arXiv subjects

Zhou Rui

Publications and source records attributed to Zhou Rui.

At least 37 records · Page 2Linked to original sources

arXiv2022

$CP$-violating observables in four-body $B\rightarrow ϕ(\rightarrow K\bar K)K^*(\rightarrow Kπ)$ decays

We analyse the four-body $B\rightarrow ϕ(\rightarrow K\bar K)K^*(\rightarrow Kπ)$ decays in the perturbative QCD approach,where the invariant mass of $K\bar K$($Kπ$) system is limited in a window of $\pm 15$ MeV ($\pm150$ MeV) around the $ϕ(K^*(892))$ mass.In addition to the P wave resonances,two important S wave backgrounds in the selected invariant mass region are also accounted for. Angular momentum conservation allows six helicity amplitudes to contribute,including three P waves, two single S waves,and one double S wave. We calculated the branching ratio for each component and found sizable S wave contributions,coincide with the experimental observation.The obtained branching ratios of $B^{0(+)}\rightarrow ϕK^{*0(+)}$ are comparable with the previous predictions and support the measurements, whereas the predicted $\mathcal{B}(B^0_s\rightarrow ϕ\bar K^{*0})$ is smaller than the world average. The longitudinal polarizations are predicted to be around 0.7,consistent with previous PQCD results but larger than the data. Aside from the direct CP asymmetries,the true and fake triple product asymmetries(TPAs) are calculated in this work. In the case of neutral modes, both direct CP asymmetries and true TPAs are expected to be zero due to the vanishing weak phase difference. The direct CP asymmetries for the $B^+$ mode are predicted to be tiny,since the tree contributions are suppressed with respect to the penguin ones. The true asymmetries have shown no significant deviations from zero.In contrast,large fake asymmetries are observed in these decays,indicating the presence of significant final state interactions.We give the predictions of the S wave induced TPAs for the first time,which is consistent with LHCb data and would be checked with future measurements from Belle and BABAR experiments if the S wave components can be properly taken into account in angular analysis.

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arXiv2021

Global determination of two-meson distribution amplitudes from three-body $B$ decays in the perturbative QCD approach

We perform a global analysis of three-body charmless hadronic decays $B\to VP_3\to P_1P_2P_3$ in the perturbative QCD (PQCD) approach, where $V$ denotes an intermediate vector resonance, and $P_i$, $i=1,2,3$, denote final-state pseudoscalar mesons. Fitting the PQCD factorization formulas at leading order in the strong coupling $α_s$ to measured branching ratios and direct $CP$ asymmetries, we determine the Gegenbauer moments in the two-meson distribution amplitudes (DAs) for the meson pairs $P_1P_2=ππ, Kπ, KK$. The fitted Gegenbauer moments are then employed to make predictions for those observables, whose data are excluded in the fit due to larger experimental uncertainties. A general consistency between our predictions and data is achieved, which hints the validity of the PQCD formalism for the above three-body $B$ meson decays and the universality of the nonperturbative two-meson DAs. The obtained two-meson DAs can be applied to PQCD studies of other multi-body $B$ meson decays involving the same meson pairs. We also attempt to determine the dependence of the Gegenbauer moments on the meson-pair invariant mass, and demonstrate that this determination is promising, when data become more precise.

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arXiv2021

$S$-wave contributions to the $B_{(s)}\rightarrow χ_{c1} (ππ,Kπ,KK)$ decays

We make a detailed study of the three-body decays $B_{(s)}\rightarrow χ_{c1} hh'$, where $h^{(')}$ is either a pion or kaon, by taking into account the $S$-wave states in the $hh'$ invariant mass distribution within the perturbative QCD approach. The two meson distribution amplitudes (DAs) are introduced to capture the strong interaction related to the production of the $hh'$ system. We calculate the branching ratios for the $S$-wave components and observe large values of order $10^{-4}$ for some Cabibbo-favored decays, which are accessible to the LHCb and Belle II experiments. The obtained branching ratio $\mathcal{B}(B\rightarrow χ_{c1}K^*_{0}(1430)(\rightarrow K^+π^-))=(5.1^{+0.6}_{-0.8})\times 10^{-5}$ consistent with the data from Belle within errors. Moreover, we also predict the differential distributions in the $hh'$ invariant mass for the decays under consideration, which await the future experimental test. In addition, the corresponding $χ_{c1}(2P)$ channels are also investigated, which are helpful to clarify the nature of the $X(3872)$ state.

