arXiv subjects

Xian-Qiao Yu

Publications and source records attributed to Xian-Qiao Yu.

At least 19 recordsLinked to original sources

arXiv2026

Quasi-two-body decays $B_c^+ \to \chi_{c0,c1} [\rho(K^*) \to] \pi\pi(K\pi)$ in the PQCD approach

We study the quasi-two-body decays $B_c^+ \to \chi_{c0,c1} [\rho(K^*) \to] \pi^+\pi^0(K^0\pi^+)$ in the perturbative QCD framework at leading order. The $\pi\pi$ and $K\pi$ pairs are produced via the P-wave resonances $\rho(770)$, $\rho(1450)$, $\rho(1700)$, and $K^*(892)$, parametrized by the Gounaris-Sakurai and relativistic Breit-Wigner models. The $\rho$ channels, dominated by the $\rho(770)$ resonance, yield $\mathcal{B}(B_c^+ \to \chi_{c0} \pi^+\pi^0) = 7.33 \times 10^{-4}$ and $\mathcal{B}(B_c^+ \to \chi_{c1} \pi^+\pi^0) = 1.02 \times 10^{-3}$, with constructive $\rho$ interference making the coherent total $\sim 26\%$--$30\%$ larger than the $\rho(770)$ contribution alone. The Cabibbo-suppressed $K\pi$ channels yield branching ratios roughly a factor of five below those of the $\pi\pi$ modes, $\mathcal{B}(B_c^+ \to \chi_{c0} K^0\pi^+) = 1.49 \times 10^{-4}$ and $\mathcal{B}(B_c^+ \to \chi_{c1} K^0\pi^+) = 1.94 \times 10^{-4}$, the Cabibbo suppression being only partially compensated by the narrow $K^*(892)$ resonance and the normalization factor $N_{K^*}=1.48$. For $\chi_{c1}$ modes, $f_L \approx 93\%$ dominates and decreases with increasing resonance mass. The ratio $R_{\chi_{c1}/\chi_{c0}}^{\pi\pi} \approx 1.38$ reflects the common resonant $\rho$ production mechanism shared by $\chi_{c0}$ and $\chi_{c1}$, with the charmonium decay-constant hierarchy and phase space determining the relative yield of P-wave charmonia. The analogous ratio in the Cabibbo-suppressed $K\pi$ channel, $R_{\chi_{c1}/\chi_{c0}}^{K\pi} \approx 1.30$, is consistent with this value, confirming that the spin ratio is governed by charmonium-side dynamics.

hep-ph↗

arXiv2025

Study of $B_{c} \to J/\psi (a_1(1260)$, $b_1(1235)$, $a_2(1320)$, $K_2^*(1430)) $ decay with a perturbative QCD approach

Motivated by systematic observations of $ B_c $ decays at LHCb, we analyze $B_c^+ \to J/\psi (A, T)$ decays (where $A$ denotes axial-vector mesons $a_1(1260)^+$, $b_1(1235)^+$, and $T$ denotes tensor mesons $a_2(1320)^+$, $K_2^*(1430)^+$) within the perturbative QCD (pQCD) factorization framework. The framework employs light-cone distribution amplitudes (LCDAs) to regulate nonperturbative dynamics, utilizing Sudakov suppression to control endpoint divergences. Our predictions indicate branching ratios of $10^{-3}\sim 10^{-2}$ for $B_c^{+} \to J/\psi A$ and $10^{-5}\sim 10^{-4}$ for $B_c^{+} \to J/\psi T$ decays, which seem to be in the reach of future experiments. We also provide predictions for the polarization fractions of these decays. Based on quark helicity analysis, the longitudinal polarization amplitudes are expected to dominate the branching ratios.

hep-ph↗

arXiv2024

Study of quasi-two-body B^{0}\rightarrow T(\pi\pi, K\bar{K},\pi\eta) decays in perturbative QCD approach

