DSpace community: 物理研究所

Estimation of Fake Hadronic Tau Lepton Background in the HH → bbττ LepHad Channel Using Run 2 and Run 3 Data with the ATLAS Detector

Fri, 06 Mar 2026 11:19:25 GMT

title: Estimation of Fake Hadronic Tau Lepton Background in the HH → bbττ LepHad Channel Using Run 2 and Run 3 Data with the ATLAS Detector abstract: 本研究提出一種以資料為基礎的方法，用於估計 ????→????????過程中假強子衰變 ?? 輕子背景，並著重於輕子–強子（??lep??had）道的分析。對希格斯玻色子對產生的搜尋具有特別重要的意義，因為此類研究能直接探測希格斯自耦合，並對標準模型進行關鍵檢驗。本文使用 ATLAS 偵測器在 Run 2 期間所量測、對應質心能量 √??=13TeV 的質子–質子對撞資料，以及 2022 至 2023 年 Run 3 所收集、質心能量 √??=13.6TeV 的可用資料。在 ATLAS 中，?? 輕子僅能透過其可見衰變產物加以重建，而涉及強子衰變 ?? 輕子的分析，特別容易受到由夸克與膠子噴注被誤辨識為 ??had 候選體所造成的背景影響。為了刻畫這些貢獻，本文採用 Fake Factor 方法，在富含 ????ˉ 與多噴注事例的控制區中量測 fake factor，並將其套用至訊號區。透過專門設計的 closure 測試對該方法進行驗證，結果顯示在兩個 run 期間，預測與實測資料之間具有良好的一致性，確認了假背景估計的穩健性。 ;This study presents a data-driven estimation of fake hadronic τ-lepton backgrounds in the HH → bbττ process, focusing on the lepton–hadronic (τlepτhad) channel. The search for Higgs-boson pair production is of particular importance, as it provides direct sensitivity to the Higgs self-coupling and offers a critical test of the Standard Model. The analysis uses proton–proton collision data recorded by the ATLAS detector during Run 2 at √s = 13 TeV and available Run 3 data collected in 2022 to 2023 at √s = 13.6 TeV. In ATLAS, τ leptons are reconstructed only through their visible decay products, and analyses involving hadronically decaying τ leptons are especially affected by backgrounds from quark- and gluon initiated jets misidentified as τhad candidates. To model these contributions, a Fake Factor Method is employed, with fake factors derived in control regions enriched in t¯tand multijet events and subsequently applied to the signal region. The method is validated through dedicated closure tests, demonstrating good agreement between the prediction and observed data across both run periods, thereby confirming the robustness of the fake-background estimation

基於幾何接收度的渺子成像探測器幾何優化;Geometric Optimization of Muography Detectors Based on Acceptance

Fri, 06 Mar 2026 10:36:54 GMT

title: 基於幾何接收度的渺子成像探測器幾何優化;Geometric Optimization of Muography Detectors Based on Acceptance abstract: 渺子成像術（Muography）是一種利用渺子來探測物體內部結構的成像技術。渺子具有能夠穿透數百至數千公尺岩層的能力，使其成為掃描山體與礦脈等大型結構的最佳粒子。同時，宇宙射線提供了一種天然且穩定的渺子來源，使渺子成像術得以實現。然而，與其他高能物理實驗相同，渺子成像術本質上是一種計數實驗。因此，建立事件數與積分通量之間的轉換方法是必要的。在此背景下，幾何接受度（geometry acceptance）是轉換事件數量到粒子通量的必要參數。本文發展了一套演算法，可用於計算任何，可以被描述為凸多邊形平面集合之探測器的幾何接受度。此外，幾何接受度同時也是決定探測器探測事件速率的關鍵因素。由於大多數渺子成像術實驗的事件數量很低，統計不確定性往往成為主要誤差來源。因此，透過對幾何接受度的研究，數種探測器形狀被提出，能夠提供調整和最佳化探測器形狀的方法，並讓探測器形狀可以最適合觀測任務。總結而之，本文所提出的形狀，可以客製化探測器縮短觀測時間或降低探測器建造成本。;Muography is a tomography technique that detects internal structures using muons. The ability of muons to pass through hundreds to thousands of meters of rock makes them the best particles for scanning large-scale structures, such as mountains and ore veins. On the other hand, cosmic rays provide an excellent natural radiation source for muography. However, like other high-energy physics experiments, muography is fundamentally an event-counting experiment. Therefore, a method to convert the event number into the integrated flux is required. To achieve this, a method for calculating the geometry acceptance is necessary. Consequently, an algorithm capable of calculating the geometry acceptance for any detector that can be described as a group of convex polygonal planes was developed. Furthermore, geometry acceptance is also the major factor determining detector efficiency. This is particularly important due to the low event rate in most muography experiments, which causes statistical error to become the dominant source of uncertainty. Therefore, a variety of detector geometries were developed and studied through geometry acceptance analysis, enabling methods to adjust and optimize detector geometry for specific observation missions. In summary, a custom detector design that achieves shorter detection duration or lower construction cost becomes possible.

