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Qin Chang

Publications and source records attributed to Qin Chang.

At least 91 records · Page 5Linked to original sources
arXiv2015

$B_s^0-\bar{B}_s^0$ mixing within minimal flavor-violating two-Higgs-doublet models

In the "Higgs basis" for a generic 2HDM, only one scalar doublet gets a nonzero vacuum expectation value and, under the criterion of minimal flavor violation, the other one is fixed to be either color-singlet or color-octet, which are named as the type-III and type-C models, respectively. In this paper, the charged-Higgs effects of these two models on $B_s^0-\bar{B}_s^0$ mixing are studied. Firstly, we perform a complete one-loop computation of the electro-weak corrections to the amplitudes of $B_s^0-\bar{B}_s^0$ mixing. Together with the up-to-date experimental measurements, a detailed phenomenological analysis is then performed in the cases of both real and complex Yukawa couplings of charged scalars to quarks. The spaces of model parameters allowed by the current experimental data on $B_s^0-\bar{B}_s^0$ mixing are obtained and the differences between type-III and type-C models are investigated, which is helpful to distinguish between these two models.

hep-ph↗
arXiv2015

Probing Spectator Scattering and Annihilation Corrections in $B_{s}$ $\to$ $PV$ Decays

Motivated by the recent LHCb measurements on $\bar{B}_{s}$ $\to$ $π^{-}K^{*+}$ and $\bar{B}_{s}$ $\to$ $K^{\pm}K^{*\mp}$ decay modes, we revisit the $B_{s}$ $\to$ $PV$ decays within QCD factorization framework. The effects of hard-spectator scattering and annihilation corrections are studied in detail. After performing a $χ^2$-fit on the end-point parameters $X_A^{i,f}$ ($ρ_A^{i,f}$, $ϕ_A^{i,f}$) and $X_H$ ($ρ_H$, $ϕ_H$) with available data, it is found that although some possible mismatches exist, the universalities of $X_A^{i,f}$ and $X_H$ in $B_s$ and $B_{u,d}$ systems are still allowed within theoretical uncertainties and experimental errors. With the end-point parameters gotten from $B_{u,d}$ $\to$ $PV$ decays, the numerical results and detailed analyses for the observables of $\bar{B}_{s}$ ${\to}$ $πK^{\ast}$, $ρK$, $πρ$, $πϕ$ and $Kϕ$ decay modes are presented. In addition, we have identified a few useful observables, especially the ones of $\bar{B}_{s}$ $\to$ $π^{0}ϕ$ decay for instance, for probing hard-spectator scattering and annihilation contributions.

hep-ph↗
arXiv2015

$B_{c}$ ${\to}$ $BP$, $BV$ decays with the QCD factorization approach

We studied the nonleptonic $B_{c}$ ${\to}$ $BP$, $BV$ decay with the QCD factorization approach. It is found that the Cabibbo favored processes of $B_{c}$ ${\to}$ $B_{s}π$, $B_{s}ρ$, $B_{u}\bar{K}$ are the promising decay channels with branching ratio larger than 1\%, which should be observed earlier by the LHCb Collaboration.

hep-ph↗
arXiv2015

Constraints on hard spectator scattering and annihilation corrections in $B_{u,d}$ ${\to}$ $PV$ decays within QCD factorization

In this paper, we investigate the contributions of hard spectator scattering and annihilation in $B\to PV$ decays within the QCD factorization framework. With available experimental data on $B\to πK^{\ast}$, $ρK$, $πρ$ and $Kϕ$ decays, comprehensive $χ^2$ analyses of the parameters $X_{A,H}^{i,f}(ρ_{A,H}^{i,f},ϕ_{A,H}^{i,f})$ are performed, where $X_A^f$ ($X_A^i$) and $X_H$ are used to parameterize the endpoint divergences of the (non)factorizable annihilation and hard spectator scattering amplitudes, respectively. Based on $χ^2$ analyses, it is observed that (1) The topology-dependent parameterization scheme is feasible for $B\to PV$ decays; (2) At the current accuracy of experimental measurements and theoretical evaluations, $X_H=X_A^i$ is allowed by $B\to PV$ decays, but $X_{H}\neq X_A^f$ at $68%$ C. L.; (3) With the simplification $X_H=X_A^i$, parameters $X_A^f$ and $X_A^i$ should be treated individually. The above-described findings are very similar to those obtained from $B\to PP$ decays. Numerically, for $B\to PV$ decays, we obtain $(ρ_{A,H}^i,ϕ_{A,H}^i[^{\circ}]) =(2.87^{+0.66}_{-1.95}, -145^{+14}_{-21})$ and $(ρ_A^f,ϕ_A^f[^{\circ}]) = (0.91^{+0.12}_{-0.13}, -37^{+10}_{-9})$ at $68%$ C. L.. With the best-fit values, most of the theoretical results are in good agreement with the experimental data within errors. However, significant corrections to the color-suppressed tree amplitude $α_2$ related to a large $ρ_H$ result in the wrong sign for $A^{dir}_{CP}(B^- \to π^0 K^{{\ast}-})$ compared with the most recent BABAR data, which presents a new obstacle in solving "$ππ$" and "$πK$" puzzles through $α_2$. A crosscheck with measurements at Belle (or Belle II) and LHCb, which offer higher precision, is urgently expected to confirm or refute such possible mismatch.

