arXiv subjects

Yan-Chao Zhao

Publications and source records attributed to Yan-Chao Zhao.

5 recordsLinked to original sources

arXiv2023

Covariant Light-Front Approach for $B_c$ Decays into Charmonium: Implications on Form Factors and Branching Ratios

In this work, we investigate the form factors of $B_c$ decays into $J/Ψ, ψ(2S,3S)$, $η_c, η_c(2S,3S), χ_{c0}, χ_{c1}, h_c$ and $X(3872)$ mesons in the covariant light-front quark model (CLFQM). For the purpose of the branching ratio calculation, the form factors of $B_c\to D^{(*)}, D^{(*)}_s$ transitions are also included. In order to obtain the form factors for the physical transition processes, we need extend these form factors from the space-like region to the time-like region. The $q^2$-dependence for each transition form factor is also plotted. Then, under the factorization method, we calculate the branching ratios of 80 $B_c$ decay channels with a charmonium involved in each mode. Most of our predictions are comparable with the results given by most of other approaches. As to the decays with the radially excited state S-wave charmonia, such as $ψ(2S,3S)$ and $η_c(2S,3S)$, involved, there are two sets of parameters for their light-front wave functions, corresponding to scenario I (SI) and scenario II (SII), are adopted to calculate the branching ratios. Comparing with the future experimental data, one can discriminate which parameters are more favored.

hep-ph↗

arXiv2023

Quasi-two-body decays $B_c\to D^*h\to Dπh$ in the perturbative QCD

In this work, we investigate the quasi-two-body decays $B_c\to D^*h\to Dπh$ with $h = (K^0,π^0,η,η^{\prime})$ using the perturbative QCD(PQCD) approach. The description of final state interactions between the $Dπ$ pair is achieved through the two-meson distribution amplitudes(DAs), which are normalized to the time-like form factor. The PQCD predictions on the branching ratios of the quasi-two-body decays $B_c\to D^*h\to Dπh$ show an obvious hierarchy: $Br(B_{c}^+ \to D^{*+} K^{0}\to D^0π^+K^{0})=({5.22}_{-0.74}^{+0.86})\times{10}^{-6}, Br(B_{c}^+ \to D^{*+} π^{0}\to D^0π^+π^{0})=(0.93\pm0.26)\times{10}^{-7}, Br(B_{c}^+ \to D^{*+} η\to D^0π^+η) =({2.83}_{-0.52}^{+0.59})\times{10}^{-8}$ and $Br(B_{c}^+ \to D^{*+} η^\prime\to D^0π^+η^\prime)=({1.89}_{-0.36}^{+0.40})\times{10}^{-8}$. From the invariant mass $m_{Dπ}$-dependence of the decay spectrum for each channel, one can find that the branching fraction is concentrated in a narrow region around the $D^{*}$ pole mass. So one can obtain the branching ratios for the corresponding two-body decays $B_c\to D^{*+}h$ under the narrow width approximation. We find that the branching ratios of the decays $B_c\to D^{*+}h$ are consistent well with the previous PQCD calculations within errors. These predictions will be tested by the future experiments.

hep-ph↗

arXiv2022

Insights into the nature of the $X(3872)$ through B meson decays

We study the decays $B_{c,u,d}\to X(3872)P$ in the perturbative QCD (PQCD) approach, where the puzzling resonance $X(3872)$ is involved and $P$ represents a light pseudoscalar meson $K$ and $π$. Assuming the $X(3872)$ as a $1^{++}$ charmonium state, we find the following results: (a) The branching ratios for the decays $B^+_c\to X(3872)π^+$ and $B^+_c\to X(3872) K^+$ agree with the results predicted by the covariant light-front approach within errors, but are larger than those given by the generalized factorization approach; (b) The branching ratio for the decay $B^+\to X(3872)K^+$ is predicted as $(3.8^{+1.1}_{-1.0})\times10^{-4}$, which is smaller than the previous PQCD calculation result, but still slightly larger than the upper limits set by Belle and BaBar. So we suggest that the decays $B^{0,+}\to X(3872)K^{0,+}$ should be precisely measured by the running LHCb and Belle II experiments, which is very helpful to probe the inner structure of the $X(3872)$; (c) Compared with the decays $B_{u,d}\to X(3872)K$, the decays $B_{u,d}\to X(3872)π$ have much smaller branching ratios, which drop to as low as $10^{-6}$; (d) The direct CP violations for these considered decays are very small, only $10^{-3}\sim 10^{-2}$, because the penguin contributions are loop suppressed compared with the tree contributions. Testing the results for the branching ratios and the CP violations including the implicit $SU(3)$ and isospin symmetries in these decays by experiments is helpful to probe the nature of the $X(3872)$.

hep-ph↗

arXiv2022

Quasi-two-body decays $B_{(s)}\to K^*γ\to Kπγ$ in perturbative QCD approach

In this work we study the quasi-two-body decays $B\to K^*γ\to Kπγ$ in the perturbative QCD (PQCD) approach. The two-meson distribution amplitudes (DAs) are introduced to describe the final state interactions of the $Kπ$ pair, which involve the time-like form factors and the Gegenbauer polynomials. We calculate the CP averaged branching ratios for the decays $B_{(s)}\to K^*γ\to Kπγ$. Our results are in agreement with the new update data measured by Belle II, which suggests these quasi-two-body decays are more appropriate to be analyzed in three-body framework than in the two-body one. We also predict the direct CP-violation asymmetries for the considered decay modes and find that $A_{CP}(B_{u,d}\to K^*γ\to Kπγ)$ is small and less than $1\%$ in magnitude, while $A_{CP}(B_{s}\to K^*γ\to Kπγ)$ is larger and can arrive at a few percent. Our predictions can be tested by the future B meson experiments.

hep-ph↗

arXiv2021

Probing $D^*_{s0}(2317)$ in the decays of $B$ to two charmed mesons

We probe the inner structure of the meson $D^*_{s0}(2317)$ through the decays of $B_{(s)}$ to two charmed mesons within pQCD approach. Assuming $D^*_{s0}(2317)$ as a scalar meson with $\bar cs$ structure, we find that the predictions for the branching ratios of the decays $B^+\to D^{*+}_{s0}(2317)\bar D^{(*)0}, B^0\to D^{*+}_{s0}(2317)D^{(*)-}$ can explain data within errors. The branching ratios for the decays $B_s\to D^{*+}_{s0}(2317)D_s^{(*)+}$ are estimated to reach up to $10^{-3}$ order, which can be observed by the present LHCb and SuperKEKB experiments. In this work, the decay constant of the meson $D^*_{s0}(2317)$ is an input parameter. Unfortunately, its value has been studied by many references but with large uncertainties. Our calculation shows that a smaller decay constant of the meson $D^*_{s0}(2317)$ is supported by compared with the present data, say $55\sim70$ MeV. We also calculate the ratios $R_1=\frac{Br(B^+\to D^{*+}_{s0}(2317)\bar D^0)}{Br(B^+\to D^{*+}_{s0}(2317)\bar D^{*0})})$ and $R_2=\frac{Br(B^0\to D^{*+}_{s0}(2317)D^-)}{Br(B^0\to D^{*+}_{s0}(2317)D^{*-})}$, which are valuable to determine the inner structure of $D^*_{s0}(2317)$ by compared with the experimental results. Our predictions for the ratios $R_{1,2}$ are consistent with the present data within errors.We expect that these two ratios can be well measured by the future experiments through improving the measurement accuracy for the decays $B^+\to D^{*+}_{s0}(2317)\bar D^{*0}$ and $B^0\to D^{*+}_{s0}(2317)D^{*-}$.

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