D介子衰变中的奇异轴矢介子(英文)

目前,奇异轴矢介子的性质并没有被很好地理解,而这类介子是可以在D介子衰变中得到更多的研究。将窄宽近似下的等式关系和强衰变中CP守恒应用到四体衰变D0 → K+K-π+π-中的D0 → K±K₁?（1270）（→ρK or K*π）的实验数据中,可以发现实验数据与理论存在矛盾,然而,当考虑更多K₁（1270）的衰变过程后,可以发现,B（D0 → K-K₁+（1270）（→ K*0π+））的实验数据很可能被高估了一个量级。考虑共振态K₁（1400）的贡献,利用因子化方法计算相应的衰变过程的分支比,可以发现,B（D0 → K-K₁+（1400）（→ K*0π+））的分支比与使用等式关系得到的B（D0 → K-K₁+（1270）（→ K*0π+））的分支比在量级上是相同的。另外,对于含有奇异轴矢介子的D介子衰变实验数据的合理性,实验可以通过测量K₁（1270）→ ρK和K*π分支比的比值来检验,或者通过验证D介子衰变中的等式关系来检验。     

Semileptonic and Nonleptonic Decays of B s Mesons

We investigate the semileptonic and nonleptonic decays of B _s mesons. We work within the context of nonrelativistic constituent quark models. We calculate the different form factors that parameterize the hadron matrix elements.     

QCD Aspects of Exclusive B Decays

We review QCD approaches to exclusive B meson decays, concentrating on QCD-improved factorization and perturbative QCD. The ideas of soft-collinear effective theory and light-cone sum rules are briefly explained. We discuss the recently measured time-dependent CP asymmetry of the B⁰ _d^{+ –} modes, from which the unitarity angle can be extracted.     

D介子稀有衰变研究

利用工作在北京正负电子对撞机(BEPC)上的北京谱仪(BES)收集到的33pb^－1的Ψ(3770)数据,寻找D介子味道改变中性流(FCNC)和轻子数不守恒(LNV)的稀有衰变, 包括4个D⁰介子的衰变模式(K⁰e⁺e^－,Φe⁺e^－,ρ⁰e⁺e^－和K^*0e⁺e^－)和6个D⁺介子的衰变模式(K^－e⁺e⁺,K⁺e⁺e^－,π^－e⁺e⁺, π⁺e⁺e^－,K^*－e⁺e⁺和K^*+e⁺e^－). 没有发现信号,给出90%置信水平的上限. 其中, D⁺介子的两个衰变模式D⁺→K^*－e⁺e⁺和D⁺→K^*+e⁺e^－的上限是首次测量.     

Double Charm Decays of B Mesons in mSUGRA Model

Based on the low energy effective Hamiltonian with naive factorization, we calculate the branching ratios (BRs) and CP asymmetries (CPAs) for the twenty three double charm decays B/B_s \to D^{(*)}_{(s)} D^{(*)}_{(s)} in both the standard model (SM) and the minimal supergravity (mSUGRA) model. Within the considered parameter space, we find that (a) the theoretical predictions for the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are all consistent with the currently available data within±2σ errors; (b) For all the considered decays, the supersymmetric contributions in
the mSUGRA model are very small, less than7% numerically. It may be difficult to observe so small SUSY contributions even at LHC.     

Monte Carlo Simulation on Measurements of Branching Fractions for Some Exclusive Semileptonic Decays of Neutral D Mesons on BES-III

Using the Monte Carlo samples of about 800 pb^-1 and 500pb^-1 generated at and around 3.773GeV with BOSS (BESIII Offline Software System) 6.0.2 and BOSS 6.1.0, we have studied the branching fractions for D⁰ →K^-l⁺ν_l and D⁰ →πi^-l⁺ν_l (l=e, μ). According to the simulation results, the expected precision of these measurements for 20fb^-1 ψ(3770) data which will be collected on BESIII are well estimated.     

遍举衰变过程D0→Ks0π+π–和D0→Ks0K+K–及其共振态结构的实验研究

利用北京谱仪(BES–Ⅰ)在北京正负电子对撞机(BEPC)e+e–质心系能量为4.03GeV处采集的积分亮度为22.3pb–1的数据,研究了D0→K0sπ+π–,D0→K0sK+K–的衰变及其末态的共振结构.实验测得D0→K0sπ+π–过程的分支比为(5.32±0.53±0.40)%;D0→K–π+,D0→K0ρ0和D0→K0s(π+π–)non resonance过程的分支比分别为(6.05±0.32±0.49)%,(1.17±0.17±0.13)%和(1.35±0.22±0.17)%;测得D0→K0sK+K–,D0→K0和D0→K0(K+K–)non?的分支比分别为(1.04±0.2?4±0?.16)%,(1.12±0.34±0.15)%和(0.27±0.13±0.03)%.     

