arXiv subjects

A. P. Vischer

Publications and source records attributed to A. P. Vischer.

7 recordsLinked to original sources

arXiv1997

Charmlets

We discuss the possibility, that multiply charmed exotics are produced in ultrarelativistic heavy ion collisions. Production probabilities at RHIC are estimated and found to be large enough to allow for the possible detection of single and double charmed exotics. We demonstrate that charm matter is bound due to an attractive one-gluon exchange potential. Furthermore, we study the color magnetic and color electric potential separately, as well as the group structure of such exotics and estimate their masses.

nucl-th↗

arXiv1997

The Phase in Three-Pion Correlations

We discuss the complex phase generated in three pion correlation functions. The lowest order contribution to the phase is of order $q^2 R/K$, where $q$ is a typical relative momentum, $K$ is a typical center of mass momentum and $R$ is a typical radius parameter. This contribution is of purely kinematic origin. At next order we find a generic contribution of order $(qR)^3$ which is a result of odd modifications to the source emission function. We argue, that the scale for typical HBT correlations in ultrarelativistic heavy ion collisions is $q/K \ll qR \sim 1$, so that the third order correction actually dominates the phase in the experimentally relevant momentum range. We study in detail such contributions which arise from source asymmetries generated by flow, the source geometry and resonance decays.

nucl-th↗

arXiv1997

Bose-Einstein Correlations from Opaque Sources

Bose-Einstein correlations in relativistic heavy ion collisions are very different for opaque sources than fortransparent ones. The Bose-Einstein radius parameters measured in two-particle correlation functions depend sensitively on the mean free path of the particles. In particular we find that the outward radius for an opaque source is smaller than the sidewards radius for sufficiently short duration of emission. A long duration of emission can compensate the opacity reduction of the longitudinal radius parameter and explain the experimental measurements of very similar side- and outward radius parameters.

nucl-th↗

arXiv1997

Fluctuations and HBT Scales in Relativistic Nuclear Collisions

Bose-Einstein correlations in relativistic heavy ion collisions are examined in a general model containing the essential features of hydrodynamical, cascade as well as other models commonly employed for describing the particle freeze-out. In particular the effects of longitudinal and transverse expansion, emission from surfaces moving in time, the thickness of the emitting layer varying from surface to volume emission and other effects are studied. Model dependences of freeze-out sizes and times are discussed and compared to recent $Pb+Pb$ data at 160A$\cdot$GeV.

nucl-th↗

arXiv1996

Many--Particle Correlations in Relativistic Nuclear Collisions

Many--particle correlations due to Bose-Einstein interference are studied in ultrarelativistic heavy--ion collisions. We calculate the higher order correlation functions from the 2--particle correlation function by assuming that the source is emitting particles incoherently. In particular parametrizations of and relations between longitudinal, sidewards, outwards and invariant radii and corresponding momenta are discussed. The results are especially useful in low statistics measurements of higher order correlation functions. We evaluate the three--pion correlation function recently measured by NA44 and predict the 2--pion--2--kaon correlation function. Finally, many particle Coulomb corrections are discussed.

nucl-th↗

arXiv1996

Nucleation of Quark--Gluon Plasma Droplets

The energy densities achieved during central collisions of large nuclei at the AGS may be high enough to allow the formation of quark--gluon plasma. We propose that most collisions at AGS energies produce superheated hadronic matter, but in rare events a droplet of quark--gluon plasma is nucleated. We estimate the probability of this to occur based on homogeneous and inhomogeneous nucleation theory and discuss possible experimental signals.

nucl-th↗

arXiv1994

Nucleation of Quark--Gluon Plasma from Hadronic Matter

The energy densities achieved during central collisions of large nuclei at Brookhaven's AGS may be high enough to allow the formation of quark--gluon plasma. Calculations based on relativistic nucleation theory suggest that rare events, perhaps one in every 10$^2$ or 10$^3$, undergo the phase transition. Experimental ramifications may include an enhancement in the ratio of pions to baryons, a reduction in the ratio of deuterons to protons, and a larger source size as seen by hadron interferometry.

nucl-th↗