作者机构：
[Yang, Ya-Dong; Yuan, Xing-Bo; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong; Yuan, Xing-Bo; Li, Xin-Qiang] Minist Educ, Key Lab Quark & Lepton Phys, Wuhan, Peoples R China.;[Li, Xin-Qiang] Chinese Acad Sci, Inst Theoret Phys, State Key Lab Theoret Phys, Beijing 100190, Peoples R China.
通讯机构：
Institute of Particle Physics, Central China Normal University, China
摘要：
In the “Higgs basis” for a generic two-Higgs-doublet model, only one 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, referred to, respectively, as the type-III and type-C models. Both of them can naturally avoid large FCNC transitions and provide very interesting phenomena in some low-energy processes. In this paper, we study their effects on exclusive radiative B-meson decays due to the exchange of colorless or colored charged Higgs. It is found that while constraints from the branching ratios are slightly weaker than the ones from the inclusive B→Xsγ decay, the isospin asymmetries in exclusive decays provide very complementary bounds on the model parameters. As the two models predict similar corrections to the dipole coefficient C7eff, but similar magnitudes with opposite signs to C8eff, the branching ratios cannot discriminate the two models, and we have to resort to the direct CP and isospin asymmetries of b→s processes, which are more sensitive to C8eff. Due to the CKM factors |λu(d)|∼|λt(d)|, the terms proportional to λu(d) make the observables of b→d processes exhibit a different dependence on the possible new physics phase. In addition, correlations between the various observables in the exclusive B→Vγ and the inclusive B→Xs,dγ decays are investigated, which could provide further insights into the models with more precise experimental measurements and theoretical predictions for these decays.
期刊：
European Physical Journal C,2017年77(3):1-15 ISSN：1434-6044
通讯作者：
Li, X.-Q.
作者机构：
[Hu, Quan-Yi] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
摘要：
In the aligned two-Higgs-doublet model, we perform a complete one-loop computation of the short-distance Wilson coefficients \(C_{7,9,10}^{(\prime )}\), which are the most relevant ones for \(b\rightarrow s\ell ^+\ell ^-\) transitions. It is found that, when the model parameter \(\left| \varsigma _{u}\right| \) is much smaller than \(\left| \varsigma _{d}\right| \), the charged scalar contributes mainly to chirality-flipped \(C_{9,10}^\prime \), with the corresponding effects being proportional to \(\left| \varsigma _{d}\right| ^2\). Numerically, the charged-scalar effects fit into two categories: (A) \(C_{7,9,10}^\mathrm {H^\pm }\) are sizable, but \(C_{9,10}^{\prime \mathrm {H^\pm }}\simeq 0\), corresponding to the (large \(\left| \varsigma _{u}\right| \), small \(\left| \varsigma _{d}\right| \)) region; (B) \(C_7^\mathrm {H^\pm }\) and \(C_{9,10}^{\prime \mathrm {H^\pm }}\) are sizable, but \(C_{9,10}^\mathrm {H^\pm }\simeq 0\), corresponding to the (small \(\left| \varsigma _{u}\right| \), large \(\left| \varsigma _{d}\right| \)) region. Taking into account phenomenological constraints from the inclusive radiative decay \(B\rightarrow X_{s}{\gamma }\), as well as the latest model-independent global analysis of \(b\rightarrow s\ell ^+\ell ^-\) data, we obtain the much restricted parameter space of the model. We then study the impact of the allowed model parameters on the angular observables \(P_2\) and \(P_5'\) of \(B^0\rightarrow K^{*0}\mu ^+\mu ^-\) decay, and we find that \(P_5'\) could be increased significantly to be consistent with the experimental data in case B.
期刊：
European Physical Journal C,2019年79(3):1-20 ISSN：1434-6044
通讯作者：
Li, X.-Q.
