TC2模型中顶夸克的FCNC衰变和在LHC上的产生
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摘要
在过去的几十年里,实验和理论的惊人吻合表明标准模型在描述电弱物理方面是成功的,例如发现了规范玻色子W,Z,粲,底,顶夸克以及解决了曾经引起物理学家普遍关注的Rb,Rc问题,但是,标准模型也存在着问题,它没有给出中微子质量,不能提供暗物质的候选者,存在规范等级,平庸性等一系列问题.因此,标准模型只能作为一个低能有效理论,在某一能标之上的东西需引入新的理论来解释。
顶夸克是标准模型中最重的费米子,巨大的顶夸克质量为研究其他大质量粒子提供了条件,而且,在顶夸克的产生和衰变过程中极有可能探测到新物理信号。因此顶夸克将是探测新物理的有效的手段。目前,由于费米实验室的Tevatron对撞机发现的顶夸克事例数还很少,这为新物理探测顶夸克的性质提供了很大的空间.LHC的能量很高,是一个很大的顶夸克工厂,可以获得大量的统计事例,因此很多顶夸克相关的新物理研究都可以在这里展开.
作为新物理的一个候选者,顶色辅助的Technicolor(TC2)理论尝试不用Higgs场,而另外引入一种强相互作用(Technicolor)来代替,同时考虑Technicolor和Topcolor作用,其中前者提供电弱对称破缺,而后者则用来产生大的顶夸克质量.TC2模型预言了一些中性标量玻色子,例如top-pions和top-Higgs,这些标量粒子在树图结构有顶夸克味改变中性流(FCNC)耦合,在这些FCNC耦合中顶-粲夸克耦合起主要作用.我们的工作主要是在TC2模型框架下围绕着顶夸克的产生和衰变展开的.主要包括:LHC上顶夸克产生,LHC伴有中性标量粒子的单顶夸克产生,以及顶夸克的FCNC衰变。
In the past decades, the remarkable agreement of experiment with theory testifies the correctness of the Standard Model (SM) in describing the electroweak physics. However, the theoretical defects of the SM itself suggest the existence of new physics. In general, new physics may significantly affect electroweak observables. Studying such effects to probe new physics is the main goal of this thesis.
As the heaviest fermion in the Standard Model (SM), the top quark may be a sensitive probe of new physics. So far there remain plenty of room for new physics in top quark sector due to the small statistics of the top quark events at the Fermilab Tevatron colMder.Since the upcoming Large Hadron Collider (LHC) at CERN will produce top quarks copiously and allow to scrutinize the top quark nature, the new physics related to the top quark will be either uncovered or stringently constrained.
The topcolor-assisted technicolor (TC2) model combines technicolor interaction with topcolor interaction, with the former being responsible for electroweak symmetry breaking and the latter for generating large top quark mass.The TC2 predicts a number of neutral scalar bosons like the top-pions and top-Higgs at the weak scale [?]. These scalars have flavor-changing neutral-current(FCNC) top couplings at tree-level, among which the top-charm FCNC couplings are most significant. We studied the top-quark productions at LHC in TC2,single top production associated with a neutral scalar at LHC in TC2 and top quark FCNC decay in TC2.
顶夸克是标准模型中最重的费米子,巨大的顶夸克质量为研究其他大质量粒子提供了条件,而且,在顶夸克的产生和衰变过程中极有可能探测到新物理信号。因此顶夸克将是探测新物理的有效的手段。目前,由于费米实验室的Tevatron对撞机发现的顶夸克事例数还很少,这为新物理探测顶夸克的性质提供了很大的空间.LHC的能量很高,是一个很大的顶夸克工厂,可以获得大量的统计事例,因此很多顶夸克相关的新物理研究都可以在这里展开.
