi-slits was estimated to provide 2 – 3 μm resolution for 10 – 25 μm of vertical beam sizes at 1 mA bunches. For larger

3

beam sizes (> 30 μm), the 12-slits URA mask has better resolution than the 17 multi-slits.

Several calibration studies (geometrical scale factors, emittance control knob, and beam lifetime studies) were carried out during Phase 1 of SuperKEKB commissioning from February until June 2016. The ratio of the geometrical scale factors recorded by tape-measurement (physical measurement) and beam-based measurement mostly agrees within a few percents at both beamlines. The studies suggested that during the Phase 1 commissioning, the measured vertical emittances 𝜀𝜀𝑦𝑦 are ~10 pm for LER (consistent with the optical estimation) and ~ 35 pm for HER (3.5 times greater than the optic estimation). Analysis of the beam size and lifetime measurements suggests unexpectedly large smearing factors, particularly in the HER. In Phase 2 (May to Juli 2018), several new types of equipment were installed (thinner beryllium filter, new optical element, He gas filling, and new CCD camera) with the primary purpose to reduce the smearing factor in the HER beamline that we faced in Phase 1. Several calibration studies as in Phase 1 have been carried out and suggested a good improvement in the smearing size, which is about 5 times smaller than in Phase 1.

For further explorations and refinement following the present work, we will supplement the scintillator with 128 channels of silicon with 2-mm sensing depth and a pixel pitch of 50 μm. This detector system will have the capability for single-shot measurement which is useful for studying beam instabilities. In the current phase, we are using the template-fitting method that has excellent capability in the reconstruction of the image source, but in the future, for single-bunch measurements this method cannot keep up with the vast volumes of data in real-time. An investigation of fast reconstruction method based on URA coded aperture imaging for XRM is of great interest. This method is essential for measuring the beam sizes of all 2500 bunches in the SuperKEKB accelerator over thousands of turns, as needed for instability studies and luminosity tuning.

氏名 TRAN NGUYEN THUY NGAN

学位（専攻分野）博士（学術）



学位授与の要件高エネルギー加速器科学研究科加速器科学専攻


学位論文題目 Study on Properties of Plastic Scintillators for Designing a

Tissue- Equivalent LET Spectrometer

論文審査委員主査教授波戸芳仁

教授佐波俊哉

准教授齋藤究

助教岸本祐二

教授佐々木慎一

名誉教授柴村英道

埼玉県立大学

(Form 3)

Summary of Doctoral Thesis

TRAN NGUYEN THUY NGAN

Title

Study on Properties of Plastic Scintillators for Designing a Tissue -Equivalent LET

Spectrometer

In radiation dosimetry, the absorbed dose D (Gy) which is the total energy absorbed

per unit mass can quantify the effect of radiation. However, using D to evaluate the

biological damage caused by radiation is inadequate because D does not indicate the

specific radiation type. The radiation effects on the human body are normally evaluated

by using the equivalent dose H(Sv), which is defined as the product of the absorbed

dose D and the quality factor Q given as a function of the linear energy transfer (LET):

H = DQ. LET (keV/m) indicates the energy deposited per unit path length (dE/dx) of

different radiation types. The quality factor Q varies from 1 to 30 depending on species

of radiation and its energy.

Space radiation consists of galactic cosmic rays (GCR), geomagnetic trapped

particles, solar energetic particles (SEP) and their secondary particles. The amount of

the dose equivalent in space reaches to 1 mSv per day, which is comparable with that

received on the ground in one year. The main components of doses in space are primary

charged particles (protons and heavy ions) and secondary neutrons produced by the

interaction between cosmic rays and the spacecraft materials. Thus, astronauts would

face the risk of intense radiation exposure. In addition, the LET of these radiations

distributes from 0.2 to 600 keV/m.

The operation of the high energy accelerators requires the observation and

maintenance of radiation safety in the environment around accelerators. Small amounts

of radioactivity are generated in the environment of accelerator during its operation,

and a mixed radiation field consisting of gamma rays, neutrons and charged particles

with a wide range of energies is formed around accelerators. The monitoring of such

radiation and radioactivity, as well as the measurement of the radiation dose due to them,

are the important task to maintain the radiation protection in accelerator facilities.

However, it is normally difficult to measure precisely a small amount of radioactivity

produced and contaminated in accelerator environments such as air tunnel, cooling

water, and structures of accelerators, or to determine radiation dose of the mixed

radiation field. Particularly, there is a little of dosimeters which are usable for mixed

radiation as well as some complicated methods using a combination of several detector

systems are employed.

