In this work we provide a dispersive analysis of $ππ\rightarrow K\bar{K}$ scattering. For this purpose we present a set of partial-wave hyperbolic dispersion relations using a family of hyperbolas that maximizes the applicability range of the hyperbolic dispersive representation, which we have extended up to 1.47 GeV. We then use these equations first to test simple fits to different and often conflicting data sets, also showing that some of these data and some popular parameterizations of these waves fail to satisfy the dispersive analysis. Our main result is obtained after imposing these new relations as constraints on the data fits. We thus provide simple and precise parameterizations for the S, P and D waves that describe the experimental data from $K\bar K$ threshold up to 2 GeV, while being consistent with crossing symmetric partial-wave dispersion relations up to their maximum applicability range of 1.47 GeV. For the $S$-wave we have found that two solutions describing two conflicting data sets are possible. The dispersion relations also provide a representation for $S$, $P$ and $D$ waves in the pseudo-physical region.
The cross sections of $e^+e^- \rightarrow πZ_c(3900) \rightarrow ππJ/ψ$ and $e^+e^- \rightarrow πZ_c(3900) \rightarrow πD\bar{D}^{*}$ have been measured by BESIII experiment. We try to perform a combined fit to the cross sections with one Breit-Wigner function, the fit results show the structure's mass and width are $M=(4232\pm5)$ MeV/$c^2$, $Γ=(65\pm21)$ MeV. The ratio $\frac{\mathcal{B}(Z_c(3900)\rightarrow D\bar{D}^{*})}{\mathcal{B}(Z_c(3900)\rightarrowπJ/ψ)}$ is determined to be $(16\pm6)$. We also try to fit the cross sections with two Breit-Wigner functions, while we can't come to any de…
Within the quasi-two-body decay model, we study the localized $CP$ violation and branching fraction of the four-body decay $\bar{B}^0\rightarrow [K^-π^+]_{S/V}[π^+π^-]_{V/S} \rightarrow K^-π^+π^-π^+$ when $K^-π^+$ and $π^-π^+$ pair invariant masses are $0.35<m_{K^-π^+}<2.04 \, \mathrm{GeV}$ and $0<m_{π^-π^+}<1.06\, \mathrm{GeV}$, with the pairs being dominated by the $\bar{K}^*_0(700)^0$, $\bar{K}^*(892)^0$, $\bar{K}^*(1410)^0$, $\bar{K}^*_0(1430)$ and $\bar{K}^*(1680)^0$, and $f_0(500)$, $ρ^0(770)$ , $ω(782)$ and $f_0(980)$ resonances, respectively. When dealing with the dynamical functions o…
In this work, we study the localized $CP$ violation and the branching fraction of the four-body decay $\bar{B}^0\rightarrow K^-π^+π^-π^+$ by employing a quasi-two-body QCD factorization approach. Considering the interference of $\bar{B}^0\rightarrow \bar{K}_0^*(700)ρ^0(770)\rightarrow K^-π^+π^-π^+$ and $\bar{B}^0\rightarrow \bar{K}^*(892)f_0(500)\rightarrow K^-π^+π^-π^+$ channels, we predict $\mathcal{A_{CP}}(\bar{B}^0\rightarrow K^-π^+π^-π^+)\in[0.15,0.28]$ and $\mathcal{B}(\bar{B}^0\rightarrow K^-π^+π^-π^+)\in[1.73,5.10]\times10^{-7}$, respectively, which shows that this two channels' interf…
We investigate roads for evaluating model-independent cross-section distributions for the sequential hyperon decay $Σ^0\rightarrowΛγ;Λ\rightarrow pπ^- $ and its corresponding antihyperon decay. The hyperons are produced in the reaction $e^+e^-\rightarrow J/ψ\rightarrow Σ^0\barΣ^0$. Cross-section distributions are calculated using the folding technique.
We study the three-body baryonic B decay $\bar{B}^{0}_{s}\rightarrow p\barΛ K^{-}$ within the framework of the pole model via the baryonic $Λ_{b}$ pole. In our calculation, we require the strong coupling constant $g_{Λ_{b}B_{s}Λ}$ and investigate if $g_{Λ_{b}B_{s}Λ}=10.49\pm1.57$ is adopted, the branching ratio agrees with the experimental result, reported by the LHCb collaboration.