In this study, we calculate the CP-averaged branching ratios and the direct CP-violating asymmetries of the three body decays B^{0}\rightarrow T(\pi\pi, K\bar{K},\pi\eta) in the perturbative QCD approach, where T denotes tensor mesons a_{2}(1320), K^{*}_{2}(1430), f_{2}(1270) and f^{'}_{2}(1525), and the daughter branching is f_{0}(980)\rightarrow \pi\pi, K\bar{K},f_{0}(500)\rightarrow \pi\pi, a_{0}(980)\rightarrow K\bar{K}, \pi\eta. We found the following (a) With \theta=135^{\circ}, we evaluate the branching fractions of B^{0} \rightarrow K^{*}_{2}(1430)f_{0}(980)[ \rightarrow \pi^ {+}\pi^{-}] to be 4.30\times10^{-6},then under the narrow-width approximation we extract the branching fraction of the decay B^{0} \rightarrow K^{*}_{2}(1430)f_{0}(980) to be 8.78\times10^{-6},which is consistent with the current experimental data well. (b) The decay rates for the considered decay modes are generally in the order of 10^{-8} to 10^{-5}. (c) The branching fractions are sensitive to the \theta, and the opposite is true for \phi. The \phi is really small, so the decay branching ratio has only little change, except for some decays involving f^{'}_{2}(1525). (d) The \theta and \phi can bring remarkable change to the direct CP asymmetries of pure penguin processes so that it is not 0. (e) We calculate the relative partial decay widths {\Gamma}(a_{0} \rightarrow K\overline{K})/{\Gamma}(a_{0} \rightarrow \pi\eta) and the ratio {\cal B}(f_{0} \rightarrow K^{+}K^{-})/{\cal B}(f_{0} \rightarrow \pi^{+}\pi^{-}), which are in agreement with the existing experimental values. Our results can help one to understand the internal structure of scalar mesons and the nature of tensor mesons and can be tested by future experiments.

hep-ph↗

arXiv2024

Study of B^{0}_{s} \rightarrow \ TT(a_{2}(1320),K^{*}_{2}(1430),f_{2}(1270),f^{'}_{2}(1525)) in the perturbative QCD approach

In the present study, the calculations of two-body decays B^{0}_{s} \rightarrow \ TT [ T denotes tensor mesons, a_{2}(1320), K^{*}_{2}(1430), f_{2}(1270), f^{'}_{2}(1525)] in the perturbative QCD approach are presented. The ensuing predictions encompass branching ratios, polarization fractions, and direct CP violations, all elucidated in comprehensive detail. It is discerned that (1) for pure annihilation decay, the longitudinal polarization is around 90.0\%, whereas the transverse polarizations manifest comparatively diminutive magnitudes. (2) The direct CP asymmetry is directly proportional to the interference between the tree and penguin contributions. For most of the decays investigated within this discourse, the direct CP asymmetry remains modest in magnitude. (3) There are precisely six distinct categories of Feynman diagrams for B^{0}_{s} \rightarrow \ TT , because the tensor mesons cannot be produced through the (V \pm A) currents or (S \pm P) density, thereby prohibiting factorizable emission diagrams. The nonfactorizable and annihilation contributions are ascertained to be pivotal in these decay modes. The calculated branching ratios of our calculation for B^{0}_{s} \rightarrow \ TT are at the order of 10^{-6} and 10^{-7}, which can be tested in the LHCb and Belle II experiments. (4) Mixing exists for the f_{2}(1270) and f^{'}_{2}(1525), just as the ηand η^{'} mixing, the branching ratios about the mixing angle θare given in this work. However, it is different from f_{1}(1285)-f_{1}(1420), the mixing angle is notably small, thereby resulting in only marginal alterations in the decay branching ratios.

hep-ph↗

arXiv2023

Investigating $B_s$ three-body decays to scalar mesons in perturbative QCD approach

In this work, we study the branching ratios of B^{0}_{s}\rightarrow a_{0}(980)[ \rightarrow K\overline{K}, πη]a_{0}(980), B^{0}_{s} \rightarrow f_{0}(980)[ \rightarrow π^{+}π^{-}, K^{+}K^{-}]f_{0}(980) and B^{0}_{s} \rightarrow f_{0}(500)[ \rightarrow π^{+}π^{-}]f_{0}(500) decays in the pQCD approach, in which the scalar mesons a_{0}(980), f_{0}(980) and f_{0}(500) are regarded as the lowest-lying q\overline{q} state. In the SU(3) nonet, there exists a mixing between the scalars f_{0}(980) and f_{0}(500), so we have considered the mixing effect in our calculations to obtain more reliable data, and the mixing angle θis set at [15^{\circ}, 82^{\circ}] and [105^{\circ}, 171^{\circ}]. Based on the isospin symmetry, we also estimate the branching ratios of the B^{0}_{s} \rightarrow f_{0}(980)[ \rightarrow π^{0}π^{0}]f_{0}(980) and B^{0}_{s} \rightarrow f_{0}(500)[ \rightarrow π^{0}π^{0}]f_{0}(500) decays. The branching ratios of the B^{0}_{s}\rightarrow a_{0}(980)[ \rightarrow K\overline{K}, πη]a_{0}(980) decays are much small, while the results of the B^{0}_{s} \rightarrow f_{0}(980)[ \rightarrow ππ, K\overline{K}]f_{0}(980) and B^{0}_{s} \rightarrow f_{0}(500)[ \rightarrow ππ]f_{0}(500) decays are at the order of 10^{-6}\sim10^{-5}, which can be tested in the LHCb and Belle II experiments, hopefully.