Therefore, it is necessary to directly measure the LET of radiation for evaluating H

in space and accelerator facilities.

Regarding the measurement of radiation dose in space, a Tissue Equivalent

Proportional Counter (TEPC) has been used by NASA as a s tandard space dosimeter.

TEPC is a simple gas proportional counter made of tissue equivalent plastics and filled

with tissue-equivalent gas. The LET is obtained from the TEPC by assuming that the

LET is equal to the lineal energy (the deposited energy divided by the mean chord length

of the detector) because position information cannot be given in TEPC. Then, the lineal

energy does not represent the LET precisely, and systematic errors of 51 % are the result

of this assumption.

RRMD (Real-time Radiation Monitoring Device) is an active detector telescope

which utilizes silicon semiconductor detector and others. RRMD has been used as real-

time monitoring of space radiation which can achieve the LET distribution, particle

count rates, rates of absorbed dose and dose equivalent. However, it is not tissue-

equivalent made.

Recently, PS-TEPC (Position Sensitive Tissue Equivalent Proportional Counter) has

been developed as a space dosimeter with the property of sensitivity to the position. PS-

TEPC is a dosimeter based on LET measurement, which can measure energies and tracks

of radiation simultaneously, give us the radiation dose for any kinds of radiation without

knowing their species. The detector of PS-TEPC is a time projection chamber (TPC)

made of tissue equivalent materials, where a micro pixel chamber (-PIC) is used as a

two-dimensional position sensor. By using the PS-TEPC, three-dimensional tracks of

radiation as well as its energy can be measured, and obtain LET from the measured

energy and the track length of radiation. PS-TEPC can be used for radiation dose

management onboard the ISS and future manned space missions since it can precisely

measure the doses due to various charged particles covered under a wide range of the

LET energy spectrum.

An ideal tissue-equivalent dosimeter based on LET measurement should have the

following properties: an active (real-time) detector, having sensitivity to detect many

radiation types, having the ability to detect the incident position of radiation (position

sensitivity), being formed with tissue-equivalent materials, having sensitivity for

radiations incident isotropically, being stable and long-lived operation, and having

simple structures as possible.

The aim of this study is to examine the properties of PLSs in order to develop a tissue

equivalent LET spectrometer. Then, a new dosimetric system based on the LET

measurement can be established. This LET spectrometer would give the response to

many kinds of radiation and is constructed of materials which are close to water or

human tissues. This system offers the potential for using a straightforward method to

measure dose equivalent, which differs from existing methods where doses are

evaluated only for a known species of radiation.

To obtain the LET value, the deposited energy and path length of radiation in the

spectrometer must be measured simultaneously. Thus, for any candidate materials for

constructing a LET spectrometer, the material’s properties must be examined carefully.

For deposited energy information, the response of PLSs radiation must be studied.

Besides, for the path length of radiation in the spectrometer, the incidence position,

incidence angle of the radiation, and position resolution must be determined.

PLSs are selected as the candidate for constructing a LET spectrometer because of

their beneficial properties:

- PLSs are inexpensive materials which have the flexibility in shape and size

(cylinders, rods, flat sheets, etc.)

- PLSs have a very rapid decay time constant of about 2 – 3 ns.

- PLSs have the effective atomic number and density similar to those of water and

human tissues (because PLSs are composed mainly of hydrocarbon molecules).

Thus, plastic scintillators are the potential tissue-equivalent materials for

developing a dosimeter.

- PLSs can detect a variety of radiation types (photons, charged particles , and

neutrons).

However, PLSs have disadvantages as well :

- The non-proportionality between light yield and deposited energy, especially at

low energy region.

- The light yield is affected by quenching effect when irradiated with charged

particles.

- The response of PLSs to charged particles shows the particle species dependency

at the high value of the specific energy loss dE/dx.

To obtain the LET value, the deposited energy and path length of radiation in the

spectrometer must be measured simultaneously. Thus, the response of PLSs to different

radiation types as well as the incident position and incident angle of radiation in the

spectrometer need to be studied in detail. Additionally, the method for distinguishing

output signals from different types of radiation must be established.

In this study, three PLSs EJ-200, EJ-212, EJ-252 (2 2), which are polyvinyl-

toluene base, are examined.

