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Qin Chang

Publications and source records attributed to Qin Chang.

At least 73 records · Page 4Linked to original sources
arXiv2017

Study of $B_{c}^{\ast}$ ${\to}$ $ψ(1S,2S)P$, $η_{c}(1S,2S)P$ weak decays

Motivated by the potential prospects of the $B_{c}^{\ast}$ meson samples at hadron colliders, the bottom-changing $B_{c}^{\ast}$ ${\to}$ $ψ(1S,2S)P$, $η_{c}(1S,2S)P$ weak decays are first studied with the perturbative QCD approach, where $P$ $=$ $π$ and $K$. It is found that branching ratio of the CKM-favored $B_{c}^{\ast}$ ${\to}$ $J/ψπ$ decay is about ${\sim}$ ${\cal O}(10^{-8})$, which might be measurable at the future LHC experiments.

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arXiv2017

Study of $Υ(nS)$ ${\to}$ $B_{c}P$ decays with perturbative QCD approach

With the potential prospects of the $Υ(nS)$ at high-luminosity dedicated heavy-flavor factories, the color-favored $Υ(nS)$ ${\to}$ $B_{c}π$, $B_{c}K$ weak decays are studied with the pQCD approach. It is found that branching ratios for the $Υ(nS)$ ${\to}$ $B_{c}π$ decay are as large as the order of ${\cal O}(10^{-11})$, which might be measured promisingly by the future experiments.

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arXiv2016

Light-front holographic distribution amplitudes of pseudoscalar mesons and their application to $B$-meson decays

In this paper the dynamical spin effects of the light-front holographic wavefunctions for light pseudoscalar mesons are studied using two different assumptions. These improved wavefunctions are then confronted with a number of sensitive hadronic observables: the decay constants of $π$ and $K$ mesons, their $ξ$-moments, the pion-to-photon transition form factor, and the pure annihilation $\bar{B}_{s}\to π^+ π^-$ and $\bar{B}_{d}\to K^+K^-$ decays. Taking $f_π$, $f_{K}$ and their ratio $f_{K}/f_π$ as constraint conditions, the $χ^2$ analyses for holographic parameters, including the mass scale parameter $\sqrtλ$ and effective quark masses, are all consistent with the mass scale which controls the slopes of the light-quark hadronic Regge trajectories. In addition, we also show how the improved light-front holographic distribution amplitudes regulate the end-point divergences which appear in the annihilation amplitudes of $B\to PP$ decays.

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arXiv2016

$Υ(1S)$ ${\to}$ $B_{c}π$, $B_{c}K$ decays with perturbative QCD approach

With the potential prospects of the $Υ(1S)$ at high-luminosity dedicated heavy-flavor factories, the bottom-changing $Υ(1S)$ ${\to}$ $B_{c}π$, $B_{c}K$ weak decays are studied with the pQCD approach. It is found that branching ratio for the color-favored and CKM-favored $Υ(1S)$ ${\to}$ $B_{c}π$ decay can reach up to ${\cal O}(10^{-11})$. So the $Υ(1S)$ ${\to}$ $B_{c}π$ decay might be measured promisingly by the future experiments.

hep-ph↗
arXiv2016

Study on $Υ(nS)$ ${\to}$ $B_{c}M$ decays

With anticipation of abundant Upsilons data sample at high-luminosity heavy-flavor experiments in the future, we studied nonleptonic two-body weak decays of $Υ(nS)$ below the open-bottom threshold with $n$ $=$ $1$, $2$ and $3$. It is found that branching ratios for $Υ(1S,2S,3S)$ ${\to}$ $B_{c}ρ$ decays are relatively large among upsilons decay into $B_{c}M$ final states ($M$ $=$ $π$ $ρ$, $K$ and $K^{\ast}$) and can reach up to $10^{-10}$, which is promisingly detected by experiments at the running LHC and forthcoming SuperKEKB.

hep-ph↗
arXiv2016

Study on the $Υ(1S)$ ${\to}$ $B_{c}M$ weak decays

Motivated by the prospects of the potential $Υ(1S)$ particle at high-luminosity heavy-flavor experiments, we studied the $Υ(1S)$ ${\to}$ $B_{c}M$ weak decays, where $M$ $=$ $π$, $ρ$, $K^{(\ast)}$. The nonfactorizable contributions to hadronic matrix elements are taken into consideration with the QCDF approach. It is found that the CKM-favored $Υ(1S)$ ${\to}$ $B_{c}ρ$ decay has branching ratio of ${\cal O}(10^{-10})$, which might be measured promisingly by the future experiments.

