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Semileptonic decays Bc → (ηc, J/ψ)lν¯l in the "PQCD + Lattice" approach

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arXiv 2019年

作者： Hu, Xue-Qing Jin, Su-Ping Xiao, Zhen-Jun Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

In this paper, we studied the semileptonic decays Bc− → (ηc,J/ψ)l−ν¯l by employing the PQCD factorization approach, using the newly defined distribution amplitudes of the Bc meson and the new kind of parametrization for extrapolation of the form factors, and also taking into account the lattice QCD results about the relevant form factors at several points. We found the following main results: (a) the PQCD predictions for the branching ratios of Bc → (ηc,J/ψ)lν¯ decays will become a little smaller by about (5 − 16)% when the lattice input are taken into account in the extrapolation of the relevant form factors;(b) the PQCD predictions for the ratio Rηc,J/ψ and the longitudinal polarization Pτ are Rηc = 0.34±0.01,RJ/ψ = 0.28±0.01, Pτ(ηc) = 0.37±0.01 and Pτ(J/ψ) = −0.55±0.01;and (c) after the inclusion of the lattice input the theoretical predictions changed slightly: Rηc = 0.31 ± 0.01, RJ/ψ = 0.27 ± 0.01, Pτ(ηc) = 0.36 ± 0.01 and Pτ(J/ψ) = −0.53 ± 0.01. The theoretical predictions for RJ/ψ agree with the measured one within errors, and other predictions could be tested in the near future LHCb experiments. Copyright © 2019, The Authors. All rights reserved.

关键词： Forecasting

Perturbative QCD factorization of ργ⋆→π

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Physical Review D 2014年第7期90卷 076001-076001页

作者： Shan Cheng Zhen-Jun Xiao Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu 210023 People’s Republic of China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing Jiangsu 210023 People’s Republic of China

In this paper, we firstly verify that the factorization hypothesis is valid for the exclusive process ργ⋆→π at the next-to-leading order (NLO) with the collinear factorization approach, and then extend this proof to the case of the kT factorization approach. We particularly show that at the NLO level, the soft divergences in the full quark level calculation could be canceled completely as for the πγ⋆→π process where only the pseudoscalar π meson is involved, and the remaining collinear divergences can be absorbed into the NLO hadron wave functions. The full amplitudes can be factorized as the convolution of the NLO wave functions and the infrared-finite hard kernels with these factorization approaches. We also write out the NLO meson distribution amplitudes in the form of nonlocal matrix elements.

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Structure of pentaquarks Pc+ in the chiral quark model

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Physical Review D 2017年第1期95卷 014010-014010页

作者： Gang Yang Jialun Ping Fan Wang Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People’s Republic of China Department of Physics Nanjing University Nanjing 210093 People’s Republic of China

The recent experimental results of the LHCb Collaboration suggested the existence of pentaquark states with a charmonium. To understand the structure of the states, a dynamical calculation of 5-quark systems with quantum numbers IJP=12(12)±, 12(32)± and 12(52)± is performed in the framework of the chiral quark model with the help of the Gaussian expansion method. The results show that there are several negative parity resonance states while all of the positive parity states are the scattering states. The Pc(4380) state is suggested to be the pentaquark state of Σc*D¯. Although the energy of ΣcD¯* is very close to the mass of Pc(4450), the inconsistent parity prevents the assignment. The calculated distances between quarks confirm the molecular nature of the states.

关键词： Hadron-hadron interactions Quark model Exotic baryons

Exploring the effects of phase modulation on the dynamics of the kicked rotor systems

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Physical Review E 2022年第1期105卷 014212-014212页

作者： Mengyao Li Yingying Xiao Yongchun Tao Yi Gao Peiqing Tong Center for Quantum Transport and Thermal Energy Science Jiangsu Key Lab on Opto-Electronic Technology School of Physics and Technology Nanjing Normal University Nanjing 210023 China. School of Physics and Technology Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 China.

Inspired by the recent experimental progress in the time-driven phase transition in quantum chaos, we investigate comprehensively the energy diffusion of a kicked rotor in the presence of phase modulation. In the classical case, we found that there always exists anomalous diffusion as long as the phase is modulated periodically and changes by 0 or π from kick to kick. On the contrary, for quasiperiodic and random phase modulation, anomalous diffusion is suppressed. On the other hand, in the quantum case, there exist only ballistic energy diffusion and dynamical localization in the standard and periodically shifted cases, while random phase modulation destroys the quantum coherence and totally suppresses the dynamical localization. Furthermore, the quasiperiodic phase modulation is an intermediate phase between the standard case and the random one. In both the classical and quantum cases, quasiperiodic phase modulation is inequivalent to random phase modulation at large kicking times (>103), thus caution has to be taken when dealing with these two kinds of phase modulation in experiments.