作者机构：
[Yang, Ya-Dong; Hu, Quan-Yi; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Key Laboratory of Quark and Lepton Physics (MOE), Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China
摘要：
The \(R(D^{(*)})\) anomalies observed in \(B\rightarrow D^{(*)}\tau \nu \) decays have attracted much attention in recent years. In this paper, we study the \(B\rightarrow D^{(*)}\tau \nu \), \(\Lambda _b\rightarrow \Lambda _c\tau \nu \), \(B_c\rightarrow (J/\psi ,\,\eta _c)\tau \nu \), \(B\rightarrow X_c\tau \nu \), and \(B_c\rightarrow \tau \nu \) decays, all being mediated by the same quark-level \(b\rightarrow c\tau \nu \) transition, in the Standard Model Effective Field Theory. The most relevant dimension-six operators for these processes are \(Q_{lq}^{(3)}\), \(Q_{ledq}\), \(Q^{(1)}_{lequ}\), and \(Q^{(3)}_{lequ}\) in the Warsaw basis. Evolution of the corresponding Wilson coefficients from the new physics scale \(\Lambda =1\) TeV down to the characteristic scale \(\mu _b\simeq m_b\) is performed at three-loop in QCD and one-loop in EW/QED. It is found that, after taking into account the constraint \({{\mathcal {B}}}(B_c\rightarrow \tau \nu )\lesssim 10\%\), a single \(\left[ C_{lq}^{(3)}\right] _{3323}(\Lambda )\) or \(\left[ C^{(3)}_{lequ}\right] _{3332}(\Lambda )\) can still be used to resolve the \(R(D^{(*)})\) anomalies at \(1\sigma \), while a single \(\left[ C^{(1)}_{lequ}\right] _{3332}(\Lambda )\) is already ruled out by the measured \(R(D^{(*)})\) at more than \(3\sigma \). By minimizing the \(\chi ^2(C_i)\) function constructed based on the current data on R(D), \(R(D^*)\), \(P_\tau (D^*)\), \(R(J/\psi )\), and \(R(X_c)\), we obtain eleven most trustworthy scenarios, each of which can provide a good explanation of the \(R(D^{(*)})\) anomalies at \(1\sigma \). To further discriminate these different scenarios, we predict thirty-one observables associated with the processes considered under each NP scenario. It is found that most of the scenarios can be differentiated from each other by using these observables and their correlations.
作者机构：
[Zhang, Xin; Chen, Feng-Zhi; Yang, Ya-Dong; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
摘要：
Motivated by the 2.8σ discrepancy observed between the BABAR measurement and the standard model prediction of the CP asymmetry in τ→KSπντ decays, as well as the prospects of future measurements at Belle II, we revisit this observable in this paper. Firstly, we reproduce the known CP asymmetry due to K0−K¯0 mixing by means of the reciprocal basis, which is convenient when a KS(L) is involved in the final state. As the Kπ tensor form factor plays a crucial role in generating a nonzero direct CP asymmetry that can arise only from the interference of vector and tensor operators, we then present a dispersive representation of this form factor, with its phase obtained in the context of chiral theory with resonances, which fulfills the requirements of unitarity and analyticity. Finally, the τ→KSπντ decays are analyzed both within a model-independent low-energy effective theory framework and in a scalar leptoquark scenario. It is observed that the CP anomaly can be accommodated in the model-independent framework, even at the 1σ level, together with the constraint from the branching ratio of τ−→KSπ−ντ decay; it can be, however, marginally reconciled only at the 2σ level, due to the specific relation between the scalar and tensor operators in the scalar leptoquark scenario. Once the combined constraints from the branching ratio and the decay spectrum of this decay are taken into account, these possibilities are, however, both excluded, even without exploiting further the stronger bounds from the (semi)leptonic kaon decays under the assumption of lepton-flavor universality, as well as from the neutron electric dipole moment and D−D¯ mixing under the assumption of SU(2) invariance of the weak interactions.
期刊：
European Physical Journal C,2017年77(4):1-13 ISSN：1434-6044
通讯作者：
Li, X.-Q.
