期刊：
Journal of High Energy Physics,2021年(1) ISSN：1029-8479
通讯作者：
Li, Shao-Ping
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.
通讯机构：
[Li, Shao-Ping] C;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.
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,2021年(2) ISSN：1029-8479
通讯作者：
Hu, Quan-Yi
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.
通讯机构：
[Hu, Quan-Yi] A;Anyang Normal Univ, Sch Phys & Elect Engn, Anyang 455000, Henan, 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：
EUROPEAN PHYSICAL JOURNAL C,2020年80(3):1-9 ISSN：1434-6044
通讯作者：
Li, Xin-Qiang
作者机构：
[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：
[Li, Xin-Qiang] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
摘要：
We implement a symmetry violation guideline into a two-Higgs-doublet model embedded with three right-handed neutrinos, and exploit the generic Yukawa structures of the model via a hypothetical symmetry restoration of a global \(U_Q(1)^3\times U_L(1)^3\) symmetry. We then apply a mass-powered parametrization to construct the phenomenologically motivated Yukawa interactions, which enables us to incorporate correlatively the neutrino mass, dark matter, as well as the lepton-flavor universality violations in \(R_{K^{(*)}}\) and \(R_{D^{(*)}}\). Specifically, two atmospheric-scale neutrino masses are generated by a low-scale seesaw mechanism, while the much lighter one, being of \(\mathcal {O}(10^{-6})~{{\mathrm{eV}}}\), is fixed by a \(7.1~{\mathrm{keV}}\) sterile neutrino dark matter produced primordially by the freeze-in mechanism. On the other hand, the neutrino and the charged-lepton mass hierarchies encoded in the mass-powered textures can naturally account for the \(R_{K^{(*)}}\) and the \(R_{D^{(*)}}\) anomalies, respectively. As a further application, a milder discrepancy of the muon \(g{-}2\) is observed, which has also been implied by the recently refined lattice results.
期刊：
Journal of High Energy Physics,2020年2020(4):1-41 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
作者机构：
[Bell, Guido; Huber, Tobias] Univ Siegen, Theoret Phys 1, Nat Wissenschaftlich Tech Fak, Walter Flex Str 3, D-57068 Siegen, Germany.;[Beneke, Martin] Tech Univ Munich, Phys Dept T31, James Franck Str 1, D-48 Garching, Germany.;[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.
通讯机构：
[Li, Xin-Qiang] C;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.
关键词：
Effective Field Theories;Heavy Quark Physics;Perturbative QCD
摘要：
We complete the calculation of the QCD penguin amplitude at next-to-next- to-leading order in the QCD factorization approach to non-leptonic B-meson decays. This provides the last missing piece in the computation of the QCD correction to direct CP asymmetries at leading power in the heavy-quark expansion.
期刊：
Journal of High Energy Physics,2020年2020(5):1-18 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
作者机构：
[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.
通讯机构：
[Li, Xin-Qiang] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Chiral Lagrangians;CP violation
摘要：
In this work, we study the C P asymmetry in the angular distribution of τ → KSπντ decays, taking into account the known C P violation in
$$ {K}^0-{\overline{K}}^0 $$
mixing. It is pointed out for the first time that, once the well-measured C P violation in the neutral kaon system is invoked, a non-zero C P asymmetry would appear in the angular observable of the decays considered, even within the Standard Model. By employing the reciprocal basis, which is most convenient when a KS(L) is involved in the final state, the C P -violating angular observable is derived to be two times the product of the time-dependent C P asymmetry in K → π+π− and the mean value of the angular distribution in
$$ {\tau}^{\pm}\to {K}^0\left({\overline{K}}^0\right){\pi}^{\pm }{\overline{\nu}}_{\tau}\left({\nu}_{\tau}\right) $$
decays. Compared with the Belle results measured in four different bins of the K π invariant mass, our predictions lie within the margins of these measurements, except for a 1.7 σ deviation for the lowest mass bin. While being below the current Belle detection sensitivity that is of
$$ \mathcal{O} $$
(10−3), our predictions are expected to be detectable at the Belle II experiment, where
$$ \sqrt{70} $$
times more sensitive results will be obtained with a 50 ab−1 data sample.