The absolute light yield of PLSs is evaluated as Ws which is defined as the average

energy required to produce on scintillation photon in a scintillator. The Ws is determined

as the result of deposited energy divided by the number of scintillation photon generated

in a scintillator. For incident gamma rays, the deposited energy corresponding to the

maximum Compton electron (Compton edge).

For incident gamma rays, Compton scattering which is the dominant interaction in

PLSs results in a Compton continuum in the energy distribution, hence, the deposited

energies are difficult to determine precisely. Then, the response of Compton electrons

represents the response of gamma rays. The relative light yield (relative scintillation

response) per unit energy deposited by electrons (called as “electron response”) of PLSs

are examined by using Compton Coincidence Technique.

For determining the deposited energy, an energy resolution is one of the essential

factors which must be evaluated, and the light yield is a significant feature in

consideration of the energy resolution. In this study, the energy resolution of PLSs is

evaluated from the results of the electron response and Ws measurement.

In order to compare energy resolutions, the pulse height distribution for 60-keV

gamma rays from an 241Am was measured with the EJ-200 detector. This pulse height

distribution corresponds to the photopeak as the result of the interaction between low

energy gamma rays with low atomic number materials .

Besides the energy deposition feature, the position sensitivity of PLSs is examined

by using square-aligned PLS rods, and multi-segmented photomultiplier tubes (PMTs)

are attached to both ends of the rods. By employing signals from both-end PMTs, the

possibility of using PLSs for position sensitivity would be confirmed. The

measurements using beta and alpha particles were performed, and preliminary data are

obtained. Then, a method to determine the incidence position of radiation into the

spectrometer, as well as the trajectory of this radiation, can be developed.

The plastic scintillator rod was used to study the response to ions also. The rod was

irradiated by heavy ions generated from an accelerator at HIMAC (H – 230 MeV, Si –

800 MeV/u, and C – 400 MeV/u).

Then, the energy resolution of PLSs can also be evaluated by comparing the

difference in the energy resolution due to different types of radiation.

Then, the operation principle and the design of a prototype for LET spectrometer is

considered and developed.

氏名 Widya Rika Puspita



学位授与の日付平成 30 年 9 月２8 日

学位授与の要件高エネルギー加速器科学研究科物質構造科学専攻


学位論文題目 Crystal Structures and Thermoelectric Properties of Type-I

Clathrate Ba8Al16-xGaxGe30

論文審査委員主査教授大友季哉

教授伊藤晋一

准教授池田一貴

准教授米村雅雄

教授神山崇

主席研究員竹屋浩幸

国立研究開発法人物質・材料研究機構

ナノフロンティア超伝導材料グループ

研究員石川喜久

総合科学研究機構

中性子科学センター研究開発部

(Form 3)


Widya Rika Puspita

Crystal Structures and Thermoelectric Properties of

Type-I Clathrate Ba8Al16-xGaxGe30

The demand for energy across the world is continuing to grow. This issue is driving the urgency for improving the energy efficiency. Thermoelectric materials which can directly convert waste heat into electricity have been considered as an effective solution. The performance of thermoelectric materials is characterized in the term of dimensionless figure of merit ZT, defined as 𝑍𝑍𝑍𝑍= 𝑆𝑆2𝜎𝜎/𝜅𝜅, where 𝜅𝜅, 𝜎𝜎, 𝑆𝑆, and T represent thermal conductivity, electrical conductivity, Seebeck coefficient, and temperature, respectively. Based on the definition, a good performance of thermoelectric materials can be achieved by increasing the electrical properties while the thermal properties should be suppressed.

Clathrates have gained much attention as the potential candidate for thermoelectric materials due to their unique structure and properties. Type I clathrates (space group: Pm3�n) with general formula G8AyB46-y (G = Ba, Sr, Eu; A = Al, Ga, In; B = Si, Ge, Sn) are the cage-type structure materials where the A and B play roles as host atoms forming two different types of cages, oversized tetrakaidecahedron and small dodecahedron cages, which enclosed the G guest metal atom. The Wyckoff sites for guest atoms at the oversized and smaller cages are 6d and 2a sites, respectively. For the host atoms, there are three types of sites: 6c, 16i, and 24k.

The clathrates investigations have been mainly focused on the guest atom which provides a route to control the thermal conductivity for the purpose of enhancing the thermoelectric performance. Another approach to improve the thermoelectric performance is “cross-substitution” of the host atoms, which aims at tuning the electrical properties. However, the study of Ba8Al16Ge30 reported that a small change in the host structure also affect the thermal conductivity. By host substitution, controlling both electronic and thermal properties are possible.

