【作者】 宋昴；

【导师】 马文淦；

【作者基本信息】 中国科学技术大学 ， 粒子物理与原子核物理， 2011， 博士

【摘要】 标准模型虽然取得了巨大的成功,但是它所预言的Higgs粒子一直没有找到。为了研究电弱对称性破缺机制,寻找Higgs粒子以及研究它的耦合性质,是目前和将来高能物理对撞机实验的最重要的目标之一。其中,研究Higgs的耦合特性是重建Higgs势的关键,这也将为确定标准模型以外的新物理模型提供有力的理论依据。在本文中,我们分别计算了大型强子对撞机(LHC)和国际直线对撞机(ILC)上Higgs与W对伴随产生过程的NLO QCD和电弱辐射修正,并且给出了次领头阶的总截面,以及末态粒子横动量和不变质量的分布等精确的理论预言。我们发现在LHC上,NLO QCD修正达到了50%,ILC上的NLO电弱修正最大也达到了负的百分之十几,这么显著的NLO修正的效应在将来的实验上是必须要考虑的。通过精确的理论预言,我们为LHC和未来的ILC上研究Higgs与W玻色子耦合特性的精确实验提供了理论支持。在NLO QCD修正的计算中,红外发散的处理是一个难点。这里,我们采用维数正规化来分离红外发散。其中,圈图中的红外发散,我们给出了解析的表达式,对于实辐射部分,我们采用两截断相空间分割(TCPSS)的方法进行了处理。重夸克偶素的衰变和产生的研究一直是粒子物理中的一个热点和前沿问题。非相对论量子色动力学(NRQCD)的因子化方法是目前许多研究重夸克偶素产生的理论工作中一个比较好的方法。NRQCD理论一个重要的特点是预言了色八重态的存在,并且非微扰部分的长程矩阵元不依赖于具体过程,具有普适性。J/ψ与W/Z玻色子伴随产生的过程,色八重态的贡献占主要地位,所以可以用来进一步检验色八重态机制和提取普适性的色八重态的长程矩阵元。另外,W,Z和J/ψ粒子都是通过纯轻子衰变来鉴别,这样可以大大压低强子对撞机上复杂的背景信号。最近,人们发现NLO QCD修正的贡献非常重要,通过次领头阶的计算,许多试验结果得到了很好的解释。在本文中,我们研究了LHC上J/ψ伴随W,Z粒子产生的(αs3v7)阶的贡献,给出了J/ψ粒子横动量的分布和对应的K-因子。在pp→J/ψ+ W + X过程的计算中,我们发现只有同时考虑了短程部分和长程矩阵元次领头阶的贡献后,该过程中出现的红外发散才可以完全消除。本论文研究中的主要创新之处如下:本文首次系统的研究了高能对撞机上H0W+W?伴随产生的过程,分别计算了LHC和ILC上该过程的QCD和电弱单圈修正,得到了该过程目前最精确的理论预言,这对于检验Higgs与W粒子的耦合性质有重要意义,为将来LHC和ILC上研究H0W+W?的产生信号提供了理论支持。在计算NLO QCD修正时,对于标量积分函数中的红外发散,我们采用了维数正规化(D = 4?2?)来分离红外发散,给出了包含红外发散的两点,三点,四点的标量积分函数的解析表达式。我们首次把这些解析结果添加进圈图计算的程序中,并且应用到其它的NLO QCD的计算过程。本文在NRQCD的理论下,我们首次研究了LHC上J/ψ与规范粒子W/Z伴随产生αs3v7阶的贡献,为研究色八重态机制和提取色八重态的长程矩阵元提供了理论支持。这里,我们统一采用维数正规化来处理紫外和红外发散。由于红外发散的种类比较复杂,我们完整的分析并给出了各部分红外发散相互消除的关系。更多还原

【Abstract】 Although the Standard Model (SM) achieves great success, the Higgs boson hasnot been discovered yet. The search for the Higgs boson and exploring the electroweaksymmetrybreakingmechanismarethemainmissionsforpresentandfuturehigh-energyexperiments. In order to reconstruct Higgs potential, the precise study of the couplingsbetween Higgs boson and other particles are necessary and their observable predictionswill provide strong support for exploring the new physics beyond the SM.In this thesis, we calculate the next-to-leading-order (NLO) Quantum Chromody-namics (QCD) and electroweak (EW) radiative corrections to Higgs boson productionassociatedwith a W boson pair at the LargeHadron Collider (LHC)and the Internation-al Linear Collider (ILC), respectively. We present the accurate theoretical predictionsfor the integrated cross sections, the distributions of invariant mass of W boson pairand the transverse momenta of final W and Higgs boson up to NLO. We find that theNLOQCDcorrectionstotheH0W+W? productionprocessattheLHCcanreach50%,and the NLO EW corrections to the H0W+W? production process at the ILC can alsoreach ?19% at most. Those corrections must be considered in the future experiments.The precise predictions for the Higgs production associated with a W pair at the LHCand the ILC will be very useful for probing the Higgs coupling with W bosons. Inthe calculations of the NLO corrections, we use dimensional regularization method toregularizetheinfrared(IR)divergences. Wegivealltheanalyticformulasofscalarone-loop integrals with the IR divergences in the virtual correction, and adopt the two-cutoffphase space slicing (TCPSS) method to isolate the IR divergences for the real emissionprocess.The decay and production of heavy quarkonium are important topics in heavyquarkonium physics. Non-relativistic quantum chromodynamics (NRQCD) is an at-tractive theory in heavy quarkonium physics. An important feature of the NRQCD isthe prediction of Color Octet. In order to investigate the effects of the Color OctetMechanism (COM) in heavy quarkonium, it is an urgent task to study the processeswhich heavily depend on the production mechanism. The J/ψproduction associatedwith a gauge boson at LHC, is a suitable process for studying COM. In high-energycollider experiments, W±, Z0 and J/ψcan be identified by using their purely leptonicdecays, whichareparticularlyusefulinhadroncolliders, becausetheyprovideanheavysuppression of the background. Recently, substantial progress has been achieved in the calculation of high order QCD corrections to J/ψhadroproduction and we find that theNLO effects are usually significant. In this thesis, we calculate the NLO QCD correc-tions to the associated J/ψproduction with a gauge boson in the NRQCD at the LHC.We present the distribution of the transverse momenta of J/ψand the correspondingK-factor. For the process pp→J/ψ+ W + X, we find that when we take into ac-count both the NLO short-distance part and long-distance matrix contributions, the IRdivergences can be completely eliminated.In this thesis, there are the following innovations:Inthisthesis,wehavesystematicallystudiedtheHiggsproductionassociatedwitha W pair at the high-energy collider, and calculated NLO QCD and electroweakcross sections at LHC and ILC, respectively. We present the most accurate the-oretical predictions of this process so far, which will provide theoretical supportfor the test of the H0W+W? coupling at the LHC and the ILC.We use dimensional regularization (D = 4?2?) to regularize the IR divergencesand give all the related analytical formulas of bubble, triangle and box integralswithinfrareddivergences. WefirstaddedtheseanalyticalresultstotheLoopToolsprogram, which can also be applicable to other processes.Inthisthesis, wefirstcalculatetheJ/ψproductionassociatedwithagaugebosonat the LHC up toαs3v7 order within the NRQCD framework, which is useful forstudying COM and the universal LDMEs. Here, we use the dimensional regu-larization method to regularize UV and IR divergences. As the structures of theIR divergences are very complex, we have analyzed the IR divergences from allparts, and demonstrated an overview of the IR singularity structure.更多还原