Weak Decays of D and Ds Mesons in a Relativistic Quark Model

The transitions of D and D_s, mesons to light vector states are studied in a relativistic constituent quark model based on the Bethe-Salpeter formalism. The form factors are calculated, and the branching fractions for both semileptonic and nonleptonic decays are given. The results show that the form factors for these transitions deviate substantie from the request of heavy quark symmetry. All the branching ratios for D and D_s semileptonic decays are found to be consistent with data, whereas the calculations of nonleptonic D and D_s decays under the factorization assumption do not agree with experiments. This confirms the conjecture that the factorization scheme is much less applicable in D and D_s decays than in B and B_s decays.     

QCD中等时方程的赝标介子解

本文讨论在背景场量子色动力学框架中的等时方程赝标介子解. 方程的积分核由微扰和非微扰贡献两部分组成．微拔部分是通常的单胶子交换图的贡献；非微扰部分的贡献来自于最低阶的夸克和胶子凝聚效应. 当输入合理的夸克质量参数和耦合常数时，可以得到与实验相符合的赝标介子谱．     

用QCD因子化方法研究B→PV两体弱衰变过程

基于最近CLEO实验和B介子物理中理论研究的进展, 在QCD因子化方案下研究了B介子到一个赝标π, K和一个矢量介子ρ,ω的两体弱衰变过程.在合理的参数范围内, 理论计算与实验相符得很好.     

Role of Electromagnetic Dipole Operator in the Electroweak Penguin Dominated Vector Meson Decays of B Meson

The pure annihilation type decays Dd^0→Фγand Bs→ργ receive only colour suppressed penguin contributions with a very small branching ratio in the standard model. When we include the previously neglected electromagnetic dipole operator, the branching ratios can be enhanced to R（^-Bd^0→Фγ）≈ 1×10^-11 and R（^-Bs→ργ）～（6 - 16） ×10^-10, which are one order magnitude larger than previous study using the QCD factorization approach. The new effect can also give a large contribution, of order 10^-9, to transverse polarization of B→Фρ and B →ωФ, which is comparable to the longitudinal part. These effects can be detected in the LHCb experiment and the super-B factories.     

Leptonic Decays of Heavy Vector and Pseudoscalar Mesons

Pure leptonic decays of D~*0)(B_~(*s),B_d~*)→l~+l~- and D~(±*)(D_s~*,B~(*+),B_c~*)→lν_l are investigated.The hadronic contributions such as D~0→D~(*0)γ→μ~+μ~- are also explored.We then obtain the updated branching fractions of the pseudoscalar mesons to lepton pairs are modified by a factor of few percentages.Specifically,the Br(B+→e~+ν_e)is reduced by a factor 13%.     

Radiative Decays of Charmonium into Light Mesons

We apply perturbative QCD to the radiative decays of charmonia J/ψ and χcJ into light mesons. We perform a complete numerical calculation for the quark-gluon loop diagrams involved in these processes. The calculated J/ψ decay branching ratios into p-wave mesons f2（1270） and f1（1285） fit the data well, while that of fo（980） （if treated as an ss meson） is predicted to be 1.6×10^-4, which implies that f0（1710） can not be the ss or （uu＋dd）/√2 meson. Decays of p-wave charmonia χcJ→ρ（ω;φ）γ （J = 0, 1, 2） are also studied, and the branching ratio of χc1→ργ is predicted to be 1.4×10^-5, which may be tested by CLEO-c collaboration and BESlg collaboration with future experiments.     

The Decays of Glueballs to Two Light Mesons

We solve the BS equation of glueballs under instantaneous approximation. With the BS wavefunction obtained we calculate the decay widths of glueballs to two pseudoscalar mesons, Г(ππ), Г(KK) and Г(ηη). Г(ηη') from QCD anomaly is also estimated.     

Semileptonic Decays of Heavy Mesons to Light Pseudoscalar Mesons in the BS Formalism

The decay processes from heavy to light pseudoscalar mesons such as π, K, η,η' are studied in a relativistic constituent quark model based on the BS formalism. It is emphasized that the negative energy projector operators's contributions in the BS wavefunctions for light pseudoscalar mesons have to be considered. By taking into account these contributions, the previously encountered difficulties in calculating the decay constants and form factors are found to be removed. A11 the form factors for transitions such as D→π, D→K, D_s→K, D_s→η, D_s→η', B→π, B_s→K are estimated and the branching ratios for these semileptonic decays are calculated. The results of our calculations are consistent with experimental values.