hep-ph↗
arXiv2016

Fits of Weak Annihilation and Hard Spectator Scattering Corrections in $B_{u,d}\to VV$ Decays

In this paper, the contributions of weak annihilation and hard spectator scattering in $B\to ρK^*$, $ K^* \bar{K}^*$, $ϕK^*$, $ρρ$ and $ϕϕ$ decays are investigated within the framework of QCD factorization. Using the experimental data available, we perform $χ^2$ analyses of end-point parameters in four cases based on the topology-dependent and polarization-dependent parameterization schemes. The fitted results indicate that: (i) In the topology-dependent scheme, the relation $(ρ_A^{i},ϕ_A^{i})\neq (ρ_A^{f},ϕ_A^{f})$ gotten through $B\to PP$ and $PV$ decays is favored by the penguin-dominated $B\to VV$ decays at 95\% C. L., (ii) The large hard spectator scattering corrections and/or the simplification $ (ρ_H,ϕ_H)= (ρ_A^{i},ϕ_A^{i})$ are challenged by ${\cal B}(\bar{B}^0\to ρ^0 ρ^0)$, even though they are allowed by $B\to PP$ and $PV$ decays and helpful for resolving "$ππ$ puzzle", (iii) In the polarization-dependent scheme, the relation $(ρ_A^{L},ϕ_A^{L})\neq (ρ_A^{T},ϕ_A^{T})$ is always required. Moreover, we have updated the theoretical results for $B\to VV$ decays with the best-fit values of end-point parameters. A few observables, such as the ones of pure annihilation $B_d\to ϕϕ$ decay, are also identified for probing the annihilation corrections.

hep-ph↗
arXiv2016

$\bar{B}_{d,s} \to D^{*}_{d,s} V$ and $\bar{B}_{d,s}^* \to D_{d,s} V$ decays within QCD Factorization and Possible Puzzles

Motivated by the rapid development of heavy-flavor experiments, phenomenological studies of nonleptonic $\bar{B}_{d,s} \to D^{*}_{d,s} V$ and $\bar{B}_{d,s}^* \to D_{d,s} V$~($V=ρ\,,K^*$) decays are performed within the framework of QCD Factorization. Relative to previous works, the QCD corrections to the transverse amplitudes are evaluated at next-to-leading order. The theoretical predictions of the observables are updated. For the measured $\bar{B}_{d,s} \to D^{*}_{d,s} V$ decays, two tensions between theoretical results and experimental measurements, {\it i.e.} "$R_{ds}^{V}$ puzzle" and "$D^{*} V$~(or $R_{V/\ell\barν_\ell}$) puzzle", are presented after detailed analyses. For the $\bar{B}_{d,s}^* \to D_{d,s} V$ decays, they have relatively large branching fractions of the order $\gtrsim{\cal O}(10^{-9})$ and are in the scope of Belle-II and LHCb experiments. Moreover, they also provide a way to crosscheck the above-mentioned possible puzzles through the similar ratios $R_{ds}^{\prime V}$ and $R_{V/\ell\barν_\ell}^{\prime}$. More refined experimental measurements and theoretical efforts are required to confirm or refute such two anomalies.

hep-ph↗
arXiv2016

Study of semileptonic $\bar{B}^* \to P \ell \barν_\ell$ decays

In anticipation of abundant $B^*$ data samples at high-luminosity heavy-flavor experiments in the future, the tree-dominated semileptonic $\bar{B}^*_{u,d,s} \to P \ell^- \barν_\ell$ $(P=D\,,D_s\,,π\,,K)$ decays are studied within the Standard Model. After a detailed calculation of the helicity amplitudes, the theoretical predictions for branching fraction~(decay rate), lepton spin asymmetry, forward-backward asymmetry and ratio $R_D^{\ast(L)}$ are firstly presented. It is found that the CKM-favored $\bar{B}^* \to D \ell^- \barν_\ell$ decays have relatively large branching fractions of ${\cal O}(10^{-9})$$\sim$${\cal O}(10^{-7})$, and are in the scope of running LHC and forthcoming SuperKEKB/Belle-II experiments.

hep-ph↗
arXiv2016

The $Υ(nS)$ ${\to}$ $B_{c}^{\ast}π$, $B_{c}^{\ast}K$ decays with perturbative QCD approach

