以大型強子對撞機裡的緊湊渺子線圈偵測器尋找重夸克在半輕子頻道衰變成頂夸克和光子;Search for pair production of a heavy quark decaying into top quark and photon in semi-leptonic channel with the CMS detector in the LHC

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/65273

Title:	以大型強子對撞機裡的緊湊渺子線圈偵測器尋找重夸克在半輕子頻道衰變成頂夸克和光子;Search for pair production of a heavy quark decaying into top quark and photon in semi-leptonic channel with the CMS detector in the LHC
Authors:	張祐祥;Chang,Yu-hsiang
Contributors:	物理學系
Keywords:	重夸克;緊湊渺子線圈;大型強子對撞機;頂夸克;光子;heavy quark;CMS;LHC;top quark;photon
Date:	2014-07-21
Issue Date:	2014-10-15 14:48:16 (UTC+8)
Publisher:	國立中央大學
Abstract:	我們使用CMS在2012年所蒐集的積分亮度為19.7-1 fb、LHC質子對撞質心能量為8 TeV的數據來找尋激發態頂夸克。在我們分析中的衰變過程和最終產物是：激發態頂夸克、反激發態頂夸克->頂夸克、光子、反頂夸克、光子->底夸克、W玻色子、光子、反底夸克、W玻色子、光子，然後其中一個W玻色子以輕子的方式衰變而另一個W玻色子以夸克的方式衰變，所以我們藉著要求事件中有兩個光子、一個輕子和至少四個噴流來定義訊號區域。χ2排序法被用來重建激發態頂夸克的質量，並且從數據中有十二個事件在訊號區域被觀察到。矩陣法被用在兩個光子的頻道裡來估計這十二個事件中的背景貢獻。這個研究的結果是沒有顯著的超過預期的多餘事件被觀察到，所以對於激發態頂夸克的質量我們以95%的信心水準設了一個低限在969 GeV/c2。;Using the data collected by the CMS detector in 2012, corresponding to a luminosity of 19.7 / fb of proton-proton collisions at LHC center-of-mass energy of 8 TeV, we search for the excited top quark, T. The decay process and the final states studied in our analysis are: T Tbar -> t γ tbar γ -> b W+ γ bbar W- γ, where one W boson decays hadronically and the other leptonically, so we define a signal region by requesting events with 2 photons, 1 lepton and >= 4jets. To reconstruct the invariant mass of T, a χ2-sorting method is used and 12 events are observed in the signal region from data. The matrix method is used to estimate the background contribution among the observed 12 events in the di-photon channel. As a result of this study, no significant excess is observed over expectations and a lower limit is set on a t* quark mass of 969 GeV/c2 at 95% confidence level.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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