Measurement of Electron Trigger Efficiency and Scale Factor with the CMS Detector Using LHC Run 3

Fri, 06 Mar 2026 10:36:33 GMT

title: Measurement of Electron Trigger Efficiency and Scale Factor with the CMS Detector Using LHC Run 3 abstract: 本論文利用 LHC Run 3（2022 年）期間在 √s = 13.6 TeV 下收集的質子-質子碰撞數據（積分亮度約為 27.0 fb−1），呈現了 CMS 探測器中電子觸發效率的測量結果。準確的數據與模擬校正對於標準模型的精確測量以及新物理現象的搜尋至關重要。單電子高階觸發（High-Level Trigger）的效率是利用應用於 Z → ee 事件的 Tag-and-Probe 方法測量的。通過（passing）和未通過（failing）探測電子的不變質量分佈是使用標稱的信號加背景模型同時擬合的，而替代的信號和背景參數化模型則用於評估系統誤差。測量是在電子橫向動量 (pT ) 和贗快度 (η) 的二維區間中進行的。結果顯示，對於 pT 遠高於觸發閾值的電子，觸發效率在桶部區域達到 96% 至 98%的平原值，在端蓋區域則在 90% 至 92% 之間。數據與模擬之間的殘餘差異已被量化，得出的數據對模擬比例因子（Scale Factors）在大多數運動學相空間中通常在 1 的 5%以內。這些比例因子以及詳細的效率圖和相關誤差，為 Run 3 期間依賴單電子觸發的CMS 分析提供了可靠的校正。;This thesis presents a measurement of the electron trigger efficiencies in the CMS detector using proton–proton collision data collected during LHC Run 3 (2022) at √s=13.6 TeV with an integrated luminosity of ~27.0 〖fb〗^(-1). Accurate data-to-simulation corrections are crucial for precision measurements of the Standard Model and for searches for new physics phenomena. The efficiency of the single-electron High-Level Trigger is measured using the Tag-and-Probe method applied to Z→ee events. The invariant-mass distributions of passing and failing probes are simultaneously fitted using a nominal signal-plus-background model, while alternative signal and background parameterizations are employed to evaluate systematic uncertainties. The measurement is performed in two-dimensional bins of electron transverse momentum (p_T) and pseudorapidity (η). The results indicate that the trigger efficiency reaches a plateau of between 96% and 98% in the barrel region and between 90% and 92% in the endcaps for electrons with p_T well above the trigger threshold. Residual discrepancies between data and simulation are quantified, yielding data-to-simulation scale factors that are typically found to be within 5% of unity across the majority of the kinematic phase space. These scale factors, along with detailed efficiency maps and associated uncertainties, provide reliable corrections for CMS analyses relying on single-electron triggers during Run 3.

