Top-Higgs和top-charm在高能正负电子对撞机上的联合产生

在顶色辅助的人工色(TC2)模型框架下, 研究了top-Higgs和t-c夸克的联合产生过程e⁺e^-→tch_t⁰.结果显示此过程的产生截面在合理的参数空间内可达到10fb, 在高能直线对撞机(LC)上每年可产生几百个事例. 通过此过程可用来探测top-Higgs.     

高能e+e-对撞机上top介子辅助的b夸克对产生

在顶色辅助的人工色模型下计算了高能e^ e^-对撞机上top介子辅助的b夸克对产生过程e^ e^-→bb^-π^0t的产生截面．发现在一定的参数范围内，这个过程的产生截面大于lOfb，比标准模型下标量Higgs粒子辅助的b夸克对产生过程大许多，与最小超对称模型下标量和赝标量Higgs粒子h^0，H^0，A^0的相应产生截面大致相当．人工色理论的信息可能在下一代正负电子对撞实验中探测到．     

高能e+e－对撞机上top介子辅助的b夸克对产生

在顶色辅助的人工色模型下计算了高能e⁺e^－对撞机上top介子辅助的b夸克对产生过程e⁺e^－→bbπ0t的产生截面.发现在一定的参数范围内,这个过程的产生截面大于10fb,比标准模型下标量Higgs粒子辅助的b夸克对产生过程大许多,与最小超对称模型下标量和赝标量Higgs粒子h⁰,H⁰,A⁰的相应产生截面大致相当.人工色理论的信息可能在下一代正负电子对撞实验中探测到.     

Top介子与HERA和THERA对撞机上的单顶夸克产生

讨论计算了TC2模型预言的Top介子在HERA和构想中的THERA对撞机上对t道eq→et过程中的单顶夸克产生的贡献.结果表明:中性Top介子对ec→et过程中的单顶夸克产生有较大的贡献.在绝大部分参数空间内,过程的产生截面在1—6pb范围内,因此,在HERA和THERA对撞机上通过eq→et过程可探测中性Top介子的可能物理迹象     

TC2理论在LC实验中的可能物理迹象

在高能e⁺e^－碰撞实验(LC)中，研究了顶色辅助的人工色(TC2)理论所预言的中性top介子 的产生. 结果表明，在LC实验中通过过程e⁺e^－→tc, e⁺e^－→γtc和e⁺e^－→Ztc可以探测到πt0的物理迹象.     

强子对撞机上中性top-pion介子产生过程的研究pp（pp-）∏0t∏0t,b∏0t的研究

在TC2模型框架下研究了强子对撞机Tevatron和LHC上中性top-pion介子∏0t的产生过程pp（p-p）→∏0t∏0t和pp（p-p）→b∏0t.研究结果表明,在Tevatron上,这两个过程的产生截面都很小,通过这两个过程我们无法探测到中性top-pion介子.在LHC上,产生截面会大大增加,但通过∏0t∏0t的产生仍无法探测到中性top-pion介子.b∏0t在LHC上的产生截面能达到几百个fb甚至pb的量级,LHC每年能产生104-105个b∏0t事例.另外,味改变耦合∏0tt-c的存在,使得实验能通过背景非常干净的衰变道∏0t→t-c来探测∏0t.因此,通过b∏0t这一产生机制,未来的LHC实验应能获得足够多的可鉴别的∏0t事例.我们的研究结果,可为LHC上寻找中性top-pions介子检验TC2模型提供有价值的理论指导.     

强子对撞机上中性top-pion介子产生过程pp(pp)→Π0tΠ0t,bΠ0t的研究

在TC2模型框架下研究了强子对撞机Tevatron和LHC上中性top-pion介子Π0t的产生过程pp(pp)→Π0tΠ0t和pp(pp)→bΠ0t. 研究结果表明, 在Tevatron上, 这两个过程的产生截面都很小, 通过这两个过程我们无法探测到中性top-pion介子. 在LHC上, 产生截面会大大增加, 但通过Π0tΠ0t的产生仍无法探测到中性top-pion介子. bΠ0t在LHC上的产生截面能达到几百个fb甚至pb的量级, LHC每年能产生10⁴—10⁵个bΠ0t事例. 另外, 味改变耦合Π0t tc的存在, 使得实验能通过背景非常干净的衰变道Π0t→tc来探测Π0t. 因此, 通过bΠ0t这一产生机制, 未来的LHC实验应能获得足够多的可鉴别的Π0t事例. 我们的研究结果, 可为LHC上寻找中性top-pions介子检验TC2模型提供有价值的理论指导.     

通过味改变过程探测TC2理论中的中性toppion介子

在Topcolor辅助的Technicolor(TC2)模型下,研究了一个产生中性toppion介子(Π0t)的味改变过程:e+e–→tcΠ0t.研究结果表明,在TESLA对撞机上,当质心能量高时,在大多数参数区间,e+e–→tcΠ0t的产生截面可达到0.1fb量级,每年可有数十个Π0t介子事例产生.当Π0t质量较小时,由于共振效应,产生截面可达几个fb.由于背景干净,有可能在TESLA对撞机上探测到Π0t介子事例.另一方面,研究发现,可以在实验中清晰地探测到toppion-charm不变质量分布中的共振峰.因此,Π0t介子的产生过程e+e–→tcΠ0t为人们提供了一个极好的机会,来探测中性Π0t介子,从而检验TC2模型.     

