247 research outputs found
Mini-clusters
Experimental results of mini-clusters observed in Chacaltaya emulsion chamber no.19 are summarized. The study was made on 54 single core shower upper and 91 shower clusters of E(gamma) 10 TeV from 30 families which are visible energy greater than 80 TeV and penetrate through both upper and lower detectors of the two-story chamber. The association of hadrons in mini-cluster is made clear from their penetrative nature and microscopic observation of shower continuation in lower chamber. Small P sub t (gamma) of hadrons in mini-clusters remained in puzzle
Event-by-Event Search for Charged Neutral Fluctuations in Pb - Pb Collisions at 158-A-GeV
Results from the analysis of data obtained from the WA98 experiment at the
CERN SPS have been presented. Some events have been filtered which show photon
excess in limited zones within the overlap region of the charged
particle and photon multiplicity detectors.Comment: 6 pages, 4 figure
Pseudovector vs. pseudoscalar coupling in one-boson exchange NN potentials
We examine the effects of pseudoscalar and pseudovector coupling of the pi
and eta mesons in one-boson exchange models of the NN interaction using two
approaches: time-ordered perturbation theory unitarized with the relativistic
Lippmann-Schwinger equation, and a reduced Bethe-Salpeter equation approach
using the Thompson equation. Contact terms in the one-boson exchange amplitudes
in time-ordered perturbation theory lead naturally to the introduction of
s-channel nucleonic cutoffs for the interaction, which strongly suppresses the
far off-shell behavior of the amplitudes in both approaches. Differences
between the resulting NN predictions of the various models are found to be
small, and particularly so when coupling constants of the other mesons are
readjusted within reasonable limits.Comment: 24 pages, 4 figure
Dissipation, noise and DCC domain formation
We investigate the effect of friction on domain formation in disoriented
chiral condensate. We solve the equation of motion of the linear sigma model,
in the Hartree approximation, including a friction and a white noise term. For
quenched initial condition, we find that even in presence of noise and
dissipation domain like structure emerges after a few fermi of evolution.
Domain size as large as 5 fm can be formed.Comment: 7 pages, 3 figure
Threshold meson production and cosmic ray transport
An interesting accident of nature is that the peak of the cosmic ray
spectrum, for both protons and heavier nuclei, occurs near the pion production
threshold. The Boltzmann transport equation contains a term which is the cosmic
ray flux multiplied by the cross section. Therefore when considering pion and
kaon production from proton-proton reactions, small cross sections at low
energy can be as important as larger cross sections at higher energy. This is
also true for subthreshold kaon production in nuclear collisions, but not for
subthreshold pion production.Comment: 9 pages, 1 figur
Effect of friction on disoriented chiral condensate formation
We have investigated the effect of friction on the DCC domain formation. We
solve the Newton equation of motion for the O(4) fields, with quenched initial
condition. The initial fields are randomly distributed in a Gaussian form. In
one dimensional expansion, on the average, large DCC domains can not be formed.
However, in some particular orbits, large instabilities may occur. This
possibility also greatly diminishes with the introduction of friction. But, if
the friction is large, the system may be overdamped and then, there is a
possibility of large DCC domain formation in some events.Comment: 9 pages, including figure
Model of Centauro and strangelet production in heavy ion collisions
We discuss the phenomenological model of Centauro event production in
relativistic nucleus-nucleus collisions. This model makes quantitative
predictions for kinematic observables, baryon number and mass of the Centauro
fireball and its decay products. Centauros decay mainly to nucleons, strange
hyperons and possibly strangelets. Simulations of Centauro events for the
CASTOR detector in Pb-Pb collisions at LHC energies are performed. The
signatures of these events are discussed in detail.Comment: 19 pages, LaTeX+revtex4, 14 eps-figures and 3 table
Strangelet spectra from type II supernovae
We study in this work the fate of strangelets injected as a contamination in
the tail of a "strange matter-driven" supernova shock. A simple model for the
fragmentation and braking of the strangelets when they pass through the
expanding oxygen shell is presented and solved to understand the reprocessing
of this component. We find that the escaping spectrum is a scaled-down version
of the one injected at the base of the oxygen shell. The supernova source is
likely to produce low-energy particles of quite independently
of the initial conditions. However, it is difficult that ultrarrelativistic
strangelets (such as the hypothetical Centauro primaries) can have an origin in
those explosive events.Comment: RevTex file, 5 pp., no figure
Multiplicity Distributions of Squeezed Isospin States
Multiplicity distributions of neutral and charged particles arising from
squeezed coherent states are investigated. Projections onto global isospin
states are considered. We show how a small amount of squeezing can
significantly change the multiplicity distributions. The formalism is proposed
to describe the phenomenological properties of neutral and charged particles
anomalously produced in hadronic and nuclear collisions at very high energies.Comment: 17 pages, 6 figures sent upon request ([email protected]
Time evolution of the chiral phase transition during a spherical expansion
We examine the non-equilibrium time evolution of the hadronic plasma produced
in a relativistic heavy ion collision, assuming a spherical expansion into the
vacuum. We study the linear sigma model to leading order in a large-
expansion. Starting at a temperature above the phase transition, the system
expands and cools, finally settling into the broken symmetry vacuum state. We
consider the proper time evolution of the effective pion mass, the order
parameter , and the particle number distribution. We
examine several different initial conditions and look for instabilities
(exponentially growing long wavelength modes) which can lead to the formation
of disoriented chiral condensates (DCCs). We find that instabilities exist for
proper times which are less than 3 fm/c. We also show that an experimental
signature of domain growth is an increase in the low momentum spectrum of
outgoing pions when compared to an expansion in thermal equilibrium. In
comparison to particle production during a longitudinal expansion, we find that
in a spherical expansion the system reaches the ``out'' regime much faster and
more particles get produced. However the size of the unstable region, which is
related to the domain size of DCCs, is not enhanced.Comment: REVTex, 20 pages, 8 postscript figures embedded with eps
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