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ργ*→π(ρ) transition form factors in the perturbative QCD factorization approach

Physical Review D 2015年第9期92卷 094031-094031页

作者： Ya-Lan Zhang Shan Cheng Jun Hua Zhen-Jun Xiao Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu 210023 People’s Republic of China Theoretische Elementarteilchenphysik Naturwissenschaftlich Technische Fakultät Universiät Siegen 57068 Siegen Germany 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 studied the ργ*→π and ργ*→ρ transition processes and made the calculations for the ρπ transition form factor Q4Fρπ(Q2) and the ρ-meson electromagnetic form factors, FLL,LT,TT(Q2) and F1,2,3(Q2), by employing the perturbative QCD (PQCD) factorization approach. For the ργ*→π transition, we found that the contribution to form factor Q4Fρπ(Q2) from the term proportional to the distribution amplitude combination ϕρT(x1)ϕπP(x2) is absolutely dominant, and the PQCD predictions for both the size and the Q2-dependence of this form factor Q4Fρπ(Q2) agree well with those from the extended anti-de Sitter/QCD models or the light-cone QCD sum rule. For the ργ*→ρ transition and in the region of Q2≥3 GeV2, furthermore, we found that the PQCD predictions for the magnitude and their Q2-dependence of the F1(Q2) and F2(Q2) form factors agree well with those from the QCD sum rule, while the PQCD prediction for F3(Q2) is much larger than the one from the QCD sum rule.

关键词： Perturbative quantum chromodynamics Wave functions Factorization method (Quantum theory)

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The semileptonic decays of B/B_s meson in the perturbative QCD approach:a short review

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Chinese Science Bulletin 2014年第29期59卷 3787-3800页

作者： Zhen-Jun Xiao Ying-Ying Fan Wen-Fei Wang Shan Cheng Department of Physics and Institute of Theoretical Physics Nanjing Normal University Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Institute of High Energy Physics and Theoretical Physics Center for Science Facilities Chinese Academy of Sciences

In this short review,we present the current status about the theoretical and experimental studies for some important semileptonic decays of B=*** firstly gave a brief introduction for the experimental measurements for B=Bs!Peltl;l ml;m mT decays,the BaBar’s ReDT and ReD T anomaly,the P05deviation for B0!K 0ltl *** then made a careful discussion about the evaluations for the relevant form factors in the light-cone QCD sum rule,the heavy quark effective theory,and the perturbative QCD factorization *** using the form factors calculated in the perturbative(pQCD)approach,we then calculate and show the pQCD predictions for the decay rates of many semileptonic decays of B=*** also made careful phenomenological analysis for these pQCD predictions and found,in general,the following points:(a)For all the considered B=Bssemileptonic decays,the next-to-leading order pQCD predictions for their decay rates agree well with the data and those from other different theoretical methods;(b)For ReDT and ReD T,the pQCD predictions agree very well with the data,the BaBar’s anomaly of ReDe TT are therefore explained successfully in the standard model by employing the pQCD approach;and(c)We defined several new ratios Rl;s Dand Rl;s Ds,they may be more sensitive to the QCD dynamics which controls the B=Bs!eDe T;De T sT transitions than the old ratios,we therefore strongly suggest LHCb and the forthcoming Super-B experiments to measure these new ratios.

关键词：微扰QCD 衰变率 BS 介子光锥QCD求和规则实验测量评论 QCD因子化

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The effects of the Dzyaloshinskii-Moriya interaction on the ground-state properties of the XY chain in a transverse field

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Chinese Physics B 2013年第9期22卷 285-291页

作者：钟鸣徐卉刘小贤童培庆 Department of Physics and Institute of Theoretical Physics Nanjing Normal University Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University

The effects of the Dzyaloshinski-Moriya （DM） interaction on the ground-state properties of the anisotropic XY chain in a transverse field have been studied by means of correlation functions and entanglement. Different from the case without the DM interaction, the excitation spectra ek of this model are not symmetrical in the momentum space and are not always positive. As a result, besides the ferromagnetic （FM） and the paramagnetic （PM） phases, a gapless chiral phase is induced. In the chiral phase, the von Neumann entropy is proportional to log2 L （L is the length of a subchain） with the coefficient A ~ 1/3, which is the same as that of the XY chain in a transverse field without the DM interaction for 7 = 0 and 0 〈 h 〈 1. And in the vicinity of the critical point between the chiral phase and the FM （or PM） phase, the behaviors of the nearest- neighbor concurrence and its derivative are like those for the anisotropy transition.

关键词： Dzyaloshinskii-Moriya interaction the XY chain in a transverse field quantum entanglement,ground-state properties

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A first-principles study of the structural and elastic properties of orthorhombic and tetragonal Ca_3Mn_2O_7

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Chinese Physics B 2013年第6期22卷 465-471页

作者：张玮童培庆 Department of Physics Institute of Theoretical PhysicsNanjing Normal University Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University

The structural and elastic properties of multiferroic Ca3Mn2O7 with ferroelectric orthorhombic （O-phase） and paraelectric tetragonal structures （T-phase） have been studied by first-principles calculations within the generalized gradient approximation （GGA） and the GGA plus Hubbard U approaches （GGA ＋ U）. The calculated theoretical structures are in good agreement with the experimental values. The T-phase is found to be antiferromagnetic （AFM） and the AFM O-phase is more stable than the T-phase, which also agree with the experiments. On these bases, the single-crystal elastic constants （Cijs） and elastic properties of polycrystalline aggregates are investigated for the two phases. Our elasticity calculations indicate Ca3Mn2O7 is mechanically stable against volume expansions. The AFM O-phase is found to be a ductile material, while the AFM T-phase shows brittle nature and tends to be elastically isotropic. We also investigate the influence of strong correlation effects on the elastic properties, qualitatively consistent results are obtained in a reasonable range of values of U. Finally, the ionicity is discussed by Bader analysis. Our work provides useful guidance for the experimental elasticity measurements of Ca3Mn2O7, and makes the strain energy calculation in multiferroic Ca3Mn2O7 thin films possible.