hep-ph↗
arXiv2014

A Combined Fit on the Annihilation Corrections in $B_{u,d,s}$ $\to$ $PP$ Decays Within QCDF

Motivated by the possible large annihilation contributions implied by recent CDF and LHCb measurements on nonleptonic annihilation B meson decays, and the refined experimental measurements on hadronic B meson decays, we study the strength of annihilation contributions within QCD factorization (QCDF) in this paper. With the available measurements of two-body B_{u,d,s} -> pi pi, pi K, K K decays, a comprehensive fit on the phenomenological parameters X_A^{i,f} (or rho_A^{i,f} and phi_A^{i,f}) which are used to parameterize the endpoint singularity in annihilation amplitudes is performed with the statistical chi^2 approach. It is found that (1) flavor symmetry breaking effects are hardly to be distinguished between X_{A,s}^i and X_{A,d}^i due to the large experimental errors and theoretical uncertainties, where X_{A,s}^i and X_{A,d}^i are related to the nonfactorization annihilation contributions in B_s and B_{u,d} decays, respectively. So X_{A,s}^i = X_{A,d}^i is a good approximation by now. (2) In principle, parameter X_{A}^f which is related to the factorization annihilation contributions and independent of the initial state can be regarded as the same variable for B_{u,d,s} decays. (3) Numerically, two solutions are found, one is (rho_A^i, phi_A^i) = (2.98^+1.12_-0.86,-105^+34_-24) and (rho_A^f, phi_A^f) = (1.18^+0.20_-0.23,-40^+11_-8), the other is (rho_A^i, phi_A^i) = (2.97^+1.19_-0.90,-105^+32_-24) and (rho_A^f, phi_A^f) = (2.80^+0.25_-0.21,165^+4_-3). Obviously, nonfactorization annihilation parameter X_A^i is generally unequal to factorization annihilation parameter X_A^f, which differ from the traditional treatment. With the fitted parameters, all results for observables of B_{u,d,s} ->pi pi, pi K, K K decays are in good agreement with experimental data.

hep-ph↗
arXiv2014

Spectator Scattering and Annihilation Contributions as a Solution to the $πK$ and $ππ$ Puzzles within QCD Factorization Approach

The large branching ratios for pure annihilation $\bar{B}_s^0$ $\to$ $π^+ π^-$ and $\bar{B}_d^0$ $\to$ $K^+ K^-$ decays reported by CDF and LHCb collaborations recently and the so-called $πK$ and $ππ$ puzzles indicate that spectator scattering and annihilation contributions are important to the penguin-dominated, color-suppressed tree dominated, and pure annihilation nonleptonic $B$ decays. Combining the available experimental data for $B_{u,d}$ ${\to}$ $ππ$, $πK$ and $K \bar{K}$ decays, we do a global fit on the spectator scattering and annihilation parameters $X_H(ρ_H$, $ϕ_H)$, $X_A^i(ρ_A^{i},ϕ_A^{i})$ and $X_A^f(ρ_A^{f},ϕ_A^{f})$, which are used to parameterize the endpoint singularity in amplitudes of spectator scattering, nonfactorizable and factorizable annihilation topologies within the QCD factorization framework, in three scenarios for different purpose. Numerically, in scenario II, we get $(ρ_A^{i},ϕ_A^{i}[^{\circ}])=(2.88^{+1.52}_{-1.30},-103^{+33}_{-40})$ and $(ρ_A^{f},ϕ_A^{f}[^{\circ}])=(1.21^{+0.22}_{-0.25},-40^{+12}_{-8})$ at the $68\%$ confidence level, which are mainly demanded by resolving $πK$ puzzle and confirm the presupposition that $X_A^i\neq X_A^f$. In addition, correspondingly, the $B$-meson wave function parameter $λ_B$ is also fitted to be $0.18^{+0.11}_{-0.08}\, MeV$, which plays an important role for resolving both $πK$ and $ππ$ puzzles. With the fitted parameters, the QCDF results for observables of $B_{u,d}$ $\to$ $ππ$, $πK$ and $K \bar{K}$ decays are in good agreement with experimental measurements. Much more experimental and theoretical efforts are expected to understand the underlying QCD dynamics of spectator scattering and annihilation contributions.