作为新物理的一个候选者,顶色辅助的Technicolor(TC2)理论尝试不用Higgs场,而另外引入一种强相互作用(Technicolor)来代替,同时考虑Technicolor和Topcolor作用,其中前者提供电弱对称破缺,而后者则用来产生大的顶夸克质量.TC2模型预言了一些中性标量玻色子,例如top-pions和top-Higgs,这些标量粒子在树图结构有顶夸克味改变中性流(FCNC)耦合,在这些FCNC耦合中顶-粲夸克耦合起主要作用.我们的工作主要是在TC2模型框架下围绕着顶夸克的产生和衰变展开的.主要包括:LHC上顶夸克产生,LHC伴有中性标量粒子的单顶夸克产生,以及顶夸克的FCNC衰变。
In the past decades, the remarkable agreement of experiment with theory testifies the correctness of the Standard Model (SM) in describing the electroweak physics. However, the theoretical defects of the SM itself suggest the existence of new physics. In general, new physics may significantly affect electroweak observables. Studying such effects to probe new physics is the main goal of this thesis.
As the heaviest fermion in the Standard Model (SM), the top quark may be a sensitive probe of new physics. So far there remain plenty of room for new physics in top quark sector due to the small statistics of the top quark events at the Fermilab Tevatron colMder.Since the upcoming Large Hadron Collider (LHC) at CERN will produce top quarks copiously and allow to scrutinize the top quark nature, the new physics related to the top quark will be either uncovered or stringently constrained.
The topcolor-assisted technicolor (TC2) model combines technicolor interaction with topcolor interaction, with the former being responsible for electroweak symmetry breaking and the latter for generating large top quark mass.The TC2 predicts a number of neutral scalar bosons like the top-pions and top-Higgs at the weak scale [?]. These scalars have flavor-changing neutral-current(FCNC) top couplings at tree-level, among which the top-charm FCNC couplings are most significant. We studied the top-quark productions at LHC in TC2,single top production associated with a neutral scalar at LHC in TC2 and top quark FCNC decay in TC2.
引文
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[2]M.Schmaltz(Boston U.),Nucl.Phys.Proc.Suppl.,2003,117:40.hep-ph/0210415.
[3]TESLA Technical Design Report Part Ⅰ:Executive Summary,hep-ph/0106314;
[4]E.H.Simmons,BUHEP-00-23,hep-ph/0011244.
[5]DO Collaboration,Nature,2004,429:638-642.hep-ex/0406031.
[6]D.Chakraborty,J.Konigsberg,D.Rainwater,Ann.Rev.Nucl.Part.Sci.2003,53:301-351 hep-ph/0303092.
[7]Top Mass Measurements at the Tevatron Run Ⅱ,G.V.Velev,hep-ex/0510007.
[8]Reinhard Schwienhorst,for the DO,CDF collaborations,hep-ex/0411041.
[9]Review of Recent Top Quark Measurements,A.P.Heinson,hep-ex/0502023.
[10]Measurement of the Top Quark Mass In All-Jet Events,DO Collaboration,V.M.Abazov,et al.,PLB 606(2005)25-33,hep-ex/0410086.
[11]Combination of CDF and DO Results on the Top-Quark Mass,The CDF Collaboration,the DO Collaboration,the Tevatron Electroweak Working Group,hep-ex/0507091.
[12]Top quark mass and properties at the Tewtron,J.-F.Arguin,for the CDF,DO Collaborations,hepex /0507106.
[13]R.Bonciani,S.Catani,M.L.Mangano,P.Nason,Nucl.Phys.B,1998,529:424-450,hep-ph/9801375.
[14]N.Kidonakis,E.Laenen,S.Moch,R.Vogt,Phys.Rev.D,2001,64:114001,hep-ph/0105041.
[15]T.M.Liss,hep-ph/9510274;M.Beneke,et.al.,hep-ph/0003033.
[16]R.H.Dalitz,G.R.Goldstein,Proc.Roy.Soc.Lond.A,1999,455:2803,hep-ph/9802249.
[17]G.Mahlon,S.J.Parke,Phy.Let.B,1995,347:394,hep-ph/9412250.
[18]G.Unal,L.Fayard,"Prospecte for Top Search and Top Mass Measurements at the LHC",in Large Hadron Collider Workshop,Proceedings Vol.Ⅱ,CERN 90-10,pp.360-413.
[19]D.Froidevaux,Top Quark Physics at LHC/SSC,preprint CERN/PPE/93-148,1993.