关键词： elastic constant elastic anisotropy strong correlation effect multiferroic

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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.

关键词： YANG-Baxter equation QUARKS WAVE functions MESONS PARTICLE physics

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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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Feedback control of wave segments in an excitable medium

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Chinese Physics B 2013年第5期22卷 187-190页

作者：吴宁杰高洪俊应和平 Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems School of Mathematical SciencesNanjing Normal University Institute of Modern Physics and Department of Physics Zhejiang University

Depending on the excitability of the medium, a propagating wave segment will either contract or expand to fill the medium with spiral waves. This paper aims to introduce a simple mechanism of feedback control to stabilize such an expansion or contraction. To do this, we lay out a feedback control system in a block diagram and reduce it into a bare, universal formula. Analytical and experimental findings are compared through a series of numerical simulations of the Barkley model.

关键词： feedback control wave segments excitable medium

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Theoretical study of a d* resonance in the coupled 3D3−3G3 partial waves of nucleon-nucleon scattering

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Physical Review C 2014年第6期90卷 064003-064003页

作者： Hongxia Huang Jialun Ping Chengrong Deng Fan Wang Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 China School of Mathematics and Physics Chongqing Jiaotong University Chongqing 400074 China Department of Physics Nanjing University Nanjing 210093 China

We calculated the phase shifts of the coupled 3D3−3G3 partial waves of nucleon-nucleon scattering taking into account the 7S3 Δ−Δ channel coupling in the framework of two constituent quark models: the quark delocalization color screening model and the chiral quark model. Our results show that there is a resonance from 7S3ΔΔ coupling to the 3D3NN and 3G3NN partial waves in both of these two models, which is consistent with the d* resonance observed by WASA-at-COSY collaboration. The resonance structure in the 3D3NN partial wave is remarkable, whereas in the 3G3NN phase shifts there is only a small bump around the resonance energy. This result is in agreement with the recent experimental results of WASA-at-COSY Collaboration.

关键词： NUCLEON-nucleon scattering NEUTRON resonance QUARK models DELOCALIZATION energy QUANTUM chromodynamics

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B¯s0→Kπ,KK decays and effects of the next-to-leading order contributions

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Physical Review D 2014年第7期89卷 074046-074046页

作者： Jing-Jing Wang Dong-Ting Lin Wen Sun Zhong-Jian Ji Shan Cheng Zhen-Jun Xiao Department of Physics 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

By employing the perturbative QCD (pQCD) factorization approach, we calculate the branching ratios and charge parity (CP)-violating asymmetries of the four B¯s0→Kπ and KK decays, with the inclusion of all known next-to-leading order (NLO) contributions. We find numerically that (a) the NLO contribution can interfere with the leading order (LO) part constructively or destructively for different decay modes; (b) the NLO contribution leads to a 22% decrease for the central values of the LO pQCD prediction for Br(B¯s0→K+π−), but ∼50% enhancement to the other three considered B¯s decays, the agreement between the central values of the pQCD predictions and the data are therefore improved effectively after the inclusion of the NLO contributions; (c) for both B¯s0→K+π− and B¯s0→K+K− decays, the NLO pQCD predictions for the direct and mixing induced CP-violating asymmetries agree well with the measured values in both the sign and the magnitude; and (d) the theoretical errors of the pQCD predictions for decay rates are about 35% of the cental values and larger than that of the relevant data.

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NLO twist-3 contributions to B→π form factors in kT factorization

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Physical Review D 2014年第9期89卷 094004-094004页

作者： Shan Cheng Ying-Ying Fan Xin Yu Cai-Dian Lü Zhen-Jun Xiao Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu 210023 People’s Republic of China Institute of High Energy Physics and Theoretical Physics Center for Science Facilities Chinese Academy of Sciences Beijing 100049 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 calculate the next-to-leading-order (NLO) twist-3 contribution to the form factors of B→π transitions by employing the kT factorization theorem. All the infrared divergences regulated by the logarithms ln(kiT2) cancel between those from the quark diagrams and from the effective diagrams for the initial B meson wave function and the final pion meson wave function. An infrared finite NLO hard kernel is, therefore, obtained, which confirms the application of the kT factorization theorem to the B meson semileptonic decays at the twist-3 level. From our analytical and numerical evaluations, we find that the NLO twist-3 contributions to the form factors f+,0(q2) of the B→π transition are similar in size but have an opposite sign with the NLO twist-2 contribution, which leads to a large cancellation between these two NLO parts. For the case of f+(0), for example, the 24% NLO twist-2 enhancement to the full LO prediction is largely canceled by the negative (about −17%) NLO twist-3 contribution, leaving a small and stable 7% enhancement to the full LO prediction in the whole range of 0≤q2≤12 GeV2. At the full NLO level, the perturbative QCD prediction is FB→π(0)=0.269−0.050+0.054. We also study the possible effects on the perturbative QCD predictions when different sets of the B meson and pion distribution amplitudes are used in the numerical evaluation.

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