Top Quark Pair Production at e^＋e^— Colliders in the Topcolor—Assisted Technicolor Model

In the framework of topcolor-assisted technicolor model we calculate the contributions from the preudo Goldstone bosons and new gauge bosons to e^ e^-→ttk.We find that for reasonable ranges of the parameters,the preudo Goldstone bosons afford dominate contribution,the correction arising from new gauge bosons is negligibly small,the maximum of the relative corrections is-10% with the center-of-mass energy √s=500GeV;whereas in the case of √s=1500 GeV,the relative corrections could be up to 16%.Thus large new physics might be observable at the experiments of next-generation linear colliders.     

Spin Correlations in Top Quark Pair Production Near Threshold at the e+e- Linear Collider

We investigate the spin correlations in top quark pair production near the threshold at the e e- linear collider. Comparing with the results above the threshold region, we find that near the threshold region the off-diagonal basis, the optimized decomposition of the top quark spins above the threshold region, does not exist, and the beamline basis is the optimal basis, in which there are the dominant spin components: the up-down (UD) component for e-Le scattering and the down-up (DU) component for e-Re scattering can make up more than 50% of the total cross section,respectively.     

Spin Correlations in Top Quark Pair Production Near Threshold at the e^＋e^- Linear Collider

We investigate the spin correlations in top quark pair production near the threshold at the e^ e^- linear collider. Comparing with the results above the threshold region, we find that near the threshold region the off-diagonal basis, the optimized decomposition of the top quark spins above the threshold region, does not exist, and the beamline basis is the optimal basis, in which there are the dominant spin components: the up-down (UD) component for e^-le^ scattering and the down-up (DU) component for eR^-e^ scattering can make up more than 50% of the total cross section,respectively.     

Precision Calculations for the T-Odd Quark Pair Production at the CLIC e+e- Linear Collider

We perform the precision calculations for the e⁺e^-→q_q_(q_q_=u_u_, c_c_, d_d_,s_s_) processes up to the QCD next-to-leading order (NLO) including full weak decays for the final T-odd mirror quarks in the littlest Higgs model with T-parity (LHT) at the Compact Linear Collider (CLIC). We show the dependence of the leading order (LO) and NLO QCD corrected cross sections on the colliding energy √s, and provide the LO and QCD NLO kinematic distributions of final particles. The results show that the LO cross section can be enhanced by the NLO QCD correction and the K-factor increases obviously when the threshold of the on-shell q_q_-pair production approaches the colliding energy √s. The K-factor value varies in the range of 1.04 ～ 1.41 in our chosen parameter space. We find that a simple approximation of multiplying the LO kinematic distribution with the integrated K-factor is not appropriate for precision study of the e⁺e^-→q_q_(q_q_=u_u_, c_c_, d_d_,s_s_) processes, since the NLO QCD corrections are phase space dependent. It is necessary to calculate the differential cross sections including full NLO QCD corrections to get reliable results.     

e＋e－湮没为轻夸克对的强子产率

通过分析e^＋e^－→q₀q₀→h′s过程轻味夸克jet事例中电磁与强作用激发夸克的平均产生几率,得出初始轻味uds夸克jet中各种粒子的产率与初始夸克味道和夸克对数N的依赖关系.进一步给出领头强子的相对产率,同样明显与初始夸克味道和夸克对数N有关.这种依赖关系在低能区更明显     

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．     

Charged Higgs Pair Production in a General Two Higgs Doublet Model at e^＋e^- and μ^＋μ^- Linear Colliders