The objectives of this study are to analyze the effect of Ga substitution for Al to the Ba2 guest atom feature of Ba8Al16-xGaxGe30 from the neutron powder diffraction data and MEM analysis and to clarify the effect of Ga substitution for Al to the thermoelectric properties in wide range temperature.

The high purity of raw materials was used to prepare the samples. The samples were synthesized by arc melting method for neutron powder diffraction (NPD) experiment and followed by Spark Plasma Sintering (SPS) for thermoelectric properties measurement at high temperature. The sample quality has been examined by X-ray

powder diffraction (XRD). The thermoelectric properties were performed using ZEM-3 and Laser Flash apparatus to measure the samples at high temperature (943 K) and PPMS apparatus for sample measurement at low-temperature (10 K).

The structural analysis shows that the lattice constants of Ba8Al16-xGaxGe30

(x=0,2,4,6,8) shrink with increasing Ga ratio, closer to the lattice constant of Ba8Ga16Ge30. Ga substitution for Al does not affect to the Ge occupancies, where Ge is occupied approximately 30% at 6c site and dominantly occupied the 16i and 24k site for about 70%. Al occupancies with the site preference at 6c site decrease with increasing the Ga concentration. There are two kinds of Ga site preferences. For 6c site, the Ga occupancies at x = 2 and 4 are small while at x = 6 and 8, they are as large as 18%, shown in Figure.

The refinement results reveal an expansion of lattice parameter with increasing the temperature. For the atomic displacement parameters (ADPs), Ba8Al8Ga8Ge30 has larger ADPs compared to the Ba8Al16Ge30, however the off-centered displacement shows the opposite behavior. The MEM results clearly show that the Ba2 guest atom is located at an off center 24k site and the distribution size enlarges with increasing temperature. A clear effect of the substitution is observed at higher temperature. The Ba2 distribution of Ba8Al16Ge30 at 900 K is isotropic in the xz plane, whereas the Ba2 distribution of Ba8Al8Ga8Ge30 only grow wider along to the y direction, anharmonic distribution. This can be a proof that the host structure substitution, affect the guest atom behavior.

The Ga substitution for Al suppresses the thermal conductivity with lattice contributes more than the electronic at high temperature. The thermoelectric properties measurement revealed that Ba8Al8Ga8Ge30 has ZT value higher than Ba8Al16Ge30.

氏名 Zhijian TAN



学位授与の日付平成 30 年 9 月２8 日

学位授与の要件高エネルギー加速器科学研究科物質構造科学専攻


学位論文題目 The investigation of negative thermal expansion and

magnetic structure in La0.5Ba0.5CoO3-x by neutron powder

diffraction

論文審査委員主査教授伊藤晋一

教授大友季哉

准教授池田一貴

准教授米村雅雄

助教萩原雅人

教授神山崇

主幹研究員茂筑高士

国立研究開発法人物質・材料研究機構

先端材料解析研究拠点光・量子ビーム応用

分野中性子散乱グループ

(Form 3)


Name in full Zhijian TAN

Title The investigation of negative thermal expansion and magnetic structure in

La0.5Ba0.5CoO3-x by neutron powder diffraction

(負の熱膨張を示す La0.5Ba0.5CoO3-x の結晶構造と磁気構造の研究)

Negative thermal expansion (NTE) describes the phenomenon of lattice constriction as temperature increase. Since thermal expansion may cause significant problems in engineering fields, NTE is very important for industrial application, from large structural components such as railroad tracks and bridges, to precision instruments and electronic devices such as optical instruments and sensors. Recently, our group observed large NTE in cobaltite perovskite, PrBaCo2O5.74 below Neel temperature TN =120 K. Moreover, NTE in La0 . 5Ba0 . 5CoO3 - x can be tuned by changing the hole doping level x. Through the comprehensive study with multiple techniques, it is found this NTE is closely associated with the ferromagnetic (FM) and antiferromagnetic (AFM) competition. Now I am motivated to investigate NTE in the A-site disordered La0.5Ba0.5CoO3-x. Firstly, the bandwidth can be control by changing to La. Secondly, compare with Pr, La has no magnetic moment so that it will be easier to analyze the relationship of NTE and magnetism in A-site disordered La0.5Ba0.5CoO3-x than in the PrBaCo2O5.5+x. Furthermore, since the structure of A-site disorder La0.5Ba0.5CoO3-x is cubic, this leads to the isotropic NTE. It will be simpler to understand the fundamental physics. So in this research I expect to search possible NTE in A-site disordered La0.5Ba0.5CoO3−x and investigate the new phenomenon of this sample.

