在質子對撞能量8TeV下尋找具有雙電子雙渺子末態的激發態輕子;Search for excited leptons in the 2e2μ final state in pp collisions at $\sqrt{s}$ = 8 TeV

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题名:	在質子對撞能量8TeV下尋找具有雙電子雙渺子末態的激發態輕子;Search for excited leptons in the 2e2μ final state in pp collisions at $\sqrt{s}$ = 8 TeV
作者:	麥書豪;Mai,Shu-Hao
贡献者:	物理學系
关键词:	激發態輕子;標準模型外物理;基本粒子;緊湊渺子線圈;大強子對撞機;excited lepton;beyond standard model;elementary particle;CMS;LHC
日期:	2014-10-07
上传时间:	2014-11-24 15:21:36 (UTC+8)
出版者:	國立中央大學
摘要:	我們在此呈現一次針對激發態輕子於2e2μ末態之搜尋結果。此分析為CMS實驗在尋找激發態輕子於四輕子末態實驗之部分。此次實驗利用LHC於√s = 8 TeV撞擊之數據。數據的蒐集由CMS偵測器完成，使用數據之累積照度達到19.7 fb-1。激發態輕子(l^)預期將透過接觸相互作用與一標準模型之輕子伴隨生成。而後，激發態輕子將以l^→lZ→lll (l=e,μ)的機制衰變，造成四輕子之末態。這是LHC第一個針對激發態輕子於四輕子末態之搜尋。實驗結果並未超出標準模型背景的預期。激發態輕子的預期生成截面積受到T_3耦合因子f以及Y耦合因子f′的選擇影響。對於2e2μ之末態，當f/f^′=1 (f/f^′=-1)及在Λ=M_(l^)時，激發態電子與渺子之質量上限皆設在1.60(1.85) TeV於95%的信心水準。結合4e與4μ之實驗結果，激發態電子與渺子之質量上限可分別設在1.70(1.95) TeV以及1.75(2.00) TeV。;A search of excited lepton in 2e2μ fi nal state is performed using a data sample of pp collisions at a center-of-mass energy √s = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb-1. This is a part of the excited lepton search in 4-lepton final state in CMS. Excited leptons (l^) are assumed to be produced via contact interactions in conjunction with a standard model lepton and to decay via l^→lZ→lll (l=e,μ), yielding a fi nal state with four leptons. We present the first study of the search for excited lepton in 4-lepton fi nal state at LHC. No signi cant excess is observed in the data above the expected standard model background. The expect cross section of l^ can be signi cantly aff ected by diff erent choice of coupling constant f and f′ to T_3 and Y. For f/f′=1(f/f′=-1), upper bounds at 95% confi dence level are set to 1.60(1.85) TeV for both e^* and μ^* in 2e2μ fi nal state with Λ=M_(l^). Combining these results with 4e and 4μ channels, the limits can be set to 1.70(1.95) TeV and 1.75(2.00) TeV for e^ and μ^*, respectively.
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