期刊：
EUROPEAN PHYSICAL JOURNAL C,2017年77(4):1-13 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, MOE, Key Lab Quark & Lepton Phys, 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：
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.
期刊：
Journal of High Energy Physics,2017年2017(2):1-24 ISSN：1029-8479
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.
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.
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
$$ {\overline{B}}_{(s)}\to {D}_{(s)}^{\left(\ast \right)+}{L}^{-} $$
and Λ
b
→ Λ
+
L
−, where L is a light meson from the set {π, ρ, 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
$$ \mathcal{O}\left({\alpha}_s^2\right) $$
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 ∼ 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 High Energy Physics,2016年2016(8):1-25 ISSN：1029-8479
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.
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.
作者机构：
[Bell, G.] Univ Oxford, Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3NP, England.;[Beneke, M.] Tech Univ Munich, Phys Dept T31, D-85748 Garching, Germany.;[Huber, T.] Univ Siegen, Nat Wissensch Tech Fak, Theoret Phys 1, D-57068 Siegen, 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.
摘要：
The computation of direct CF asymmetries in charmless B decays at next-to-next-to-leading order (NNLO) in QCD is of interest to ascertain the short-distance contribution. Here we compute the two-loop penguin contractions of the current-current operators Q(1,2) and provide a first estimate of NNLO CP asymmetries in penguin-dominated b -> s transitions. (C) 2015 The Authors. Published by Elsevier B.V.
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2015年42(12):125005- ISSN：0954-3899
通讯作者：
Li, Xin-Qiang
作者机构：
[Zhang, Xin; Cheng, Xiao-Dong; Yang, Ya-Dong; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Zhang, Xin; Cheng, Xiao-Dong; Yang, Ya-Dong; 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.
通讯机构：
[Li, Xin-Qiang] C;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.
作者：
Abbas, Gauhar;Celis, Alejandro;Li, Xin-Qiang*;Lu, Jie;Pich, Antonio
期刊：
Journal of High Energy Physics,2015年2015(6):1-26 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
作者机构：
[Abbas, Gauhar; Pich, Antonio] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain.;[Celis, Alejandro] Univ Munich, Fak Phys, Arnold Sommerfeld Ctr Theoret Phys, D-80333 Munich, 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.;[Li, Xin-Qiang] Chinese Acad Sci, Inst Theoret Phys, State Key Lab Theoret Phys, Beijing 100190, 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：
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 $t \rightarrow c h$ and $t \rightarrow c V$ ($V= \gamma, Z$), 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 $t \rightarrow c h$ decay rate when the charged scalar of the model is light.
作者：
Abbas, Gauhar;Celis, Alejandro;Li, Xin-Qiang;Lu, Jie;Pich, Antonio
期刊：
Proceedings of Science,2015年22-29-July-2015 ISSN：1824-8039
作者机构：
[Abbas, Gauhar; Pich, Antonio] IFIC, Universitat de Valè,ncia, CSIC, Apt. Correus 22085, Valè,ncia, E-46071, Spain;[Lu, Jie] Department of Physics, Shanghai University, Shanghai, 200444, China;[Li, Xin-Qiang] State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China;[Li, Xin-Qiang] Institute of Particle Physics, Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei, 430079, China;[Celis, Alejandro] Ludwig-Maximilians-Universitä,t Mü,nchen, Fakultä,t fü,r Physik, Arnold Sommerfeld Center for Theoretical Physics, Mü,nchen, 80333, Germany
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：
[Li, Xin-Qiang] C;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→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：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2014年41(10):105002- ISSN：0954-3899
通讯作者：
Chang, Qin
作者机构：
[Chang, Qin] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.;[Yang, Ya-Dong; Chang, Qin; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong; Chang, Qin; 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 100080, Peoples R China.
通讯机构：
[Chang, Qin] H;Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
关键词：
B-physics;rare decays;beyond standard model
摘要：
Motivated by the latest improved measurements of B-meson decays, we make a comprehensive analysis of the impact of a family non-universal Z' boson on B-s - (B) over bar (s) mixing and two-body hadronic B-meson decays, all being characterized by the quark-level b -> s transition. Explicitly 22 decay modes and the related 52 observables are considered, and some interesting correlations between them are also carefully examined. Firstly, the allowed oases of b - s - Z' coupling parameters |B-sb(L, R)| and phi(L, R)(s) are extracted from B-s - (B) over bar (s) mixing. Then, in the 'SM limit' (i.e., no new types of Z'-induced four-quark operators arise compared to the SM case), we study the Z' effects on B -> pi K, pi K* and rho K decays. It is found that a new weak phase phi(L)(s) similar to - 90 degrees is crucial for resolving the observed 'pi K CP puzzle' and the allowed cases of the other Z' coupling parameters are also strongly restricted. Moreover, the Z' effects on (B) over bar (s) -> KK, KK* and pi(0)phi decays, being induced by the same quark-level b -> sq (q) over bar (q = u, d) transitions, are also investigated. In particular, it is found that the decay (B) over bar (s) -> pi(0)phi, once measured, would play a key role in revealing the observed 'pi K CP puzzle' and probing possible new physics hints. Finally, to check the non-universality of Z' couplings to light-quark pairs, we have studied the B -> phi K decays in detail and found that the left-handed s - s - Z' coupling is different from the d - d - Z' one, which is due to the large A(CP)(dir)(B- -> phi K-) reported by the BaBar Collaboration.
期刊：
Journal of High Energy Physics,2014年2014(6):1-39 ISSN：1029-8479
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.;[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.;[Lu, Jie; Pich, Antonio] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain.