hep-ph↗
arXiv2014

A Comprehensive Analysis of Hadronic b->s Transitions in a Family Non-universal Z' Model

Motivated by the latest improved measurements of B-meson decays, we make a comprehensive analysis of the impact of a family non-universal $Z^{\prime}$ boson on $B_s-\bar{B}_s$ mixing and two-body hadronic B-meson decays, all being characterized by the quark-level $b\to s$ transition. Explicitly 22 decay modes and the related 52 observables are considered, and some interesting correlations between them are also carefully examined. Firstly, the allowed oases of $b-s-Z^{\prime}$ coupling parameters $|B^{L,R}_{sb}|$ and $ϕ^{L,R}_s$ are extracted from $B_s-\bar{B}_s$ mixing. Then, in the "SM limit"~({\it i.e.,} no new types of $Z^{\prime}$-induced four-quark operators arise compared to the SM case), we study the $Z^{\prime}$ effects on $B\toπK$, $πK^{\ast}$ and $ρK$ decays. It is found that a new weak phase $ϕ^{L}_s\sim -90^{\circ}$ is crucial for resolving the observed "$πK$ CP puzzle" and the allowed oases of the other $Z^{\prime}$ coupling parameters are also strongly restricted. Moreover, the $Z^{\prime}$ effects on $\bar{B}_s\to K K$, $K K^{\ast}$ and $π^0 ϕ$ decays, being induced by the same quark-level $b\to s q\bar{q}~(q=u,d)$ transitions, are also investigated. Especially, it is found that the decay $\bar{B}_s \to π^0 ϕ$, once measured, would play a key role in revealing the observed "$πK$ CP puzzle" and probing possible new physics hints. Finally, to check the non-universality of $Z^{\prime}$ couplings to light-quark pairs, we have studied the $B\to ϕK$ decays in detail and found that the left-handed $s-s-Z^{\prime}$ coupling is different from the $d-d-Z^{\prime}$ one, which is due to the large $A_{CP}^{dir}(B^-\toϕK^-)$ reported by the BaBar collaboration.

hep-ph↗
arXiv2014

Phenomenological study of the $B_{c}$ ${\to}$ $BP$, $BV$ decays with perturbative QCD approach

Inspired by the recent LHCb measurements and forthcoming great potential on $B_{c}$ meson, we study the exclusive $B_{c}$ ${\to}$ $B_{q}P$, $B_{q}V$ decays with the perturbative QCD approach, where $q$ $=$ $u$, $d$, $s$; $P$ and $V$ denote the lightest pseudoscalar and vector $SU(3)$ nonet meson, respectively. By retaining the quark transverse momentum, employing the Sudakov factors, and choosing the typical scale as the maximum virtualities of the internal particles, we calculate the $B_{c}$ ${\to}$ $B$ transition from factors, and our results show that about 90\% contribution to form factors come from the $α_{s}/π$ $<$ $0.3$ region. The contributions of penguin and annihilation to branching ratios are very small due to the serious suppression by the CKM factors. There is some hierarchy relations among the $B_{c}$ ${\to}$ $BP$, $BV$ decays. The branching ratios for $B_{c}$ ${\to}$ $B_{d,s}π$, $B_{d,s}ρ$, $B_{s}K$ are large and could be measured by the running LHCb.

hep-ph↗
arXiv2012

Revisiting the Annihilation Corrections in Non-leptonic $\bar{B}_s^0$ Decays within QCD Factorization