hep-ph↗

arXiv2022

Study of the four-body decays $B^{0}_{S} \rightarrow ππππ$ in the perturbative QCD approach

In this work, we analyse the CP-averaged branching ratios and direct CP-violating asymmetries of the four-body decays B_{S} \rightarrow ππππdecay from the S-wave resonances, f_{0}(980) and f_{0}(500) and P-wave resonances, ρ(770) by introducing the S-wave and P-wave ππdistribution amplitudes within the framework of the perturbative QCD approach. We also calculate branching ratios of the two-body decays B^{0}_{S}\rightarrowρ^{0}ρ^{0}, B^{0}_{S}\rightarrowρ^{+}ρ^{-} from the corresponding quasi-two-body decays models and compare our results with those obtained in previous perturbative QCD approach, QCD factorization approach and FAT approach, it is found that the predictions are consistent with present data within errors. The branching ratios of our calculations for the four-body decays B_{S}\rightarrow ππππare at the order of the 10^{-7}. For the CP-violating asymmetries, we found that CP-violating asymmetry can be enhanced largely by the ρ-ωmixing resonances when ππpairs masses are in the vicinity of ωresonance.

hep-ph↗

arXiv2022

Study the contributions of S, P, and D-wave resonances to the quasi-two-body decays $B^{0}_{s} \rightarrow ψ(3686,3770)Kπ$ in perturbative QCD approach

Based on the perturbative quantum chromodynamics (pQCD) approach and the quasi-two-body approximation, we have studied the three-body decays B^{0}_{s}\rightarrow ψ(3686,3770)\emph{K}π, which include the contributions of the intermediate resonances \bar{\emph{K}}^{*}_{0}(1430)^{0}, \bar{\emph{K}}^{*}(892)^{0}, \bar{\emph{K}}^{*}(1410)^{0}, \bar{\emph{K}}^{*}(1680)^{0}, and \bar{\emph{K}}^{*}_{2}(1430)^{0}. The time-like form factors corresponding to the distribution amplitudes of the S, P, and D-wave of the kaon-pion pair have been adopted in the parameterized form, which describe the interactions between \emph{K} and πin the resonance region. First, the decays B^{0}_{s}\rightarrow ψ(2S,1D)\emph{K}^{-}π^{+} have been calculated followed by the calculation of the branching ratios of the decays B^{0}_{s}\rightarrow ψ(3686,3770)\emph{K}^{-}π^{+} using the 2S-1D mixing scheme. In addition, the pQCD predictions for the decays B^{0}_{s}\rightarrow ψ(2S,1D)\emph{K}πand B^{0}_{s}\rightarrow ψ(3686,3770)\emph{K}πhave been obtained using the narrow-width approximation relation given by the Clebsch-Gorden coefficients. Our work shows that the \bar{\emph{K}}^{*}(892)^{0} resonance is the main contributor to the total decay, and the branching ratio and the longitudinal polarization fraction of the ψ(2S)\bar{\emph{K}}^{*}(892)^{0} decay mode agree well with the currently available data within errors. Furthermore, the theoretical predictions of the ψ(2S) and ψ(3686) decay modes are very close, indicating that they can be regarded as the same meson state. Finally, the pQCD predictions for branching ratios of decays B^{0}_{s}\rightarrow ψ(3686,3770)\emph{K}πare of the order of 10^{-5} and 10^{-6}, respectively, which can be verified using the ongoing LHCb and Belle II experiments.

hep-ph↗

arXiv2020

The perturbative QCD predictions for the decay B^{0}_{s}\rightarrow SS(a_{0}(980),f_{0}(980),f_{0}(500))

