We perform a detailed Regge analysis of NN , πN , KN , ππ and πK scattering. From it, we find expressions that represent the ππ scattering amplitudes with an accuracy of a few percent, for exchange of isospin zero, and ∼ 15% for exchange of isospin 1, and this for energies s > 1.4GeV and for momentum transfers |t| < ∼ 0.4GeV. These Regge formulas are perfectly compatible with the low energy (s ...

We describe the present status of the pion distribution amplitude as originated from two sources: (i) a nonperturbative approach, based on QCD sum rules with nonlocal condensates, and (ii) a NLO QCD analysis of the CLEO data on Fγγ ∗π(Q2), supplemented by the E791 data on diffractive dijet production, and the JLab F(pi) data on the pion electromagnetic form factor. 1. PION DISTRIBUTION AMPLITUD...

We study the pion structure function in nuclear medium using the Nambu and JonaLasinio model, and its implication for the nuclear pion enhancement of the sea quark distribution in nuclei. By using the operator product expansion, medium effect of the nuclear matter is incorporated in calculations of the twist-2 operators. We find density dependence of the pion structure function is rather weak a...

The off–shell electromagnetic vertex function of pions and kaons is studied in a bosonized Nambu–Jona-Lasinio model with a gauge–invariant proper–time cutoff. The slope of the pion form factor with respect to the pion 4–momentum is equal to the on–shell pion charge radius in the chiral limit. The off–shell slope of the K form factor is zero, that of the K about 15% smaller than that of the pion...

We analyse pion–nucleus reactions in a microscopic transport model of the BUU type, which propagates nucleons, pions, deltas and N (1440)-resonances explicitly in space and time. In particular we examine pion absorption and inelastic scattering cross sections for pion kinetic energies T π = 85 − 315M eV and various target masses. In general, the mass–dependence of the experimental data is well ...

We propose a theory which exploits the charge-exchange reactions (3He,3Hπ+) and (p,nπ+) as effective sources of virtual pions. We consider processes in which the creation of virtual pions is followed by conventional coupled-channel pion scattering to discrete nuclear states. This picture allows us to incorporate successful theories of pion scattering and utilize virtual pions as probes of the n...

After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion–pion scattering to two–loop accuracy. In the pion–nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy–nucleon expansion is used to construct the effective pion...

snn = 17GeV a sudden increase in the pion source volume is observed for central PbPb collisions. This seems to imply that the pion phase density has reached a limit. The source size of different particles decreases with mass when the transverse velocity is held constant but increases with mass when mT is held constant. The antiproton source radius is larger than the proton source radius. So far...

Results of the computer simulation of dilepton production from the expanding pion gas created in ultrarelativistic Pb+Pb 160 GeV/n collisions are presented. Finite size of the expanding pion gas influences invariant mass spectrum of dileptons. Sensitivity of the shape of dilepton mass spectrum to the initial stage of the pion gas is discussed. Second order asymmetry in azimuthal distribution of...

To explain the production of light nuclei in heavy-ion collisions at extreme energies, we focus on deuteron case. A Gibbs ensemble chemical freeze-out is a prerequisite to investigate non-equilibrium evolution expanding fireball. Quantum statistical approaches allow describe correlations including bound state formation strongly interacting and hot system. We consider virial approach evaluate pr...