Motivated by the recent measurements of non-leptonic $\bar{B}_s^0$ decays by CDF and LHCb collaborations, especially the large ${\cal B}(\bar{B}_s^0\toπ^+π^-)$, we revisit the hard spectator and annihilation corrections in $\bar{B}_s^0$ decays within QCD factorization approach with two schemes for the possible parameters for the known end-point divergence appeared in the estimation of the hard spectator and annihilation diagrams. The first one is to conservatively estimate the possible contributions by parameterization (scheme I); another one uses an infrared finite gluon propagator (scheme II) to regulate the end-point singularity. In scheme I, with the constraints from the measured $\bar{B}_s^0\to PP (VV)$ decays, two (four) restricted solutions of the parameters spaces are found. In scheme II, we find that most of the theoretical predictions agree well with the experimental data with single parameter $m_{g}\sim 0.5{\rm GeV}$. However, within both schemes, ${\cal B}(\bar{B}_s^0\toϕϕ)$ are always much larger than ${\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$ in contrast to the experimental results ${\cal B}(\bar{B}_s^0\toϕϕ)\simeq{\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$. It is noted that the pattern ${\cal B}(\bar{B}_s^0\toϕϕ)>{\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$ also persists in other theoretical framework, thus the present experimental result ${\cal B}(\bar{B}_s^0\toϕϕ) \simeq {\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$ rises a challenge to theoretical approaches for B non-leptonic decays. Further refined measurements and theoretical studies are called for to resolve such a possible anomaly.

hep-ph↗
arXiv2011

Implications of the Anomalies in B_s^0-\bar{B}_s^0 Mixing for Anomalous Tensor Couplings

Motivated by the recently observed anomalous large dimuon charge asymmetry in neutral B decays and the unexpected large CP phase in the mixing-induced CP asymmetry for B_s-->J/ψϕdecay, we study the effects of the anomalous tensor couplings to pursue possible solution. With the constraints from the obsevables ϕ^{J/ψϕ}_s, a_{sl}^s and ΔM_s, the parameter spaces are severely restricted. Numerically, we find the anomalies in B_s^0-\bar{B}_s^0 mixing system could be moderated simultaneously by the contributions induced by the color-singlet or color-octet tensor operators with their respective nontrivial new weak phase ϕ_{T1}\approx28.0(15.6) degree or ϕ_{T8}\approx-62.1(-74.2) degree and relevant strength parameters g_{T1}\approx6.7(8.5)\times10^{-2} or g_{T8}\approx1.9(2.4)\times10^{-2} for the CP-violating phase ϕ^{J/ψϕ}_s=-0.77(+0.29,-0.37)(-2.36(+0.37,-0.29)), respectively.

hep-ph↗
arXiv2011

The Effects of a Family Non-universal Z' Boson in the \bar{B}_s->πK, πK*, ρK Decays and B_d-\bar{B_d} mixing

We revisit $\bar{B}_s\to πK$, $πK^{\ast}$ and $ρK$ decays within QCDF formalism and examine the possible effects of a family non-universal $Z^\prime$ boson in these decays. In our evaluations, the strong constraints from $B_d-\bar{B_d}$ mixing on the strength of the left-handed flavor-changing $d-b-Z^{\prime}$ coupling $B_{db}^{L}$ ~($\sim0.2\times10^{-3}$) is also included. Numerically, we find that a new weak phase $ϕ^L_d\sim-50^{\circ}$ involved in $B_{db}^{L}$, the negative combination of the $u-u-Z^{\prime}$ and $d-d-Z^{\prime}$ couplings $P_{ud}^{R}$ and/or $D_{ud}^{L}$ with larger absolute value are crucial to improve the agreement of ${\cal B}(\bar{B}_s\to π^- K^+)$ between the SM prediction and the experimental measurement. Generally, ${\cal B}(\bar{B}_s\to π^- K^+)$ could be reduced by about 18% at most by $Z^{\prime}$ contributions. Moreover, combining with the recent updated measurement on $β_s$ by CDF and D0 collaborations, we also find that $Z^{\prime}$ effects in $\bar{B}_s\to π^- K^+$ decays are very important for examining whether the CKM-like hierarchy persists in a family non-universal $Z^{\prime}$ coupling matrix.

hep-ph↗
arXiv2011

Studying of B_s^0-\bar{B}_s^0 mixing and B_{s}\to K^{(*)-}K^{(*)+} decays within supersymmetry

