arXiv subjects

Zhou Rui

Publications and source records attributed to Zhou Rui.

45 records · Page 3Linked to original sources

arXiv2017

Branching ratios, $CP$ asymmetries and polarizations of $B\rightarrow ψ(2S) V$ decays

We analyzed the nonleptonic decays $B/B_s\to ψ(2S) V $ with $V=(ρ, ω, K^{*}, ϕ)$ by employing the perturbative QCD (PQCD) factorization approach. Here the branching ratios, the $CP$ asymmetries and the complete set of polarization observables are investigated systematically. Besides the traditional contributions from the factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order (NLO) vertex corrections could also provide considerable contributions. The PQCD predictions for the branching ratios of the $B_{(s)}\to ψ(2S)K^{*}, ψ(2S) ϕ$ decays are consistent with the measured values within errors. As for $B\to ψ(2S) ρ, ψ(2S) ω$ decays, the branching ratios can reach the order of $10^{-5}$ and could be measured in the LHCb and Belle-II experiments. The numerical results show that the direct $CP$ asymmetries of the considered decays are very small. Thus the observation of any large direct $CP$ asymmetry for these decays will be a signal for new physics. The mixing induced $CP$ asymmetries in the neutral modes are very close to $\sin 2β_{(s)}$, which suggests that these channels can give a cross-check on the measurement of the Cabbibo-Kobayashi-Maskawa (CKM) angle $β$ and $β_s$. We found that the longitudinal polarization fractions $f_0$ are suppressed to $\sim 50\%$ due to the large nonfactorizable contributions. The magnitudes and phases of the two transverse amplitudes $\mathcal {A}_{\parallel}$ and $\mathcal {A}_{\perp}$ are roughly equal, which is an indication for the approximate light quark helicity conservation in these decays. The overall polarization observables of $B\to ψ(2S) K^{*0}$ and $B_s\to ψ(2S) ϕ$ channels are also in good agreement with the experimental measurements as reported by LHCb and BaBar. Other results can also be tested by the LHCb and Belle-II experiments.

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arXiv2017

The S-wave resonance contributions in the $B^0_s$ decays into $ ψ(2S,3S)$ plus pion pair

The three-body decays $B^0_s \rightarrow ψ(2S,3S) π^+ π^-$ are studied based on the perturbative QCD approach. With the help of the nonperturbative two-pion distribution amplitudes, the analysis is simplified into the quasi-two-body processes. Besides the traditional factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order vertex corrections are also included to cancel the scale dependence. The $f_0(980)$, $f_0(1500)$ resonance contributions as well as the nonresonant contributions are taken into account using the presently known $ππ$ time-like scalar form factor for the $s\bar{s}$ component. It is found that the predicted $B^0_s \rightarrow ψ(2S) π^+ π^-$ decay spectra in the pion pair invariant mass shows a similar behavior as the experiment. The calculated S-wave contributions to the branching ratio of $B^0_s \rightarrow ψ(2S) π^+ π^-$ is $6.0\times 10^{-5}$, which is in agreement with the LHCb data $\mathcal {B}(B^0_s \rightarrow ψ(2S) π^+ π^-)=(7.2\pm 1.2)\times 10^{-5} $ within errors. The estimate of $\mathcal {B}(B^0_s \rightarrow ψ(3S) π^+ π^-)$ can reach the order of $10^{-5}$, pending for the corresponding measurements.

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arXiv2016

Semileptonic decays of $B_c$ meson to S-wave charmonium states in the perturbative QCD approach

Inspired by the recent measurement of the ratio of $B_c$ branching fractions to $J/ψπ^+$ and $J/ψμ^+ν_μ$ final states at the LHCb detector, we study the semileptonic decays of $B_c$ meson to the S-wave ground and radially excited 2S and 3S charmonium states with the perturbative QCD approach. After evaluating the form factors for the transitions $B_c\rightarrow P,V$, where $P$ and $V$ denote pseudoscalar and vector S-wave charmonia, respectively, we calculate the branching ratios for all these semileptonic decays. The theoretical uncertainty of hadronic input parameters are reduced by utilizing the light-cone wave function for $B_c$ meson. It is found that the predicted branching ratios range from $10^{-6}$ up to $10^{-2}$ and could be measured by the future LHCb experiment. Our prediction for the ratio of branching fractions $\frac{\mathcal {BR}(B_c^+\rightarrow J/Ψπ^+)}{\mathcal {BR}(B_c^+\rightarrow J/Ψμ^+ν_μ)}$ is in good agreement with the data. For $B_c\rightarrow V l ν_l$ decays, the relative contributions of the longitudinal and transverse polarization are discussed in different momentum transfer squared regions. These predictions will be tested on the ongoing and forthcoming experiments.

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arXiv2015

The $B_c\rightarrow ψ(2S)π$, $η_c(2S)π$ decays in the perturbative QCD approach

Nonleptonic two body $B_c$ decays including radially excited $ψ(2S)$ or $η_c(2S)$ mesons in the final state are studied using the perturbative QCD approach based on $k_T$ factorization. The charmonium distribution amplitudes are extracted from the $n = 2, l = 0$ Schr$\ddot{o}$dinger states for the harmonic oscillator potential. Utilizing these distribution amplitudes, we calculate the numerical results of the $B_c\rightarrow ψ(2S),η_c(2S)$ transition form factors and branching fractions of $B_c\rightarrow ψ(2S)π, η_c(2S)π$ decays. The ratio between two decay modes $B_c\rightarrow ψ(2S)π$ and $B_c\rightarrow J/ψπ$ is compatible with the experimental data within uncertainties, which indicate that the harmonic oscillator wave functions for $ψ(2S)$ and $η_c(2S)$ work well. It is found that the branching fraction of $B_c\rightarrow η_c(2S)π$, which is dominated by the twist-3 charmonium distribution amplitude, can reach the order of $10^{-3}$. We hope it can be measured soon in the LHCb experiment.

