Strange Meson Photo-production and Its Associated Radiative Capture on Proton in Low-Energy QCD Lagrangian

Based on the low energy QCD Lagrangian theory and the crossing symmetry relation, strange meson photoproduction and its associated radiative capture on the proton are investigated in the [SUSF（6） × O（3）]sym . × SUc（3） quark mode/of baryon structure with only one same input parameter, the only strong coupling constant aM. Calculations for the cross sections, p-polarization of γ ＋ P → K^＋ ＋ A reaction and the branching ratios for K^- radiative capture of K^- ＋ p → γ ＋ Y with Y = A, ∑^0 are performed. Good agreements to data are obtained and the results show that, compared to traditional phenomenological models, the low energy QCD Lagrangian theory provides a successful, unifled description of the strange meson photo-production and its associated radiative capture.

Excited state mass spectra, decay properties and Regge trajectories of charm and charm-strange mesons

The framework of a phenomenological quark-antiquark potential（Coulomb plus linear confinement）model with a Gaussian wave function is used for detailed study of masses of the ground, orbitally and radially excited states of heavy-light Qq^-,（Q=c,q=u/d,s） mesons. We incorporate a O（1/m） correction to the potential energy term and relativistic corrections to the kinetic energy term of the Hamiltonian. The spin-hyperfine, spin-orbit and tensor interactions incorporating the effect of mixing are employed to obtain the pseudoscalar, vector, radially and orbitally excited state meson masses. The Regge trajectories in the（J,M^2） and（nr,M^2） planes for heavy-light mesons are investigated with their corresponding parameters. Leptonic and radiative leptonic decay widths and corresponding branching ratios are computed. The mixing parameters are also estimated. Our predictions are in good agreement with experimental results as well as lattice and other theoretical models.

Hyperon coupling dependence of hadron matter properties in relativistic mean field model

The properties of hadronic matter at β equilibrium in a wide range of densities are described by appropriate equations of state in the framework of the relativistic mean field model. Strange meson fields, namely the scalar meson field σ＊（975） and the vector meson field φ（1020）, are included in the present work. We discuss and compare the results of the equation of state, nucleon effective mass, and strangeness fraction obtained by adopting the TM1, TMA, and GL parameter sets for nuclear sector and three different choices for the hypcron couplings. We find that the parameter set TM1 favours the onset of hyperons most, while at high densities the GL parameter set leads to the most hyperon-rich matter. For a certain parameter set （e.g. TM1）, the most hyperon-rich matter is obtained for the hyperon potential model. The influence of the hyperon couplings on the effective mass of nucleon, is much weaker than that on the nucleon parameter set. The nonstrange mesons dominate essentially the global properties of dense hyperon matter. The hyperon potential model predicts the lowest value of the neutron star maximum mass of about 1.45 Msun to be 0.4--0.5 Msun lower than the prediction by using the other choices for hyperon couplings.

Study of excited D_s mesons

The spectrum of D s mesons is systematically studied in a semi-classic mass loaded flux tube model.D s in D-wave multiplets is predicted to have lower masses in comparison with most theoretical predictions.D sJ （2632） ＋,D s1 （2700） ±,D sJ （2860） ＋ and D sJ （3040） ＋ are interpreted in the constituent quark model.

Precision measurements of strangeness photoproduction at threshold energies with the Crystal Ball at MAMI-C

The photoproduction of K＋ mesons from the nucleon provides important constraints on the nucleon excitation spectrum and at threshold energies challenges effective field theories based on chiral perturbation in the strange quark sector. Preliminary cross-section measurements for γ（P, K＋）A are presented at an unprecedented beam energy resolution. The data was collected at the MAMI-C facility in Mainz using the Crystal Ball Detector. A new method of K＋ detection was used in which the K＋ is tagged from its weak decay products in the detector crystals. This technique has application with other calorimeters at present and future hadron facilities.