作者机构：
[Hu, Quan-Yi] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, MOE, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
摘要：
The rare baryonic decay \(\Lambda _b\rightarrow \Lambda (\rightarrow p\pi ^-)\mu ^+\mu ^-\) provides valuable complementary information compared to the corresponding mesonic \(b\rightarrow s\mu ^+\mu ^-\) transition. In this paper, using the latest high-precision lattice QCD calculation of the \(\Lambda _b\rightarrow \Lambda \) transition form factors, we study this interesting decay within the aligned two-Higgs-doublet model, paying particularly attention to the effects of the chirality-flipped operators generated by the charged scalars. In order to extract the full set of angular coefficients in this decay, we consider the following ten angular observables, which can be derived from the analysis of the subsequent parity-violating \(\Lambda \rightarrow p\pi ^-\) decay: the differential branching fraction \(\mathrm{d}\mathcal{B}/\mathrm{d}q^2\), the longitudinal polarization fraction \(F_\mathrm{L}\), the lepton-, hadron- and combined lepton–hadron-side forward–backward asymmetries \(A_\mathrm{FB}^\ell \), \(A_\mathrm{FB}^\Lambda \) and \(A_\mathrm{FB}^{\ell \Lambda }\), as well as the other five asymmetry observables \(Y_i\) (\(i=\mathrm{2,\,3s,\,3sc,\,4s,\,4sc}\)). Detailed numerical comparisons are made between the SM and NP values for these angular observables. It is found that, under the constraints from the inclusive \(B\rightarrow X_s\gamma \) branching fraction and the latest global fit results of \(b\rightarrow s\ell \ell \) data, the contributions of right-handed semileptonic operators \(O^{\prime }_{9,10}\), besides reconciling the \(P_5^{\prime }\) anomaly observed in \(B^0\rightarrow K^{*0}\mu ^+\mu ^-\) decay, could also enhance the values of \(\mathrm{d}\mathcal{B}/\mathrm{d}q^2\) and \(A_\mathrm{FB}^\ell \) in the bin \([15,20]~\mathrm{GeV}^2\), leading to results consistent with the current LHCb measurements.
作者机构：
[Li, Xin-Qiang] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.;[Li, Xin-Qiang] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain.;[Yang, Ya-Dong; Su, Fang] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Huazhong Normal Univ Wuhan, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Department of Physics, Henan Normal University, China
摘要：
According to heavy-meson chiral perturbation theory, the vector form factor f+(q2) of exclusive semileptonic decay B→πℓν is closely related, at least in the soft-pion region (i.e., q2∼(mB−mπ)2), to the strong coupling gB*Bπ or the normalized coupling g^. Combining the precisely measured q2 spectrum of B→πℓν decay by the BABAR and Belle collaborations with several parametrizations of the form factor f+(q2), we can extract these couplings from the residue of the form factor at the B* pole, which relies on an extrapolation of the form factor from the semileptonic region to the unphysical point q2=mB*2. Comparing the extracted values with the other experimental and theoretical estimates, we can test these various form-factor parametrizations, which differ from each other by the amount of physical information embedded in. It is found that the extracted values based on the Bećirević-Kaidalov, Ball-Zwicky and Bourrely-Caprini-Lellouch parametrizations are consistent with each other and roughly in agreement with the other theoretical and lattice estimates, while the Boyd-Grinstein-Lebed ansatz, featured by a spurious, unwanted pole at the threshold of the cut, gives a neatly larger value.
作者机构：
[Yang, Ya-Dong; Li, Shao-Ping; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics, Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
摘要：
We show in this paper that, in a U(1)-symmetric two-Higgs-doublet model, the two additional neutral Higgs bosons would become nearly degenerate in the large tanβ regime, under the combined constraints from both theoretical arguments and experimental measurements. As a consequence, the excess observed in the anomalous magnetic moment of the muon could not be addressed in the considered framework, following the usual argument where these two neutral scalars are required to manifest a large mass hierarchy. On the other hand, we find that, with an O(1) top-Yukawa coupling and a relatively light charged Higgs boson, large contributions from the two-loop Barr-Zee-type diagrams can account for the muon g−2 anomaly at the 1σ level, in spite of a large cancellation between the scalar and pseudoscalar contributions. Furthermore, the same scenario can survive the tight constraints from the B-physics observables.
作者机构：
[Chang, Qin; Li, Xiao-Nan] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.;[Yang, Ya-Dong; Chang, Qin; Li, Xin-Qiang; Su, Fang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong; Chang, Qin; Li, Xin-Qiang; Su, Fang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics, Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
摘要：
In this paper, we test the self-consistencies of the standard and the covariant light-front quark model and study the zero-mode issue via the decay constants of pseudoscalar ( P), vector ( V) and axial-vector ( A) mesons, as well as the P→P weak transition form factors. With the traditional type-I correspondence between the manifestly covariant and the light-front approach, the resulting fV as well as fA1 and fA3 obtained with the λ=0 and λ=± polarization states are different from each other, which presents a challenge to the self-consistency of the covariant light-front quark model. However, such a self-consistency problem can be “resolved” within the type-II scheme, which requires an additional replacement M→M0 relative to the type-I case. Moreover, the replacement M→M0 is also essential for the self-consistency of the standard light-front quark model. In the type-II scheme, the valence contributions to the physical quantities ( Q) considered in this paper are always the same as that obtained in the standard light-front quark model, [Q]val=[Q]SLF, and the zero-mode contributions to fV,1A,3A and f−(q2) exist only formally but vanish numerically, which further implies that [Q]val=˙[Q]full. In addition, the manifest covariance of the covariant light-front quark model is violated in the traditional type-I scheme, but can be recovered by taking the type-II correspondence.