期刊：
EUROPEAN PHYSICAL JOURNAL C,2020年80(12) ISSN：1434-6044
通讯作者：
Li, Xin-Qiang
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：
[Li, Xin-Qiang] C;Cent China Normal Univ, Inst Particle Phys, 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.
期刊：
Journal of High Energy Physics,2019年2019(6):ARTN 133 ISSN：1029-8479
通讯作者：
Hu, Quan-Yi
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：
[Hu, Quan-Yi] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Heavy Quark Physics;Supersymmetric Standard Model
摘要：
In this paper, motivated by the observation that the Standard Model predictions are now above the experimental data for the mass difference M-s(d), we perform a detailed study of B-s(d) - B-s(d) mixing and B-s (+-) decay in the Z(3)-invariant NMSSM with non-minimal flavour violation, using the recently developed procedure based on the Flavour Expansion Theorem, with which one can perform a purely algebraic mass-insertion expansion of an amplitude written in the mass eigenstate basis without performing any diagrammatic calculations in the interaction/flavour basis. Specifically, we consider the finite orders of mass insertions for neutralinos but the general orders for squarks and charginos, under two sets of assumptions for the squark flavour structures (i.e., while the flavour-conserving off-diagonal element LR is kept in oth of these two sectors, only the flavour-violating off-diagonal elements LL and RR (i = 1, 2) are kept in the LL and RR sectors, respectively). Our analytic results are then expressed directly in terms of the initial Lagrangian parameters in the interaction/flavour basis, making it easy to impose the experimental bounds on them. It is found numerically that the NMSSM effects with the above two assumptions for the squark flavour structures can accommodate the observed deviation for M-s(d), while complying with the experimental constraints from the branching ratios of B-s (+-) and B X-s decays.
作者机构：
[Zhang, Xin; Chen, Feng-Zhi; Yang, Ya-Dong; Chen, FZ; Li, Xin-Qiang; Yang, YD; Zhang, X] 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：
[Chen, FZ; Li, XQ; Yang, YD; Zhang, X] C;Cent China Normal Univ, Inst Particle Phys, 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,2019年79(3):1-20 ISSN：1434-6044
通讯作者：
Hu, Quan-Yi
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：
[Hu, Quan-Yi] C;Cent China Normal Univ, Inst Particle Phys, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R 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：
[Muramatsu, Yu; Yang, Ya-Dong; Hu, Quan-Yi; Li, Xin-Qiang; Muramatsu, Y; Yang, YD] 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：
[Hu, QY; Li, XQ; Muramatsu, Y; Yang, YD] C;Cent China Normal Univ, Inst Particle Phys, 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.
作者机构：
[Yang, Ya-Dong; Li, Shao-Ping; Li, Xin-Qiang; Yang, YD] 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：
[Li, SP; Li, XQ; Yang, YD] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R 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.
期刊：
Journal of High Energy Physics,2018年2018(9):1-24 ISSN：1029-8479
通讯作者：
Li, Shao-Ping
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：
[Li, Shao-Ping] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R 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
9
NP
= − C
10
NP
< 0, with
$$ \mathcal{O}(1) $$
Yukawa couplings for the muon and the top quark.
摘要：
We calculate the decay constants of light and heavy-light pseudoscalar and vector mesons with improved soft-wall holographic wavefuntions, which take into account the effects of both quark masses and dynamical spins. We find that the predicted decay constants, especially for the ratio f_V/f_P, based on light-front holographic QCD, can be significantly improved, once the dynamical spin effects are taken into account by introducing the helicity-dependent wavefunctions. We also perform detailed χ~2 analyses for the holographic parameters (i.e. the mass-scale parameter κ and the quark masses), by confronting our predictions with the data for the charged-meson decay constants and the meson spectra. The fitted values for these parameters are generally in agreement with those obtained by fitting to the Regge trajectories. At the same time, most of our results for the decay constants and their ratios agree with the data as well as the predictions based on lattice QCD and QCD sum rule approaches, with only a few exceptions observed.