In this work, we calculate the branching ratios and CP violations of the B^{0}_{s}\rightarrow a_{0}(980)a_{0}(980) decay modes with both charged and neutral a_{0}(980) mesons and B^{0}_{s}\rightarrow f_{0}(980)(f_{0}(500))f_{0}(980)(f_{0}(500)) for the first time in the pQCD approach. Considering the recent observation of the BESIII collaboration that provide a direct information about the constituent two-quark components in the corresponding a_{0}(980) wave functions, we regard the scalar mesons a_{0}(980), f_{0}(980) and f_{0}(500) as the q\bar{q} quark component in our present work, and then make predictions of these decay modes. The branching ratios of our calculations are at the order of the 10^{-4}\sim10^{-6} when we consider the mixing scheme. We also calculate the CP violation parameters of these decay modes. The relatively large branching ratios make it easily to be tested by the running LHC-b experiments, and it can help us to understand both the inner properties and the QCD behavior of the scalar meson.

hep-ph↗

arXiv2019

Study of the quasi-two-body decays B^{0}_{s} \rightarrow ψ(3770)(ψ(3686))π^+π^- with perturbative QCD approach

In this note, we study the contributions from the S-wave resonances, f_{0}(980) and f_{0}(1500), to the B^{0}_{s}\rightarrow ψ(3770)π^ {+}π^{-} decay by introducing the S-wave ππdistribution amplitudes within the framework of the perturbative QCD approach. Both resonant and nonresonant contributions are contained in the scalar form factor in the S-wave distribution amplitude Φ^S_{ππ}. Since the vector charmonium meson ψ(3770) is a S-D wave mixed state, we calculated the branching ratios of S-wave and D-wave respectively, and the results indicate that f_{0}(980) is the main contribution of the considered decay, and the branching ratio of the ψ(2S) mode is in good agreement with the experimental data. We also take the S-D mixed effect into the B^{0}_{s}\rightarrow ψ(3686)π^ {+}π^{-} decay. Our calculations show that the branching ratio of B^{0}_{s}\rightarrow ψ(3770)(ψ(3686))π^ {+}π^{-} can be at the order of 10^{-5}, which can be tested by the running LHC-b experiments.

hep-ph↗

arXiv2018

Study of $B_{c} \rightarrow ψ(2S) K$, $η_{c}(2S)K$, $ψ(3770)K$ decays with perturbative QCD approach

We study the $B_{c}$$\rightarrow$$ψ(2S)$K, $η_{c}(2S)$K, $ψ(3770)$K decays with perturbative QCD approach (pQCD) based on $k_T$ factorization. The new orbitally excited charmonium distribution amplitudes $ψ(1^{3}D_{1})$ based on the Schrödinger wave function of the $n=1$, $l=2$ state for the harmonic-oscillator potential are employed. By using the corresponding distribution amplitudes, we calculate the branching ratio of $B_{c}$$\rightarrow$$ψ(2S)$K, $η_{c}(2S)$K, $ψ(3770)$K decays and the form factors $A_{0,1,2}$ and $V$ for the transition $B_{c}$$\rightarrow$$ψ(1^{3}D_{1})$. We obtain the branching ratio of both $B_{c}$$\rightarrow$$ψ(2S)$K and $B_{c}$$\rightarrow$$η_{c}(2S)$K are at the order of $10^{-5}$. The effects of two sets of the S-D mixing angle $θ=-12^{\circ}$ and $θ=27^{\circ}$ for the decay $B_{c}$$\rightarrow$$ψ(3770)$K are studied firstly in this paper. Our calculations show that the branching ratio of the decay $B_{c}$$\rightarrow$$ψ(3770)$K can be raised from the order of $10^{-6}$ to the order of $10^{-5}$ at the mixing angle $θ=-12^{\circ}$, which can be tested by the running LHC-b experiments.

hep-ph↗

arXiv2017

Revisiting the $B^{0} \to π^{0}π^{0} $ decays in the perturbative QCD approach

We recalculate the branching ratio and CP asymmetry for $\bar{B}^{0} (B^{0})\to π^{0}π^{0}$ decays in the Perturbative QCD approach. In this approach, we consider all the possible diagrams including non-factorizable contributions and annihilation contributions. We obtain $Br(\bar{B}^{0} (B^{0})\to π^{0}π^{0})=(1.17_{-0.12}^{+0.11})\times 10^{-6}$. Our result is in agreement with the latest measured branching ratio of $B^{0}\toπ^{0}π^{0}$ by the Belle and HFAG Collaborations. We also predict large direct CP asymmetry and mixing CP asymmetry in $B^{0}\toπ^{0}π^{0}$ decays, which can be tested by the coming Belle-II experiments.