期刊：
European Physical Journal C,2020年80(12) ISSN：1434-6044
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
摘要：
We present a freeze-in realization of the Dirac neutrinogenesis in which the decaying particle that generates the lepton-number asymmetry is in thermal equilibrium. As the right-handed Dirac neutrinos are produced non-thermally, the lepton-number asymmetry is accumulated and partially converted to the baryon-number asymmetry via the rapid sphaleron transitions. The necessary CP-violating condition can be fulfilled by a purely thermal kinetic phase from the wavefunction correction in the lepton-doublet sector, which has been neglected in most leptogenesis-based setup. Furthermore, this condition necessitates a preferred flavor basis in which both the charged-lepton and neutrino Yukawa matrices are non-diagonal. To protect such a proper Yukawa structure from the basis transformations in flavor space prior to the electroweak gauge symmetry breaking, we can resort to a plethora of model buildings aimed at deciphering the non-trivial Yukawa structures. Interestingly, based on the well-known tri-bimaximal mixing with a minimal correction from the charged-lepton or neutrino sector, we find that a simultaneous explanation of the baryon-number asymmetry in the Universe and the low-energy neutrino oscillation observables can be attributed to the mixing angle and the CP-violating phase introduced in the minimal correction.
作者机构：
[Muramatsu, Yu; Yang, Ya-Dong; Hu, Quan-Yi; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
摘要：
Recently, several B-physics experiments report interesting anomalies in the semi-leptonic decays of B-mesons, such as the excess in the RD(*) measurements. These anomalies seem to suggest intriguing hints of lepton flavor nonuniversality, and the R-parity violating (RPV) interactions are candidates for explaining this nonuniversality. In this paper, we discuss the RPV interactions for resolving the RD(*) anomaly with the grand unified theory (GUT) assumption. To solve the RD(*) anomaly, it is known that large RPV couplings and around 1 TeV sfermion masses are required. At the same time, large RPV couplings are conducive to realize the bottom-tau Yukawa unification which appears in the GUT models. On the other hand, there are problems for realizing favorable sfermion masses in the constrained minimal supersymetric standard model. To resolve these problems, we show that two nonuniversalities, the nonuniversal sfermion masses and the nonuniversal gaugino masses, are favorable.
期刊：
Journal of High Energy Physics,2008年(9) ISSN：1029-8479
通讯作者：
Yang, Ya-Dong
作者机构：
[Yang, Ya-Dong; Chang, Qin] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Chang, Qin] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.;[Li, Xin-Qiang] Rhein Westfal TH Aachen, D-52056 Aachen, Germany.
通讯机构：
[Yang, Ya-Dong] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
rare decays;beyond standard model;B-physics;CP violation
摘要：
Combining the up-to-date experimental information on B -> pi K, pi K* and rho K decays, we revisit the decay rates and CP asymmetries of these decays within the framework of QCD factorization. Using an infrared finite gluon propagator of Cornwall prescription, we find that the time-like annihilation amplitude could contribute a large strong phase, while the space-like hard spectator scattering amplitude is real. Numerically, we find that all the branching ratios and most of the direct CP violations, except A(CP)(B-+/- -> K-+/-pi(0)), agree with the current experimental data with an effective gluon mass m(g) similar or equal to 0.5 GeV. Taking the unmatched difference in direct CP violations between B -> pi(0) K-+/- and pi K--/+(+/-) decays as a hint of new physics, we perform a model-independent analysis of new physics contributions with a set of (s) over bar (1 + gamma(5))b circle times (q) over bar (1 + gamma(5))q (q=u,d) operators. Detail analyses of the relative impacts of the operators are presented in five cases. Fitting the twelve decay modes, parameter spaces are found generally with nontrivial weak phases. Our results may indicate that both strong phase from annihilation amplitude and new weak phase from new physics are needed to resolve the pi K puzzle. To further test the new physics hypothesis, the mixing-induced CP violations in B -> pi K-0(s) and rho K-0(s) are discussed and good agreements with the recent experimental data are found.