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arXiv2021

Study of $B_{(s)} \to (ππ)(Kπ)$ decays in the perturbative QCD approach

In this work, we provide estimates of the branching ratios, direct $CP$ asymmetries and triple product asymmetries in $B_{(s)} \to (ππ)(Kπ)$ decays in the perturbative QCD approach, where the $ππ$ and $Kπ$ invariant mass spectra are dominated by the vector resonances $ρ(770)$ and $K^*(892)$, respectively. Some scalar backgrounds, such as $f_0(500,980) \to ππ$ and $K^*_0(1430) \to Kπ$ are also accounted for. The $ρ(700)$ is parametrized by the Gounaris-Sakurai function. The relativistic Breit-Wigner formula for the $f_0(500)$ and Flatté model for the $f_0(980)$ are adopted to parameterize the time-like scalar form factors $F_S(ω^2)$. We also use the D.V. Bugg model to parameterize the $f_0(500)$ and compare the relevant theoretical predictions from different models. While in the region of $Kπ$ invariant mass, the $K^*_0(1430)$ is described with the LASS lineshape and the $K^*(892)$ is modeled by the Breit-Wigner function. We find that the decay rates for the considered decay modes agree with currently available data within errors. As a by-product, we extract the branching ratios of two-body decays $B_{(s)} \to ρ(770)K^*(892)$ from the corresponding four-body decay modes and calculate the relevant polarization fractions. Our prediction of longitudinal polarization fraction for $B^0\to ρ(770)^0 K^*(892)^0$ decay deviates a lot from the recent LHCb measurement, which should be resolved. It is shown that the direct $CP$ asymmetries are large due to the sizable interference between the tree and penguin contributions, but they are small for the tree-dominant or penguin-dominant processes. The PQCD predictions for the triple product asymmetries are small which are expected in the standard model, and consistent with the current data reported by the LHCb Collaboration.Our results can be tested by the future precise data from the LHCb and Belle II experiments.

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arXiv2021

Four-body decays $B_{(s)} \rightarrow (Kπ)_{S/P} (Kπ)_{S/P}$ in the perturbative QCD approach

We investigate the four-body decays $B_{(s)} \rightarrow (Kπ)_{S/P} (Kπ)_{S/P}$ in the $Kπ$-pair invariant mass region around the $K^*(892)$ resonance in the perturbative QCD (PQCD) approach, where $(Kπ)_{S/P}$ denotes a $S$- or $P$-wave $Kπ$ configuration. The contributions from the $P$-wave resonance $K^*(892)$ and from possible $S$-wave components are included into the parametrization of the $Kπ$ two-meson distribution amplitudes, which are the nonperturbative inputs in this formalism. We calculate the branching ratio for each resonance and observe sizable $S$-wave contributions to the $B_s$ modes, well consistent with recently available LHCb data. We also deduce the polarization fractions for the $K^*\bar{K}^*$ final states, and compare our predictions to those in previous PQCD analyses of the corresponding two-body $B\to K^*\bar{K}^*$ decays. The polarization puzzle associated with the two $U$-spin related channels $B^0\rightarrow K^{*0}\bar{K}^{*0}$ and $B^0_s\rightarrow K^{*0}\bar{K}^{*0}$ still exists. In addition to direct $CP$ asymmetries, triple-product asymmetries and $S$-wave induced direct $CP$ asymmetries originating from the interference among various helicity amplitudes, are presented. It is shown that true triple-product asymmetries are rather small, while direct $CP$ asymmetries and $S$-wave-induced direct $CP$ asymmetries are significant in some decays. Our results will be subject to stringent tests with precise data from $B$ factories in the near future.