In this paper, charged Higgs pair production through l^＋l^- → H^＋ H^-, where l = e or μ, is studied within the framework of a general Two Higgs Doublet Model （2HDM）. The analysis is relevant to a future e^＋e^- or μ^＋ μ^- collider operating at center of mass energy of √s = 500 GeV. Two different scenarios of small and large a values are studied. Here a is the parameter, which diagonMizes the neutral CP-even Higgs boson mass matrix. Within the Minimal Supersymmetric Standard Model （MSSM）, cross section of this process is almost the same at e＋ e- and #＋#- colliders. It is shown that at e^＋e^- eolliders within a general 2HDM, cross section is not sensitive to the mass of neutral Higgs bosons, however, it can acquire large values up to several picobarn at μ^＋μ^- colliders with the presence of heavy neutral Higgs bosons. A scan over Higgs boson mass parameter space is performed to analyze the effect of large masses of neutral Higgs bosons involved in the s-channel propagator and thus in the total cross section of this process.     

Production of charmonium(like) states in e+e- interactions

We present a search for new charmonium like states in e+e- annihilation using the initial-state radiation and the process e+e-→J/ψ D(*)D(*). The analyses are based on a huge data sample recorded near the T(4S) resonance with the Belle detector at the KEKB e+e- asymmetric-energy collider.     

Littlest Higgs Model and Higgs Boson Associated Production with Top Quark Pair at High Energy Linear e+e- Collider

In the parameter space allowed by the electroweak precision measurement data, we consider the contributions of the new particles predicted by the littlest Higgs model to the Higgs boson associated production with top quark pair in the future high energy linear e⁺e^- collider (ILC). We find that the contributions mainly come from the new gauge bosons Z_H and B_H. For reasonable values of the free parameters, the absolute value of the relative correction parameter δσ/σ^SM can be significanly large, which might be observed in the future ILC experiment with √{S}=800 GeV.     

Heavy quarks in e+e- annihilation

There are many speculations that there exist quarks Q considerably heavier than the charmed quark. Their Q$\text{Q}$ states will display a far richer spectrum of monochromatic photon and hadron transitions than charmonium. The most important features of this spectrum — in particular, its dependence on the mass of Q — are outlined.     

Cltzster Effect in e+ e- Annihilation

Based on the picture of hadron cluster, some parameters about cluster are obtained in e⁺ e^- annihilation and it is found that the intermittent behavior in e⁺ e^- annihilation is closely related with short-range correlation from hadron cluster.     

高能电子-正电子碰撞中产生喷注的标度

对高能电子-正电子对撞产生实验上可以直接观察的可视喷注的标度进行了仔细研究.根据在s=17—30Gev的电子-正电子对撞实验中最先观察到三喷注这一历史事实,论证了可视喷注的相对横动量kt.在5—10GeV/c的范围.并通过一个具体例子说明,只有k_t在这一范围时才能正确地判定事件中的喷注数.仔细比较了由不同k_t得到的喷注内部的动力学起伏,发现只有k_t在5—10GeV/c范围时,喷注内部系统才有最好的反常标度性.从而得到,可视喷注的标度是k_t～5—10GeV/c.讨论了这一标度和微扰QCD的标度1—2GeV之间的关系.     

Single Charged Top-Pion Production at the Next Generation e+e- Colliders

The single charged top-pion production processes e⁺e^-→t\bar{b}Π_t^- and e⁺e^-→ W⁺Π_t^- are studied in the framework of top-color-assisted technicolor (TC2) model. Our studies show that the cross section σ(e⁺e^-→t\bar{b}Π_t^-) reaches the level of tens of fb and σ(e⁺e^-→W⁺Π_t^-) reaches the level of a few fb. With the yearly integrated luminosity of L～500 fb^-1 expected at the planned colliders, one could collect thousands of charged top-pion of events via the process e⁺e^-→t\bar{b}Π_t^- and hundreds of events via the process e⁺e^-→W⁺Π_t^-. The flavor changing decay mode Π_t^-→b\bar{c} is the best channel to detect charged top-pion due to the clean SM background. With a large number of events and the clean background, the charged top-pion should be observable at the planned colliders. Therefore, our studies in this paper can help us to search for charged top-pion, and furthermore, to test the TC2 model.