This thesis is concerned with sample synthesis and investigation of magnetic structure and NTE property of the A-site disordered La0.5Ba0.5CoO3−x. The present thesis contains five chapters. In the first chapter the application of NTE material as well as the common NTE material are introduced. Then the detailed properties and magnetism of NTE are reviewed. This chapter also includes the structure and the unusual properties of the cobaltite perovskites.

For the second chapter the focus changes to the experimental part. I prepared high-quality La0.5Ba0.5CoO3-x polycrystalline samples by solid-state reaction method and controlled the oxygen content by annealing as-synthesized sample in pure Ar atmosphere at various temperatures. The oxygen content is determined by the iodometric titration method. A combination of X-ray powder diffraction (XRD), high resolution neutron powder diffraction (NPD) and the superconducting quantum

interference device (SQUID) magnetometer (MPMS) was used to investigate the crystal structure and magnetic structure.

In the third chapter, the experiment results are presented. The crystal and magnetic structures are determined by the Z-Rietveld refinement. Based on the magnetization data and NPD data, the phase diagram of this La0.5Ba0.5CoO3-x is obtained. From the temperature dependence of volume, the large NTE is observed in the hole doping A-site disordered La0.5Ba0.5CoO3-x. This NTE can be tuned by changing the oxygen content and the largest NTE occurs near the boundary between FM and AFM phases in the phase diagram. The phase separation of AFM and FM state or paramagnetic (PM) state was observed in very large range of oxygen content f rom 2.82 to 2 .89. I t is found that this NTE is related to the magnetic ordering. The transition of LV phase with AFM state to SV phase with FM or paramagnet ic s ta te resul ts in the NTE. The resul ts of NPD under magnetic field confirm that the large volume (LV) phase is related to the AFM and small volume (SV) phase is related to the FM. It is also found that the average volume is suppressed under magnetic field, which reveals that the NTE can be tuned by the magnetic field.

In the fourth chapter, I discuss about the new phenomenon of this sample. From the phase diagram of La0.5Ba0.5CoO3−x and Pr0.5Ba0.5CoO3-x, the phase separation is observed in a much larger range of oxygen content from 2.82 to 2.89 in La0.5Ba0.5CoO3−x. The Curie temperatures TC of the two samples are very close while the TN in La0.5Ba0.5CoO3−x is much high than that of Pr0.5Ba0.5CoO3-x. The phase diagram shows large differences in the two samples. It may come from the different radius of La and Pr or from the A-site disordered effect. I also found that the relative difference of volume between the LV and SV (∆VLV-SV/V) in La0.5Ba0.5CoO3−x is much larger than that in Pr0.5Ba0.5CoO3-x. From the phase diagram and the analysis of the volume in AFM and FM phase between these two samples, it is suggested that the much larger ∆VLV-SV/V is related to the much stronger AFM in La0.5Ba0.5CoO3−x.

In the last chapter, the summary and future work of the thesis are presented.

氏名小川智久




学位授与の要件高エネルギー加速器科学研究科素粒子原子核専攻


学位論文題目 Sensitivity to anomalous VVH couplings induced by

dimension-6 operators at the ILC

論文審査委員主査講師大森恒彦

教授野尻美保子

准教授 JEANS, Daniel Thomelin Dietrich

講師杉本康博

教授藤井恵介

特任助教 Junping Tian

東京大学素粒子物理国際研究センター

(Form 3)


Name in full

Tomohisa Ogawa

Title

Sensitivity to anomalous VVH couplings induced by dimension-6 operators at the ILC