期刊：
Journal of High Energy Physics,2021年(2) ISSN：1029-8479
作者机构：
[Hu, Quan-Yi] Anyang Normal Univ, Sch Phys & Elect Engn, Anyang 455000, Henan, Peoples R China.;[Yang, Ya-Dong; Zheng, Dong-Hui; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong; Zheng, Dong-Hui; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
In Lambda b0</mml:msubsup>-> Lambda c+</mml:msubsup><mml:mfenced close=")" open="(">-> Lambda 0 pi+</mml:mfenced>tau -v<overbar></mml:mover>tau decay, the solid angle of the final-state particle tau (-) cannot be determined precisely since the decay products of the tau (-) include an undetected nu (tau). Therefore, the angular distribution of this decay cannot be measured. In this work, we construct a measurable angular distribution by considering the subsequent decay tau (-)-> pi (-)nu (tau). The full cascade decay is Lambda b0</mml:msubsup>-> Lambda c+</mml:msubsup><mml:mfenced close=")" open="(">-> Lambda 0 pi+</mml:mfenced>tau-<mml:mfenced close=")" open="(">-> pi -v tau</mml:mfenced>v<overbar></mml:mover>tau. The three-momenta of the final-state particles Lambda (0), pi (+), and pi (-) can be measured. Considering all Lorentz structures of the new physics (NP) effective operators and an unpolarized initial Lambda (b) state, the five-fold differential angular distribution can be expressed in terms of ten angular observables Ki<mml:mfenced close=")" open="(" separators=",">q2E pi</mml:mfenced>. By integrating over some of the five kinematic parameters, we define a number of observables, such as the Lambda (c) spin polarization P Lambda c<mml:mfenced close=")" open="(">q2</mml:mfenced> and the forward-backward asymmetry of pi (-) meson A(FB)(q(2)), both of which can be represented by the angular observables K</mml:mover>i<mml:mfenced close=")" open="(">q2</mml:mfenced>. We provide numerical results for the entire set of the angular observables K</mml:mover>i<mml:mfenced close=")" open="(">q2</mml:mfenced> and K</mml:mover>i both within the Standard Model and in some NP scenarios, which are a variety of best-fit solutions in seven different NP hypotheses. We find that the NP which can resolve the anomalies in B<overbar></mml:mover>-> D<mml:mfenced close=")" open="("><mml:mo></mml:mfenced>tau <mml:mo>-<mml:msub><mml:mover accent="true">v<mml:mo stretchy="true"><overbar></mml:mover>tau decays has obvious effects on the angular observables <mml:msub><mml:mover accent="true">K<mml:mo stretchy="true"></mml:mover>i<mml:mfenced close=")" open="(">q2</mml:mfenced>, except <mml:msub><mml:mover accent="true">K<mml:mo stretchy="true"></mml:mover>1ss<mml:mfenced close=")" open="(">q2</mml:mfenced> and <mml:msub><mml:mover accent="true">K<mml:mo stretchy="true"></mml:mover>1cc<mml:mfenced close=")" open="(">q2</mml:mfenced>.
期刊：
Journal of High Energy Physics,2010年2010(4):1-16 ISSN：1029-8479
通讯作者：
Lia, X.-Q.
作者机构：
[Chang, Qin; Li, Xin-Qiang] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.;[Yang, Ya-Dong; Chang, Qin] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang] Rhein Westfal TH Aachen, Inst Theoret Phys E, D-52056 Aachen, Germany.;[Yang, Ya-Dong] Huazhong Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Department of Physics, Henan Normal University, China
关键词：
Rare Decays;Beyond Standard Model;B-Physics
摘要：
Motivated by the observed forward-backward asymmetry in B → K*ℓ + ℓ − decay, we perform a detailed analysis of this decay mode within a family non-universal Z′ model. With the related coupling \( Z' - \bar sb \) constrained by \( {B_s} - {\bar B_s} \) mixing, B → πK and B → X s μ + μ − decays, we look for further constraint on the couplings Z′ − μ + μ − from \( {A_{FB}}{\left( {B \to {K^*}{\mu^{+} }{\mu^{-} }} \right)_{0{\text{Ge}}{{\text{V}}^2} \leqslant {q^2} \leqslant 2{\text{Ge}}{{\text{V}}^2}}} \) and get numerically \( B_{\mu \mu }^{L,R} \sim \mathcal{O}\left( {{{10}^{ - 2}}} \right) \). Moreover, we find that the relations \( B_{\mu \mu }^L < B_{\mu \mu }^R \) and \( B_{\mu \mu }^L + B_{\mu \mu }^R < 0 \), with a small negative phase ϕ s L, are crucial to moderate the discrepancy for A FB (B → K*μ + μ −) between the SM prediction and the experimental data. Numerically, comparing with the SM prediction, we find that \( {A_{FB}}{\left( {B \to {K^*}{\mu^{+} }{\mu^{-} }} \right)_{0{\text{Ge}}{{\text{V}}^2} \leqslant {q^2} \leqslant 2{\text{Ge}}{{\text{V}}^2}}} \) could be enhanced about 80% and 50% by Z′ 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.