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arXiv2015

S-wave ground state charmonium decays of $B_c$ mesons in the perturbative QCD approach

We make a systematic investigation on the two-body nonleptonic decays $B_c\rightarrow J/Ψ(η_c),M$ by employing the perturbative QCD approach based on $k_T$ factorization, where $M$ is a light pseudoscalar or vector or a heavy charmed meson. We predict the branching ratios and direct CP asymmetries of these $B_c$ decays and also the transverse polarization fractions of $B_c\rightarrow J/ΨV,J/ψD^{*}_{(s)}$ decays. It is found that these decays have a large branching ratios of the order of $10^{-4} - 10^{-2}$ and could be measured by the future LHC-b experiment. Our predictions for the ratios of branching fractions $\frac{\mathcal {BR}(B_c^+\rightarrow J/ΨD_s^+)} {\mathcal {BR}(B_c^+\rightarrow J/Ψπ^+)}$ ,$\frac{\mathcal {BR}(B_c^+\rightarrow J/ΨD_s^{*+})} {\mathcal {BR}(B_c^+\rightarrow J/ΨD_s^+)}$ and $\frac{\mathcal {BR}(B_c^+\rightarrow J/ΨK^+)} {\mathcal {BR}(B_c^+\rightarrow J/Ψπ^+)}$ are in good agreement with the data. A large transverse polarization fraction which can reach $48\%$ is predicted in $B_c^+\rightarrow J/ΨD_s^{*+}$ decay, which is consistent with the data. We find a possible direct CP violation in $B_c\rightarrow J/ψD^{*}$ decays, which are helpful to test the CP violating effects in $B_c$ decays.

hep-ph↗

arXiv2012

The two-body B_c {\to} D^{()}_{(s)}P, D^{()}_{(s)}V decays in the Perturbative QCD Approach

We make a systematic investigation on the two-body nonleptonic decays B_c {\to} D^{(*)}_{(s)}P, D^{(*)}_{(s)}V, by employing the perturbative QCD approach based on k_T factorization, where P and V denote any light pseudoscalar meson and vector meson, respectively. We predict the branching ratios and direct CP-asymmetries of these B_c decays and also the transverse polarization fractions of B_c {\to} D^{*}_{(s)}V decays. It is found that the non-factorizable emission diagrams and annihilation type diagrams have remarkable effects on the physical observables in many channels, especially the color-suppressed and annihilation-dominant decay modes. A possible large direct CP-violation is predicted in some channels; and a large transverse polarization contribution that can reach 50% ~ 70% is predicted in some of the Bc {\to} D^{*}_{(s)}V decays.

hep-ph↗

arXiv2012

The double charm decays of $B_c$ Meson in the Perturbative QCD Approach

We make a systematic investigation on the double charm decays of $B_c$ meson, by employing the perturbative QCD approach based on $k_T$ factorization. It is found that the non-factorizable emission diagrams are not negligible in these channels. We predict the branching ratios of these $B_c$ decays and also the transverse polarization fractions of $B_c\rightarrow D_{(s)}^{*+}\bar D^{*0}, D_{(s)}^{*+}D^{*0}$ decays, % where V denote the vector $D^*_{(s)}$ meson. We find that the magnitudes of the branching ratios of the decays $B_c\rightarrow D_s\bar{D}^0$ and $B_c\rightarrow D_sD^0$ are very close to each other, which are well suited to extract the Cabibbo-Kobayashi-Maskawa angle $γ$ through the amplitude relations. In addition, a large transverse polarization contribution that can reach $50%\sim 60%$ is predicted in some of the $B_c$ meson decay to two vector charmed mesons.

hep-ph↗

arXiv2012

The pure annihilation type decays $B^0\rightarrow D_{s}^{-}K_{2}^{*+}$ and $B_{s}\rightarrow \bar{D}a_{2}$ in perturbative QCD approach

We calculate the branching ratios of pure annihilation type decays $B^0\rightarrow D_{s}^{-}K_{2}^{*+}$ and $B_s\rightarrow \bar{D}a_{2}$ using the perturbative QCD approach based on $k_T$ factorization. The branching ratios are predicted to be $(60.6_{-16.5\,-10.4\,-2.1}^{+17.3\,+4.3\,+3.2}) \times 10^{-6}$ for $B^0\rightarrow D_{s}^{-}K_{2}^{*+}$, $(1.1_{-0.4\,-0.2\,-0.1}^{+0.4\,+0.1\,+0.1})\times 10^{-6}$ for $B_s\rightarrow \bar{D}a_{2}^{0}$ and $(2.3_{-0.8\,-0.4\,-0.1}^{+0.8\,+0.2\,+0.1})\times 10^{-6}$ for $B_{s}\rightarrow D^{-}a_{2}^{+}$. They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the standard model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments to test the accuracy of theory and search of new physics signal.

hep-ph↗

arXiv2012

Revisiting the B {\to} π ρ, π ω Decays in the Perturbative QCD Approach Beyond the Leading Order

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.

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