Ba（d）^o-Ba（d）^o Mixing and New Physics Effects in a Top Quark Two-Higgs Doublet Model

We calculate the new physics contributions to the neutral Bd^o and Ba^o meson mass splitting △Md and △Ma induced by the box diagrams involving the charged-Higgs bosons in the top quark two-Higgs doublet model （T2HDM）. Using the precision data, we obtain the bounds on the parameter space of the T2HDM： （a） For fixed MH = 400 GeV and 5= [0°, 60°], the upper bound on tan β is tan β≤ 30 after the inclusion of major theoretical uncertainties; （b） For the case of tan β≤ 20, a light charged Higgs boson with a mass around 300 GeV is allowed; and （c） The bounds on tan β and MH are strongly correlated： a smaller （larger） tan β means a lighter （heavier） charged Higgs boson.     

代非普适Z＇模型下中性Bs介子混合的研究

基于LHCb,Tevatron以及DO实验组关于中性Bs介子混合的最新实验结果,Г12s中有可能存在大的新物理贡献,本文在代非普适Z’模型下对Bs-Bs混合进行了研究．假定Z’玻色子不仅对非对角矩阵元M12s有贡献,还考虑了由树图交换Z’玻色子所导致的b→scc算符对非对角矩阵元Г12s的贡献．结果表明：在△Ms,φs和豆Bd→J/φKs的间接CP不对称这些物理可观测量的联合限制下,实验值afss得不到解释．因此,在对非普适Z’模型假定下,不能同时对所有中性Bs介子混合观测量给出解释．伴随着LHCb以及未来的超级B工厂的运行,尤其是对CP不对称afss的测量,期望这一问题将得到解答．     

Mixing of meson isosinglets in SU(5) and an extension to SU(N)

The mixing angles of meson isosinglets belonging to the 24-dimensional and singlet representations of SU(5) are calculated under specific assumptions in the non-relativistic quark model. The procedure to extend the scheme to SU(N) has been outlined. The results have been compared with other earlier estimates.     

A Study of One S- and One P-Wave Heavy Meson Interaction in a Chiral Quark Model

The analytical forms of the interaction potentials between one pseudo-scalar/vector and one scalar/tensor/axial-vector heavy mesons are deduced based on a chiral quark model. Our results explicitly show the attractive property between the two heavy mesons. Consequently, a series of possible molecular states are obtained. It is expected that our study might shed some light on the popular discussions of the newly observed XYZ states.     

Color-Flavor Locked Strangelets in a New Quark Model with Linear Confinement and Coulomb-Type Interactions

The color-flavor locked (CFL) strangelets have been investigated in a new quark model with linear confinement and one-gluon-exchange interactions. Considering Coulomb energy, we have studied the properties of three kinds of CFL strangelets, namely, positively charged, negatively charged and nearly neutral CFL strangelets. It is found that the one-gluon-exchange effect lowers the energy of a strangelet considerably and thus makes it much more stable than without considering the effect. The charge of a positive strangelet is larger than 0.15A^2/3 with A being the baryon number, but smaller than that in bag model. The charge of a negatively charged or nearly neutral CFL strangelet is nearly proportional to A^1/3.     

The Effects of Simplest Little Higgs Model on the Spin Correlations in the Top Quark Pair Production at the LHC and ILC

In the simplest little Higgs model (SLH),we study the spin correlations in the top quark pair production at the LHC and ILC.We find that the SLH always suppresses the t spin correlations compared to the SM values.At the LHC,the suppression can be over 10% for mZ′ 750 GeV.The SLH prediction value is outside the 1σ range of the experimental data from ATLAS,and within 1σ range of the experimental data from CMS.At the ILC,the SLH can sizably suppress the t spin correlation for mZ′approaching the center-of-mass energy √s.For example,the maximal suppression can reach-22.5%,-14.5%,and-9.5% for √s=500 GeV,800 GeV,and 1000 GeV,respectively.Therefore,the t spin correlation at the ILC can be a sensitive probe for the SLH.     

SU（3） Simple Group Model and New Z＇ Properties in Future Linear Colliders

In the SU（3） simple group model, the new neutral gauge boson Z＇ couples to pairs of SM fermions with couplings fixed in terms of the SM gauge couplings and depending only on the choice of the fermion embedding. In this paper, we calculate the contributions of this new particle to the processes e^＋e^-→l^＋l^-, bb^-, and cc^- and study the possibility of detecting this new particle via these processes in the future high-energy linear e^＋e^- collider（LC） experiments with √s= 500 GeV and ￡int= 340 fb^-1. We find that the new gauge boson Z＇ is most sensitive to the process e^＋e^-→b^＋b^-. As long as Mz,≤2 TeV , the absolute values of the relative correction parameter are larger than 5%. We calculate the forward-backward asymmetries and left-right asymmetries for the process e^＋e^-→c^＋c^-, with both the universal and anomaly-free fermion embeddings. Bounds on Z＇ masses are also estimated within 95% confidence level.     

Model spectral function and superconductivity in BaxK1−xBiO3 (x=0.5-0.7)

The Eliashberg spectral density function is constructed for the superconducting compound Ba_xK_1−xBiO₃ with x=0.5, 0.6, 0.7. The functions, besides yielding some prominent structures, show widely spreading spectra that inhibit lattice instability by yielding not too large values of λ(<1.32). The resulting spectral functions show similar shape as other results, where available, and also successfully reproduce the observed critical temperature, isotope exponent, gap ratio and several other parameters.     

The Role of a1(1260) in π-p→a1-(1260)p and π-p→π-ρ0p Reactions Near Threshold

We report on a theoretical study of the π^-p→a₁^-(1260) p and π^-p→π^-ρ⁰p reactions near threshold within an effective Lagrangian approach. The production process is described by t-channel ρ⁰ meson exchange. For the π^-p→π^-ρ⁰p reaction, the final π^-ρ⁰ results from the decay of the a₁(1260) resonance, which is assumed as a dynamically generated state from the K^*K and ρπ coupled channel interactions. We calculate the total cross section of the π^-p→a₁^-(1260)p reaction. It is shown that, with the coupling constant of the a₁(1260) to ρπ channel obtained from the chiral unitary theory and a cut off parameter Λρ~1.5 GeV in the form factors, the experimental measurement can be reproduced. Furthermore, the total and differential cross sections of π^-p→a₁^-(1260)p→π^-ρ⁰p reaction are evaluated, and it is expected that our model calculations can be tested by future experiments. These reactions are important for the study of the a₁(1260) resonance and would provide further constraints on the properties of the a₁(1260) state.     

Fractal Dromion, Fractal Lump, and Multiple Peakon Excitations in a New (2+1)-Dimensional Long Dispersive Wave System

By means of variable separation approach, quite a general excitation of the new (2 + 1)-dimensional long dispersive wave system: λqt + qxx - 2q ∫ (qr)xdy ＝ 0, λrt - rxx + 2r ∫(qr)xdy ＝ 0, is derived. Some types of the usual localized excitations such as dromions, lumps, rings, and oscillating soliton excitations can be easily constructed by selecting the arbitrary functions appropriately. Besides these usual localized structures, some new localized excitations like fractal-dromion, farctal-lump, and multi-peakon excitations of this new system are found by selecting appropriate functions.