期刊：
Journal of High Energy Physics,2009年2009(5) ISSN：1029-8479
通讯作者：
Yang, Ya-Dong
作者机构：
[Yang, Ya-Dong; Chang, Qin] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Chang, Qin] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.;[Li, Xin-Qiang] Rhein Westfal TH Aachen, Inst Theoret Phys E, D-52056 Aachen, Germany.
通讯机构：
[Yang, Ya-Dong] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
B-physics;Beyond standard model;CP violation;Rare decays
摘要：
Motivated by the large difference between the direct CP asymmetries A(CP)(B- -> pi K-0(-)) and A(CP) ((B) over bar (0) -> pi K-+(-)), we combine the up-to-date experimental information on B -> pi K, pi K* and rho K decays to pursue possible solutions with the nonuniversal Z' 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, xi(LL) and xi(LR) with a common nontrivial new weak phase phi(L) similar to -86 degrees, which are relevant to the Z' contributions to the electroweak penguin sector Delta C-9 and Delta C-7, are crucial to the observed "pi K puzzle". Furthermore, they are found to be definitely unequal and opposite in sign. We also find that A(CP)(B- -> rho(0) K-) can put a strong constraint on the new Z' couplings, which implies the Z' contributions to the coefficient of QCD penguins operator O-3 involving the parameter zeta(LL) required.
期刊：
Journal of High Energy Physics,2011年2011(8):1-22 ISSN：1029-8479
通讯作者：
Li, X.-Q.
作者机构：
[Li, Xin-Qiang] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.;[Li, Xin-Qiang] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain.;[Yang, Ya-Dong; Yuan, Xing-Bo] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Huazhong Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Department of Physics, Henan Normal University, China
关键词：
Beyond Standard Model;B-Physics
摘要：
The top-quark FCNC processes will be searched for at the CERN LHC, which are correlated with the B-meson decays. In this paper, we study the e ff ects of top-quark anomalous interactions tq gamma in the exclusive radiative B --> K*gamma and B --> rho gamma decays. With the current experimental data of the branching ratios, the direct CP and the isospin asymmetries, bounds on the coupling kappa(gamma)(tcR) from B --> K*gamma and kappa(gamma)(tuR) from B --> rho gamma decays are derived, respectively. The bound on vertical bar kappa(gamma)(tcR)vertical bar from B (B --> K*gamma) is generally compatible with that from B (B --> X-s gamma). However, the isospin asymmetry Delta (K*gamma) further restrict the phase of kappa(gamma)(tuR), and the combined bound results in the upper limit, B (t --> c gamma) < 0 : 21%, which is lower than the CDF result. For real kappa(gamma)(tuR), the upper bound on B (t --> c gamma) is about of the same order as the 5 sigma discovery potential of ATLAS with an integrated luminosity of 10 fb(-1). For B --> rho gamma decays, the NP contribution is enhanced by a large CKM factor vertical bar V-ud/V-td vertical bar, and the constraint on tu gamma coupling is rather restrictive, B (t --> u gamma) < 1 : 44 x 10(-5). With re fi ned measurements to be available at the LHCb and the future super-B factories, we can get close correlations between B --> V gamma and the rare t --> q gamma decays, which will be studied directly at the LHC ATLAS and CMS.
期刊：
Journal of High Energy Physics,2021年(1) ISSN：1029-8479
作者机构：
[Li, Yuan-Yuan; Yang, Ya-Dong; Li, Shao-Ping; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Yuan-Yuan; Yang, Ya-Dong; Li, Shao-Ping; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Zhang, Xin] Hubei Univ, Fac Phys & Elect Sci, Wuhan 430062, Hubei, Peoples R China.