Besides the traditional strong and electromagnetic decay modes, $Υ(nS)$ meson can also decay through the weak interactions within the standard model of elementary particle. With anticipation of copious $Υ(nS)$ data samples at the running LHC and coming SuperKEKB experiments, the two-body nonleptonic bottom-changing $Υ(nS)$ ${\to}$ $B_{c}^{\ast}π$, $B_{c}^{\ast}K$ decays ($n$ $=$ 1, 2, 3) are investigated with perturbative QCD approach firstly. The absolute branching ratios for $Υ(nS)$ ${\to}$ $B_{c}^{\ast}π$ and $B_{c}^{\ast}K$ decays are estimated to reach up to about $10^{-10}$ and $10^{-11}$, respectively, which might possibly be measured by the future experiments.

hep-ph↗
arXiv2016

The $Υ(1S)$ ${\to}$ $B_{c}ρ$ decay with perturbative QCD approach

With the potential prospects of the $Υ(1S)$ data samples at the running LHC and upcoming SuperKEKB, the $Υ(1S)$ ${\to}$ $B_{c}ρ$ weak decays are studied with the pQCD approach. It is found that (1) the lion's share of branching ratio comes from the longitudinal polarization helicity amplitudes; (2) branching ratio for the $Υ(1S)$ ${\to}$ $B_{c}ρ$ decay can reach up to ${\cal O}(10^{-9})$, which might be hopefully measurable.

hep-ph↗
arXiv2016

Study of Nonleptonic $B^{\ast}_{(s)}\to M_1 M_2$ $(M=D$, $D_s$, $π$, $K)$ Weak Decays with Factorization Approach

Motivated by the experiments of heavy flavor physics at running LHC and upgrading SuperKEKB/Belle-II in the future, the nonleptonic $B^{\ast}_{(s)}\to M_1 M_2$ $(M=D$, $D_s$, $π$, $K)$ weak decays are studied in this paper. The amplitudes are calculated with factorization approach, and the transition form factors $A_0^{B^{\ast}_{(s)}\to M_1}(0)$ are evaluated within BSW model. With the reasonable approximation $Γ_{tot}(B^*_{(s)})\simeq Γ(B^*_{(s)}\to B_{(s)}γ)$, our predictions of branching fractions are presented. Numerically, the CKM-favored tree-dominated $\bar{B}^{*0} \to D^+D^-_s$ and $\bar{B}^{*0}_s \to D^+_sD^-_s$ decays have the largest branching fractions of the order $\sim{\cal O}(10^{-8})$, and hence will be firstly observed by forthcoming Belle-II experiment. However, most of the other decay modes have the branching fractions~$<{\cal O}(10^{-9})$ and thus are hardly to be observed soon. Besides, for the possible detectable $B^{\ast}_{(s)}$ decays with branching fractions $\gtrsim{\cal O}(10^{-9})$, some useful ratios, such as $R_D$ {\it et al.,} are presented and discussed in detail.

hep-ph↗
arXiv2016

Study of nonleptonic $B_{q}^{\ast}$ ${\to}$ $D_{q}V$ and $P_{q} D^*$ weak decays

Motivated by the powerful capability of measurement for the $b$-flavored hadron rare decays at LHC and SuperKEKB/Belle-II, the nonleptonic $\bar{B}^{\ast}$ ${\to}$ $D\bar{D}^{\ast}$, $D{ρ^-}$, $DK^{\ast-}$, $πD^{\ast}$ and $KD^{\ast}$ weak decays are studied in detail. With the amplitudes calculated with factorization approach and the form factors of $B^{\ast}$ transition into pseudoscalar meson evaluated with the BSW model, branching fractions and polarization fractions are firstly presented. Numerically, the CKM-favored $\bar{B}_{q}^{\ast}$ ${\to}$ $D_{q}D_{s}^{{\ast}-}$ and $D_{q}ρ^{-}$ decays have large branching fractions, $\sim$ $10^{-8}$, which should be sought for with priority and firstly observed by LHC and Belle-II experiments. The $\bar{B}^{\ast}_q$ ${\to}$ $D_qK^{\ast}$ and $D_qρ$ decays are dominated by the longitudinal polarization states. While, the parallel polarization fractions of $\bar{B}^{\ast}_q$ ${\to}$ $D_q\bar{D}^{\ast}$ decays are comparable with the longitudinal ones, numerically, $f_{\parallel}$ $+$ $f_{L}$ ${\simeq}$ 95\% and $f_{L}:f_{\parallel}$ $\simeq$ $5:4$. Some comparisons between $\bar{B}^{*0}_q$ $\to$ $D_q V$ and their corresponding $\bar{B}^{0}_q$ $\to$ $D^*_q V$ decays are performed, and the relation $ f_{L,\parallel}(\bar{B}^{\ast 0}\to D V)\simeq f_{L,\parallel}(\bar{B}^0\to D^{\ast +} V^-) $ is presented. Besides, with the implication of $SU(3)$ flavor symmetry, some useful ratios $ R_{\rm du}$ and $ R_{\rm ds}$ are discussed in detail, and suggested to be verified experimentally.

