导读:本文包含了双玻色子论文开题报告文献综述及选题提纲参考文献，主要关键词:粒子物理,ATLAS实验,ZZ,标准模型
双玻色子论文文献综述
徐来林[1]（2015）在《ATLAS实验上ZZ双玻色子产生的物理研究》一文中研究指出在大型强子对撞机LHC上的质子-质子对撞中,有多种物理机制可以产生ZZ双玻色子末态。利用Z玻色子的轻子衰变(Z→ll)和中微子衰变(Z→vv),即双轻子和丢失横动量的实验末态,本论文研究了ATLAS实验上在质心系对撞能量为8TeV下采集的ZZ事例,总积分亮度为20.3fb-1。首先,利用ZZ→llvv衰变道,我们测量了标准模型下ZZ产生的反应截面。这一产生过程在粒子物理标准模型下可以进行精确的理论计算,通过实验测量,我们可以与标准模型的预言相比较,验证理论计算。实验测得的8TeV能量下ZZ产生的总截面为σZZtot=8.84-0.88+1.04(stat.)-0.85+0.87(syst.)-0.28+0.33(lumi.)pb；而在NLO精度下的理论预言结果为6.58-0.28+0.30pb；两者相差为1.8个标准差。在最新的NNLO QCD修正下,理论计算结果为7.74-0.31+0.35pb,与我们的测量结果符合的更好。我们还进一步利用实验数据寻找了叁玻色子异常耦合对ZZ产生的可能贡献。由于在实验上没有观察到与标准模型预言的明显偏差,我们给出了异常耦合参数的上限值。与ATLAS先前发表的实验结果相比,我们获得了对异常耦合最严格的限制。2012年在LHC上发现的希格斯(Higgs)粒子被发现同样具有离壳效应(off-shell),这一效应在Higgs质量高于2倍于Z玻色子质量(2mz)的范围内可以被观察到,并对ZZ事例的产生增加额外的贡献。因此H*→ZZ衰变提供了一个独特的机制来测量Higgs粒子的离壳耦合强度。利用ZZ→llvv末态,在95%的置信水平下,Higgs离壳信号强度的上限被确定为在9.6-12.4的范围内,预期的上限区间为8.8-13.3。进一步与ZZ→4l及WW→evμv衰变道的实验结果相结合,我们观察到(预期)的约束范围为5.1-8.6(6.7-11.0)。在每种情况下,上限范围是通过改变未知gg→ZZ和gg→WW本底的高阶QCD修正因子与已知的gg→H→ZZ和gg→H→WW信号的高阶QCD修正因子之间的比值来确定的,并且这一比值的变化区间为0.2-2。假设相关的Higgs的耦合是独立于Higgs生产的能标,与在壳(on-shell)测量的耦合强度相结合,我们可以进一步限制Higgs粒子的总的质量宽度ΓH。在95%的置信水平下,我们获得的观察(预期)的ΓH/THSM范围是4.5-7.5(6.5-11.2)。假定未知的gg→VV本底的高阶QCD修正因子与信号的相同,这一结果可以转化成Higgs总宽度在95%的置信水平下的上限,即观察(预期)结果为22.7(33.0)MeV。最后,基于H→ZZ→llvv衰变,我们寻找了质量在240和1000GeV之间的新的Higgs粒子。实验数据与本底假设相符合,我们设定了在双Higgs二重态模型(2HDM)中的额外Higgs粒子产生的截面的上限。在这一模型中,tanβ的很大一部分范围被排除了,并且排除范围取决于cos(β-α)；对于cos(β-α)=±0.1,tanβ<1的区域,在95%的置信水平下,Higgs质量在250-350GeV区间内被排除了。我们还提供了独立于任何物理模型的关于Higgs产生截面与H→ZZ分支比的乘积的上限。在胶子-胶子融合(ggG)反应道下,对于一个质量为400GeV的Higgs粒子,σggF×BΥH→ZZ在95%的置信水平下的上限为227fb,预期的上限为209fb。在矢量玻色子融合(VBF)反应道下,σggF×BΥH→ZZ在95%的置信水平下的上限为248fb,预期的上限为136fb。(本文来源于《中国科学技术大学》期刊2015-05-01）
吴雨生[2]（2012）在《大型强子对撞机ATLAS探测器上对WZ双玻色子产生截面的测量以及相关新物理过程的探索》一文中研究指出This dissertation presents my research work with the ATLAS experiment at the Large Hadron Collider (LHC). The LHC is built in a circular tunnel of27km in circumference buried around50to175m underground and straddles the Swiss and French borders on the outskirts of Geneva. It is designed to produce proton-proton collisions at center-of-mass energy (CME) of14TeV with peak luminosity of1034cm-2s-1. ATLAS is a particle physics experiment at the LHC. The ATLAS detector is a state of art general purpose detector with almost4π coverage to detect particles created in the proton-proton collisions from the LHC. The LHC is a dream machine for particle physicists to create particles that existed about0.001ns after Big Bang, the start of the universe. Research conducted in experiments at the LHC will significantly advance our understanding how our universe works at its most fundamental level. My thesis work has focused on studies of the vector boson pair, W±Z, productions at the LHC to search for new physics through the measurements of the W±Z production cross-section and the triple-gauge couplings.The LHC and the ATLAS detector have been operated remarkably since fall of2009. The peak luminosity of the LHC increased from2x1029cm-2s-1to7.7×1033cm-2s-1, more than4orders of magnitude increase over past three years. With over93%data taking efficiency, ATLAS has collected data with an integrated luminosity of5fb-1at7TeV in2011, and15fb-1at8TeV up to