我们为什么提出建造环形正负电子对撞机

<正>一、粒子物理和标准模型自从20世纪30年代物理学家建立了原子模型之后,人类对亚原子和更深层次物质结构、相互作用和自然规律的实验、理论的探索和研究揭示了自然界基本粒子的存在和他们的特性,以及由这些基本粒子组成的各类介子,重子,原子,分子和它们形成的丰富和多样的自然物质世界。粒子物理硕果累累,标准模型在过去50多年得到发展和实验验证,成为一套能够全面解释已知粒子物理实验现象     

Detecting Toppion via a Flavor-Changing Single Top Quark Production Process

In the framework of topcolor-assisted technicolor (TC2) theory, we study a flavor changing single top quarkproduction process pp(pp) →Ⅱ0t → tc(tc) at upgraded Tevatron and LHC. The results show that with the flavor changingcoupling of neutral toppion to top and charm quark, toppion provides a large te-channel resonance effect. The signal ofsingle top production could be detected at LHC. Otherwise, the narrow peak in the invariant mass distribution could beclearly detected both at upgraded Tevatron and LHC. Therefore, such single top production process provides a uniqueway to test TC2 model via the detection of tc-channel neutral toppion contribution.     

Lepton-Flavor Violating Processes li → ljγ in Topcolor-Assisted Technicolor Models

We consider the lepton-flavor violating (LFV) processes li → ljγ in the framework of topcolor-assistedtechnicolor (TC2) models. We find that the new gauge boson Z‘ predicted by TC2 models can give significantlycontributions to these processes via the flavor-changing couplings Z‘lilj. The present experimental bound on the LFVprocess μ→ eγ gives severe constraints on the TC2 models. Using other experimental constraints on the Z‘ mass Mz,we obtain constraints on the lepton mixing factors KTμ and KTe. The future LFV experiments will probe into TC2models.     

Searching for a neutral top-Higgs in association with top-quark pairs at an e~+e~- collider in the TC2 model

We investigate the associated production of the neutral top-Higgs h_t⁰ with a pair of top-quarks in the context of the topcolor-assisted technicolor (TC2) model at the future e⁺e^- Linear Colliders (LC) i.e. e⁺e^- → tt h_t⁰. We calculate the production rate and present the distributions of the transverse momenta of top-Higgs and top-quarks. The results show that the total cross section is typically of the order of 1.0-7.5 fb in the energy range between 1000 GeV and 2000 GeV of the LC for the whole top-Higgs mass region of interest. It should be distinctly possible that hundreds or even thousands of h_t⁰ signals can be produced per year at the LC given the luminosity L=500 fb^-1.     

Production of Neutral Top-Pion Associated with a Gauge Boson at LHC

In this paper, we study the production of the neutral top-pion (Π⁰_t) associated with a gauge boson at the LHC, i.e. pp→Π⁰_tV(V=g,W,Z,γ). The cross section of pp→Π⁰_tg is at the level of 10² pb in the most parameter space. Such a process with the flavor-changing decay mode Π⁰_t→ tc might provide viable signatures to detect Π⁰_t at the LHC. The cross sections of other processes pp→Π⁰_tW(Z,γ) are too small to detect Π⁰_t, which open a window to distinguish the Higgs boson in the SM or MSSM from Π⁰_t.     

TC2模型下的顶夸克稀有衰变t→cV

在顶色辅助的人工色(TC2)理论框架下,研究了顶夸克稀有衰变t→cV过程.结果表明TC2模型预言的标量粒子top-pions和top-Higgs对顶夸克稀有衰变分支比的贡献可以使其比标准模型预言值大6—9个数量级.在大多数参数范围内,分支比的数量级为:Br(t→cg)～10^－5,Br(t→cZ)～10^－5,Br(t→cγ)～10^－7.在合理的参数范围内,顶夸克稀有衰变t→cV过程能够被未来的对撞机实验探测到.因此,顶夸克稀有衰变过程为我们提供了一种检验TC2理论的方法.     

顶色辅助的人工色理论中荷电的Top介子在LC实验中对顶夸克产生的修正

讨论了顶色辅助的人工色理论预言的赝标量Goldstones粒子(TC介子和Top介子)在LC实验中对顶夸克产生的贡献,发现Top介子对顶夸克产生截面σ_tt的贡献是主要的,在大部分参数空间中荷电Top介子的贡献非常大.当取合理的参数时,荷电Top介子对的σ_tt贡献可以达到8%左右,能够被LC的实验探测到.     

Production of a neutral scalar associated with a photon at the LHC in the topcolorassisted technicolor model

In the context of the topcolor-assisted technicolor (TC2) model, we consider the production of the neutral scalar S(π_t⁰ or h_t⁰) associated with a photon at the LHC and compare our results with those given by the minimal supersymmetric extension of the Standard Model (MSSM). We find that its production cross section is larger or smaller than that of the scalar particle predicted by the MSSM model, depending on the values of the relevant free parameters.     

The Signatures of the Neutral Top-Pion at the NLC and the Tevatron in Topcolor-Assisted MWTC Model

The neutral top-pion π_t⁰ can couple to the gluons and the photons through the top quark triangle-loop. we calculate the corrections of the neutral top-pion π_t⁰ to the tt production cross section in topcolor-assisted multiscale walking technicolor model. We find that, for a heavy neutral top-pion, the corrections are quite significant. For m_t = 175 GeV, 5 GeV ≤ m_t¹ ≤ 20 GeV and M_πt = 350 GeV, the relative correction Δσ/σ₀ is larger than 10% which might be observed at a high-luminosity Tevatron. We further estimate the production cross section of π_t⁰ at the NLC experiment. We find that the production rate is significantly large. The neutral top-pion π_t⁰ may be detected in future e⁺e^- linear collider experiments.