The Standard Model (SM), which is comprised of the Glashow-Weinberg-Salam theory describing electro-weak interaction based on SU(2)×U(1) gauge symmetry, quantum chromodynamics representing strong interaction based on SU(3) gauge symmetry, where the Higgs mechanism has a critical role for giving rise to mass to matter and gauge particles, has successfully interpreted phenomena which are observed in reality in the field of elementary particle physics. However, several phenomena which have not been included in the SM yet are known such as dark matter, neutrino mass and so on. Therefore, the SM must be expanded to explain more observation, which is called beyond the SM (BSM). In 2012 the SM-like Higgs boson was discovered at the Large Hadron Collider (LHC) and the SM was completed through verifications afterwards. At the same time, we entered a new phase where we do not have a clear map like the SM to lead us to the BSM, and we expect that one of the hints exists in the discovered Higgs boson. A lot of BSM models, such as a general extension of the SM and a super symmetry model, predict that Higgs couplings to the SM particles would be shifted because of mixing and corrections originating from a new heavier particle and such variation will appear with a specific pattern from the SM expectations, or these models require new Lorentz structures for describing new interactions between the Higgs boson and the SM particles. Therefore, the most important task for elementary particle physicists is to explore and verify the structures relevant to the Higgs boson and those couplings. One theoretical framework for exploring the Lorentz structures, which is rather physics driven, is to employ an Effective Field Theory (EFT) where it is possible to introduce higher dimension field operators which satisfy the gauge invariance and are restrained with inverse power of a new physics scale. The EFT can verify the structures more model-independently compared to the traditional κ-framework. Furthermore, measurements which are not related to the Higgs boson can also effectively contribute to constraining the Higgs related Lorentz structures in the EFT.

In this thesis, we focus on the couplings and the structures between the Higgs boson and the vector bosons, γ, Z, and W, which are a critical part in the Higgs sector of the SM, especially responsibility for the mass generation. By introducing relevant dimension-6 field operators to the VVH (V= γ, Z, and W) couplings under the EFT, an effective Lagrangian is given, which naturally includes the anomalous VVH couplings after imposing the symmetry breaking. Effects coming from these anomalous VVH couplings will appear in cross-sections of corresponding processes and kinematical shape distributions as deviations from the SM expectations. We expect that the future International Linear Collider (ILC) can perform measurements for these anomalous VVH couplings very precisely. To evaluate the reachable sensitivity to these anomalous VVH couplings at the ILC, full detector simulation was performed at both operation energies of √s = 250 and 500 GeV using the International Large Detector (ILD) model, which is one of the detector concepts of the ILC. The evaluation was done by analyzing all Higgs production processes such as Higgs-strahlung, ZZ-fusion, and WW-fusion, and also the decay channel of H→ WW, where all SM background are also considered. To evaluate the variation of the kinematical shape distributions, a detector response function is considered, which can describe smearing effects derived from detector resolution and physical effects. The response function can apply to any generated distributions to transfer the distribution to the detector-level distribution. The beam polarization, which is one strong point of the linear collider, can also give impact on disentanglement of γ and Z by exploiting the physics that the gauge fields B and W3 differ in their interactions, and give the sensitivities to both of the anomalous ZZH and γZH couplings. It turned out, as our results, that the reachable sensitivities to the anomalous VVH couplings, assuming a certain ILC full operation program, are 0.55%, 0.17%, and 0.27% for the anomalous ZZH couplings of ηZ, ζZZ, and ζtZZ. The reachable sensitivities to the anomalous γZH couplings are less than 0.06% for both ζAZ and ζtAZ. The reachable sensitivities to the anomalous WWH couplings are respectively 0.45%~0.80%, 0.88%~1.72%, and 4.40% for ηW, ζWW, and ζtWW.

氏名 Dong Van Thanh




学位授与の要件高エネルギー加速器科学研究科素粒子原子核専攻


学位論文題目 Study of lepton flavor violation with a high-resolution

tracking device for Belle II experiment

論文審査委員主査教授中尾幹彦

教授藤井恵介

准教授西田昌平

講師上原貞治

教授宇野彰二

教授宮林謙吉

奈良女子大学自然科学系・物理学領域

(Form 3)


Name in full: Dong Van Thanh

Title: Study of lepton flavor violation with a high-resolution tracking device in BelleII experiment

The Belle II / SuperKEKB experiment is an upgrade of the successful Belle / KEKBexperiment with 40 times higher luminosity. Collecting a huge number of B, Dmesons and τ leptons will enable Belle II to perform rich physics programs to searchfor new physics beyond the standard model (SM) of elementary particles from raredecay modes and decays which are forbidden in the SM such as the charged leptonflavor violation (LFV), as well as searching for exotic particles like the four-quarkstate.

In the SM, LFV is not protected by a symmetry, the branching fraction predicted forLFV in the SM is very small and inaccessible with current experiments, even thefinite neutrino mass are taken into consideration. In well-motivated extensions of theSM, LFV is naturally introduced with the branching fraction which can be reached bycurrent planned experiments. An observation of LFV would provide a clear signatureof new physics.

