期刊：
EUROPEAN PHYSICAL JOURNAL C,2017年77(3) ISSN：1434-6044
通讯作者：
Hu, QY
作者机构：
[Hu, Quan-Yi] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Hu, QY] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R 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((t)), which are the most relevant ones for b -> sl(+) l(-) transitions. It is found that, when the model parameter vertical bar zeta(u)vertical bar is much smaller than vertical bar zeta(d)vertical bar, the charged scalar contributes mainly to chirality- flipped C-7, 9,10((t)), with the corresponding effects being proportional to vertical bar zeta(d)vertical bar. Numerically, the charged- scalar effects fit into two categories: (A) CH7,9,10H +/- are sizable, but C-9,10(H +/-), corresponding to the (large vertical bar zeta(u)vertical bar smallii) region; ( B) C-7(H +/-) and C-9,10(H +/-) are sizable, but C-9,10(H +/-) similar or equal to, corresponding to the (small vertical bar zeta(u)vertical bar, large I rd 1) region. Taking into account phenomenological constraints from the inclusive radiative decay B -> X-s y, as well as the latest modelindependent global analysis of b -> sl(+) l(-) 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 -> K*(0) mu(+) u(-) 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,2017年77(4) ISSN：1434-6044
通讯作者：
Hu, QY
作者机构：
[Hu, Quan-Yi] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Hu, QY] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
摘要：
The rare baryonie decay Lambda b -> Lambda(-> p pi- ) &- provides valuable complementary information com pared to the corresponding mesonie b -> s &-- transition. In this paper, using the latest high-precision lattice QCD calculation of the Lambda b -> 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 angu lar coefficients in this decay, we consider the following ten angular observables, which can be derived from the analysis of the subsequent parity-violating Lambda -> p pi- decay: the differential branching fraction dB/dq2, the longitudinal polarization fraction FL , the lepton-, hadron- and com bined lepton-hadron-side forward-backward asymmetries AlFB, A Lambda FB and Al Lambda FB as well as the other five asymmetry observables Y-i (i = 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 -> Xsy branching fraction and the latest global fit results of b -> sll data, the contributions of right-handed semileptonic operators 0'9 10, besides reconciling the P'5 anomaly observed in B0 -> K*0 &-. decay, could also enhance the values dB/dq2 and AlFB in the bin [15, 20] GeV2, leading to results consistent with the current LHCb measurements.
作者机构：
[Li, Xin-Qiang; Yuan, Xing-Bo; Yang, Ya-Dong] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang; Yuan, Xing-Bo; Yang, Ya-Dong] 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：
[Li, XQ] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R 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 -> X-s gamma 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 C-7(eff), but similar magnitudes with opposite signs to C-8(eff), 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 C-8(eff). Due to the CKM factors vertical bar lambda((d))(u)vertical bar similar to vertical bar lambda((d))(t)vertical bar, the terms proportional to lambda((d))(u) 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 -> V gamma and the inclusive B -> X-s,X-d gamma decays are investigated, which could provide further insights into the models with more precise experimental measurements and theoretical predictions for these decays.
作者机构：
[Su, Fang; Yang, Ya-Dong] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[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] Huazhong Normal Univ Wuhan, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Li, XQ] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.
摘要：
According to heavy-meson chiral perturbation theory, the vector form factor f+(q(2)) of exclusive semileptonic decay B -> pi l nu is closely related, at least in the soft-pion region ( i.e., q(2) similar to (m(B) - m(pi))(2)), to the strong coupling g(B*B pi) or the normalized coupling (g)over-cap. Combining the precisely measured q2 spectrum of B -> pi l nu decay by the BABAR and Belle collaborations with several parametrizations of the form factor f +(q(2)), 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 q(2) = m(B*)(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 Becirevic-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.
期刊：
JOURNAL OF HIGH ENERGY PHYSICS,2017年(2) ISSN：1029-8479
通讯作者：
Li, XQ
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Li, XQ] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
It has been shown that the anomalies observed in B -> D(*)tau nu(tau) and B -> Kl(+)l(-) 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 Lambda(b) -> Lambda(c)tau nu(tau) . 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 B(Lambda(b)-> Lambda(c)tau nu(tau) ) and the ratio R-Lambda c = B(Lambda(b) -> Lambda(c)tau nu(tau) )/B(Lambda(b) -> Lambda(c)l nu(l)), (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 Lambda(c), and tau as well as the lepton-side forward-backward asymmetry. With future measurements of these observables in Lambda(b) -> Lambda(c)tau 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(*) 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,2010年(4) ISSN：1029-8479
通讯作者：
Li, XQ
作者机构：
[Li, Xin-Qiang; 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.;[Chang, Qin; Yang, Ya-Dong] 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：
[Li, XQ] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R 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' - (s) over barb constrained by B-s - (B) over bar (s) mixing, B -> pi K and B -> X-s mu(+)mu(-) decays, we look for further constraint on the couplings Z' - mu(+)mu(-) from A(FB)(B -> K*mu(+)mu(-))(0GeV2 <= q2 <= 2GeV2) and get numerically B-mu mu(L,R) similar to O(10(-2)). 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 phi(L)(s), are crucial to moderate the discrepancy for A(FB)(B -> K*mu(+)mu(-)) between the SM prediction and the experimental data. Numerically, comparing with the SM prediction, we find that A(FB)(B -> K*mu(+)mu(-))(0GeV2 <= q2 <= 2GeV2) could be enhanced about 80% and 50% by Z' contribution at most in scenarios S1 and S2, corresponding to the two fitted results of phi(s) by UTfit collaboration, respectively. However, the results are still about 1.5 sigma lower than the experimental measurement.