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：
[Su, Fang] C;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：
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,2017年77(3):1-15 ISSN：1434-6044
通讯作者：
Hu, Quan-Yi
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：
[Hu, Quan-Yi] C;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
$$C_{7,9,10}^{(\prime )}$$
, 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.
作者机构：
[Chang, Qin] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.;[Brodsky, Stanley J.; Chang, Qin] Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94309 USA.;[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.
通讯机构：
[Chang, Qin] H;[Chang, Qin] S;Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94309 USA.
摘要：
In this paper the dynamical spin effects of the light-front holographic wave functions for light pseudoscalar mesons are studied. These improved wave functions are then confronted with a number of hadronic observables: the decay constants of π and K mesons, their ξ-moments, the pion-to-photon transition form factor, and the pure annihilation B¯s→π+π− and B¯d→K+K− decays. Taking fπ, fK, and their ratio fK/fπ as constraints, we perform a χ2 analysis for the holographic parameters, including the mass scale parameter λ and the effective quark masses, and find that the fitted results are quite consistent with the ones obtained from the light-quark hadronic Regge trajectories. In addition, we also show that the end point divergence appearing in the pure annihilation B¯s→π+π− and B¯d→K+K− decays can be controlled well by using these improved light-front holographic distribution amplitudes.
摘要：
Recently, BaBar, Belle and LHCb have found hints of lepton flavour universality violation in B -> D-(*)tau(nu) over bar (tau) decays, i.e., the measured ratios R(D-(*)) = B(B -> D-(*)tau(nu) over bar (tau))/B(B -> D((*))l (nu) over bar (l)) (l = e/mu) show a combined 3.8 sigma deviation from the SM predictions. In this talk, we will discuss two possible solutions to the observed R(D) and R(D*) anomalies: one with an EW-scale charged scalar and the other with a TeV-scale scalar leptoquark transforming as (3, 1, -1/3) under the SM gauge group. Their phenomenological implications for the other decays are also briefly discussed.
作者机构：
[Celis, Alejandro] Ludwig Maximilians Univ Munchen, Fak Phys, Arnold Sommerfeld Ctr Theoret Phys, D-80333 Munich, Germany.;[Jung, Martin] TUM Inst Adv Study, Lichtenbergstr 2a, D-85747 Garching, Germany.;[Jung, Martin] Tech Univ Munich, Excellence Cluster Univ, Boltzmannstr 2, D-85748 Garching, Germany.;[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.
通讯机构：
[Li, Xin-Qiang] C;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 perform a comprehensive analysis of scalar contributions in b -> c tau nu transitions including the latest measurements of R(D-(*)), the q(2) differential distributions in B -> D-(*) tau nu the tau polarization asymmetry for B -> D*tau nu, and the bound derived from the total width of the B-c meson. We find that scalar contributions with the simultaneous presence of both left- and right-handed couplings to quarks can explain the available data, specifically R(D-(*)) together with the measured differential distributions. However, the constraints from the total B-c width present a slight tension with the current data on B -> D*tau nu in this scenario, preferring smaller values for R(D*). We discuss possibilities to disentangle scalar new physics from other new-physics scenarios like the presence of only a left-handed vector current, via additional observables in B -> D(*)tau nu decays or additional decay modes like the baryonic Lambda(b) -> Lambda(c)tau nu and the inclusive B -> X-c tau nu decays. We also analyze scalar contributions in b -> u tau nu transitions, including the latest measurements of B -> tau nu providing predictions for Lambda(b) -> p tau nu and B -> pi tau nu decays. The potential complementarity between the b -> u and b -> c sectors is finally investigated once assumptions about the flavour structure of the underlying theory are made. (C) 2017 The Author(s). Published by Elsevier B.V.