τ is the heaviest charged lepton, it is expected to have a large coupling to new physics,and offers a long decay list for searching LFV. With a huge number of τ+τ− pairs willbe produced by SuperKEKB, Belle II provides a good opportunity for studying theLFV in decays of the τ lepton. Good reconstructed mass and energy resolutions whichmeasured by tracking detectors are important to reduce the background and improvethe efficiency in the LFV study. To do this, Central Drift Chamber (CDC) is the keydevice.

The CDC of contains 14300 drift cells is the main tracking device of the Belle IIdetector, CDC plays an important role in measuring momentum of charged particles,and the particle identification using energy loss information, dE/dx. To realize thedesigned performance of CDC, the calibration and alignment are crucial. In this thesis,

methods for calibration and alignment of CDC are described.

The time offset, the crucial parameter to obtain the drift time, is calibrated for eachchannel. The time walk effect is corrected for each of electronics board. Thepropagation velocity of the signal on the wire is examined. The time to space relationand the position resolution as a function of the drift distance are calibrated for eachlayer in different incident angles and left-right sides. A procedure to combine allalgorithms for the full CDC calibration is established. The position resolution becomebetter than 120 μm after the calibration.

CDC is aligned using cosmic-ray muon data taken without magnetic field. The x(t)relation is calibrated in the different way from the standard calibration where hits atthe left and right side, are merged to cancel the bias of the x(t) relation on thesystematic mis-alignments. By treating a cosmic track as a single track and using twoouter most super-layers as a reference for the first step of the alignment, the positionsat both sides of each layer in all three directions are aligned together. The globalrotation of the forward end-plate with respected to the backward one (twist effect) iscorrected using the dependence of the residual on the layer radius and the dip angle ofcosmic tracks, four innermost super-layers serve as a reference for the twist alignment.The displacement of each wire due to the mechanical imperfection and the bush, glueeffect in Φ direction is also corrected using the observed residual at the end-plates ofeach channel. The position resolution is significantly improved after alignment.

The performance of CDC after the calibration and the alignment is verified withcosmic-ray data taken under a 1.5 T magnetic field of Belle II solenoid. One singlecosmic muon is fitted as two separate tracks at upper and lower sectors of CDC. Thetrack parameter resolutions are obtained by comparing track parameters of these twotracks with an assumption that their resolutions are identical.

After the alignment, the negative shift of the impact parameter in x-y plane (d0)disappears, the fluctuation of the impact parameter in the z direction (z0) whichcauses by wire by wire displacements becomes close to zero. After the calibration, themomentum resolution is greatly improved as compared with the result of Belle CDC,this improvement is not only the result of the extending outer radius of CDC, but alsothe contribution better calibration and better alignment. The transverse momentumdependence of the momentum resolution is parameterized as σPt/Pt = (0.127 ±0.001)PT ⊕ (0.321 ± 0.003) (%) after the alignment, the constant term is worse thanthe expected performance of CDC due to the presence of a large amount of material ofthe B-field mapper inside CDC during the data taking which causes the multiple

scattering effect.

Studying the LFV in the decay τ→μ−μ+μ− is performed using 1 ab−1 Monte-Carlo datawhich is equivalent to the 10-year accumulated data of the Belle experiment. Fourgood charged track events in which one τ decay into three muons (signal) and anotheris one prog decay of generic τ (tag) are selected. At least one particle at the signalside is required to be identified as muon. The background suppression is doneseparately for different decay modes in the tag side. The efficiency of the analysis is11.04%, which is 1.5 times improvement as compared with the result of Belle analysis(7.6%). The upper limit for the branching fraction of the decay is set atBr(τ→μμμ)<1.1×10−8 at the 90% confident level for 1 ab−1 data.

氏名 Emy Mulyani 学位（専攻分野）博士（理学）学位記番号 ...

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氏 名 Emy Mulyani 学位（専攻分野） 博士（理学） 学 位 記 番 号 ...

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Transcript of 氏 名 Emy Mulyani 学位（専攻分野） 博士（理学） 学 位 記 番 号 ...

氏名 Emy Mulyani 学位（専攻分野）博士（理学）学位記番号 ...

Transcript of 氏名 Emy Mulyani 学位（専攻分野）博士（理学）学位記番号 ...