摘要：
The semitauonic
$$ {B}_c^{-}\to J/\psi {\tau}^{-}{\overline{\nu}}_{\tau } $$
decay provides an ideal and clean mode to scrutinize possible new physics effects in
$$ b\to c{\tau}^{-}{\overline{\nu}}_{\tau } $$
transitions as indicated by the current data on R(D(*)) anomalies. In this work, we use the spin density matrix method to obtain the maximum information on the underlying physics of
$$ {B}_c^{-}\to J/\psi {\tau}^{-}{\overline{\nu}}_{\tau } $$
decay with both polarized τ lepton and J/ψ meson. Their subsequent decays, with J/ψ → μ+μ− as well as τ− → π−ντ, τ− → ρ−ντ and
$$ {\tau}^{-}\to {\ell}^{-}{\overline{\nu}}_{\ell }{\nu}_{\tau } $$
, are exploited to extract the energy and angular distributions of the charged final-state particles in the processes. Starting with the most general effective Hamiltonian relevant for the
$$ b\to c{\tau}^{-}{\overline{\nu}}_{\tau } $$
transitions, including all possible Lorentz structures of the dimension-six operators with both left- and right-handed neutrinos, we first derive the five-fold differential decay rate in terms of the visible final-state kinematics. From this distribution, we then construct in total 34 normalized observables, among which nine refer to the CP-violating triple product asymmetries that vanish within the Standard Model. We also construct five new observables based on the combinations of these normalized observables that can only be attributed to the right-handed neutrinos. On the other hand, considering the low statistics of the fully differential distribution, we introduce some integrated observables with only one kinematic variable left, which are more promising to be measured due to the largely increased statistics. The sensitivities of all these observables to the different new physics scenarios are investigated in detail. Finally, assuming an ideal circumstance, we give an estimate of the statistical uncertainties of the nine CP-conserving observables at LHCb and found that τ− → π−ντ has the highest analyzing power among the three τ decay channels.
作者机构：
[Yang, Ya-Dong; Zheng, Dong-Hui; Kong, Ya-Ru; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong; Zheng, Dong-Hui; Kong, Ya-Ru; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Lai, Li-Fen] Shangrao Normal Univ, Sch Phys & Elect Informat, Shangrao 334001, Peoples R China.;[Li, Xin-Qiang] Peking Univ, Ctr High Energy Phys, Beijing 100871, Peoples R China.;[Yan, Xin-Shuai; Yang, Ya-Dong; Yan, XS] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
通讯机构：
[Yan, XS ] H;Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
摘要：
The absence of semitauonic decays of charmed hadrons makes the decay processes mediated by the quark-level c -> d tau thorn nu tau transition inadequate for probing a generic new physics (NP) with all kinds of Dirac structures. To fill in this gap, we consider in this paper the quasielastic neutrino scattering process nu tau thorn n -> tau- thorn Lambda c, and propose searching for NP through the polarizations of the tau lepton and the Lambda c baryon. In the framework of a general low-energy effective Lagrangian, we perform a comprehensive analysis of the (differential) cross sections and polarization vectors of the process both within the Standard Model and in various NP scenarios, and scrutinize possible NP signals. We also explore the influence on our findings due to the uncertainties and the different parametrizations of the Lambda c -> N transition form factors, and show that they have become one of the major challenges to further constrain possible NP through the quasielastic scattering process.
作者机构：
[Yuan, Xing -Bo; Yang, Ya-Dong; Xie, Ze-Jun; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yuan, Xing -Bo; Yang, Ya-Dong; Xie, Ze-Jun; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
通讯机构：
[Xing-Bo Yuan] I;Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei 430079, China
摘要：
The recently updated measurement of the W-boson mass by the CDF collaboration exhibits a 7cr deviation from the SM expectation, which may imply a sign of new physics beyond the SM. The observed discrepancy could be explained by new fermions that carry the electroweak gauge charges and affect the vacuum polarization of gauge bosons. Notably, if the new fermions also have the same quantum numbers as of the SM quarks, they can mix with the latter and thus modify the penguin diagrams governing the b -> st+t- transitions. Therefore, the W-boson mass shift could be related to the b -> st+t- anomalies observed by the LHCb collaboration during the past few years. To investigate this possibility, we consider in this letter a model containing a vector-like top partner gauged under a new U (1)(gamma) symmetry. It is found that the latest CDF mW measurement and the b -> st+t- anomalies can be simultaneously accommodated at 2cr level.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).
