Semi-leptonic Octet Baryon Weak Axial-Vector Form Factors in the Chiral Constitutent Quark Model

Associated Production of Upsilon and Weak Gauge Bosons at the Tevatron

We calculate the rate of production of W+Upsilon and Z+Upsilon at the Tevatron. We find the cross sections at a center-of-mass energy of 1.8 TeV to be roughly 450 pb for W+Upsilon and 150 pb for Z+Upsilon. The dominant production mechanism involves the binding of a color-octet b-bbar pair into a P-wave bottomonium state which subsequently decays into Upsilon. The purely leptonic decay modes of Upsilon, W, and Z provide signatures with small backgrounds. In Run I of the Tevatron, the number of events in the purely leptonic decay channels before allowing for detector acceptances and efficiencies…

Electromagnetic and weak hyperon properties in the Skyrme model

We report on the result of some investigations concerning the radiative decays of decuplet baryons and the non-leptonic weak decays of the octet baryons in the context of topological chiral soliton models. Our results are compared with those of alternative baryon models. For the radiative decays we find that the predictions are similar to those of quark models. In the case of the non-leptonic weak decays, we find that although the predicted S-wave amplitudes are in rather good agreement with the observed values, the model is not able to reproduce the empirical P-wave amplitudes. Thus, in contr…

Chiral Perturbation Theory for Vector Mesons

The interactions of $ρ$, $K^*$, $ϕ$ and $ω$ vector-mesons with low-momentum $π$, $K$ and $η$ pseudoscalar mesons are constrained by chiral symmetry. We derive a heavy vector-meson chiral Lagrangian in which the vector mesons are treated as heavy static matter fields. The unknown couplings of the chiral Lagrangian are further related using the $1/N_c$ expansion. Chiral perturbation theory is applied to the vector-meson mass matrix. At one-loop there are large corrections to the individual vector meson masses, but the singlet-octet mixing angle remains almost unchanged. The parity-violating $s$-…

Strangeness in the baryon ground states

We compute the strangeness content of the baryon octet and decuplet states based on an analysis of recent lattice simulations of the BMW, PACS, LHPC and HSC groups for the pion-mass dependence of the baryon masses. Our results rely on the relativistic chiral Lagrangian and large-$N_c$ sum rule estimates of the counter terms relevant for the baryon masses at N$^3$LO. A partial summation is implied by the use of physical baryon and meson masses in the one-loop contributions to the baryon self energies. A simultaneous description of the lattice results of the BMW, LHPC, PACS and HSC groups is ach…

粲重子衰变的末态重散射机制

Final-state rescattering mechanism of charmed baryon decays

本文提出末态重散射机制研究粲重子两体非轻子衰变，通过圈积分完整计算振幅实部和虚部，仅用一个模型参数即可解释Λ_c^+衰变的全部九个分支比实验数据，并降低了CP破坏等观测量的理论不确定性。

Studying $\mathcal{B}_1(\frac{1}{2}^+)\to \mathcal{B}_2(\frac{1}{2}^+)\ell^+\ell^-$ Semi-leptonic Weak Baryon Decays with the SU(3) Flavor Symmetry

Motivated by recent anomalies in FCNC $b\to s\ell^+\ell^-$, we study $B_1\to B_2\ell^+\ell^-(\ell=e,μ,τ)$ semi-leptonic weak decays with the SU(3) flavor symmetry, where $B_{1,2}$ are the spin-1/2 baryons of single bottomed anti-triplet $T_{b3}$, single charmed anti-triplet $T_{c3}$ or light baryon octet $T_{8}$. Using the SU(3) irreducible representation approach, we first obtain the amplitude relations among different decays, and then predict the relevant not-yet measured observables of these decays. (a) We calculate the branching ratios of the $T_{b3}\to T_8 μ^+μ^-$ and $T_{b3}\to T_8 τ^+τ^…

Charmed Baryon Weak Decays with SU(3) Flavor Symmetry

We study the semileptonic and non-leptonic charmed baryon decays with $SU(3)$ flavor symmetry, where the charmed baryons can be ${\bf B}_{c}=(Ξ_c^0,Ξ_c^+,Λ_c^+)$, ${\bf B}'_{c}=(Σ_c^{(++,+,0)},Ξ_{c}^{\prime(+,0)},Ω_c^0)$, ${\bf B}_{cc}=(Ξ_{cc}^{++},Ξ_{cc}^+,Ω_{cc}^+)$, or ${\bf B}_{ccc}=Ω^{++}_{ccc}$. With ${\bf B}_n^{(\prime)}$ denoted as the baryon octet (decuplet), we find that the ${\bf B}_{c}\to {\bf B}'_n\ell^+ν_\ell$ decays are forbidden, while the $Ω_c^0\to Ω^-\ell^+ν_\ell$, $Ω_{cc}^+\toΩ_c^0\ell^+ν_\ell$, and $Ω_{ccc}^{++}\to Ω_{cc}^+\ell^+ν_\ell$ decays are the only existing Cabibbo-…

拓扑 $SU(3)_f$ 方法用于两体 $Ω_c$ 弱衰变

Topological $SU(3)_f$ approach for two-body $Ω_c$ weak decays

本文用拓扑 $SU(3)_f$ 方法分析 $Ω_c^0$ 两体弱衰变，解释分支比并预测 $Ξ^0π^0$ 分支比，为检验 $SU(3)_f$ 对称性破缺提供候选。