通讯机构：
[Li, Xin-Qiang] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Higgs Physics;Rare Decays;Beyond Standard Model;B-Physics
摘要：
The rare decays
$ B_{s,d}^0 $
→ ℓ
+
ℓ
− are analyzed within the general framework of the aligned two-Higgs doublet model. We present a complete one-loop calculation of the relevant short-distance Wilson coefficients, giving a detailed technical summary of our results and comparing them with previous calculations performed in particular limits or approximations. We investigate the impact of various model parameters on the branching ratios and study the phenomenological constraints imposed by present data.
期刊：
Journal of High Energy Physics,2012年2012(5):1-27 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
作者机构：
[Lu, Gong-Ru; Li, Yan-Min; 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.;[Su, Fang] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Li, Xin-Qiang] H;Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.
关键词：
Beyond Standard Model;B-Physics;CP violation
摘要：
Motivated by the very recent measurements performed at the LHCb and the Tevatron of the
$ B_s^0 - \overline B_s^0 $
mixing, in this paper we revisit it in a family non-universal Z′ model, to check if a simultaneous explanation for all the mixing observables, especially for the like-sign dimuon charge asymmetry observed by the D0 collaboration, could be made in such a specific model. In the first scenario where the Z′ boson contributes only to the off-diagonal element
$ M_{{{12}}}^s $
, it is found that, once the combined constraints from ΔM
s
, ϕ
s
and ΔΓ
s
are imposed, the model could not explain the measured flavour-specific CP asymmetry
$ a_{{fs}}^s $
, at least within its 1σ ranges. In the second scenario where the NP contributes also to the absorptive part
$ \Gamma_{{{12}}}^s $
via tree-level Z′-induced b →
$ c\overline c s $
operators, we find that, with the constraints from ΔM
s
, ϕ
s
and the indirect CP asymmetry in
$ {{\overline B }_d} $
→ J/ψK
S
taken into account, the present measured 1σ experimental ranges for
$ a_{{fs}}^s $
could not be reproduced too. Thus, such a specific Z′ model with our specific assumptions could not simultaneously reconcile all the present data on
$ B_s^0 - \overline B_s^0 $
mixing. Future improved measurements from the LHCb and the proposed superB experiments, especially of the flavour-specific CP asymmetries, are expected to shed light on the issue.
作者机构：
[Li Yan-Min; Lu Gong-Ru; Li Xin-Qiang] Henan Normal Univ, Dept Phys, Xinxiang 453007, Peoples R China.;[Su Fang] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Lu Gong-Ru] H;Henan Normal Univ, Dept Phys, Xinxiang 453007, Peoples R China.
期刊：
Journal of High Energy Physics,2012年2012(3):1-22 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
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：
[Li, Xin-Qiang] H;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 \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,2011年2011(8):1-22 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
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：
[Li, Xin-Qiang] H;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 effects of top-quark anomalous interactions tqγ in the exclusive radiative B → K
∗
γ and B → ργ decays. With the current experimental data of the branching ratios, the direct CP and the isospin asymmetries, bounds on the coupling κγ
tcR
from B → K
∗
γ and κγ
tcR
from B → ργ decays are derived, respectively. The bound on |κγ
tcR
| from
$ \mathcal{B}\left( {B \to {K^*}\gamma } \right) $
is generally compatible with that from
$ \mathcal{B}\left( {B \to {K_s}\gamma } \right) $
. However, the isospin asymmetry ∆(K
∗
γ) further restrict the phase of κγ
tcR
, and the combined bound results in the upper limit,
$ \mathcal{B}\left( {t \to c\gamma } \right) $
< 0.21%, which is lower than the CDF result. For real κγ
tcR
, the upper bound on
$ \mathcal{B}\left( {t \to c\gamma } \right) $
is about of the same order as the 5σ discovery potential of ATLAS with an integrated luminosity of10 fb−1. For B → ργ decays, the NP contribution is enhanced by a large CKM factor |V
ud
/V
td
|, and the constraint on tuγ coupling is rather restrictive,
$ \mathcal{B}\left( {t \to u\gamma } \right) $
< 1.44× 10−5. With refined measurements to be available at the LHCb and the future super-B factories, we can get close correlations between B → Vγ and the rare t → qγ decays, which will be studied directly at the LHC ATLAS and CMS.
期刊：
INTERNATIONAL JOURNAL OF MODERN PHYSICS A,2011年26(7-8):1273-1294 ISSN：0217-751X
通讯作者：
Chang, Qin
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] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain.;[Yang, Ya-Dong] Huazhong Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Chang, Qin] H;Henan Normal Univ, Dept Phys, Xinxiang 453007, Henan, Peoples R China.
关键词：
B-physics;rare decays;beyond Standard Model
摘要：
Motivated by the measured large branching ratio of (B) over bar (0) --> pi(0)pi(0) (the so-called pi pi puzzle), we investigate the effects of a family nonuniversal Z' model on the tree-dominated B --> pi pi decays. We find that the Z' coupling parameter zeta(LR)(d) similar to 0.05 with a nontrivial new weak phase phi(L)(d) similar to -50 degrees, which is relevant to the Z' contributions to the QCD penguin sector Delta C-5, is needed to reconcile the observed discrepancy. Combined with the recent fitting results from B --> pi K, pi K* and rho K decays, the Z' parameter spaces are severely reduced but still not excluded entirely, implying that both the "pi pi" and "pi K" puzzles could be accommodated simultaneously within such a family nonuniversal Z' model.
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：
[Li, Xin-Qiang] H;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+(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.
