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Top quark decays in the flavor-dependent model

The European Physical Journal C 2024年第11期84卷 1-10页

作者： Ge, Zhao-feng Yang, Jin-lei Department of Physics Hebei University Baoding China Radiation Monitoring Technical Center of Ministry of Ecology and Environment State Environmental Protection Key Laboratory of Radiation Environmental Monitoring Key Laboratory of Radiation Environmental Safety Monitoring of Zhejiang Province Hangzhou China Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province Baoding China

The branching ratios of the flavor changing top quark decays in the SM are too small to be detected experimentally. Therefore, any observable signal for these processes at the LHC would serve as compelling evidence for new physics. In the flavor-dependent $$U(1)_X$$ model, a newly introduced Higgs singlet interacts directly with the quark sector and mixes with the SM-like Higgs, influencing the $$t\rightarrow ch$$ and $$t\rightarrow uh$$ process. Additionally, the flavor dependence of the $$U(1)_X$$ charge affect the $$t\rightarrow cZ$$ process. In this work, we investigate these process within the framework of the flavor-dependent $$U(1)_X$$ model. Numerical results indicates that with suitable choices of new physics parameters, the branching ratios of these processes in the flavor-dependent $$U(1)_X$$ model can be significantly enhanced. Specifically, the branching ratios of $$t\rightarrow ch$$ and $$t\rightarrow uh$$ can reach the order of $$10^{-4}$$ in some chosen parameter spaces, which is close to the current experimental upper limit. This suggests that these processes have significant opportunities to be observed experimentally, and the parameter space of the model will face constraints from the experimental upper bounds.

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Phase diagrams of neutron-proton superfluid in asymmetric nuclear matter

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Physical Review C 2025年第1期111卷 014320-014320页

作者： K. D. Duan H. B. Zhang X. L. Shang Department of Physics Hebei University Baoding 071002 China CAS Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China School of Nuclear Science and Technology University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of High-Precision Computation and Application of Quantum Field Theory of Hebei Province Baoding 071002 China

The finite-temperature phase structures for neutron-proton superfluidity in asymmetric nuclear matter are investigated, with a particular focus on the angular dependence of the pairing gap induced by the SD13 nucleon-nucleon interaction. This angular dependence of the pairing gap results in the Cooper pair momentum in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state exhibiting exactly two distinct stable orientations: one orthogonal (FFLO-ADG-O) and the other parallel (FFLO-ADG-P) to the symmetry axis of the pairing gap. The FFLO-ADG-O state dominates at low asymmetries, while the FFLO-ADG-P state prevails at high asymmetries. Additionally, this analysis of normal-superfluid phase separation reveals that the angular dependence of the pairing gap eliminates phase separation in the low-asymmetry regime, whereas the Cooper pair momentum effectively suppresses phase separation at high asymmetries. These two mechanisms act in concert to significantly prevent the occurrence of normal-superfluid phase separation across the entire phase diagram, ensuring the stability of the homogeneous superfluid state over a broad range of asymmetries. These results provide new insights into the interplay between the angular dependence of the pairing gap and the stability of superfluidity in asymmetric nuclear matter.

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Theoretical corrections of and

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The European Physical Journal C 2023年第10期83卷 1-14页

作者： Long, Xin-Xin Zhao, Shu-Min Liu, Ming-Yue Wang, Xi Wang, Yi-Tong Yang, Zhong-Jun Dong, Xing-Xing Feng, Tai-Fu Department of Physics Hebei University Baoding China Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province Baoding China Research Center for Computational Physics of Hebei Province Baoding China Department of Physics Chongqing University Chongqing China

$$R_{D^{(*)}}$$ is the ratio of branching ratio $$\overline{B} \rightarrow D^{(*)}\tau \overline{\nu }_{\tau }$$ to $$\overline{B} \rightarrow D^{(*)}l\overline{\nu }_{l}~(l=e,~\mu )$$ . There is a gap of 2 $$\sigma _{exp}$$ or more between its experimental value and the prediction under the standard model (SM). People extend the MSSM with the local gauge group $$U(1)_X$$ to obtain the $$U(1)_X$$ SSM. Compared with MSSM, $$U(1)_X$$ SSM has more superfields and effects. In $$U(1)_X$$ SSM, we research the semileptonic decays $$\overline{B} \rightarrow D^{(*)}l\overline{\nu }_{l}$$ and calculate $$R_{D^{(*)}}$$ . The numerical results of $$R_{D^{(*)}}$$ are further corrected under $$U(1)_X$$ SSM, which are much better than the SM predictions. After correction, the theoretical value of $$R_{D^{(*)}}$$ can reach one $$\sigma _{exp}$$ range of the averaged experiment central value.