Recent results from CDF and DØ collaborations favor a large CP asymmetry in B_s^0-\bar{B}_s^0 mixing, while the standard model prediction is very small. Such a large phase may imply sizable new physics effects in B_s^0-\bar{B}_s^0 mixing. We compute the gluino-mediated supersymmetry contributions to B_s^0-\bar{B}_s^0 mixing, B_s->K^{(*)-}K^{(*)+} and B->X_sγdecays in the frame of the mass insertion approximation. Combining the constraints of \DeltaM_s, ΔΓ_s, ϕ^{J/ψϕ}_s, B(B_s->K^{-}K^{+}) and B(B->X_s γ), we find that the effects of the constrained LL and RR insertions in B_s->K^{(*)-}K^{(*)+} decays are small because of the absence of gluino mass enhancement. For m^2_{\tilde{g}}/m^2_{\tilde{q}}=9, the constrained LR insertion can provide sizable contributions to all observables of B_s->K^{(*)-}K^{(*)+} decays except A^{dir}_{CP}(B_s->K^{-}K^{+}), and many observables are sensitive to the modulus and the phase of the LR insertion parameter. Near future experiments at Fermilab Tevatron and CERN LHC-b can test these predictions and shrink/reveal the mass insertion parameter spaces.

hep-ph↗
arXiv2011

The effects of a family non-universal Z-prime boson on B--->pipi decays

Motivated by the measured large branching ratio of $\bar{B}^{0}\toπ^0π^0$ (the so-called "$ππ$" puzzle), we investigate the effects of a family non-universal $Z^{\prime}$ model on the tree-dominated $B\toππ$ decays. We find that the $Z^{\prime}$ coupling parameter $ζ_{d}^{LR}\sim0.05$ with a nontrivial new weak phase $ϕ_d^L\sim-50^{\circ}$, which is relevant to the $Z^{\prime}$ contributions to the QCD penguin sector $\triangle C_5$, is needed to reconcile the observed discrepancy. Combined with the recent fitting results from $B\toπK$, $πK^{\ast}$ and $ρK$ decays, the $Z^{\prime}$ parameter spaces are severely reduced but still not excluded entirely, implying that both the "$ππ$" and "$πK$" puzzles could be accommodated simultaneously within such a family non-universal $Z^{\prime}$ model.

hep-ph↗
arXiv2011

Probe a family non-universal Z' boson effects in B(s)-> phi mu(+) mu(-)decay

Motivated by the recent measurement on ${\cal B}(\bar{B}_s\to ϕμ^+μ^-)$ by CDF collaboration, we study the effects of a family non-universal $Z^{\prime}$ boson on rare semileptonic $\bar{B}_s \to ϕμ^+μ^-$ decay. In our evaluations, we analyze the dependences of the dimuon invariant mass spectrum and normalized forward-backward asymmetry on $Z^{\prime}$ couplings and show that these observables are highly sensitive to new $Z^{\prime}$ contributions. Three limiting scenarios are presented in the detailed analyses. Numerically, within the allowed ranges of $Z^{\prime}$ couplings under the constraints from $\bar{B}_s-B_s$ mixing, $B\toπK$, $\bar{B}_d\to(X_s,K,K^{\ast})μ^+μ^-$ decays and so on, ${\cal B}(\bar{B}_s\to ϕμ^+μ^-)$ and $A_{FB}^{(L)}(\bar{B}_s\to ϕμ^+μ^-)$ could be enhanced by about 96% and $17%\,(133%)$ respectively at most by $Z^{\prime}$ contributions. However, ${\cal B}(\bar{B}_s\to ϕμ^+μ^-)$ is hardly to be reduced. Furthermore, the zero crossing in $A_{FB}(\bar{B}_s\to ϕμ^+μ^-)$ spectrum at low dimuon mass always exists.

hep-ph↗
arXiv2010

$B \to K^{\ast} l^+ l^-$, $K l^+ l^-$ decays in a family non-universal $Z^{\prime}$ model

Motivated by the observed forward-backward asymmetry in $B\to K^{\ast} l^+ l^-$ decay, we perform a detailed analysis of this decay mode within a family non-universal $Z^{\prime}$ model. With the related coupling $Z^{\prime}-\bar{s}b$ constrained by $\bar{B}_s-B_s$ mixing, $B\to πK$, and $B\to X_s μ^{+}μ^{-}$ decays, we look for further constraint on the couplings $Z^{\prime}-μ^{+}μ^{-}$ from $A_{FB}(B\to K^{\ast} μ^{+}μ^{-})_{0 {\rm GeV}^2\leqslant q^2\leqslant 2 {\rm GeV}^2}$ and get numerically $B_{μμ}^{L,R}\sim{\cal O}(10^{-2})$. Moreover, we find that the relations, $B_{μμ}^{L}<B_{μμ}^{R}$ and $B_{μμ}^{L}+B_{μμ}^{R}<0$, with a small negative $ϕ_{s}^{L}$, are crucial to moderate the discrepancy for $A_{FB}(B\to K^{\ast} μ^{+}μ^{-})$ between the SM prediction and the experimental data. Numerically, comparing with the SM prediction, we find that $A_{FB}(B\to K^{\ast} μ^{+}μ^{-})_{0 {\rm GeV}^2\leqslant q^2\leqslant 2 {\rm GeV}^2}$ could be enhanced about 80% and 50% by $Z^{\prime}$ contribution at most in scenarios S1 and S2, corresponding to the two fitted results of $ϕ_{s}$ by UTfit collaboration, respectively. However, the results are still about $1.5σ$ lower than the experimental measurement.