hep-ph↗

arXiv2016

Parton distribution of nucleon and nuclear EMC effect in a statistical model

We study the parton distribution of nucleon and nuclear EMC effect in a statistical model. We find when we choose the parameters appropriately, the predictions given by pure statistical laws can fit the experimental data well in most range of $x$, this reveal statistical law play an important role in the parton distribution of nucleon.

hep-ph↗

arXiv2012

Concerning the searches for Higgs bosons

The great successes achieved by the Standard Model(SM) lead us to believe the existence of the Higgs particle. On the other hand, there are many evidences indicate that some unknown dark matter particle must exist in our universe. To identify the Higgs boson as the dark matter particle is difficult in the present SM, the challenge is: the Higgs particle is unstable while the dark matter particle is stable. A solution of this problem is proposed in this paper. We will describe a model in which almost all the predictions made by the present SM remain unchanged but leave two neutral stable Higgs particles, which may be the dark matter particle. Some possible experimental tests of Higgs particle are also suggested in this paper.

physics.gen-ph↗

arXiv2010

Study of B_{c}\to J/ψK decays in the perturbative QCD approach

In this note, we calculate the branching ratio of B_c\to J/ψK in the framework of perturbative QCD approach based on k_T factorization. This decay can occur only via tree level diagrams in the Standard Model. We find that the branching ratio of B_c\to J/ψK is about (1-3)\times10^{-4}. The large branching ratio and the clear signals of the final states make the measurement of B_c\to J/ψK easily at LHC-b experiments.

hep-ph↗

arXiv2009

Nucleon electromagnetic form factors in a quark-gluon core model

We study the nucleon electromagnetic form factors in a quark-gluon core model framework, which can be viewed as an extension of the Isgur-Karl model of baryons. Using this picture we derive nucleon electromagnetic dipole form factors at low Q^2 and the deviation from the dipole form at high Q^2, that are consistent with the existing experimental data.

hep-ph↗

arXiv2009

Branching ratio and CP violation of $B_c \to D K$ decays in the perturbative QCD approach

In this paper, we calculate the branching ratio and direct CP asymmetry parameter of $B_c^{\pm}\to D^{0}K^{\pm}$ in the framework of perturbative QCD approach based on $k_T$ factorization. Besides the usual factorizable diagrams, both non-factorizable and annihilation type contributions are taken into account. We find that (a) the branching ratio is at the order of $10^{-5}$; (b) the tree annihilation diagrams and the penguin diagrams dominate the total contribution; and (c) the direct CP asymmetry is about 7%, which can be tested in the Large Hadron Collider beauty experiments (LHC-b) at CERN.

hep-ph↗

arXiv2006

Study of $B_{s}\to πρ$ decays in the perturbative QCD approach

In this note, we calculate the branching ratio and CP asymmetry parameters of $B_s\toπρ$ in the framework of perturbative QCD approach based on $k_T$ factorization. This decay can occur only via annihilation diagrams in the Standard Model. We find that (a)the charge averaged $Br(B_s\toπ^{+}ρ^{-}+π^{-}ρ^{+})$ is about $(9-12)\times10^{-7}$; $Br(B_s\toπ^{0}ρ^{0}) \simeq 4\times10^{-7}$; and (b) there are sizable CP asymmetries in the processes, which can be tested in the near future Large Hadron Collider beauty experiments (LHC-b) at CERN or BTeV experiments at Fermilab.

hep-ph↗

arXiv2005

Branching ratio and CP violation of $B_{s}\to πK$ decays in the perturbative QCD approach

In the framework of perturbative QCD approach, we calculate the branching ratio and CP asymmetry for $B_{s}^0(\bar{B}_{s}) \to π^{\pm} K^\mp$ and $B_{s}(\bar{B}_{s})\to π^{0}\bar{K}^{0}(K^{0})$ decays. Besides the usual factorizable diagrams, both non-factorizable and annihilation type contributions are taken into account. We find that (a) the branching ratio of $B_{s}^0(\bar{B}_{s}) \to π^{\pm} K^\mp$ is about $(6-10) \times 10^{-6}$; $Br(B_{s}(\bar{B}_{s})\to π^{0}\bar{K}^{0}(K^{0}))$ about $ (1-3) \times 10^{-7}$; and (b) there are large CP asymmetries in the two processes, which can be tested in the near future LHC-b experiments at CERN and BTeV experiments at Fermilab.

hep-ph↗