Particle production in nuclear collisions from pQCD

Particle production is calculated in high-energy proton-proton and nuclear collisions. Non-perturbative ingredients are reviewed. Fragmentation function uncertainties and the transverse momentum dependence of parton distributions are studied. Perturbative QCD results are compared to data.     

Covariant change of signature in classical relativity

This paper gives a covariant formalism enabling investigation of the possibility of change of signature in classical General Relativity, when the geometry is that of a Robertson-Walker universe. It is shown that such changes are compatible with the Einstein field equations, both in the case of a barotropic fluid and of a scalar field. A criterion is given for when such a change of signature should take place in the scalar field case. Some examples show the kind of resulting exact solutions of the field equations.     

Particle production in curved spacetime

Particle production in curved spacetime has been discussed through the method of complex time WKB approximation. We consider Dirac equation in non-flat spacetime to understand particle production as particle-antiparticle rotation. The method is also generalized to understand particle production through parametric resonance. To understand the method of CWKB we consider particle production in Kasner spacetime as an example.     

Particle production at high gluon density: from ep to AA

We review the physics of gluon saturation and some of its phenomenological applications.     

Particle production in hadron-nucleus collisions at 100 GeV from a parton-string model

We calculate the inclusive momentum distribution of particles produced in a hadron-nucleus (hA) collision. The exchange of colour between the projectile and target nucleons leads to the formation of colour strings which are assumed to fragment like strings formed in deep inelastic lepton-nucleon scattering. Making a few basic hypotheses we consistently and parameterfree describe the projectile fragmentation region in collisions of the typehA→h′X withh=p, π⁺ andh′=p, π⁺, π^? at 100 GeV incident energy.     

Particle production in higher derivative theory

The effect of particle production on the evolution of the spatially flat Friedmann-Lemaitre-Robertson-Walker cosmological model during the early stages of the universe is analysed in the framework of higher derivative theory. The universe has been considered as an open thermodynamic system where particle production gives rise to a supplementary negative creation pressure in addition to the thermodynamic pressure. The dynamical behaviour of both exponential as well as power law solutions have been discussed.     

Particle production in high-energy hadron-nucleus interactions

The pseudorapidity (η) distributions of fast particles (β>0.7) emitted in inelastic hadron interactions with carbon, copper and lead were measured for incoming energies from 50 to 150GeV at the CERN Super Proton Synchrotron. Their dependence on target mass (A) and projectile (h) obeys <v>-scaling as expected. Their energy dependence is in contrast with most model predictions.     

Particle production at large transverse momentum

From a simple fragmentation approach to inelastic production at large fixed angles, we obtain an inclusive cross-section which falls as an inverse power of large transverse momentum p_T and which scales according to (p_T/√s), both consistent with ISR data. Predictions for charge ratios and associated multiplicities are also presented and compared with available data.     

Particle production by the Čerenkov mechanism

The rate of electron-positron pair creation and rho-meson creation by uniformly moving charges in condensed matter is calculated in the framework of the Schwinger source theory.