Searches for Higgs pair production and probing the Higgs self-couplings in the HH→bbττ decay channel at the ATLAS Experiment and performance studies for the High-Granularity Timing Detector for ATLAS phase-2 upgrade

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题名:	Searches for Higgs pair production and probing the Higgs self-couplings in the HH→bbττ decay channel at the ATLAS Experiment and performance studies for the High-Granularity Timing Detector for ATLAS phase-2 upgrade
作者:	李杉拉;Ali, Shahzad
贡献者:	物理學系
日期:	2024-01-15
上传时间:	2024-09-19 15:56:38 (UTC+8)
出版者:	國立中央大學
摘要:	這項研究聚焦於在 CERN 大型強子對撞機（LHC）由 ATLAS 探測器記錄的質心能量為 13 TeV 的質子-質子碰撞中，使用 140 fb−1 數據尋找 H H → b¯b τ+τ− 非共振希格斯玻色子對產生的信號。分析策略旨在探測希格斯玻色子 κλ 和四重 H H V V (V = W, Z ) 交互作用強度 κ2V 的異常值。然而，在標準模型 (SM) 預期的背景中未觀察到顯著超出的訊號。在 95% 的信心水準下，觀測到的 (期望的) 雙希格斯玻色子的產生率上限為標準模型預測的 5.9 (3.1) 倍。在假設所有其他希格斯玻色子交互作用固定為標準模型預測的情况下，交互作用強度被限制在觀測到的 (期望的) 95% 信賴區間 −3.2 < κλ < 9.1 (−2.4 < κλ < 9.2) −0.5 < κ2V < 2.7(−0.2 < κ2V < 2.4) 内。該研究還包括使用在 2018 年至 2019 年在 CERN SPS 和 DESY 收集的測試數據，對具有 50 μ m 有效厚度的低增益雪崩探測器 (LGADs) 進行性能評估，重點關注 ATLAS 第二階段升级的高粒度定時探測器 (HGTD)。HGTD 旨在通過精確測量軌跡時間，分辨率約為 30 ps 到 50 ps, 提高粒子-頂點分配的精度，從而減輕 LHC 高亮度運行期間的堆積效應。;This study focuses on searches for non-resonant Higgs boson pair production in the HH → b¯bτ+τ− channel using 140 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider (LHC). The analysis strategy aims to probe anomalous values of the Higgs boson (H) self-coupling modifier κλ and quartic HHV V (V = W,Z) coupling modifier κ2V. However, No significant excess above the expected background from Standard Model (SM) processes is observed. Observed (expected) upper limit at 95% confidence-level on the di-Higgs boson production rate is set at 5.9 (3.1) times the SM prediction. The coupling modifiers are constrained within an observed (expected) 95% confidence interval of −3.2 < κλ < 9.1 (−2.4 < κλ < 9.2) and −0.5 < κ2V < 2.7 (−0.2 < κ2V < 2.4), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The study also includes performance evaluations of Low Gain Avalanche Detectors (LGADs) with a 50 μm active thickness using testbeam data collected at CERN SPS and DESY between 2018 and 2019, focusing on the High-Granularity Timing Detector (HGTD) for the ATLAS phase-2 upgrade. The HGTD aims to enhance particle-vertex assignments by precisely measuring track time with resolutions ranging from approximately 30 ps to 50 ps, thereby mitigating pile-up effects during the High-Luminosity phase of the LHC operations.
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