关键词：
Beyond Standard Model;Higgs Physics
摘要：
With the hypothesis of minimal flavor violation, we find that there exists a power-aligned relation between the Yukawa couplings of the two scalar doublets in the two-Higgs-doublet model with Hermitian Yukawa matrices. Within such a power-aligned framework, it is found that a simultaneous explanation of the anomalies observed in the electron and muon anomalous magnetic moments can be reached with TeV-scale quasi-degenerate Higgs masses, and the resulting parameter space is also phenomenologically safer under the B-physics, Z and tau decay data, as well as the current LHC bounds. Furthermore, the flavor-universal power that enhances the charged-lepton Yukawa couplings prompts an interesting correlation between the two anomalies, which makes the model distinguishable from the (generalized) linearly aligned and the lepton-specific two-Higgs-doublet models that address the same anomalies but in a non-correlative manner, and hence testable by future precise measurements.
期刊：
Journal of High Energy Physics,2018年2018(9):1-24 ISSN：1029-8479
通讯作者：
Li, X.-Q.
作者机构：
[Li, Shao-Ping] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys, MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
Given that the two-Higgs-doublet model of type III (2HDM-III) has the potential to address the \( {R}_{D^{\left(*\right)}} \) anomalies while the resolution to the \( {R}_{K^{\left(*\right)}} \) deficits requires new degrees of freedom within this framework, we consider in this paper a unified scenario where the low-scale type-I seesaw mechanism is embedded into the 2HDM-III, so as to accommodate the \( {R}_{D^{\left(*\right)}} \) and \( {R}_{K^{\left(*\right)}} \) anomalies as well as the neutrino mass. We first revisit the \( {R}_{D^{\left(*\right)}} \) anomalies and find that the current world-averaged results can be addressed at 2σ level without violating the bound from the branching ratio \( \mathrm{\mathcal{B}}\left({B}_c^{-}\to {\tau}^{-}\overline{\nu}\right) \) ≤ 30%. The scenario predicts two sub-eV neutrino masses based on a decoupled heavy Majorana neutrino and two nearly degenerate Majorana neutrinos with mass around the electroweak scale. For the \( {R}_{K^{\left(*\right)}} \) anomalies, the same scenario can generate the required Wilson coefficients in the direction C NP9 μ = − C NP10 μ < 0, with \( \mathcal{O}(1) \) Yukawa couplings for the muon and the top quark.
期刊：
Journal of High Energy Physics,2017年2017(2):1-24 ISSN：1029-8479
通讯作者：
Li, X.-Q.
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
It has been shown that the anomalies observed in \( \overline{B}\to {D}^{\left(\ast \right)}\tau {\overline{\nu}}_{\tau } \) and \( \overline{B}\to \overline{K}{\ell}^{+}{\ell}^{-} \) decays can be resolved by adding a single scalar or vector leptoquark to the Standard Model, while constraints from other precision measurements in the flavour sector can be satisfied without fine-tuning. To further explore these two interesting scenarios, in this paper, we study their effects in the semi-leptonic \( {\varLambda}_b\to {\varLambda}_c\tau {\overline{\nu}}_{\tau } \) decay. Using the best-fit solutions for the operator coefficients allowed by the current data of mesonic decays, we find that (i) the two scenarios give similar amounts of enhancements to the branching fraction \( \mathrm{\mathcal{B}}\left({\varLambda}_b\to {\varLambda}_c\tau {\overline{\nu}}_{\tau}\right) \) and the ratio \( {R_{\varLambda}}_{{}_c}=\mathrm{\mathcal{B}}\left({\varLambda}_b\to {\varLambda}_c\tau {\overline{\nu}}_{\tau}\right)/\mathrm{\mathcal{B}}\left({\varLambda}_b\to {\varLambda}_c\ell {\overline{\nu}}_{\ell}\right) \), (ii) the two best-fit solutions in each of these two scenarios are also indistinguishable from each other, (iii) both scenarios give nearly the same predictions as those of the Standard Model for the longitudinal polarizations of Λ c and τ as well as the lepton-side forward-backward asymmetry. With future measurements of these observables in \( {\varLambda}_b\to {\varLambda}_c\tau {\overline{\nu}}_{\tau } \) decay at the LHCb, the two leptoquark scenarios could be further tested, and even differentiated from the other NP explanations for the \( {R_D}_{{}^{\left(\ast \right)}} \) anomalies. We also discuss the feasibility for the measurements of these observables at the LHC and the future e + e − colliders.
期刊：
Journal of High Energy Physics,2012年2012(3):1-22 ISSN：1029-8479
通讯作者：
Li, X.-Q.