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Partial wave effects in the heavy quarkonium radiative electromagnetic decays

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Physical Review D 2023年第3期108卷 033003-033003页

作者： Su-Yan Pei Wei Li Ting-Ting Liu Meng Han Guo-Li Wang Tian-Hong Wang Department of Physics and Technology Hebei University Baoding 071002 China Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province Baoding China School of Physics Harbin Institute of Technology Harbin 150001 China

In a previous paper [1], it was pointed out that the wave functions of all particles are not pure waves, besides the main partial waves, they all contain other partial waves. It is very interesting to know what role these different partial waves play in particle transitions. Therefore, by using the Bethe-Salpeter equation method, we study the radiative electromagnetic decays ψ→γχcJ and ϒ→γχbJ (J=0, 1, 2). We find that for the S and P wave dominated states, like the ψ(2S), ϒ(2S), χcJ(1P), and χbJ(1P) etc., the dominant S and P waves provide main and nonrelativistic contrition to the decays; other partial waves mainly contribute to the relativistic correction. For the states like the ψ(1D), ϒ(2D), χc2(1F), and χb2(1F) etc., they are the S−P−D mixing state dominated by D wave or the P−D−F mixing state dominated by F wave. Large decay widths are found in the transitions ψ(2D)→χc2(1F), ϒ(1D)→χbJ(1P), and ϒ(2D)→χbJ(2P) etc., which may be helpful to study the missing states χc2(1F), ϒ(1D), and ϒ(2D).

关键词： Bethe-Salpeter equation Hadronic decays Leptonic, semileptonic & radiative decays quantum electrodynamics Quark model Heavy mesons Quarkonia

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Strong decays of the isovector-scalar D∗D¯∗ hadronic molecule

arXiv

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arXiv 2024年

作者： Deng, Jin-Cheng Wang, Bo College of Physics Science and Technology Hebei University Baoding071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding071002 China

We adopt the effective Lagrangian approach to study the strong decays of the 1−(0++) D∗D¯∗ molecular state [denoted as Tψa0(4010) according to the LHCb naming convention] through triangle diagrams. The decay channels include the open-charm DD¯, and the hidden-charm ηcπ, J/ψρ, and χc1π. The coupling between the Tψa0(4010) and its constituents D∗D¯∗ is obtained by solving for the residue of the scattering T-matrix at the pole. Our calculations yield a total width of few tens MeV for the Tψa0(4010) state using three different form factors, with its main decay channels being ηcπ and χc1π. The X(4100) and X(4050) have similar masses and widths, with both masses being close to the D∗D¯∗ threshold. Additionally, their decay final states are consistent with those of the Tψa0(4010). Therefore, it is likely that they represent the same state and both potentially correspond to the Tψa0(4010). We suggest that future experiments focus on searching for the Tψa0(4010) signal in the final states ηcπ−, χc1π− and D0D− of the B0 → ηcπ−K+, χc1π−K+ and D0D−K+ processes, respectively, as well as further investigating its resonance parameters with Flatté-like formula. © 2024, CC BY.

关键词： Lagrange multipliers

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Decay property of the X(3842) as the ψ3(1D33) state

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Physical Review D 2024年第3期109卷 036011-036011页

作者： Wei Li Su-Yan Pei Tianhong Wang Tai-Fu Feng Guo-Li Wang Department of Physics Hebei University Baoding 071002 China Hebei Key Laboratory of High-Precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China School of Physics Harbin Institute of Technology Harbin 150001 China

In this paper, the new particle X(3842) discovered by the LHCb Collaboration is identified to be the ψ3(13D3) state. We study its strong decays with the combination of the Bethe-Salpeter method and the P30 model. Its electromagnetic (EM) decay is also calculated by the Bethe-Salpeter method within the Mandelstam formalism. The strong decay widths are Γ[X(3842)→D0D¯0]=1.27 MeV and Γ[X(3823)→D+D−]=1.08 MeV, and the ratio is B[X(3842)→D+D−]/B[X(3823)→D0D¯0]=0.84. The EM decay width is Γ[X(3842)→χc2γ]=0.29 MeV. We also estimate the total width to be 2.87 MeV, which is in good agreement with the experimental data 2.79−0.86+0.86 MeV. Since the used relativistic wave functions include different partial waves, we also study the contributions of different partial waves in electromagnetic decay.

关键词： Bethe-Salpeter equation Hadronic decays Leptonic, semileptonic & radiative decays Quark model Quarkonia

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Semirelativistic study of the semileptonic decays of Bq mesons to orbital excited heavy tensors

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Physical Review D 2024年第5期109卷 053004-053004页

作者： Wen-Yuan Ke Su-Yan Pei Tianhong Wang Guo-Li Wang Department of Physics Hebei University Baoding 071002 China Hebei Key Laboratory of High-Precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China School of Physics Harbin Institute of Technology Harbin 150001 China

