大型強子對撞機CMS、ATLAS和ALICE實驗物理研究2013年度報告

陳國明++金山++周代翠

摘 要：該研究分為3個研究組，分別按照任務書2013年度計劃和要求展開研究，具體研究內容如下：（1）CMS研究組。①Higgs粒子確認及其性質研究：用2012全年數據測量H->YY的截面，并與標準模型預言相比較。在測量方法上將使用2D擬合提高靈敏度。②新物理尋找：尋找W->tb。與費米實驗室合作完成，我方將負責t->wb，W->enu部分。開展SUSY粒子尋找，Top粒子產生和衰變中的新物理研究。（2）ATLAS研究組。①ATLAS實驗中Higgs粒子的尋找：VBF Higgs衰變到雙光子道研究；H->γγ中Higgs微分產生截面測量；H->WW*物理分析。②ATLAS實驗中超對稱物理研究：di-tau末態弱相互作用SUSY粒子尋找；強相互作用SUSY粒子的尋找。③top夸克物理研究：單top夸克伴隨W玻色子產生過程尋找；單top夸克模擬；TrackMET重建研究；top衰變中的W自旋分布測量。（3）ALICE研究組。①圍繞夸克物質硬探針信號，通過觀測質子-質子碰撞、質子-核碰撞和核-核碰撞中的中性粒子產生、粒子關聯、重夸克和W玻色子的muon譜，以及部分子函數矩分布，檢驗QCD預言，建立核-核碰撞粒子譜壓低參考標準，研究冷核效應影響，觀測部分子在密度物質中的能量損失效應，研究夸克物質性質。②圍繞夸克物質集體運動，通過觀測高能核-核碰撞中phi粒子和多奇異重子的橢圓流、重夸克衰變muon粒子的橢圓流，研究夸克物質的熱化程度和集體運動行為，研究夸克物質體系部分子自由度行為。

關鍵詞：大型強子對撞機 CMS 希格斯粒子 ATLAS 超對稱

The 2013 Annual Report of the CMS、ATLAS and ALICE Physics Study at LHC Experiment

Chen Guoming1 Jin Shan1 Zhou Daicui2

（1.Institute of High Energy Physics， Chinese Academy of Sciences； 2.Central China Normal University）

Abstract：IHEP CMS group made a good contribution for both discovery and property measurement. As the production rate of Higgs to two gamma is very low， while the background rate is 12 magnitudes higher. To find Higgs in this channel is just like to dig out gold sand in a heap of normal sand. To reject the background effectively is the key for success. IHEP group provided the best method to reject background， and method was accepted by CMS. So we solved a key problem in the two gamma channel. When measuring the property， IHEP group participated both two gamma and 4 lepton channel analyses. In the two gamma channel， the mass and production rate was measured and the results are consistent with the Standard Model prediction. For the analysis we provided gamma identification method， a production rate scale factor from the interference of signal and background and gamma energy calibration. In the 4 lepton channel， the mass， production rate， couplings， spin and parity was measured. And the results all agree with the Standard Model prediction. Now all the particles predicted were found， the Standard Model gained a great success. But it can not explain what is dark matter， nor dark energy， and has no idea for the asymmetry between mass and anti-mass. People believe it is only an effective theory under a certain energy scale. Something beyond must exist， and we are going to find it. CMS IHEP group tried to do it through two ways， one is to search for new physics directly， the other is to check the Standard Model predictions， any violation could hint to a new physics. ATLAS Chinese Cluster （ACC） made leading contributions in many important physics topics， including study of Higgs particle， searches of SUSY particle and study of top quark physics. In the VBF Higgs production studies， ACC firstly applied MVA technique， which significantly improve the sensitivity of the analysis so that we observed the first evidence of VBF Higgs boson production in ATLAS experment. ACC firtly performed the analysis to search for SUSY particles in the di-tau final states which is sensitive to the stau particle searches， we also deeply involved in the SUSY search with one soft lepton final state. We played leading role in the above two SUSY analyses. ACC members are the editors of physics papers of the above Higgs and SUSY papers. ACC also made major contributions to the H->WW decays and top phsycis studies， including the single top production and top spin correlation measurements.

Key Words：LHC； CMS； Higgs boson； ATLAS； SUSY