作者机构：
[Li, Xin-Qiang] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.;[Li, Xin-Qiang] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain.;[Yang, Ya-Dong; Yuan, Xing-Bo] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Huazhong Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Department of Physics, Henan Normal University, China
关键词：
B-Physics;Beyond Standard Model;Kaon Physics;Rare Decays
摘要：
As a top-factory, the LHC is performing a direct study of top-quark anomalous FCNC couplings, which are, however, correlated closely with the rare B- and K-meson decays. In this paper, we study the effects of anomalous tqZ (with q = u, c) couplings in the rare decays B s,d → μ + μ −, B → X s ν \( \overline \nu \), B → K (*) ν \( \overline \nu \), K + → π+ ν \( \overline \nu \), and K L → π0 ν \( \overline \nu \). With the up-to-date experimental bounds on the branching ratios of these channels, constraints on the left-handed anomalous couplings \( X_{{ct}}^L \) and \( X_{{ut}}^L \) are derived, respectively. With these low-energy constraints taken into account, we find that, for real couplings \( X_{{ct}}^L \) and \( X_{{ut}}^L \), the indirect upper bounds on B(t → qZ) are much lower than that from the D0 collaboration, but are still compatible with the 5σ discovery potential of ATLAS with an integrated luminosity of 10 fb−1. With refined measurements to be available at the LHCb, the future super-B factories, the NA62 at CERN, and the KOTO at J-PARC, closer correlations between the t → qZ and the rare B- and K-meson decays are expected in the near future, which will be helpful for the searches of the top-quark FCNC decays at the LHC.
期刊：
Journal of High Energy Physics,2016年2016(8):1-25 ISSN：1029-8479
通讯作者：
Li, X.-Q.
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, China
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
It has been shown recently that the anomalies observed in \( \overline{B}\to {D}^{\left(*\right)}\tau {\overline{\nu}}_{\tau } \) and \( \overline{B}\to \overline{K}{\ell}^{+}{\ell}^{-} \) decays could be resolved with just one scalar leptoquark. Fitting to the current data on R(D(∗)) along with acceptable q 2 distributions in \( \overline{B}\to {D}^{\left(\ast \right)}\tau {\overline{\nu}}_{\tau } \) decays, four best-fit solutions for the operator coefficients have been found. In this paper, we explore the possibilities of how to discriminate these four solutions. Firstly, we find that two of them are already excluded by the decay \( {B}_c^{-}\to {\tau}^{-}{\overline{\nu}}_{\tau } \), because the predicted decay widths have already overshot the total width ΓBc . It is then found that the remaining two solutions result in two effective Hamiltonians governing \( b\to c\tau {\overline{\nu}}_{\tau } \) transition, which differ by a sign and enhance the absolute value of the coefficient of \( {\overline{c}}_L{\gamma}_{\mu }{b}_L{\overline{\tau}}_L{\gamma}^{\mu }{\nu}_{\tau\ L} \) operator by about 12%. However, they give nearly the same predictions as in the SM for the D ∗ and τ longitudinal polarizations as well as the lepton forward-backward asymmetries in \( \overline{B}\to {D}^{\left(\ast \right)}\tau {\overline{\nu}}_{\tau } \) decays. For the other observables like \( \mathrm{\mathcal{B}}\left({B}_c^{-}\to {\tau}^{-}{\overline{\nu}}_{\tau}\right),\mathrm{\mathcal{B}}\left({B}_c^{-}\to \gamma {\tau}^{-}{\overline{\nu}}_{\tau}\right),{R}_{D\left(\ast \right)}\left({q}^2\right),\ \mathrm{d}\mathrm{\mathcal{B}}\left(\overline{B}\to {D}^{\left(\ast \right)}\tau {\overline{\nu}}_{\tau}\right)/\mathrm{d}{q}^2 \) and \( \mathrm{\mathcal{B}}\left({B}_c^{-}\to {X}_3\tau {\overline{\nu}}_{\tau}\right) \), on the other hand, the two solutions give sizable enhancements relative to the SM predictions. With measurement of \( {B}_c^{-}\to {\tau}^{-}{\overline{\nu}}_{\tau } \) at LHCb and refined measurements of observables in \( \overline{B}\to {D}^{\left(\ast \right)}\tau {\overline{\nu}}_{\tau } \) at both LHCb and Belle-II, such a specific NP scenario could be further deciphered.