Sept.2012. Using data collected in2011this thesis work has made the first measurement at the LHC on W±Z production cross-section, which is one of the major milestones of the LHC physics programs as the steppingstone for discovery of new physics at TeV energy scale. Using this data-set, the most stringent limits on the anomalous triple gauge boson couplings (TGCs) of the WWZ vertex are set. The massive new resonance productions are searched in the WZ mass spectrum. No evidence of new physics beyond the standard model (SM) is observed.The measurements of the WZ production cross-section provide a test of the non-Abelian SU(2)×U(1) gauge structure of the SM electroweak theory, and the understanding of the background for the Higgs searches. The WZ production cross section is measured from leptonic decay channels, namely the combination of Z→ee (μμ) and W→eve (μvμ): eeev, eeμv, evμμ and μμμv final states. Major background of this measurement comes from other physics processes, such as ZZ, Z+jets and Top. Data-driven method is developed to estimate the background contributions from Z+jets and Top, while The background from ZZ is estimated from MC simulation. The total WZ production cross-section is measured to be19.0-1.3+1.4(stat)±0.9(syst.)±0.4(lumi.) pb, based on total317events selected from data and68±10estimated background. The uncertainty of the measurement is much smaller as compared to that of previous measurements from Tevatron at1/2s=1.96TeV.The measurements of TGCs provide a sensitive probe for new physics at high energy scale beyond the SM. The anomalous triple gauge boson couplings (aTGC) are probed from the WZ events by comparing the observed transverse momentum spectrum of the Z boson with that of the theoretical predictions with aTGC. Data agree with the SM prediction from the likelihood fit, which results in confidence intervals at95%C.L. on aTGC as△g1Z∈[-0.057,0.093],△kZ∈[-0.37,0.57] and λZ∈[-0.046,0.047]. These limits are much more stringent compared to the previous measurements at Tevatron.Many physics models predict new particles decaying to WZ final state. A search for high mass WZ resonance is carried out using the same data-set. The invariant mass of the WZ system is reconstructed using measured energies and momenta of leptons and missing energy constrained to the W mass. To avoid event selection bias, a blinded analysis approach is used. In this analysis a control region is defined, where potential new physics signal is minimal. Only when the principal background from the known physics process is understood in the control region we unblind the analysis in the signal region to search for new resonance. No new physics is observed in the signal region. The result is interpreted as cross-section limits on new gauge boson W' from Extend Gauge Models (EGM) and ρτ from Low Scale Technicolor model (LSTC). The lower limit on W' mass is1.1TeV, and580GeV for ρτ at95%C.L.Searching for new physics at the LHC is still at its early stage in terms of luminosity and energy of the LHC. The methods and techniques developed in this thesis work have paved the way for the continued searches with ATLAS experiment at the LHC.(本文来源于《中国科学技术大学》期刊2012-11-01）
