We calculate the branching ratios and CP asymmetries of the $B \to πρ$, $πω$ decays in the perturbative QCD factorization approach up to the next-to-leading-order contributions. We find that the next-to-leading-order contributions can interfere with the leading-order part constructively or destructively for different decay modes. Our numerical results have a much better agreement with current available data than previous leading-order calculations, e.g., the next-to-leading-order corrections enhance the $B^0\rightarrow π^0ρ^0$ branching ratios by a factor 2.5, which is helpful to narrow the gaps between theoretic predictions and experimental data. We also update the direct CP-violation parameters, the mixing-induced CP-violation parameters of these modes, which show a better agreement with experimental data than many of the other approaches.
We study lifetimes of heavy mesons in the 't Hooft model, a large-$N_c$ theory of strong interaction in two-dimensional spacetime. Since this model is solvable, one can evaluate the total decay widths through hadronic amplitudes that are determined unambiguously within the formalism. We investigate quark-hadron duality by numerically comparing the exclusive result and one from the heavy quark expansion, with the contribution of Pauli interference being consistently incorporated. Within certain numerical accuracy, we find that the maximal difference between inclusive and exclusive rates for $τ[…
We revisit QCD factorization of $B\to ππ$ form factors at large dipion masses, by deriving new constraints based on the analyticity properties of these objects. We then propose a parametrization of the form factors, inspired by the leading-twist QCD factorization formula, that incorporates all known analytic properties. This parameterization is used to interpolate between the QCDF results and the constraints from the $B^*$ pole. Based on this interpolation, we predict the $B\to ππ\ellν$ decay rate in a larger phase space region than previous studies could. We obtain a partially-integrated bran…
We reconsider the problem of transverse momentum broadening of a highly-energetic parton suffering multiple scatterings in dense colored media, such as the thermal Quark-Gluon plasma or large nuclei. In the framework of Molière's theory of multiple scattering we re-derive a simple analytic formula, to be used in jet quenching phenomenology, that accounts for both the multiple soft and hard Rutherford scattering regimes. Further, we discuss the sensitivity of momentum broadening to modeling of the non-perturbative infrared sector by presenting a detailed analytic and numerical comparison betwee…
We make a detailed study on the typical production channel of double charmoniums, $e^+e^-\to J/ψ+η_c$, at the center-of-mass collision energy $\sqrt{s}=10.58$ GeV. The key component of the process is the form factor $F_{\rm VP}(q^2)$, which has been calculated within the QCD light-cone sum rules (LCSR). To improve the accuracy of the derived LCSR, we keep the $J/ψ$ light-cone distribution amplitude up to twist-4 accuracy. Total cross sections for $e^+e^-\to J/ψ+η_c$ at three typical factorization scales are $σ|_{μ_s} = 22.53^{+3.46}_{-3.49}~{\rm fb}$, $σ|_{μ_k} = 21.98^{+3.35}_{-3.38}~{\rm fb}…
In the framework of perturbative QCD, the radiative decays $J/ψ\rightarrowγη^{(\prime)}$ are revisited in detail, where the involved one-loop integrals are evaluated analytically with the light quark masses kept. We have found that the sum of loop integrals is insensitive to the light quark masses and the branching ratios $\mathcal{B}(J/ψ\rightarrowγη^{(\prime)})$ barely depend on the shapes of $η^{(\prime)}$ distribution amplitudes. With the parameters of $η-η^{\prime}$ mixing extracted from low energy processes and $J/ψ\rightarrowγη^{(\prime)}$ by means of nonperturbative matrix elements $\l…
We review in some detail the QCD corrections to the measurement of the forward-backward charge asymmetry of heavy quarks in the $\mathrm{e^+e^-\rightarrow Q\overline{Q}(g)}$ process at the Z pole. We show that the size of these corrections can be reduced by an order of magnitude by using simple cuts on jet acollinearity. Such a reduction is expected to lead to systematic uncertainties at the $Δ\mathrm{A_{FB}^{0,Q}} \approx 10^{-4}$ level, opening up the path to high precision electroweak measurements with heavy flavors at future high luminosity $\mathrm{e^+e^-}$ colliders like the FCC-ee.
We revisit the hidden-charm pentaquark states $P_c(4380)$ and $P_c(4450)$ using the method of QCD sum rules by requiring the pole contribution to be larger than or around 30\% to better insure the one-pole parametrization to be valid. We find two mixing currents and our results suggest that the $P_c(4380)$ and $P_c(4450)$ can be identified as hidden-charm pentaquark states having $J^P=3/2^-$ and $5/2^+$, respectively, while there still exist other possible spin-parity assignments, such as $J^P=3/2^+$ and $J^P=5/2^-$, which needs to be clarified in further theoretical and experimental studies.
Using the global properties of the QCD partition function we determine an all order perturbative beta function in the background gauge field method to find out that it has a simple expressions whose properties and consequences align with other recent results in the QCD literature. We further compute the non-perturbative beta functions for the coupling constant and the theta angle in the background of an instanton field with winding number $n$. We solve for the theta angle in the non-perturbative region to determine that it is approximately zero. By extrapolating to the full QCD beta functions …
We revisit the calculation of nonfactorizable corrections induced by charm-quark loops in exclusive FCNC $B$-decays. For the sake of clarity, we make use of a field theory with scalar particles: this allows us to focus on the conceptual issues and to avoid technical complications related to particle spins in QCD. We perform a straightforward calculation of the appropriate correlation function and show that it requires the knowledge of the full generic three-particle distribution amplitude with non-aligned arguments, $\langle 0|\bar s(y)G_{μν}(x)b(0)|B(p)\rangle$. Moreover, the dependence of th…
Extraction of the x-dependence of the non-perturbative QCD b-quark fragmentation distribution component
利用最近在Z极记录的$e^+e^- \to b \bar{b}$事件中获得的b夸克碎裂分布的测量结果，独立于任何强子物理模型，提取了该分布的非微扰QCD分量。这种分布只取决于微扰QCD分量的定义方式。当微扰QCD分量取自部分子簇射Monte-Carlo时，非微扰QCD分量与Lund或Bowler模型的结果相当相似。当微扰QCD分量是解析NLL计算的结果时，非微扰QCD分量必须在非物理区域中扩展，因此不能用任何强子模型来描述。在目前研究的用于表征这两种情况的两个例子中，提取的非微扰QCD分布具有相同的形状，在第二种方法中被简单地转换为更高的x值，说明了解析微扰QCD方法比部分子簇射发生器更能解释更软的胶子辐射。
Revisiting In-Medium QCD Effects on Spin-Polarized Strange Quark Stars
Hansraj College, University of Delhi（德里大学汉斯拉吉学院）；Sri Aurobindo College, University of Delhi（德里大学斯里奥罗宾多学院）；University of Lucknow（勒克瑙大学）；South Valley University（南谷大学）