hep-ph↗
arXiv2016

Study of the $Υ(1S)$ ${\to}$ $B_{c}D_{s}^{\ast}$ decay with pQCD approach

The $Υ(1S)$ ${\to}$ $B_{c}D_{s}^{\ast}$ weak decay is studied with the perturbative QCD approach firstly. It is found that (1) main contributions to branching ratio come from the longitudinal and parallel helicity amplitudes, (2) branching ratio, longitudinal and parallel polarization fractions are sensitive to the wave functions of the $Υ(1S)$ meson, (3) branching ratio for the $Υ(1S)$ ${\to}$ $B_{c}D_{s}^{\ast}$ decay can reach up to $10^{-9}$, which might be promisingly measured by the future experiments.

hep-ph↗
arXiv2016

Study of the $ψ(1S,2S)$ and $η_{c}(1S,2S)$ weak decays into $DM$

Inspired by the recent measurements on the $J/ψ(1S)$ ${\to}$ $D_{s}ρ$, $D_{u}K^{\ast}$ weak decays at BESIII and the potential prospects of the charmonium at the high-luminosity heavy-flavor experiments, we study $ψ(1S,2S)$ and $η_{c}(1S,2S)$ weak decays into final states including one charmed meson plus one light meson, considering the QCD corrections to hadronic matrix elements with the QCD factorization. It is found that the Cabibbo favored $ψ(1S,2S)$ ${\to}$ $D_{s}^{-}ρ^{+}$, $D_{s}^{-}π^{+}$, $\overline{D}_{u}^{0}\overline{K}^{{\ast}0}$ decays have branching ratios ${\gtrsim}$ $10^{-10}$, which might be accessible at the future experiments.

hep-ph↗
arXiv2016

$J/ψ$ ${\to}$ $DP$, $DV$ decays in the QCD factorization approach

Motivated by the recent measurements on nonleptonic $J/ψ$ weak decays at BESIII and the potential prospects of $J/ψ$ meson at the high-luminosity heavy-flavor experiments, the branching ratios of the two-body nonleptonic $J/ψ$ ${\to}$ $DP$, $DV$ decays are estimated quantitatively by considering the QCD radiative corrections to hadronic matrix elements with the QCD factorization approach. It is found that the Cabibbo favored $J/ψ$ ${\to}$ $D_{s}^{-}ρ^{+}$, $D_{s}^{-}π^{+}$, $\overline{D}_{u}^{0}\overline{K}^{{\ast}0}$ decays have branching ratios ${\gtrsim}$ $10^{-10}$, which might be promisingly detectable in the near future.

hep-ph↗
arXiv2016

Probing the R-parity violating supersymmetric effects in the exclusive b\to c\ell^-\barν_\ell decays

Motivated by recent results from the LHCb, BABAR and Belle collaborations on B\to D^{(*)}\ell^-\barν_\ell decays, which significantly deviate from the Standard Model and hint the possible new physics beyond the Standard Model, we probe the R-parity violating supersymmetric effects in B^-_c\to \ell^-\barν_\ell and B\to D^{(*)}\ell^-\barν_\ell decays. We find that (i) \mathcal{B}(B^-_c\to e^- \barν_e) and \mathcal{B}(B^-_c\toμ^-\barν_μ) are sensitive to the constrained slepton exchange couplings; (ii) the normalized forward-backward asymmetries of B\to De^-\barν_{e} decays have been greatly affected by the constrained slepton exchange couplings, and their signs could be changed; (iii) all relevant observables in the exclusive b\to cτ^-\barν_τdecays and the ratios \mathcal{R}(D^{(*)}) are sensitive to the slepton exchange coupling, \mathcal{R}(D^*) could be enhanced by the constrained slepton exchange coupling to reach each 95\% confidence level experimental range from BABAR, Belle and LHCb, but it could not reach the lower limit of the 95\% confidence level experimental average. Our results in this work could be used to probe R-parity violating effects, and will correlate with searches for direct supersymmetric signals at the running LHCb and the forthcoming Belle-II.

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