李数[3]（2012）在《ATLAS探测器上W~+W~-双玻色子产生截面的测量》一文中研究指出ATLAS探测器是欧洲核子中心的大型强子对撞机项目(LHC)的主探测器之一。基于高能粒子(质子束)的对撞和探测器数据采集,相关的高能标下基本粒子相互作用及性质的精确测量以及对新物理尤其是Higgs玻色子的寻找成为了可能。该论文的工作采用了ATLAS所采集的4.7fb-1积分亮度的7TeV(质心能量)质子-质子对撞数据,对标准模型电弱相互作用所产生的W+W-双玻色子双轻子衰变末态进行了研究,进而对W+W-产生截面进行了前所未有的新能标下的精确测量和叁玻色子耦合的研究。主要内容包括：利用双轻子衰变到对总产生截面的测量,基于高动量轻子末态横动量谱的微分截面测量,W+W-Z和W+W-γ的三玻色子耦合系数测量。(本文来源于《中国科学技术大学》期刊2012-11-01）
张沛,蒋一,汪虎林[4]（2011）在《LHC实验中双玻色子W~(±)Z产生截面测量(英文)》一文中研究指出欧洲核子中心(CERN)建造的大型强子对撞机(LHC)是槡s=14TeV的质子-质子对撞.在LHC上的ATLAS实验中,通过对衰变末态中的电子和缪子的分析,研究了标准模型理论中的双玻色子W±Z产生截面的灵敏性.同时,通过Monte Carlo模拟数据样本,也研究了双玻色子信号测量中本底的影响.研究表明,在最初的0.1fb-1积分亮度下,标准模型双玻色子W±Z信号的灵敏度可以好于5σ.(本文来源于《中国科学技术大学学报》期刊2011年01期）
张沛[5]（2009）在《ATLAS探测器上双玻色子WZ产生截面的精确测量》一文中研究指出本论文通过Monte-Carlo模拟数据测量双玻色子W±Z的产生截面,来检验粒子物理中的标准模型。标准模型预言W+Z的产生截面是29.4 pb,W?Z的产生截面是18.4 pb。欧洲核子中心(CERN)所建造的大型强子对撞机(LHC)提供了中心能量为14TeV的质子-质子对撞束流,运行在LHC上的ATLAS探测器被用来探测W和Z粒子。双玻色子WZ的研究利用了ATLAS CSC模拟数据,其中包括了触发信息、探测器刻度和位置修正。双玻色子WZ的测量是通过测量W和Z衰变产生的叁轻子末态(eeνe, eeμν,μμeν,和μμμν)进行的,其中W衰变到一个带电轻子和中微子,Z衰变到一对电荷符号相反的轻子对。有关WZ事例的判选、探测效率和本底压制都将详细讲述。经过分析,对于积分亮度1 fb?1的数据,我们可以观测到53个W±Z信号事例和8个本底事例,信噪比达到了6.7。双玻色子W±Z在pp→WZ + X( S = 14 TeV)时的测量截面为:σ?Br =53. 43?+160.5.0fb(包含了事例判选效率),这和标准模型的理论预言是相符合的。最后介绍了数据分析过程中使用的一种新的统计学方法:Boosted Decision Tree (BDT),以及如何利用TMVA (Toolkit for Multivariate Analysis)软件包进行BDT物理分析。(本文来源于《中国科学技术大学》期刊2009-04-16）
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This dissertation presents my research work with the ATLAS experiment at the Large Hadron Collider (LHC). The LHC is built in a circular tunnel of27km in circumference buried around50to175m underground and straddles the Swiss and French borders on the outskirts of Geneva. It is designed to produce proton-proton collisions at center-of-mass energy (CME) of14TeV with peak luminosity of1034cm-2s-1. ATLAS is a particle physics experiment at the LHC. The ATLAS detector is a state of art general purpose detector with almost4π coverage to detect particles created in the proton-proton collisions from the LHC. The LHC is a dream machine for particle physicists to create particles that existed about0.001ns after Big Bang, the start of the universe. Research conducted in experiments at the LHC will significantly advance our understanding how our universe works at its most fundamental level. My thesis work has focused on studies of the vector boson pair, W±Z, productions at the LHC to search for new physics through the measurements of the W±Z production cross-section and the triple-gauge couplings.The LHC and the ATLAS detector have been operated remarkably since fall of2009. The peak luminosity of the LHC increased from2x1029cm-2s-1to7.7×1033cm-2s-1, more than4orders of magnitude increase over past three years. With over93%data taking efficiency, ATLAS has collected data with an integrated luminosity of5fb-1at7TeV in2011, and15fb-1at8TeV up to Sept.2012. Using data collected in2011this thesis work has made the first measurement at the LHC on W±Z production cross-section, which is one of the major milestones of the LHC physics programs as the steppingstone for discovery of new physics at TeV energy scale. Using this data-set, the most stringent limits on the anomalous