期刊：
JOURNAL OF HIGH ENERGY PHYSICS,2016年(8) ISSN：1029-8479
通讯作者：
Li, XQ
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Li, XQ] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
It has been shown recently that the anomalies observed in and decays could be resolved with just one scalar leptoquark. Fitting to the current data on R(D(au)) along with acceptable q (2) distributions in 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 , because the predicted decay widths have already overshot the total width I"Bc . It is then found that the remaining two solutions result in two effective Hamiltonians governing transition, which differ by a sign and enhance the absolute value of the coefficient of operator by about 12%. However, they give nearly the same predictions as in the SM for the D (au) and tau longitudinal polarizations as well as the lepton forward-backward asymmetries in decays. For the other observables like and , on the other hand, the two solutions give sizable enhancements relative to the SM predictions. With measurement of at LHCb and refined measurements of observables in at both LHCb and Belle-II, such a specific NP scenario could be further deciphered.
期刊：
JOURNAL OF HIGH ENERGY PHYSICS,2011年(8) ISSN：1029-8479
通讯作者：
Li, XQ
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.;[Yuan, Xing-Bo; Yang, Ya-Dong] 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：
[Li, XQ] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R 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,2008年(9) ISSN：1029-8479
通讯作者：
Yang, YD
作者机构：
[Li, Xin-Qiang] Rhein Westfal TH Aachen, D-52056 Aachen, Germany.;[Chang, Qin; Yang, Ya-Dong] 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.
通讯机构：
[Yang, YD] 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,2012年2012(03):1-22 ISSN：1029-8479
通讯作者：
Li, XQ
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.;[Yuan, Xing-Bo; Yang, Ya-Dong] 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：
[Li, XQ] Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.
关键词：
Rare Decays;Beyond Standard Model;B-Physics;Kaon Physics
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 \( \overline u \) , B → K (*) ν \( \overline u \) , K + → π+ ν \( \overline u \) , and K L → π0 ν \( \overline u \) . 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,2009年(5) ISSN：1029-8479
通讯作者：
Yang, YD
作者机构：
[Li, Xin-Qiang] Rhein Westfal TH Aachen, Inst Theoret Phys E, D-52056 Aachen, Germany.;[Chang, Qin; Yang, Ya-Dong] 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.
通讯机构：
[Yang, YD] 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：
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：
EUROPEAN PHYSICAL JOURNAL C,2017年77(6) ISSN：1434-6044
通讯作者：
Li, XQ
作者机构：
[Li, Xin-Qiang; Chang, Qin] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang; Chang, Qin] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Sun, Junfeng; Chang, Qin; Li, Xiaonan] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
通讯机构：
[Li, XQ] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
摘要：
In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless B-s -> VV (where V stands for a light vector meson) decays, we perform the chi(2)-analyses for the endpoint parameters within the QCD factorization framework, under the constraints from the measured (B) over bar (s) -> rho(0)phi.phi k*0, phi phi and K*0 (k) over bar*(0) decays. The fitted results indicate that the endpoint parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless B -> PP and PV (where P stands for a light pseudo-scalar meson) decays observed in previous work. Moreover, the abnormal polarization fractions fL,.((B) over bar (s) -> K*(0) (K) over bar *0) = (20.1+/-7.0)%, (58.4+/-8.5)% measured by the LHCb collaboration can be reconciled through the weak annihilation corrections. However, the branching ratio of (B) over bar (s) -> phi K*0 decay exhibits a tension between the data and theoretical result, which dominates the contributions to.2 min in the fits. Using the fitted endpoint parameters, we update the theoretical results for the charmless Bs. VV decays, which will be further tested by the LHCb and Belle-II experiments in the near future.