hep-ph↗
arXiv2010

Family Non-universal Z^\prime effects on \bar{B}_q-B_q$ mixing, B\to X_s μ^+μ^- and B_s\to μ^+μ^- Decays

Motivated by the large discrepancy of CP-violating phase in $\bar{B}_s-B_s$ mixing between the experimental data and the Standard Model prediction, we pursue possible solutions within a family non-universal $Z^{\prime}$ model. Within such a specific model, we find that both the $\bar{B}_s-B_s$ mixing anomaly and the well-known "$πK$ puzzle" could be moderated simultaneously with a nontrivial new weak phase, $ϕ^L_s\sim-72^{\circ}$ (S1) or $-82^{\circ}$ (S2). With the stringently constrained $Z^{\prime}$ coupling $B_{sb}^{L}$, we then study the $Z^{\prime}$ effects on the rare $B\to X_s μ^+μ^-$ and $B_s\to μ^+μ^-$ decays, which are also induced by the same $b\to s$ transition. The observables of $B\to X_s μ^+μ^-$, at both high and low $q^2$ regions, are found to be able to put strong constraints on the $μ-μ-Z^{\prime}$ coupling, $B_{μμ}^{L,R}\sim10^{-2}$. It is also shown that the combined constraints from $\bar{B}_s-B_s$ mixing, $B\to πK$ and $B\to X_s μ^+μ^-$ do not allow a large $Z^{\prime}$ contribution to the pure leptonic $B_s\toμ^+μ^-$ decay.

hep-ph↗
arXiv2009

Rare decay $π^{0}\to e^+ e^-$ constraints on the light CP-odd Higgs in NMSSM

We constrain the light CP-odd Higgs $A_{1}^{0}$ in NMSSM via the rare decay $π^{0}\to e^{+}e^{-}$. It is shown that the possible $3σ$ discrepancy between theoretical predictions and the recent KTeV measurement of ${\cal B}(π^{0}\to e^+ e^-)$ cannot be resolved when the constraints from $Υ\toγA_1^0$, $a_μ$ and $π^{0}\to γγ$ are combined. Furthermore, the combined constraints also exclude the scenario involving $m_{A_1^0}=214.3$ MeV, which is invoked to explain the anomaly in the $Σ^{+}\to p μ^{+}μ^{-}$ decay found by the HyperCP Collaboration.

hep-ph↗
arXiv2009

Constraints on the nonuniversal Z^\prime couplings from B\toπK, πK^{\ast} and ρK Decays

Motivated by the large difference between the direct CP asymmetries $A_{CP}(B^-\to π^0 K^-)$ and $A_{CP}(\bar{B}^{0}\to π^{+} K^{-})$, we combine the up-to-date experimental information on $B\toπK$, $πK^{\ast}$ and $ρK$ decays to pursue possible solutions with the nonuniversal $Z^{\prime}$ model. Detailed analyses of the relative impacts of different types of couplings are presented in four specific cases. Numerically, we find that the new coupling parameters, $ξ^{LL}$ and $ξ^{LR}$ with a common nontrivial new weak phase $ϕ_L\sim-86^{\circ}$, which are relevant to the $Z^{\prime}$ contributions to the electroweak penguin sector $\triangle C_9$ and $\triangle C_7$, are crucial to the observed "$πK$ puzzle". Furthermore, they are found to be definitely unequal and opposite in sign. We also find that $A_{CP}(B^-\to ρ^0 K^-)$ can put a strong constraint on the new $Z^{\prime}$ couplings, which implies the $Z^{\prime}$ contributions to the coefficient of QCD penguins operator $O_3$ involving the parameter $ζ^{LL}$ required.

hep-ph↗