作者机构：
[Yan, Xin-Shuai; Lai, LF; Lai, Li-Fen; Yang, Ya-Dong; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yan, Xin-Shuai; Lai, LF; Lai, Li-Fen; Yang, Ya-Dong; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Zhengzhou Univ, Sch Phys & Microelect, Zhengzhou 450001, Henan, Peoples R China.
通讯机构：
[Lai, LF ] 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 investigate the potential for discovering new physics through the low-energy scattering processes e−p→e−(μ−)Λc , which could be accessible in the forthcoming ep scattering experiments once adapted to our proposed setups. In the framework of a general low-energy effective Lagrangian, we demonstrate that, compared with the conventional flavor-changing neutral-current weak decays of charmed hadrons and the dilepton productions at high-energy colliders, the low-energy scattering processes can provide more competitive potentials for hunting the underlying new physics. In some specific leptoquark models, we also show that promising event rates can be expected for both the scattering processes, and point out a possible way to distinguish the experimental signals due to the scalar leptoquarks from those of the vector ones.
期刊：
Journal of High Energy Physics,2022年2022(1):1-38 ISSN：1029-8479
通讯作者：
Zhang, Hong-Hao;Li, Xin-Qiang
作者机构：
[Chen, Feng-Zhi; Zhang, Hong-Hao] Sun Yat Sen Univ, Sch Phys, Guangzhou 510275, Peoples R China.;[Yang, Ya-Dong; Peng, Shi-Can; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong; Peng, Shi-Can; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Zhang, Hong-Hao] S;[Li, Xin-Qiang] C;Sun Yat Sen Univ, Sch Phys, Guangzhou 510275, Peoples R China.;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;Chiral Lagrangians;CP violation
摘要：
In this work, we proceed to study the CP asymmetry in the angular distributions of τ → KSπντ decays within a general effective field theory framework including four-fermion operators up to dimension-six. It is found that, besides the commonly considered scalar-vector interference, the tensor-scalar interference can also produce a non-zero CP asymmetry in the angular distributions, in the presence of complex couplings. Using the dispersive representations of the Kπ form factors as inputs, and taking into account the detector efficiencies of the Belle measurement, we firstly update our previous SM predictions for the CP asymmetries in the same four Kπ invariant-mass bins as set by the Belle collaboration. Bounds on the effective couplings of the non-standard scalar and tensor interactions are then obtained under the combined constraints from the CP asymmetries measured in the four bins and the branching ratio of τ − → KSπ−ντ decay, with the numerical results given respectively by
$$ \operatorname{Im}\left[{\hat{\upepsilon}}_S\right] $$
= −0.008 ± 0.027 and
$$ \operatorname{Im}\left[{\hat{\upepsilon}}_T\right] $$
= 0.03 ± 0.12, at the renormalization scale μτ = 2 GeV in the
$$ \overline{\mathrm{MS}} $$
scheme. Using the best-fit values, we also find that the distributions of the CP asymmetries can deviate significantly from the SM expectation in almost the whole Kπ invariant-mass region. Nevertheless, the current bounds on
$$ \operatorname{Im}\left[{\hat{\upepsilon}}_S\right] $$
and
$$ \operatorname{Im}\left[{\hat{\upepsilon}}_T\right] $$
are still plagued by large experimental uncertainties, but will be improved with more precise measurements from the Belle II experiment as well as the proposed Tera-Z and STCF facilities. Assuming further that the non-standard scalar and tensor interactions originate from a weakly-coupled heavy new physics well above the electroweak scale, the SU(2)L invariance of the resulting SMEFT Lagrangian would indicate that very strong limits on
$$ \operatorname{Im}\left[{\hat{\upepsilon}}_S\right] $$
and
$$ \operatorname{Im}\left[{\hat{\upepsilon}}_T\right] $$
could also be obtained from the neutron electric dipole moment and the
$$ {D}^0-{\overline{D}}^0 $$
mixing. With the bounds from these processes taken into account, it is then found that, unless there exist extraordinary cancellations between the new physics contributions, neither the scalar nor the tensor interaction can produce any significant effects on the CP asymmetries (relative to the SM predictions) in the processes considered, especially under the “single coefficient dominance” assumption.