期刊：
EUROPEAN PHYSICAL JOURNAL C,2015年75(12) ISSN：1434-6044
通讯作者：
Chang, Q
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang; Chang, Qin] Chinese Acad Sci, Inst Theoret Phys, State Key Lab Theoret Phys, Beijing, Peoples R China.;[Chang, Qin; Li, Pei-Fu] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
通讯机构：
[Chang, Q] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
摘要：
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)-(B) over bar (0)(s) mixing are studied. First of all, we perform a complete one-loop computation of the electro-weak corrections to the amplitudes of B-s(0)-(B) over bar (0)(s) 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)-(B) over bar (0)(s) mixing are obtained and the differences between type-III and type-C models are investigated, which is helpful to distinguish between these two models.
作者：
Abbas, Gauhar;Celis, Alejandro;Li, Xin-Qiang;Lu, Jie;Pich, Antonio
期刊：
JOURNAL OF HIGH ENERGY PHYSICS,2015年(6) ISSN：1029-8479
通讯作者：
Li, XQ
作者机构：
[Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang] Chinese Acad Sci, Inst Theoret Phys, State Key Lab Theoret Phys, Beijing 100190, Peoples R China.;[Celis, Alejandro] Univ Munich, Fak Phys, Arnold Sommerfeld Ctr Theoret Phys, D-80333 Munich, Germany.;[Lu, Jie] Shanghai Univ, Dept Phys, Shanghai 200444, Peoples R China.
通讯机构：
[Li, XQ] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Rare Decays;Beyond Standard Model;Heavy Quark Physics
摘要：
We perform a complete one-loop computation of the two-body flavour-changing top decays t --> ch and t --> cV (V = gamma, Z), within the aligned two-Higgs-doublet model. We evaluate the impact of the model parameters on the associated branching ratios, taking into account constraints from flavour data and measurements of the Higgs properties. Assuming that the 125 GeV Higgs corresponds to the lightest CP-even scalar of the CP-conserving aligned two-Higgs-doublet model, we find that the rates for such flavour-changing top decays lie below the expected sensitivity of the future high-luminosity phase of the LHC. Measurements of the Higgs signal strength in the di-photon channel are found to play an important role in limiting the size of the t --> ch decay rate when the charged scalar of the model is light.
关键词：
Heavy Quark Physics;Perturbative QCD;Effective field theories
摘要：
We evaluate in the framework of QCD factorization the two-loop vertex corrections to the decays (B) over bar ((s)) -> D-(s)(()*()+) L- and Lambda(b) -> Lambda(+)(c) L-, where L is a light meson from the set {pi, rho, K-(*()), a(1)}. These decays are paradigms of the QCD factorization approach since only the colour-allowed tree amplitude contributes at leading power. Hence they are sensitive to the size of power corrections once their leading-power perturbative expansion is under control. Here we compute the two-loop O (alpha(2)(s)) correction to the leading-power hard scattering kernels, and give the results for the convoluted kernels almost completely analytically. Our newly computed contribution amounts to a positive shift of the magnitude of the tree amplitude by similar to 2%. We then perform an extensive phenomenological analysis to NNLO in QCD factorization, using the most recent values for non-perturbative input parameters. Given the fact that the NNLO perturbative correction and updated values for form factors increase the theory prediction for branching ratios, while experimental central values have at the same time decreased, we reanalyze the role and potential size of power corrections by means of appropriately chosen ratios of decay channels.
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2015年42(12) ISSN：0954-3899
通讯作者：
Li, XQ
作者机构：
[Li, Xin-Qiang; Yang, Ya-Dong; Cheng, Xiao-Dong; Zhang, Xin] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xin-Qiang; Yang, Ya-Dong; Cheng, Xiao-Dong; Zhang, Xin] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, 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：
[Li, XQ] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
B-physics;rare decays;beyond Standard Model
摘要：
In this paper, we perform a complete one-loop computation of the short-distance Wilson coefficients for B-s,B-d - (B) over bar (s,d) mixings and B-s,B-d -> l(+)l(-) decays in the Manohar-Wise model, which extends the Standard Model ( SM) scalar sector by a colour-octet and weak-doublet scalar. Based on these calculations, combined constraints on the model parameters are derived from the current flavour data, including the B-s,B-d - (B) over bar (s,d) mixings, B-s,B-d -> mu(+)mu(-), B -> X-s gamma, B -> K*gamma, B -> rho gamma, and Z -> b (b) over bar decays. The future sensitivity to the model is also explored in the observables achievable with 50 fb(-1) of LHCb and 50 ab(-1) of Belle-II data. We find that the Manohar-Wise model could explain the current data, especially when the couplings of the charged colour-octet scalars to quarks are complex, with the resulting chi(2)(min) being significantly smaller than that of the SM. Finally, we investigate correlations among the two isospin asymmetries Delta(K*gamma) and Delta(rho gamma), as well as the averaged time-integrated branching ratios (B) over bar (B-s,B-d -> mu(+)mu(-)); some of them are found to be quite strong and could provide, therefore, further insights into the model, once more precise experimental measurements and theoretical predictions for these observables are available in the future.
