在8TeV質心能量的質子對撞實驗中尋找頂夸克衰變到希格斯波色子與魅夸克的事件

Search for top decays Charm and Higgs through flavor changing neutral current process in CMS

邱奕寰(I-Huan Chiu)

指導教授 ： 張寶棣

國立臺灣大學/理學院/物理研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.01352

摘要

摘要
在標準模型中，頂夸克經由希格斯波色子以及魅夸克的衰變事件是被抑制的，
此事件的衰變比率被預測只有0.9x10-13，但在其他模型中預測此事件仍在可以
觀測的範圍。
在本實驗中，我們將藉由希格斯波色子衰變至兩個底夸克的過程，嘗試尋找頂
夸克衰變至希格斯波色子以及魅夸克的事件，而本實驗中所使用的數據為緊湊
緲子線圈在2012 年紀錄的質心能量為8TeV 之對撞數據，總通量為19.8fb-1。
經由在數據中所觀察到，滿足本次實驗選擇的背景以及訊號，可以計算出頂夸
克經由希格斯波色子以及魅夸克的衰變比率在95%的信心水準之下將不超過
0.98%。
我們期待能有更多的數據來證實本衰變事件的衰變比率。
關鍵字:大型強子對撞機，緊湊緲子線圈，希格斯波色子，味變中性流，頂夸
克，希格斯波色子衰變至底夸克對

關鍵字

大型強子對撞機 ； 緊湊緲子線圈 ； 希格斯波色子 ； 味變中性流 ； 頂夸克 ； 希格斯波色子衰變至底夸克對

並列摘要

Abstract
The Standard Model shows that branching fraction of flavor-changing
neutral Higgs is 0.9 times 10−13 that means the FCNH process is be
highly suppressed in SM. However, the two Higgs doublet model provides
the branching fraction of FCNH can be 2.6 × 10−3, that is much larger
than the one from Standard Model. This study is a search for the the
branching fraction of t ! H + c, it’s interesting that might has the
new physics different from Standard Model if the BR(t ! H + c) is
larger than the one be predicted from SM. The branching fraction of
higgs to b‾b channel is the highest one of all higgs decay channel which
is about 60% where higgs mass is 125GeV, that the large efficiecy for
signal is expectable. Therefore, this study is the searching for FCNH
where higgs decay to b‾b channel with the integrated luminosity of about
19.8 fb−1 proton-proton collision data sample at a center-of-mass energy
p
s = 8TeV collected with the CMS detector. The observed upper limit
calculted by the Higgs Combination Tool package with the Asymptotic
method at 95% confidence level is 9.8 × 10−3 and the expected upper
limit is 8.6 × 10−3 with the corresponding 1-¾ and 2-¾ bound which are
[0.58%, 1.36%] and [0.42%, 2.16%]. The more powerful verification for
the two Higgs doublet model can be provided with more data.

並列關鍵字

LHC ； CMS ； Higss ； FCNH ； top ； higgs to bb

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