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arXiv2020

Revisiting nonfactorizable contributions to factorization-forbidden decays of $B$ mesons to charmonium

Motivated by the large rates of $B\rightarrow (χ_{c0}, χ_{c2}, h_c)K$ decays observed by the $BABAR$ and Belle collaborations, we investigate the nonfactorizable contributions to these factorization-forbidden decays, which can occur through a gluon exchange between the $c\bar c$ system and the spectator quark. Our numerical results demonstrate that the spectator contributions are capable of producing a large branching ratio consistent with the experiments. As a by-product, we also study the Cabibbo-suppressed decays, such as $B\rightarrow (χ_{c0}, χ_{c2}, h_c)π$ and the U-spin-related $B_s$ decay, which have so far received less theoretical and experimental attention. The calculated branching ratios reach the order of $10^{-6}$, which in within the scope of the Belle-II and LHCb experiments. Further, the $CP$-asymmetry parameters are also calculated for these decays. The obtained results are compared with the available experimental data and numbers from other predictions. We also investigate the sources of theoretical uncertainties in our calculation.

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arXiv2020

Resonant contributions to three-body $B_{(s)} \to [ D^{()}, \bar{D}^{()} ] K^+K^-$ decays in the perturbative QCD approach

In this work, we study the $S$, $P$ and $D$ wave resonance contributions to three-body decays $B_{(s)} \to [ D^{(*)}, \bar{D}^{(*)} ] K^+K^-$ by employing the perturbative QCD (PQCD) approach, where the kaon-kaon invariant mass spectra are dominated by the $f_0(980),f_0(1370),$ $ϕ(1020),ϕ(1680),f_2(1270),f^{\prime}_2(1525),f_2(1750)$ and $f_2(1950)$ resonances. The $KK$ $S$-wave component $f_0(980)$ is modeled with the Flatté formalism, while other resonances are described by the relativistic Breit-Wigner (BW) line shape. The corresponding decay channels are studied by constructing the kaon-kaon distribution amplitude $Φ_{KK}$, which captures important final state interactions between the kaon pair in the resonant region. We found that the PQCD predictions for the branching ratios for most considered decays agree with currently available data within errors. The associated polarization fractions of those vector-vector and vector-tensor decay modes are also predicted, which are expected to be tested in the near future experiments. The invariant mass spectra for the corresponding resonances in the $B_{(s)} \to [D^{(*)}, \bar{D}^{(*)} ] K^+K^-$ decays are well established, which can be confronted with the precise data from the LHCb and Belle II experiments.

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arXiv2020

$P$-wave contributions to $B_{(s)}\toψKπ$ decays in perturbative QCD approach

In this work, we studied the quasi-two-body decays $B_{(s)} \to ψ[K^*(892), K^*(1410),$ $K^*(1680)] \to ψKπ$ by employing the perturbative QCD (PQCD) factorization approach, where the charmonia $ψ$ represents $J/ψ$ and $ψ(2S)$. The corresponding decay channels are studied by constructing the kaon-pion distribution amplitude (DA) $Φ_{K π}^{\rm P}$, which contained the important final state interactions between the kaon and pion in the resonant region. The relativistic Breit-Wigner formulas are adopted to parameterize the time-like form factor $F_{Kπ}$ appeared in the kaon-pion DAs. The SU(3) flavor symmetry breaking effect resulting from the mass difference between kaon and pion is taken into account, which makes significant contributions to the longitudinal polarizations. We accommodate well the observed branching ratios and the polarization fractions of the $B_{(s)} \to ψK^*(892) \to ψKπ$ by tuning the hadronic parameters for the kaon-pion DAs. The PQCD predictions for the $B_{(s)} \to ψ[K^*(1410), K^*(1680)] \to ψKπ$ modes from the same set of parameters can be tested by the future precise data from the LHCb and the Belle II experiments.