Possible hadronic molecular states composed of S-wave heavy-light mesons

We perform a systematical study of possible molecular states composed of the S wave heavy light mesons,where the S–D mixing and η-η＇ mixing are explicitly included.Our calculation indicates that the observed X（3872） could be a loosely shallow molecular state composed of D＊＋ h.c,while neither Z_c（3900）/Z_c（4020） nor Z_b（10610）/Z_b（10650） is supported to be a molecule.Some observed possible molecular states are predicted,which could be searched for by further experimental measurements.

Near-threshold K^*(892)^+ meson production in the interaction of π−mesons with nuclei

We study the inclusive production of strange vector K^∗(892)^+ mesons in π−A reactions at near-threshold laboratory incident pion momenta of 1.4-2.0 GeV/c via a nuclear spectral function approach.The approach accounts for incoherent primary π−meson-proton π−p→K^∗(892)^+Σ^− production processes as well as the influence of the scalar K^∗(892)^+-nucleus potential(or the K^∗(892)^+ in-medium mass shift)on these processes.We calculate the absolute differential and total cross sections for the production of K∗(892)+mesons from carbon and tungsten nuclei at laboratory angles of 0∘-45∘and at the aforementioned momenta in five scenarios for the aforenoted shift.We show that the K^∗(892)^+ momentum distributions and their excitation functions(absolute and relative)possess a high sensitivity to changes in the in-medium K^∗(892)^+ mass shift in the low-momentum region of 0.1-0.6 GeV/c.Therefore,the measurement of such observables in a dedicated experiment at the GSI pion beam facility in the near-threshold momentum domain will allow us to get valuable information on the K^∗(892)^+ in-medium properties.

D and D_s in mass loaded flux tube

Heavy-light hadrons are studied in a mass loaded flux tube model. The study indicates that the dynamics of mesons and baryons containing a c quark is described well by the mass loaded flux tube. The hypothesis of good diquark-antiquark degeneracy is found reasonable in heavy-light quark systems. The spectrum of charmed （D） and charmed strange （Ds） mesons is systematically computed. D and Ds in 1D multiplets are predicted to have lower masses in comparison with other theoretical predictions. The predicted masses of the 1（13D1） and the 3（13D3） Ds agree well with those of recently observed Ds1（2700）± and DsJ（2860）, respectively.

Effects of σ*and φ on the proto-neutron star PSR J0348+0432

The influence ofσ＊andφon the proto-neutron star（PNS）PSR J0348＋0432 is described by the relativistic mean field theory（RMFT）through choosing effective coupling constants.We use an entropy per baryon S=1 to describe the thermal effects on PSR J0348＋0432 in this work and compare this PNS with and withoutσ＊,φ.These effects include the particle number distribution,mass-radius relation,moment of inertia and surface gravitational redshift.The PNS PSR J0348＋0432 withσ＊andφhas more nucleons and will push forward the threshold for the appearance of the hyperons.The mass-radius relations are（2.010M,12.6520 km）withσ＊andφand（2.010M,12.6170 km）withoutσ＊andφ.The moments of inertia corresponding to PNS PSR J0348＋0432are（2.010M,1.510×10^45g·cm^2）and（2.010M,1.559×10^45g·cm^2）respectively,and the surface gravitational redshifts are（2.010M,0.3747）and（2.010M,0.3701）respectively.With the help of these calculations,we study the restriction ofσ~＊andφon the interactions between baryons in the PNS core.

The ■_(s)^(0)→J/ψπ^(0)η decay and the a_(0)(980)-f_(0)(980) mixing

We study the ■_(s)^(0)→J/ψf_(0)(980) and ■_(s)^(0)→J/ψa_(0)(980) reactions,and pay attention to the different sources of iso spin violation and mixing of f_(0)(980) and a_(0)(980) resonances where these resonances are dynamically generated from meson-meson interactions.We find that the main cause of isospin violation is isospin breaking in the meson-meson transition T matrices,and the other source is that the loops involving kaons in the production mechanism do not cancel due to the different masses of charged and neutral kaons.We obtain a branching ratio for a_(0)(980)production of the order of 5×10^(-6).Future experiments can address this problem,and the production rate and shape of the π^(0)η mass distribution will definitely help to better understand the nature of scalar resonances.