期刊：
EUROPEAN PHYSICAL JOURNAL C,2022年82(11):1-16 ISSN：1434-6044
通讯作者：
Xin-Qiang Li
作者机构：
[Yan, Xin-Shuai; Yang, Ya-Dong; Li, Shao-Ping; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yan, Xin-Shuai; 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.;[Yang, Ya-Dong] Henan Normal Univ, Inst Particle & Nucl Phys, Xinxiang 453007, Henan, Peoples R China.
通讯机构：
[Xin-Qiang Li] I;Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics(MOE), Central China Normal University, Wuhan, China
摘要：
If the leptoquarks proposed to account for the intriguing anomalies observed in the semileptonic B-meson decays,
$$R_{D^{(*)}}$$
and
$$R_{K^{(*)}}$$
, as well as in the anomalous magnetic moment of the muon,
$$(g-2)_\mu $$
, can be embedded into the scotogenic Dirac neutrino mass models, all these flavor anomalies, together with the origin of neutrino masses and the nature of dark matter, could be potentially addressed in a unified picture. Among the minimal seesaw, one-loop, and two-loop realizations of the dimension-4 effective operator
$${\mathcal {L}}_{4}$$
for the Dirac neutrino masses, we show that plenty of diagrams associated with the two-loop realizations of
$${\mathcal {L}}_{4}$$
can support the coexistence of leptoquarks and dark matter candidates. After a simple match of these leptoquarks with the ones introduced to accommodate all the flavor anomalies, we establish the scotogenic Dirac neutrino mass models embedded with leptoquarks, which could address all the problems mentioned above.
作者机构：
[Yang, Ya-Dong; Yuan, Xing-Bo; Li, Xin-Qiang; Shen, Meng] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Wang, Dong-Yang] Jiujiang Univ, Dept Phys, Jiujiang 332005, Peoples R China.;[Yang, Ya-Dong] Zhengzhou Univ, Sch Phys & Microelect, Zhengzhou 450001, Henan, Peoples R China.;[Yang, Ya-Dong; Yuan, Xing-Bo; Li, Xin-Qiang; Shen, Meng] Cent China Normal Univ, Key Lab Quark & Lepton Phys, MOE, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Xing-Bo Yuan] I;Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei 430079, China
摘要：
Motivated by the recent anomalies in b -> sl(+)l(-) transitions, we explore a minimal Z' scenario, in which the Z' boson has a flavour-changing coupling to charm and top quarks and a flavour-conserving coupling to muons. It is found that such a Z' boson can explain the current b -> sl(+)l(-)anomalies, while satisfying other flavour and collider constraints simultaneously. The Z' boson can be as light as few hundreds GeV. In this case, the t -> c mu(+)mu(-) decay and the tZ' associated production at the LHC could provide sensitive probes of such a Z' boson. As a special feature, the Z' contributions to all rare B- and K-meson processes are controlled by one parameter. This results in interesting correlations among these processes, which could provide further insights into this scenario. In addition, an extended scenario, in which the Z' boson interacts with the SU (2)(L) fermion doublets with analogous couplings as in the minimal scenario, is also investigated. (C) 2022 Published by Elsevier B.V.
期刊：
EUROPEAN PHYSICAL JOURNAL C,2022年82(10):1-31 ISSN：1434-6044
通讯作者：
Xin-Qiang Li
作者机构：
[Cai, Fang-Min; Funatsu, Shuichiro; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Cai, Fang-Min; Funatsu, Shuichiro; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Zhengzhou Univ, Sch Phys & Microelect, Zhengzhou 450001, Henan, Peoples R China.