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arXiv2020

$S$, $P$ and $D$-wave resonance contributions to $B_{(s)} \to η_c(1S,2S) Kπ$ decays in the perturbative QCD approach

In this work, we analyze the three-body $B_{(s)} \to η_c(1S,2S) K π$ decays within the framework of the perturbative QCD approach (PQCD) under the quasi-two-body approximation, where the kaon-pion invariant mass spectra are dominated by the $K_0^*(1430)^0,K_0^*(1950)^0,K^*(892)^0,K^*(1410)^0,K^*(1680)^0$ and $K_2^*(1430)^0$ resonances. The time-like form factors are adopted to parametrize the corresponding $S$, $P$, $D$-wave kaon-pion distribution amplitudes for the concerned decay modes, which describe the final-state interactions between the kaon and pion in the resonant region. The $Kπ$ $S$-wave component at low $Kπ$ mass is described by the LASS line shape, while the time-like form factors of other resonances are modeled by the relativistic Breit-Wigner function. We find the following main points: (a) the PQCD predictions of the branching ratios for most considered $B \to η_c(1S)(K^{*0}\to )K^+π^-$ decays agree well with the currently available data within errors; (b) for ${\cal B}(B^0 \to η_c (K_0^*(1430)\to )K^+π^-)$ and ${\cal B}(B^0 \to η_c K^+π^-({\rm NR}))$ (here NR means nonresonant), our predictions of the branching ratios are a bit smaller than the measured ones; and (c) the PQCD results for the $D$-wave contributions considered in this work can be tested once the precise data from the future LHCb and Belle-II experiments are available.

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arXiv2019

Studies of the resonance components in the $B_s$ decays into charmonia plus kaon pair

In this work, the decays of $B_s$ mesons to a charmonium state and a $K^+K^-$ pair are carefully investigated in the perturbative QCD approach. Following the latest fit from the LHCb experiment, we restrict ourselves to the case where the produced $K^+K^-$ pair interact in isospin zero $S$, $P$, and $D$ wave resonances in the kinematically allowed mass window. Besides the dominant contributions of the $ϕ(1020)$ resonance in the $P$-wave and $f_2'(1525)$ in the $D$-wave, other resonant structures in the high mass region as well as the $S$-wave components are also included. The invariant mass spectra for most of the resonances in the $B_s\rightarrow J/ψK^+K^-$ decay are well reproduced. The obtained three-body decay branching ratios can reach the order of $10^{-4}$, which seem to be accessible in the near future experiments. The associated polarization fractions of those vector-vector and vector-tensor modes are also predicted, which are compared with the existing data from LHCb Collaboration.

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arXiv2019

Isovector scalar $a_0(980)$ and $a_0(1450)$ resonances in the $B\rightarrow ψ(K\bar{K},πη) $ decays

We present an analysis of two isovector scalar resonant contributions to the $B$ decays into charmonia plus $K\bar K$ or $πη$ pair in the perturbative QCD approach. The Flatté model for the $a_0(980)$ resonance and the Breit Wigner formula for the $a_0(1450)$ resonance are adopted to parametrize the timelike form factors in the dimeson distribution amplitudes, which capture the important final state interactions in these processes. The predicted distribution in the $K^+K^-$ invariant mass as well as its integrated branching ratio for the $a_0(980)$ resonance in the $B^0\rightarrow J/ψK^+K^-$ mode agree well with the current available experimental data. The obtained branching ratio of the quasi-two-body decay $B^0\rightarrow J/ψa_0(980)(\rightarrow π^0η)$ can reach the order of $10^{-6}$, letting the corresponding measurement appear feasible. For the $a_0(1450)$ component, our results could be tested by further experiments in the LHCb and Belle II. We also discuss some theoretical uncertainties in detail in our calculation.