期刊：
ADVANCES IN HIGH ENERGY PHYSICS,2017年 ISSN：1687-7357
通讯作者：
Su, F
作者机构：
[Su, Fang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Su, F] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
摘要：
The two-Higgs-doublet model (2HDM), as one of the simplest extensions of the Standard Model (SM),is obtained by adding another scalar doublet to the SM and is featured by a pair of charged Higgs, which could affect many low-energy processes. 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 type III and type C 2HDM, respectively. In this paper, we study the charged-Higgs effects of these two models on the K-0-(K) over bar (0) mixing, an ideal process to probe New Physics (NP) beyond the SM. Firstly, we perform a complete one-loop computation of the box diagrams relevant to the K-0-(K) over bar (0) mixing, keeping the mass and momentum of the external strange quark up to the second order. Together with the up-to-ate theoretical inputs, we then give a detailed phenomenological analysis, in the cases of both real and complex Yukawa couplings of the charged Higgs to quarks. The parameter spaces allowed by the current experimental data on the mass difference triangle m(k) and the CP-violating parameter epsilon(k) are obtained and the differences between these two 2HDMs are investigated, which are helpful to distinguish them from each other from a phenomenological point of view.
期刊：
JOURNAL OF HIGH ENERGY PHYSICS,2010年2010(02):1-25 ISSN：1029-8479
通讯作者：
Chang, Qin
作者机构：
[Ya-Dong Yang; Qin Chang] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hunan, Peoples R China.;[Ya-Dong Yang] Huazhong Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hunan, Peoples R China.;[Qin Chang] Henan Normal Univ, Dept Phys, Xinxiang 453007, Herts, Peoples R China.;[Xin-Qiang Lic] Univ Aachen, Rhein Westfal TH Aachen, Inst Theoret Phys E, D-52056 Aachen, Germany.
通讯机构：
[Chang, Q (reprint author)] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hunan, Peoples R China.
关键词：
Rare Decays;Beyond Standard Model;B-Physics
摘要：
Motivated by the large discrepancy of CP-violating phase in (B) over bar (s) - B-s mixing between the experimental data and the Standard Model prediction, we pursue possible solutions within a family non-universal Z' model. Within such a specific model, we find that both the (B) over bar (s) - B-s mixing anomaly and the well-known "pi K puzzle" could be moderated simultaneously with a nontrivial new weak phase, phi(L)(s) similar to -72 degrees (S1) or -82 degrees (S2). With the stringently constrained Z' coupling B-sb(L), we then study the Z' effects on the rare B -> X-s mu(+) mu(-) and B-s -> mu(+) mu(-) decays, which are also induced by the same b -> s transition. The observables of B -> X-s mu(+) mu(-), at both high and low q(2) regions, are found to be able to put strong constraints on the mu - mu - Z' coupling, B-mu mu(L,R) similar to 10(-2). It is also shown that the combined constraints from (B) over bar (s) - B-s mixing, B -> pi K and B -> X-s mu(+) mu(-) do not allow a large Z' contribution to the pure leptonic B-s -> mu(+) mu(-) decay.
作者：
Abbas, Gauhar;Celis, Alejandro;Li, Xin-Qiang;Lu, Jie;Pich, Antonio
作者机构：
[ Li, Xin-Qiang ] State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing;[ Li, Xin-Qiang ] 100190, China;[ Li, Xin-Qiang ] Institute of Particle Physics, Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei;[ Li, Xin-Qiang ] 430079, China;[ Celis, Alejandro ] Ludwig-Maximilians-Universitä
关键词：
Branching ratio - Decay rate - Higgs doublet models - Parameter spaces - Signal strengths
期刊：
JOURNAL OF HIGH ENERGY PHYSICS,2007年(6) ISSN：1029-8479
通讯作者：
Chang, Q
通讯机构：
[Chang, Q] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
sum rules;1/N expansion;chiral lagrangians
摘要：
We investigate whether the anomalous tensor operators with the Lorentz structure (sigma(mu nu)(1 + gamma(5)) circle times sigma(mu nu) (1 + gamma(5)), which could provide a simple resolution to the polarization anomaly observed in B -> phi K* decays, could also provide a coherent resolution to the large B(B -> eta K*) and survive bounds from B -> eta K decays. Parameter spaces satisfying all these experimental data are obtained, and found to be dominated by the color-octet tensor operator contribution. Constraints for the equivalent solution with (1 + gamma(5)) circle times (1 + gamma(5)) operators are also derived and found to be dominated by the color-singlet one. With the constrained parameter spaces, we finally give predictions for B-s ->phi phi decay, which could be tested at the Fermilab Tevatron and the LHC-b experiments.