通讯机构：
[Xin-Qiang Li] I;Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics(MOE), Central China Normal University, Wuhan, China
摘要：
We update the Standard Model (SM) predictions for the branching ratios of the rare top-quark decays
$$t \rightarrow cg(g)$$
, and evaluate the maximum rates that can be reached in the aligned as well as in the four conventional two-Higgs-doublet models (2HDMs) with
$$\mathcal {Z}_2$$
symmetries. Taking into account the relevant constraints on the model parameters resulting from a global fit obtained at the
$$95.5\%$$
confidence level, we find that the branching ratios of
$$t \rightarrow cg$$
and
$$t \rightarrow cgg$$
decays can reach up to
$$3.36\times 10^{-9}$$
and
$$2.95\times 10^{-9}$$
respectively, being therefore of the same order, in the aligned 2HDM (A2HDM). This is obviously different from the SM case, where the predicted branching ratio of the three-body decay
$$t \rightarrow cgg$$
is about two orders of magnitude larger than that of the two-body decay
$$t \rightarrow cg$$
. On the other hand, compared with the SM predictions, no significant enhancements are observed in the four conventional 2HDMs with
$$\mathcal {Z}_2$$
symmetries for the branching ratios of these two decays. Nevertheless, the predicted branching ratios of
$$t \rightarrow cg$$
and
$$t \rightarrow cgg$$
decays in the A2HDM are still out of the expected sensitivities of the future high-luminosity Large Hadron Collider and the Future Circular Collider in hadron-hadron mode.
作者机构：
[Yan, Xin-Shuai; Lai, Li-Fen; Yang, Ya-Dong; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Yan, Xin-Shuai; Lai, Li-Fen; Yang, Ya-Dong; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.;[Yang, Ya-Dong] Zhengzhou Univ, Sch Phys & Microelect, Zhengzhou 450001, Henan, Peoples R China.
摘要：
We investigate the potential for searching and identifying the leptoquark (LQ) effects in the charm sector through the low-energy polarized scattering processes,(e) over right arrow (-)p ->,e(-)Lambda(c), e(-)(p) over right arrow -> e-Lambda(c), (e) over right arrow (-)(p) over right arrow ->, e(-)Lambda(c) Considering only the longitudinally polarized processes, we show that the different LQ models can be disentangled from each other by measuring the four spin asymmetries, A(L)(e) , A(L)(p) , A(L3)(ep) , and A(L6)(ep) , constructed in terms of the polarized cross sections. Although it is challenging to accomplish the same goal with transversely polarized processes, we find that investing them in future experiments is especially beneficial since they can directly probe into the imaginary part of the Wilson coefficients in the general low-energy effective Lagrangian. With our properly designed experimental setups, it is also demonstrated that promising event rates can be expected for all these processes and, even in the worst-case scenario-no LQ signals observed at all-they can still provide a competitive potential for constraining the new physics, compared with those from the conventional charmed-hadron weak decays and the high-p(T) dilepton invariant mass tails at high-energy colliders.
通讯机构：
[Yuxiang Zhao] I;Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China<&wdkj&>University of Chinese Academy of Sciences, Beijing, China
关键词：
electron ion collider;nucleon structure;nucleon mass;exotic hadronic states;quantum chromodynamics;3D-tomography;helicity;transverse momentum dependent parton distribution;generalized parton distribution;energy recovery linac;polarization;spin rotator
摘要：
Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of ∼80%) and protons (with a polarization of ∼70%) with variable center of mass energies from 15 to 20 GeV and the luminosity of (2–3) × 1033 cm−2 · s−1. Polarized deuterons and Helium-3, as well as unpolarized ion beams from Carbon to Uranium, will be also available at the EicC. The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with cutting-edge technologies. This document is the result of collective contributions and valuable inputs from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China.