关键词： Cold atoms & matter waves 1-dimensional systems

Dynamical quantum phase transition in quantum spin chains with gapless phases

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arXiv 2021年

作者： Cao, Kaiyuan Ming, Zhong Tong, Peiqing Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

The dynamical quantum phase transitions (DQPTs) in quantum spin chains with gapless phases after a sudden quench are studied. We mainly consider the general systems with asymmetrical quasiparticle excitation spectra and obtain the general expression of the Loschmidt echo as well as the general conditions for the occurrence of DQPTs. As two examples, we study the DQPTs in the XY chains with Dzyaloshinskii-Moriya interaction and XZY-YZX type of three-site interaction. It's found that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Besides, we also analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. © 2021, CC BY.

关键词： Phase transitions

Further study of the NΩ dibaryon within constituent quark models

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Physical Review C 2015年第6期92卷 065202-065202页

作者： Hongxia Huang Jialun Ping Fan Wang Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People's Republic of China Department of Physics Nanjing University Nanjing 210093 People's Republic of China

Inspired by the discovery of the dibaryon d* and the experimental search of NΩ dibaryon with the STAR data, we study the strange dibaryon NΩ further in the framework of the quark delocalization color screening model and the chiral quark model. We have shown NΩ is a narrow resonance in ΛΞ D-wave scattering before. However, the Λ−Ξ scattering data analysis is quite complicated. Here we calculate the low-energy NΩ scattering phase shifts, scattering length, effective range, and binding energy to provide another approach of STAR data analysis. Our results show there exists an NΩ “bound” state, which can be observed by the N−Ω correlation analysis with RHIC and LHC data, or by the new developed automatic scanning system at J-PARC. In addition, we also find that the hidden-color channel coupling is important for the NΩ system to develop intermediate-range attraction.

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The effects of KSEA interaction on the ground-state properties of spin chains in a transverse field

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arXiv 2019年

作者： Fu, Hao Zhong, Ming Tong, Peiqing Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

The effects of symmetric helical interaction which is called the Kaplan, Shekhtman, Entin-Wohlman, and Aharony (KSEA) interaction on the ground-state properties of three kinds of spin chains in a transverse field have been studied by means of correlation functions and chiral order parameter. We find that the anisotropic transition of XY chain in a transverse field (XY TF) disappears because of the KSEA interaction. For the other two chains, we find that the regions of gapless chiral phases in the parameter space induced by the DM or XZY -Y ZX type of three-site interaction are decreased gradually with increase of the strength of KSEA interaction. When it is larger than the coefficient of DM or XZY - Y ZX type of three-site interaction, the gapless chiral phases also disappear. Copyright © 2019, The Authors. All rights reserved.

关键词： Spin dynamics

B→ππ decays and effects of the next-to-leading order contributions

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Physical Review D 2014年第1期90卷 014029-014029页

作者： Ya-Lan Zhang Xue-Yan Liu Ying-Ying Fan Shan Cheng Zhen-Jun Xiao Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu 210023 People’s Republic of China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People’s Republic of China

In this paper we perform a systematic study for the three B→(π+π−,π+π0,π0π0) decays in the perturbative QCD (pQCD) factorization approach with the inclusion of all currently known next-to-leading order (NLO) contributions from various sources. We found that (a) for the CP-averaged decay rates Br(B0→π+π−) and Br(B+→π+π0), the NLO pQCD predictions agree with the data within one standard deviation; (b) for Br(B0→π0π0), however, although the NLO contributions can provide a ∼100% enhancement to the leading-order (LO) result, it is still not large enough to interpret the data; and (c) for the CP-violating asymmetries of B0→π+π− decay, the NLO pQCD predictions for the central values of Aππ and Sππ have the same sign as the data but are still smaller in magnitude than the measured values. We also examined the relative strength of the LO and NLO contributions from different sources.

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Influences of weak disorder on dynamical quantum phase transitions of anisotropic XY chain

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arXiv 2019年

作者： Cao, Kaiyuan Li, Wenwen Zhong, Ming Tong, Peiqing Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

In this paper, the effects of disorder on the dynamical quantum phase transitions (DQPTs) in the transverse-field anisotropic XY chain are studied by numerically calculating the Loschmidt echo after quench. We obtain the formula for calculating the Loschmidt echo of the inhomogeneous system in real space. By comparing the results with that of the homogeneous chain, we find that when the quench crosses the Ising transition, the small disorder will cause a new critical point. As the disorder increases, more critical points of the DQPTs will occur, constituting a critical region. In the quench across the anisotropic transition, the disorder will cause a critical region near the critical point, and the width of the critical region increases by the disordered strength. In the case of quench passing through two critical lines, the small disorder leads to the system to have three additional critical points. When the quench is in the ferromagnetic phase, the large disorder causes the two critical points of the homogeneous case to become a critical region. And for the quench in the paramagnetic phase, the DQPTs will disappear for large disorder. Copyright © 2019, The Authors. All rights reserved.

关键词： Phase transitions