Hadron production near threshold

Final state interaction effects inpp→ pΛK ⁺ andpd →³Heη reactions are explored near threshold to study the sensitivity of the cross-sections to thepΛ potential and theηN scattering matrix. The final state scattering wave functions between Λ andp andη and³He are described rigorously. The Λ production is described by the exchange of one pion and aK-meson between two protons in the incident channel. Theη production is described by a two-step model, where in the first step a pion is produced. This pion then produces anη by interacting with another nucleon     

(K)-nucleus dynamics: from quasibound states to kaon condensation

Coupled-channel (K)N dynamics near threshold and its repercussions in few-body (K)-nuclear systems are briefly reviewed, highlighting studies of a K-pp quasibound state. In heavier nuclei, the extension of mean-field calculations to multi-(K) nuclear and hypernuclear quasibound states is discussed. It is concluded that strangeness in finite self-bound systems is realized through hyperons, with no room for kaon condensation.     

In-flight (K~-,N) Reactions for Study of Kaon-nucleus Interaction

We would like to emphasize that the in-flight (K~-,N) reactions are particularly useful for the study of the K-nucleus interaction.Since the reaction mechanism is well known,there is little ambiguity to derive the K-nucleus interaction from the measured missing mass spectra.Here we discuss the missing mass spectra of the (K~-,N) reactions on the ~(12)C and ~(16)O targets.The spectra show an appreciable amount of strength below the K-nucleus threshold which indicates that the K-nuclear potential is strongly attractive.Comparison of the missing mass spectra with theoretical calculations leads to a potential depth of around-190 MeV for the ~(12)C(K~-,n) reaction.A less deep potential of around-160 MeV reproduces well that of the ~(12)C(K~-,p) reaction.The difference can be due to isospin dependence of the interaction.Our data show that the K-nucleus potential is very deep to realize kaon condensation in the core of neutron stars.     

Strong isospin violation andη−π mixing in |ΔS|=1 weak transition

We consider the effects ofη−π mixing on the violation of the |ΔI|=1/2 rule in |ΔS|=1 weak transitions. The processes considered are theK→2π,K→3π, Λ, Ξ and Λ hyperon decays.     

Applying Bayesian neural networks to identify pion, kaon and proton in BES Ⅱ

The Monte-Carlo samples of pion, kaon and proton generated from 0.3 GeV/c to 1.2 GeV/c by the 'tester' generator from SIMBES which are used to simulate the detector of BES Ⅱ are identified with the Bayesian neural networks (BNN). The pion identification and misidentification efficiencies are obviously better at high momentum region using BNN than the methods of X2 analysis of dE/dX and TOF information.The kaon identification and misidentification efficiencies are obviously better from 0.3 GeV/c to 1.2 GeV/c using BNN than the methods of X2 analysis. The proton identification and misidentification efficiencies using BNN are basically consistent with the ones of X2 analysis. The anti-proton identification and misidentification efficiencies are better below 0.6 GeV/c using BNN than the methods of X2 analysis.     

Hyperon production in pp collisions

We report on a study of the proton induced hyperon production reactions. We discuss the theoretical efforts made towards understanding the existing data and the uncertainties involved in the calculations. Our recent calculations of the missing mass spectra for the pp → K ⁺ Λp reaction which involve a proper coupled channel treatment of the final state Λp interaction are presented. Significant differences in the results using different models of the hyperon-nucleon interaction are found.     

奇异强子与核子的相互作用

包含s夸克的强子称为奇异强子,它与核子相互作用的研究近年来有了长足发展 .在指出这种研究的重要意义后,从实验和理论两方面介绍奇异强子 (主要是K介子和超子 )与核子相互作用的研究现状及方法等 ,包括运动学和动力学机制、介子交换模型和夸克模型解释诸方面的问题. We try to highlight some of the key issues regarding the interactions between strange hadron and nucleon, which relate to the kinematics and dynamics mechanism, meson exchange model and quark model. Starting from a brief introduction on the main research goals, we focus on the status of experimental and theoretical investigations of kaon nucleon and hyperon nucleon interactions, which may be considered to be a necessary basis for the studies of nuclear physics with strangeness.     

中性K介子系统唯象理论的修正

研究中性K介子系统的唯象理论,传统上采用的是建立在Wigner–Weisskopf近似基础上的有效哈密顿量理论.为了对此系统进行更精确地描述,采用了不作Wigner–Weisskopf近似的态演化矩阵,得到了描述此系统CP和CPT破坏的4个复参数(有效哈密顿量理论用2个复参数描述),并估计出实验精确到10^－14时,必须采用这种严格地描述,而不能再近似用有效哈密顿量理论.     

Constraints of unparticle physics parameters from K^0-^-K^0 mixing

The neutral kaon meson mixing plays an important role in the test of the Standard Model （SM） and new physics beyond it. Scale invariant unparticle physics induces a flavor changing neutral current （FCNC） transition of m K^0-^-K^0 oscillation at the tree level. In this study, we investigate the scale invariant unparticle physics effects on the m K^0-^-K^0 mixing. Based on the current experimental data, we give constraints of m K0-K0 mixing on the unparticle parameters.     

Generalized form factors and spin structures of the kaon

We investigate the spin structure of the kaon, based on the nonlocal chiral quark model from the instanton vacuum. We first revisit the electromagnetic form factors of the pion and kaon, improving the results for the kaon. We evaluate the generalized tensor form factors of the kaon in order to determine the probability density of transversely polarized quarks inside the kaon. We consider the effects of flavor SU(3) symmetry breaking, so that the probability density of the up and strange quarks are examined in detail. It is found that the strange quark behaves differently inside the kaon in comparison with the up quark.