期刊：
Journal of High Energy Physics,2021年2021(10):1-49 ISSN：1029-8479
通讯作者：
Li, Xin-Qiang
作者机构：
[Cai, Fang-Min; Deng, Wei-Jun] 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, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
With updated experimental data and improved theoretical calculations, several significant deviations are being observed between the Standard Model predictions and the experimental measurements of the branching ratios of
$$ {\overline{B}}_{(s)}^0\to {D}_{(s)}^{\left(\ast \right)+}{L}^{-} $$
decays, where L is a light meson from the set {π, ρ, K(∗)}. Especially for the two channels
$$ {\overline{B}}^0\to {D}^{+}{K}^{-} $$
and
$$ {\overline{B}}_s^0\to {D}_s^{+}{\pi}^{-} $$
, both of which are free of the weak annihilation contribution, the deviations observed can even reach 4–5σ. Here we exploit possible new-physics effects in these class-I non-leptonic B-meson decays within the framework of QCD factorization. Firstly, we perform a model-independent analysis of the effects from twenty linearly independent four-quark operators that can contribute, either directly or through operator mixing, to the quark-level b →
$$ c\overline{u}d(s) $$
transitions. It is found that, under the combined constraints from the current experimental data, the deviations observed could be well explained at the 1σ level by the new-physics four-quark operators with γμ(1 − γ5) ⨂ γμ(1 − γ5) structure, and also at the 2σ level by the operators with (1 + γ5) ⨂ (1 − γ5) and (1 + γ5) ⨂ (1 + γ5) structures. However, the new-physics four-quark operators with other Dirac structures fail to provide a consistent interpretation, even at the 2σ level. Then, as two specific examples of model-dependent considerations, we discuss the case where the new-physics four-quark operators are generated by either a colorless charged gauge boson or a colorless charged scalar, with their masses fixed both at the 1 TeV. Constraints on the effective coefficients describing the couplings of these mediators to the relevant quarks are obtained by fitting to the current experimental data.
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(6) ISSN：1029-8479
作者机构：
[Hu, Quan-Yi] Anyang Normal Univ, Sch Phys & Elect Engn, Anyang 455000, Henan, Peoples R China.;[Mu, Xiao-Long; Yang, Ya-Dong; Zheng, Dong-Hui; Li, Xin-Qiang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.;[Mu, Xiao-Long; Yang, Ya-Dong; Zheng, Dong-Hui; Li, Xin-Qiang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
关键词：
Beyond Standard Model;Heavy Quark Physics
摘要：
In Bc-</mml:msubsup> -> J/psi(-> mu (+)mu (-))tau (-)nu <overbar></mml:mover>tau decay, the three-momentum p tau- cannot be determined accurately due to the decay products of tau (-) inevitably include an undetected nu (tau). As a consequence, 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 Bc-</mml:msubsup> -> J/psi(-> mu (+)mu (-))tau (-)(-> pi (-)nu (tau))nu <overbar></mml:mover>tau, in which the three-momenta p mu+,p mu-, and p pi- can be measured. The five-fold differential angular distribution containing all Lorentz structures of the new physics (NP) effective operators can be written in terms of twelve angular observables I-i(q(2), E-pi). Integrating over the energy of pion E-pi, we construct twelve normalized angular observables I</mml:mover>i(q(2)) and two lepton-flavor-universality ratios R<mml:mfenced close=")" open="(">PL,TJ/psi</mml:mfenced>(q(2)). Based on the B-c -> J/psi form factors calculated by the latest lattice QCD and sum rule, we predict the q(2) distribution of all <mml:msub>I</mml:mover>i and R<mml:mfenced close=")" open="(">PL,TJ/psi</mml:mfenced> both within the Standard Model and in eight NP benchmark points. We find that the benchmark BP2 (corresponding to the hypothesis of tensor operator) has the greatest effect on all I-i and R<mml:mfenced close=")" open="(">PL,TJ<mml:mo>/psi</mml:mfenced>, except <mml:msub><mml:mover accent="true">I<mml:mo stretchy="true"></mml:mover>5. The ratios R<mml:mfenced close=")" open="(">PL<mml:mo>,TJ<mml:mo>/psi</mml:mfenced> are more sensitive to the NP with pseudo-scalar operators than the I-i. Finally, we discuss the symmetries in the angular observables and present a model-independent method to determine the existence of tensor operators.
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：
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.