We report on a study of the sequential hyperon decay $Σ^0\rightarrowΛγ;Λ\rightarrow pπ^- $ and its corresponding anti-hyperon decay. We derive a multi-dimentional and model-independent formalism for the case when the hyperons are produced in the reaction $e^+e^-\rightarrowΣ^0\barΣ^0$. Cross-section distributions are calculated using the folding technique. We also study sequential decays of single-tagged hyperons.
Motivated by an anomaly in $R(D^{(*)})={\rm BR}(\bar{B}\rightarrow D^{(*)} τ^-\barν)/{\rm BR}(\bar{B}\rightarrow D^{(*)} l^-\barν)$ reported by BaBar, Belle and LHCb, we study $R(D^{(*)})$ in a general two Higgs doublet model (2HDM). Although it has been suggested that it is difficult for the 2HDM to explain the current world average for $R(D^{(*)})$, it would be important to clarify how large deviations from the standard model predictions for $R(D^{(*)})$ are possible in the 2HDM. We investigate possible corrections to $R(D^{(*)})$ in the 2HDM by taking into account various flavor physics con…
The rare decays $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ are important to research new physics beyond standard model. In this work, we investigate two loop electroweak corrections to $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM), under a minimal flavor violating assumption for the soft breaking terms. In this framework, new particles and new definition of squarks can affect the theoretical predictions of these two processes, with respect to the MSSM. Considering the constraints fro…
We present the two-loop master integrals relevant to the ${\mathcal O}(αα_s)$-corrections to the decay $H \rightarrow b \bar{b}$ through a $H t \bar{t}$-coupling. We keep the full dependence on the heavy particle masses, but neglect the $b$-quark mass. The occurring square roots can be rationalised and the result is expressed in terms of multiple polylogarithms.
We investigate the prospects for detecting axion-like particles (ALPs, dubbed as "a") via the decay $Z\rightarrow a f\bar{f}$ at future $Z$ factories. Considering the decay channels $a\rightarrow μ^+ μ^-$ and $a\rightarrow b \bar{b}$ , four types of signals $μ^+ μ^- /E$, $b b /E$, $e^+ e^- μ^+ μ^-$ and $e^+ e^- b b$ are explored. We demonstrate that these channels are promising for detecting ALPs at $Z$ factories and obtain the sensitivity bounds on the couplings $g_{aZZ}$ and $g_{aγZ}$.
Using the Bethe-Salpeter equation (BSE) we investigate the forward-backward asymmetries $( A_{FB}) $ in $Λ_b \rightarrow Λl^+ l^-(l=e,μ,τ)$ in the quark-diquark model. This approach provides precise form factors that are different from those of QCD sum rules. We calculate the rare decay form factors for $Λ_b \rightarrow Λl^+ l^-$ and investigate the (integrated) forward-backward asymmetries in these decay channels. We find that the integrated $A^l_{FB}$, $\bar{A}^l_{FB}(Λ_b \rightarrow Λe^+ e^-) \simeq -0.1371 $, $\bar{A}^l_{FB}(Λ_b \rightarrow Λμ^+ μ^- ) \simeq -0.1376 $, $\bar{A}^l_{FB}(Λ_b …
We report on the status of the ongoing calculation of multiparticle contributions to the inclusive radiative $\bar{B} \rightarrow X_s γ$ decay at next-to leading order. This effort amounts to the evaluation of the four-particle process $b\rightarrow s \bar{q} q γ$ at the one-loop level, supplemented by the corresponding five-particle tree-level cuts $b\rightarrow s \bar{q} q γ+ g$ of the gluon bremsstrahlung. Knowledge of these pieces will formally complete the $\bar{B} \rightarrow X_s γ$ decay at the next-to-leading order. The different steps such as the generation of the amplitude, its renor…
