The GlueX experiment aims to study meson photoproduction while utilizing the coherent bremsstrahlung technique to produce a 9 GeV linearly polarized photon beam incident on a liquid $\mathrm{H_{2}}$ target. A Start Counter detector was fabricated to properly identify the accelerator electron beam buckets and to provide accurate timing information. The Start Counter detector was designed to operate at photon intensities of up to $\mathrm{10^{8}\gamma/s}$ in the coherent peak and provides a timing resolution $\mathrm{\sim 300\ ps}$ so as to provide successful identification of the electron beam buckets to within 99\% accuracy. Furthermore, the Start Counter detector provides excellent solid angle coverage, $\sim 90 \%\ \mathrm{of}\ 4 \pi\ \mathrm{hermeticity}$, and a high degree of segmentation for background rejection. It consists of a cylindrical array of 30 scintillators with pointed ends that bend towards the beam at the downstream end. Magnetic field insensitive silicon photomultiplier detectors were selected as the readout system. An initial measurement of the beam asymmetry $\Sigma$ in the exclusive reaction $\vec{\gamma}p \rightarrow \pi^{0}p$, where $\pi^{0} \rightarrow \gamma \gamma$ has been carried out utilizing the GlueX spectrometer during the Spring 2015 commissioning run. The tagged photon energies ranged from $2.5 \leq E_{\gamma} \leq 3.0\ \mathrm{GeV}$ in the coherent peak. These measurements were then compared to the world data set and show remarkable agreement with only two hours of physics production running.

京都大学 / 0048 / 新制・論文博士 / 博士(理学) / 乙第13368号 / 論理博第1572号 / 新制||理||1666(附属図書館) / 京都大学理学研究科 / (主査)教授 永江 知文, 教授 中家 剛, 准教授 成木 恵 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM

A search for Higgs boson pairs produced in the decay of high mass exotic resonances is presented. The search uses the bb̄bb̄ final state, analyzing 139 fb⁻¹ of proton–proton collision data at √s = 13 TeV collected with the ATLAS detector. Spin-0 and spin-2 benchmark signal models are considered and no significant deviation from the Standard Model prediction is observed. The search is combined with a complementary analysis for lower mass resonances to set upper limits on the production cross-section times HH branching ratio of new resonances in the mass range of 251 GeV to 5 TeV. In addition, the methodology for the in-situ calibration of a novel double-b-tagging algorithm (Xbb2020) using gluon to bb̄ decays is presented. Preliminary scale factors for Monte-Carlo simulation are computed using 139 fb⁻¹ of √s = 13 TeV pp collision data collected with the ATLAS detector. The completed calibration will allow the Xbb2020 algorithm to be used in future ATLAS searches for H → bb̄ decays.

This work presents the search for Dark Matter particles associated with the Higgs Boson decaying into a b b-bar quark pair. The dark matter search result is based on proton-proton collision data collected at a center-of-mass energy of 13 TeV by the ATLAS detector during Run II. The results are interpreted in the context of a simplified model (Z’-2HDM) which describes the interaction of dark matter and standard model particles via new heavy mediator particles. The new powerful Higgs tagging techniques, which exploit the jet substructure and heavy flavor information to a large extent, are developed to improve the search sensitivity of the search. The target physics signals are signature with an optimized search region and interpreted with background estimation result statistically.

Unparticle physics is the physics of a hidden sector which is conformal in the infrared and coupled to the Standard Model. The concept of unparticle physics was introduced by Howard Georgi in 2007 and has since then received a lot of attention, including many studies of its phenomenology in different situations. After a review of the necessary background material, the implications of the self-interactions of the unparticle sector for LHC physics is studied. More specifically, analyses of four-body final states consisting of photons and leptons are performed. The results are upper bounds on the total cross sections as well as distributions of transverse momentum.

Two-charged-particle correlations are measured as a function of pseudorapidity and azimuthal angle difference in pp collisions at √s = 13, 2.76 and 5.02 TeV with the ATLAS detector at the Large Hadron Collider. A long-range structure in the two-dimensional function centered at ∆φ = 0 and extending over a large range of ∆η referred to as the “ridge” is seen in the three data sets. A template fitting method is implemented to extract the Fourier harmonics of the flow and gives the dependence of the harmonics on the charged-particle multiplicities. In this method a rescaled correlation function from peripheral events representing the recoil component plus a cosine modulation representing the ridge is used to describe the whole one-dimensional correlation function. Different multiplicity intervals for the peripheral events are used to extract the harmonics. The results presented show that vn,n from correlation functions can be factorized into the products of single particle vn. Significant contributions from v₂, v₃ and v₄ are obtained and their dependences on multiplicity and transverse momentum are studied. It is also shown that there is significant vn even in the lowest multiplicity bins. In addition, the second harmonics v₂ in pp do not have a significant dependence on both the multiplicity and collision energy. Results of pp and pPb at the same energy are compared with each other in both multiplicity and pT distributions. Both chᵗʳᵏ−chᵗʳᵏ and chᵗʳᵏ-muon correlations are measured in pPb collisions at √sNN = 8.16 TeV. Long-range correlations are studied through template fitting procedure. chᵗʳᵏ-v₂ increases with the number of reconstructed charged tracks at low multiplicity and saturates at high multiplicity. Muon-v₂ is considerably smaller than chᵗʳᵏ-v₂ and only has a weak dependence on event multiplicity. Factorization in both cases works pretty well. Two-charged-particle correlation functions are also measured in Xe+Xe events at √sNN = 5.44 TeV. In the most central collisions direct Fourier decomposition is preferred to avoid negative recoil component that might appear in the template fitting method. vn reaches its maximum value in the mid-centrality region and becomes smaller at both low and high centralities. Results are compared with Pb+Pb events at √sNN = 5.02 TeV showing that vn obtained from these two systems have similar values and behaviors.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18047号 / 理博第3925号 / 新制||理||1566(附属図書館) / 30905 / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)准教授 小嶋 泉, 教授 岡本 久, 教授 重川 一郎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18072号 / 理博第3950号 / 新制||理||1569(附属図書館) / 30930 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 准教授 成木 恵, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19492号 / 理博第4152号 / 新制||理||1596(附属図書館) / 32528 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 國廣 悌二, 教授 大西 明, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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