triple gauge boson couplings (TGCs) of the WWZ vertex are set. The massive new resonance productions are searched in the WZ mass spectrum. No evidence of new physics beyond the standard model (SM) is observed.The measurements of the WZ production cross-section provide a test of the non-Abelian SU(2)×U(1) gauge structure of the SM electroweak theory, and the understanding of the background for the Higgs searches. The WZ production cross section is measured from leptonic decay channels, namely the combination of Z→ee (μμ) and W→eve (μvμ): eeev, eeμv, evμμ and μμμv final states. Major background of this measurement comes from other physics processes, such as ZZ, Z+jets and Top. Data-driven method is developed to estimate the background contributions from Z+jets and Top, while The background from ZZ is estimated from MC simulation. The total WZ production cross-section is measured to be19.0-1.3+1.4(stat)±0.9(syst.)±0.4(lumi.) pb, based on total317events selected from data and68±10estimated background. The uncertainty of the measurement is much smaller as compared to that of previous measurements from Tevatron at1/2s=1.96TeV.The measurements of TGCs provide a sensitive probe for new physics at high energy scale beyond the SM. The anomalous triple gauge boson couplings (aTGC) are probed from the WZ events by comparing the observed transverse momentum spectrum of the Z boson with that of the theoretical predictions with aTGC. Data agree with the SM prediction from the likelihood fit, which results in confidence intervals at95%C.L. on aTGC as△g1Z∈[-0.057,0.093],△kZ∈[-0.37,0.57] and λZ∈[-0.046,0.047]. These limits are much more stringent compared to the previous measurements at Tevatron.Many physics models predict new particles decaying to WZ final state. A search for high mass WZ resonance is carried out using the same data-set. The invariant mass of the WZ system is reconstructed using measured energies and momenta of leptons and missing energy constrained to the W mass. To avoid event selection bias, a blinded analysis approach is used. In this analysis a control region is defined, where potential new physics signal is minimal. Only when the principal background from the known physics process is understood in the control region we unblind the analysis in the signal region to search for new resonance. No new physics is observed in the signal region. The result is interpreted as cross-section limits on new gauge boson W' from Extend Gauge Models (EGM) and ρτ from Low Scale Technicolor model (LSTC). The lower limit on W' mass is1.1TeV, and580GeV for ρτ at95%C.L.Searching for new physics at the LHC is still at its early stage in terms of luminosity and energy of the LHC. The methods and techniques developed in this thesis work have paved the way for the continued searches with ATLAS experiment at the LHC.
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双玻色子论文参考文献
[1].徐来林.ATLAS实验上ZZ双玻色子产生的物理研究[D].中国科学技术大学.2015
[2].吴雨生.大型强子对撞机ATLAS探测器上对WZ双玻色子产生截面的测量以及相关新物理过程的探索[D].中国科学技术大学.2012
[3].李数.ATLAS探测器上W~+W~-双玻色子产生截面的测量[D].中国科学技术大学.2012
[4].张沛,蒋一,汪虎林.LHC实验中双玻色子W~(±)Z产生截面测量(英文)[J].中国科学技术大学学报.2011
[5].张沛.ATLAS探测器上双玻色子WZ产生截面的精确测量[D].中国科学技术大学.2009