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arXiv2018

$P$-wave contributions to $B\toψππ$ decays in perturbative QCD approach

We present the differential branching fractions for the $B\rightarrow ψππ$ decays with the charmonia $ψ=J/ψ,ψ(2S)$ in the invariant mass of the $P$-wave pion pairs in the perturbative QCD approach. The two-pion distribution amplitudes (DAs) corresponding to both longitudinal and transverse polarizations are constructed to capture important final state interactions in the processes. The time-like form factors, normalizing the two-pion DAs, contains contributions from the $ρ$ resonance and radial excitations fitted to the BaBar data. Given the hadronic parameters for the two-pion DAs associated with the longitudinal polarization which were determined in our previous study, and tuning those associated with the transverse polarization, we accommodate well the observed branching ratios and polarization fractions of the $B\rightarrow J/ψππ$ decays. Our predictions for the $B\rightarrow ψ(2S) ππ$ modes from the same set of parameters can be tested in future LHCb and BelleII experiments. We also investigate the sources of theoretical uncertainties in our calculation.

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arXiv2018

Quasi-two-body decays $B_{(s)}\to P f_2(1270)\to Pππ$ in the perturbative QCD approach

In this work, we calculate the $CP$-averaged branching ratios and direct $CP$-violating asymmetries of the quasi-two-body decays $B_{(s)}\to P f_2(1270)\to Pππ$ with the two-pion distribution amplitude $Φ_{ππ}^{\rm D}$ by using the perturbative QCD factorization approach, where $P$ represents a light pseudoscalar meson $K, π, η$ and $η^{\prime}$. The relativistic Breit-Wigner formula for the $D$-wave resonance $f_2(1270)$ is adopted to parameterize the timelike form factor $F_π$, which contains the final state interactions between the pions in the resonant regions. The consistency of theoretical results with data can be achieved by determining the Gegenbauer moments of the $D$-wave two-pion distribution amplitudes. The decay rates for the considered decay modes are generally in the order of $10^{-9}$ to $ 10^{-6}$. The integrated direct $CP$ asymmetries for the charged modes agree with the {\it BABAR} and Belle measurements. As a by-product, we extract the branching ratios of $B_{(s)}\to Pf_2(1270)$ from the corresponding quasi-two-body decay modes, which still need experimental tests at the ongoing and forthcoming experiments.

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arXiv2018

Semileptonic decays of $B_c$ meson to $P$-wave charmonium states

Inspired by a series of unexpected measurements of semileptonic decays mediated via $b\rightarrow c $ charged current interactions, we explore semileptonic $B_c$ decays to the four lightest $P$-wave charmonium states, $χ_{c0}, χ_{c1}, χ_{c2}, h_c$, by the recently developed improved perturbative QCD formalism, in which the charm quark mass effect is included both in the Sudakov factor and the hard kernels. We first directly evaluate the concerned transition form factors with vector and axial-vector currents in the region of small momentum transfer squared, and then recast them to the full kinematical region by adopting the exponential parametrization. The obtained form factors are used to evaluate the semileptonic decay branching ratios, which can reach the order of $10^{-3}$, letting the corresponding measurement appear feasible. For a better analysis, a comparison of our results with the predictions of other models is provided. We also present the ratios between the tau and light lepton branching ratios and the polarization contributions in the relevant processes, which still need experimental tests in the ongoing and forthcoming experiments. Any significant deviations from the Standard Model results may provide some hints of new physics effects.

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arXiv2018

Branching ratios and $CP$ asymmetries of $B\rightarrow χ_{c1}K(π)$ decays

We investigate the exclusive nonleptonic decays $B\rightarrow χ_{c1}K(π)$ in the conventional perturbative QCD (PQCD) formalism. The predictions of branching ratios and $CP$ asymmetries are given in detail. We compare our results with available experimental data as well as predictions of other theoretical studies existing in the literature. It seems that the branching ratios of $B\rightarrow χ_{c1} K$ are more consistent with data than the earlier analyses. For the Cabibbo-suppressed $B_s$ decay, the branching ratio can reach the order of $10^{-5}$, which would be straight forward for experimental observations. The numerical results show that the direct $CP$ asymmetries of the concerned decays are rather small. The mixing-induced $CP$ asymmetry in the $B^0\rightarrow χ_{c1}K_S$ is very close to $\sin{2β}$, which suggests that this channel offer an alternative method for measuring the Cabbibo-Kobayashi-Maskawa (CKM) angle $β$. The obtained results in the present work could be tested by further experiments in the LHCb and forthcoming Belle II.