雷射驅動充氣毛細管波導之高階諧波產生;Laser-Driven High-Order Harmonic Generation from Gas-Filled Capillary Waveguide

Fri, 06 Mar 2026 10:36:17 GMT

title: 雷射驅動充氣毛細管波導之高階諧波產生;Laser-Driven High-Order Harmonic Generation from Gas-Filled Capillary Waveguide abstract: 高階諧波產生（High-order harmonic generation, HHG）是近二十年在超快科學中快速發展的重要技術，可產生極紫外至軟X光波段的相干光源，並廣泛應用於阿秒脈衝產生、分子動力學量測以及材料中的超快電子行為研究。過去HHG主要在稀薄氣體中進行，過程可由三步驟模型描述，其截止能量受限於原子游離能與驅動雷射強度，因此如何提高轉換效率及推進更短波長，一直是努力的方向。從研究趨勢來看，現今HHG主要朝兩個方向發展：（1）產生更短的阿秒脈衝，典型方法是使用單週期或近單週期的驅動雷射，使HHG 只在單一半週期內發生，以獲得孤立阿秒脈衝。此類脈衝品質高，但目前驅動雷射能量受限制。（2）推進更短波段（更高能量）的HHG，利用較長波長的驅動雷射可將截止能量延伸，但由於游離率極低，諧波轉換效率普遍非常低，實驗也更具挑戰。本研究希望突破低游離率的限制，探討是否能從離子（如1+、2+）產生HHG，而非只依賴中性原子。若能有效使用高游離率環境（甚至達到一半以上的游離率），驅動雷射能量即可進一步提高，使可達到的截止波長顯著縮短。如此一來，可望突破傳統HHG的能量限制並大幅擴展極短波長的應用可能。然而，高游離率環境下的關鍵挑戰是有效的相位匹配。本研究採用毛細管波導來限制雷射發散並延長雷射與氣體的作用距離，並結合自製的中間診斷系統，包括焦點品質量測與頻域干涉儀量測電漿密度，使能夠直接觀察波導中的模態演化與相位匹配狀況，提供少見的詳細中間物理資訊。本研究分別使用不同內徑的毛細管（100、150、200 µm）於氬氣與氦氣中測試HHG產生。結果顯示：150µm毛細管在短脈衝（40fs）驅動下，於第27階諧波達到高於過去實驗的轉換效率；200µm毛細管在氬氣中成功產生超越傳統原子截止能量的諧波，而氦氣則成功將波段推進至8nm。本研究的成果說明，適當的波導條件、短脈衝、以及高游離率環境確實有機會突破傳統HHG限制，並支持HHG可能由高電離態貢獻的可能性。;High-order harmonic generation (HHG) is an important nonlinear process that can produce coherent radiation in the extreme ultraviolet and soft X-ray regions. It has been widely used in attosecond science and ultrafast dynamics studies. Traditionally, HHG is generated in gases and can be de scribed by the three-step model. However, the cut-off energy and conversion efficiency are limited by the ionization potential and phase-matching conditions. In recent years, HHG research has mainly followed two directions. One direction focuses on generating isolated attosecond pulses by using single-cycle or few-cycle driving laser pulses. This method can produce high-quality ultrashort pulses, but the pulse energy is low and it is difficult to reach very short wavelengths. The other direction aims to extend the harmonic cut-off by using longer-wavelength driving lasers. Although this method can generate higher photon energies, the ionization rate and conversion efficiency are usually very low. In this work, we explore another approach to HHG by studying harmonic generation from highly ionized media instead of only neutral atoms. By increasing the ionization level of the gas, higher driving laser energy can be applied, which may allow the harmonic cut-off to extend to shorter wavelengths. A major challenge of this approach is achieving phase matching under high plasma density conditions. To address this problem, gas-filled capillary waveguides are used to confine the laser beam and increase the interaction length between the laser and the gas. Capillaries with different inner diameters (100, 150, and 200 µm) are tested under various gas pressures and laser conditions. In addition, intermediate diagnostic systems, including focal spot measurements and frequency-domain interferometry, are used to study beam evolution and phase-matching conditions inside the waveguide. The experimental results show that the 150-µm capillary achieves higher conversion efficiency around the 27th harmonic when short laser pulses (40 fs) are used. In the 200-µm capillary, argon successfully generates harmonics beyond the traditional atomic cut-off, and helium extends the harmonic wavelength down to 8 nm. These results demonstrate that short laser pulses and proper waveguide conditions are important for phase matching and may enable HHG from highly ionized media.