Based on the method of solving the complete Salpeter equation, we study the semileptonic decays of a 0− heavy meson to 1P, 2P, or 3P heavy-tensor mesons, Bq→(c¯q)(nP)ℓ+νℓ (q=u,d,s,c;n=1,2,3). The obtained branching ratio of B(B→D2⋆(2460)ℓ+νℓ) agrees with the experimental data. We predict B(Bs0→Ds2⋆−(1P)ℓ+νℓ)=3.76×10−3 and B(Bc+→χc2(1P)ℓ+νℓ)=1.82×10−3. The branching ratios of decays to 2P and 3P final states are found to be very small. The ratios R(D¯2⋆0)=0.045, R(Ds2⋆)=0.048 and R(χc2)=0.059 are also obtained. This study focuses on the contribution of relativistic corrections. The wave function of the pseudoscalar includes nonrelativistic S-wave and relativistic P-wave. While for a tensor, it contains nonrelativistic P-wave and relativistic P-, D-, and F-waves in its wave function. We find the individual contributions of relativistic partial waves are significant in the decay B→D2⋆(2460)ℓ+νℓ, but the overall contribution of the relativistic effect is 24.4%, which is small due to cancellation. Similarly, for the decay Bs0→Ds2⋆−(1P)ℓ+νℓ, the contribution of the relativistic effect is 28.8%. While for Bc+→χc2(1P)ℓ+νℓ, the individual contributions of relativistic partial waves and the overall relativistic correction are both small, the later of which is 22.1%.

关键词： Bethe-Salpeter equation Branching fraction Leptonic, semileptonic & radiative decays

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Charged lepton flavor violation in the B−L symmetric SSM

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Physical Review D 2024年第5期109卷 055019-055019页

作者： Xing-Xing Dong Shu-Min Zhao Jia-Peng Huo Tong-Tong Wang Tai-Fu Feng College of Physics Science and Technology Hebei University Baoding 071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China Department of Physics Chongqing University Chongqing 401331 China

Charged lepton flavor violation (CLFV) represents a clear new physics (NP) signal beyond the standard model (SM). In this work, we investigate CLFV processes lj−→li−γ utilizing mass insertion approximation (MIA) in the minimal supersymmetric extension of the SM with local B−L gauge symmetry (B−L SSM). The MIA method can provide a set of simple analytic formulas for the form factors and the associated effective vertices, so that the movement of the CLFV decays lj−→li−γ with the sensitive parameters will be intuitively analyzed. Considering the SM-like Higgs boson mass and the muon anomalous dipole moment (MDM) within 4σ, 3σ, and 2σ regions, we discuss the corresponding constraints on the relevant parameter space of the model.

关键词： Supersymmetric models Leptons Flavor symmetries Magnetic moment

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Spectrum of molecular hexaquarks

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Physical Review D 2024年第1期110卷 014038-014038页

作者： Bo Wang Kan Chen Lu Meng Shi-Lin Zhu College of Physics Science and Technology Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China School of Physics Institut für Theoretische Physik II School of Physics and Center of High Energy Physics

We investigate the mass spectra of molecular-type hexaquark states in the dibaryon systems. These systems are composed of the charmed baryons [Σc(*),Ξc(′,*)], doubly charmed baryons [Ξcc(*)], and hyperons [Σ(*),Ξ(*)]. We consider all possible combinations of particle-particle and particle-antiparticle pairs, including the S-wave spin multiplets in each combination. We establish the underlying connections among the molecular tetraquarks, pentaquarks, and hexaquarks with the effective quark-level interactions. We find that the existence of molecular states in DD*, DD¯*, and ΣcD¯(*) systems leads to the emergence of a large number of deuteronlike hexaquarks in the heavy flavor sectors. Currently, there have been several experimental candidates for molecular tetraquarks and pentaquarks. The experimental search for near-threshold hexaquarks will further advance the establishment of the underlying dynamical picture of hadronic molecules and deepen our understanding of the role of spin-flavor symmetry in near-threshold residual strong interactions.

关键词： Heavy quark effective theory Multiquark bound states Quark model

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Realization of zero skyrmion Hall angle by elongating skyrmions

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Physical Review B 2025年第13期111卷 134426-134426页

作者： Zhaohua Liu Shuang Li Qiyuan Zhu Xingqiang Shi Ruining Wang Jianglong Wang Hu Zhang Penglai Gong Ruqian Lian Chendong Jin Hebei Research Center of the Basic Discipline for Computational Physics Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory College of Physics Science and Technology Hebei University Baoding 071002 People's Republic of China School of Mathematical and Physical Sciences Chongqing University of Science and Technology Chongqing 401331 People's Republic of China

Magnetic skyrmions are considered to be potential information carriers in racetrack memory. However, the skyrmion Hall effect limits the maximum speed of skyrmions along the current direction, which hampers their further application. Here, we investigate the fundamental properties of an elongated skyrmion induced by an anisotropic Dzyaloshinskii-Moriya interaction (DMI). Spin-orbit torque-driven dynamics of the elongated skyrmion under various conditions, including anisotropic DMI, Gilbert damping, and current, are also performed by a combination of micromagnetic simulations and solutions of the Thiele equation. It is found that elongated skyrmions can realize a zero skyrmion Hall angle, and the gradient of Gilbert damping is an effective method to significantly control the skyrmion Hall angle. It should be noted that the rotational symmetry breaking of the elongated skyrmions results in lower thermal stability than the circular skyrmions. Our results offer the possibility of zero skyrmion Hall angle motion, which may help guide the potential application of elongated skyrmions in racetrack memory.

关键词： Anisotropy

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