We study the three-body baryonic decay $ \bar{B}^{0}\rightarrowΛ^+_c \bar{p} π^0$ based on the factorization approach. The most important Feynman diagrams for this decay mode are factorizable and non-factorizable contributions, so that the former plays the key role in the decay amplitude and the latter affects the amplitude coefficient $a_2$. We calculate the decay branching ratio for some values of $a_2$ in the range of $0.16-0.40$ and we find that the value of $a_2=0.17$ leads us to the result of $(1.50\pm0.21)\times10^{-4}$ which evidently agrees with the experimental result $(1.55\pm0.17\p…
New Analysis of $B \rightarrow Kπ$ data with Pauli blocking CP violation in $B^o$ decays, not in $B^{\pm}$ SU(3) use of $B \rightarrow ππ$ data invalid for $B \rightarrow Kπ$
The Quark Flavor Violating Higgs Decay $h \rightarrow \bar b s + b \bar s$ in the MSSM
研究了最小超对称标准模型中夸克味破坏的Higgs玻色子衰变$h \rightarrow \bar b s + b \bar s$.首先在独立模型中分析衰减，然后在第二步中在最小味道违反（MFV）约束MSSM中分析衰减。从$B$ -物理观测量（BPO）和电弱精密观测量（EWPO）的实验约束也计算和施加在参数空间。结果表明，在某些情况下，EWPO比BPO更强地限制了味道违反参数空间。在模型中，可找到${\rm BR}(h \rightarrow \bar b s + b \bar s)$的${\cal O}(10^{-4})$独立分析值。在MFV CMSSM中，这样的结果只能在参数空间的非常有限的部分中获得。结果表明，不排除在未来的$e^+e^-$对撞机上观察到MSSM中的$h \rightarrow \bar b s + b \bar s$衰变。
In this paper we present a fully-differential calculation for the contributions to the partial widths $H\rightarrow b\bar{b}$ and $H\rightarrow c\bar{c}$ that are sensitive to the top quark Yukawa coupling $y_t$ to order $α_s^3$. These contributions first enter at order $α_s^2$ through terms proportional to $y_t y_q$ ($q=b,c$). At order $α_s^3$ corrections to the mixed terms are present as well as a new contribution proportional to $y_t^2$. Our results retain the mass of the final-state quarks throughout, while the top quark is integrated out resulting in an effective field theory (EFT). Our r…
We investigate the anomalous $W^+W^-γ$ couplings through the process $e^-e^+\,\rightarrow\,ν_e\barν_eγ$ for unpolarized and polarized electron (positron) beams at the International Linear Collider. We give the 95$\%$ Confidence Level limits on the anomalous couplings with and without the systematic uncertainties for various values of center-of-mass energies and the integrated luminosities. We show that the obtained limits on the anomalous couplings through the process $e^-e^+\,\rightarrow\,ν_e\barν_eγ$ can highly improve the current experimental limits.
Study of $Λ_b\rightarrow~ Λl^+l^-$ and $Λ_b\rightarrow p l \barν$ decays in the Bethe-Salpeter equation approach
在我们以前的工作中，基于$SU(6)$自旋味波函数，我们把$Λ$和$p$看作是由不同的夸克-双夸克组态组成，建立了夸克和标量双夸克组态的Bethe-Salpeter（BS）方程。在我们目前的工作中，我们应用该模型来计算标准模型（SM）中半轻子跃迁$Λ_b\rightarrowΛl^+l^-$ $(l=μ,e,τ)$和$Λ_b\rightarrow p l\barν$的形状因子。衰变$Λ_b\rightarrowΛμ^+μ^-$是特别有趣的，因为它已经在CDF和LHCb合作中测量，这种罕见的衰变对新的物理效应非常敏感。$Λ_b\rightarrow p l\barν$衰变是在大型强子对撞机上测量Cabibbo-Kobayashi-Maskawa矩阵元$|V_{ub}|$的一种很有前途的模式。在我们的计算中，根据BS方程核中双夸克质量和夸克与双夸克相互作用强度等模型参数的取值范围，我们发现，在我们的模型中，$Λ_b\rightarrowΛμ^+μ^-$的分支比与实验数据是一致的，目前LHCb的实验结果与我们计算的$Λ_b\rightarrowΛμ^+μ^-$的微分分支比一致，只是在较大的范围内动量传递区这表明仍有可能产生新的物理效应的空间。我们也给出了$Λ_b\rightarrowΛl^+l^-$和$Λ_b\rightarrow p l\barν$的总分支比与其它唯象方法的结果的比较。
At Moriond 2019, Belle collaboration announced their new measurements on $R_D$ and $R_{D^*}$ which are in agreement with their Standard Model (SM) predictions within $1.2σ$. After inclusion of these measurements, the discrepancy between the world averages and the SM predictions of $R_D$-$R_{D^*}$ comes down from $4.1σ$ to $3.1σ$. Here we do a global fit by taking all measurements in $b\rightarrow cτ\barν$ transition. We find that there are seven allowed new physics solutions, each with different Lorentz structure. Further we show that it is possible to distinguish between them by means of the …