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arXiv2018

$S$-wave $Kπ$ contributions to the hadronic charmonium $B$ decays in the perturbative QCD approach

We extend our recent works on the two-pion $S$-wave resonance contributions to the kaon-pion ones in the $B$ meson hadronic charmonium decay modes based on the perturbative QCD approach. The $S$-wave $Kπ$ time-like form factor in its distribution amplitudes is described by the LASS parametrization, which consists of the $K^*_0(1430)$ resonant state together with an effective range nonresonant component. The predictions for the decays $B\rightarrow J/ψKπ$ in this work agree well with the experimental results from $BABAR$ and Belle Collaborations. We also discuss theoretical uncertainties, indicating the results of this work, which can be tested by the LHCb and Belle-II experiments, are reasonably accurate.

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arXiv2018

Probing the $P$-wave charmonium decays of $B_c$ meson

Motivated by the large number of $B_c$ meson decay modes observed recently by several detectors at the LHC, we present a detailed analysis of the $B_c$ meson decaying to the $P$-wave charmonium states and a light pseudoscalar($P$) or vector ($V$) meson within the framework of perturbative QCD factorization. The $P$-wave charmonium distribution amplitudes are extracted from the $n=2,l=1$ Schr$\ddot{o}$dinger states for a Coulomb potential,which can be taken as the universal nonperturbative objects to analyze the hard exclusive processes with $P$-wave charmonium production. It is found that these decays have large branching ratios of the order of $10^{-5}\sim 10^{-2}$, which seem to be in the reach of future experiments. We also provide predictions for the polarization fractions and relative phases of $B_c\rightarrow (χ_{c1},χ_{c2},h_c)V$ decays. It is expected that the longitudinal polarization amplitudes dominate the branching ratios according to the quark helicity analysis, and the magnitudes and phases of parallel polarization amplitude are approximately equal to the perpendicular ones. The obtained results are compared with available experimental data, our previous studies, and numbers from other approaches.

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arXiv2017

Quasi-two-body decays $B \to η_c {(1S ,2S)}\;[ρ(770),ρ(1450),ρ(1700) \to ]\; ππ$ in the perturbative QCD approach

In this paper, we calculated the branching ratios of the quasi-two-body decays $B \to η_c (1S ,2S)$ $[ρ(770), ρ(1450),ρ(1700)\to ] ππ$ by employing the perturbative QCD (PQCD) approach. The contributions from the $P$-wave resonances $ρ(770)$, $ρ(1450)$ and $ρ(1700)$ were taken into account. The two-pion distribution amplitude $Φ_{ππ}^{\rm P}$ is parameterized by the vector current time-like form factor $F_π$ to study the considered decay modes. We found that (a) the PQCD predictions for the branching ratios of the considered quasi-two-body decays are in the order of $10^{-7} \sim 10^{-6}$, while the two-body decay rates ${\cal B}(B \to η_c{(1S,2S)} (ρ(1450),ρ(1700)))$ are extracted from those for the corresponding quasi-two-body decays; (b) the whole pattern of the pion form factor-squared $|F_π|^2$ measured by the BABAR Collaboration could be understood based on our theoretical results; (c) the general expectation based on the similarity between $B \to η_c ππ$ and $B \to J/ψππ$ decays are confirmed: $R_2(η_c)\approx 0.45$ is consistent with the measured $R_2(J/ψ)\approx 0.56\pm 0.09$ within errors; and (d) new ratios $R_3(η_c(1S))$ and $R_4(η_c(2S))$ among the branching ratios of the considered decay modes are defined and could be tested by future experiments.

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