【作者】 杨扬；

【导师】 朱相雷；

【作者基本信息】 清华大学 ， 物理学， 2018， 硕士

【摘要】 质子-质子碰撞中重夸克偶素的产生截面测量为检验描述夸克和胶子之间强相互作用的量子色动力学(QCD)理论提供了重要信息。ψ(2S)粒子是一种粲夸克偶素,由于受更高质量粲偶素激发态退激发的影响较小,其产生截面可以直接同QCD理论比较,对于检验QCD理论是一个理想的粒子。欧洲核子研究中心(CERN)大型强子对撞机(LHC)上的LHCb探测器于2015年11月份采集了共8.11 pb-1的质心系能量为5 TeV的质子-质子碰撞数据,本论文利用这些数据,通过ψ(2S)→μ-+衰变道精确测量了(?)=5TeV质子-质子碰撞中瞬时产生的ψ(2S)和从b强子衰变产生的ψ(2S)的微分产生截面。测量的运动学区间为横动量pT<12GeV/c和快度2.0<y<4.5。在测量的整个运动学区间内的总截面实验结果分别为:σ(瞬时ψ(2S))=1.71±0.03(统计)±0.10(系统)μbσ(b强子衰变ψ(2S))=0.29±0.01(统计)±0.02(系统)μb与QCD理论计算比较,非相对论性QCD(NRQCD)的理论计算与瞬时ψ(2S)关于pT的一维微分散射截面测量结果在理论适用的pT>5 GeV/c时符合得很好;FONLL微扰QCD的理论计算与b强子衰变的ψ(2S)产生截面的测量结果符合得很好。更多还原

【Abstract】 Measurements of heavy quarkonium productions in proton-proton collisions provide important test for the theory of Quantum Chromodynamics(QCD),which describes the strong interactions between quarks and gluons.ψ(2S)is one of the cc quarkonia.It has no appreciable feed-down contributions from higher mass states,so its production cross-sections can be directly compared with QCD,making it an ideal laboratory for testing the theory.The Large Hadron Collider(LHC)at Conseil European Pour Recherches Nucleaires(CERN)is the world s largest and most powerful particle collider.The LHCb experiment is one of the four main experiments at the LHC.In this thesis,the differential production cross-sections of prompt and delayed(from b hadron decay)ψ(2S)in proton-proton collisions at a centre-of-mass energy((?))of 5 TeV are precisely measured through theψ(2S)→μ-μ+ decay channel in the kinematic range of transverse momentum pT<12 GeV/c and rapidity 2.0<y<4.5,using a data sample with the integrated luminosity of 8.11 pb-1 collected by the LHCb detector in November,2015.The integrated cross-sections of prompt ψ(2S)and ψ(2S)from b hadron decay within the whole measured kinematic range are:σ(prompt ψ(2S))=1.71±0.03(stat)±0.10(syst)μbσ(ψ(2S)fromb)=0.29±0.01(stat)±0.02(syst)μbThe experimental data are compared with the QCD theoretical calculations.A good agreement is observed between the Non-relativistic QCD(NRQCD)calculations and the measured prompt ψ(2S)cross-sections for pT>5 GeV,where NRQCD calculations are available.The FONLL perturbative QCD calculations are consistent with the measured cross-sections of ψ(2S)from b hadron decays within the whole measured kinematic range.更多还原