Investigation of the $B_c\rightarrow χ_{c2} l \barν $ transition via QCD sum rules
在QCD求和规则的框架下，考虑双胶子凝聚修正，计算了半轻子$B_c\rightarrow χ_{c2} l \barν $的跃迁形状因子。利用所得到的形状因子的结果，我们估计了在所有轻子通道中与这种跃迁有关的衰变宽度和分支比。所得结果与其他非微扰方法的预测进行了比较。不同轻子通道的分支比的顺序表明，$B_c\rightarrow χ_{c2} l \barν $跃迁可以在大型强子对撞机上利用收集到的或将来的数据进行研究。
We investigate $J/ψ$ decays into octet baryon-antibaryons pairs. The decay amplitudes are computed within the collinear QCD factorisation framework. The subleading amplitude, which describes the decay of longitudinally polarised charmonium, is computed using twist-4 three-quark distribution amplitudes. The obtained results are used for a qualitative analysis of the experimental data. It is found that the polarisation parameter $α_B$ can be described with an accuracy $10-30\%$, which may indicate that the pQCD contribution dominates this observable.
We study the electromagnetic form factors of $Λ$ hyperon in the timelike region using the recent experimental data in the exclusive production of $\barΛ Λ$ pair in electron-position annihilation. We present a pQCD inspired parametrization of $G_E(s)$ and $G_M(s)$ with only two parameters, and we consider a suppression mechanism of the electric form factor $G_E(s)$ compared to the magnetic form factor $G_M(s)$. The parameters are determined through fitting our parametrization to the effective form factor data in the reaction $e^+e^-\rightarrow \barΛΛ$. Except the threshold region, our parametri…
An investigation about localized CP asymmetries for the processes of $\bar{B}_{s}^{0} \rightarrow π^{+}π^{-}π^{0} (K^{0})$ is presented in this paper. The innovation of this paper is that there is a consideration of three-particle $ρ^0(770)$, $ω(782)$ and $ϕ(1020)$ interferences effect. Generally, $ω(782)$ and $ϕ(1020)$ both can decay into $π^+π^-$ pair where can cause extremely small contribution from isospin symmetry breaking. Nevertheless, our analysis shows that $\bar{B}_{s}^{0} \rightarrow π^+π^-π^{0}(K^{0})$ decay process can bring differential CP asymmetry about $65\%$ ($36\%$) because …
We systematically study the semileptonic decay process of $ D\rightarrow S,A l\bar{ν_{l}}(l=e,μ)$ by light-cone sum rules (LCSR) with chiral currents, calculate the form factors containing only the contribution of the leading twist light-cone distribution amplitudes (LCDAs). For scalar mesons $a_{0}(980)$ and $a_{0}(1450)$, we take them as $q\bar{q}$ states. For axial-vector meson, we study $a_{1}(1260)( 1^{3}p^{1})$ and $b_{1}(1235)( 1^{1}p^{1})$. Based on the results of these form factors, we further present the branching ratios of these semileptonic decay processes. The numerical results fo…
The observation of anomalies in the charged current $b\rightarrow c\bar{\ell}ν_{\ell}$ transitions hints the possibility of the existence of new physics beyond the standard model. Inspired by the work done in the beauty quark sector, we explore new physics in the charm quark sector with $c \rightarrow (s,d)\bar{\ell}ν_{\ell}$ charged current transitions. We analyze the decay modes $D_{(s)}^+ \to η^{(')} \bar{\ell} ν_{\ell}$ within an effective Lagrangian framework which includes both standard model and new physics contributions. We use the available experimental measurements of the semileptoni…
