461 research outputs found
Fermi motion and nuclear modification factor
It has been argued recently that the so-called nuclear modification factor
() is an observable useful for identifying the quark-gluon plasma. We
discuss the effect of Fermi motion in nuclei on at CERN SPS and BNL
RHIC energies. Contrary to the simple intuition, rather large effects are found
for CERN SPS. The Fermi motion in nuclei contributes significantly to the
Cronin effect. The effect found is qualitatively similar to the one observed
experimentally at CERN energies and similar to the one obtained in the models
of multiple scattering of initial partons. We predict different size of the
effect for different types of hadrons, especially at low energies.Comment: 16 pages + 6 figures, some calculations have been corrected, text has
been modified accordingly, 1 figure has been added, in print Modern Physics
Letters A19 (2004)
Multifragmentation and nuclear phase transitions (liquid-fog and liquid-gas)
Thermal multifragmentation of hot nuclei is interpreted as the nuclear
liquid-fog phase transition. The charge distributions of the intermediate mass
fragments produced in p(3.6 GeV) + Au and p(8.1 GeV) + Au collisions are
analyzed within the statistical multifragmentation model with the critical
temperature for the nuclear liquid-gas phase transition Tc as a free parameter.
The analysis presented here provides strong support for a value of Tc > 15 MeV.Comment: 4 pages, 2 figures, Submittet to Proc. of NN2003 to be published in
Nucl. Phys.
Multifragmentation in Collisions of 4.4gev-Deuterons with Gold Target
The relative velocity correlation function of pairs of intermediate mass
fragments has been studied for d+Au collitions at 4.4 GeV. Experimental
correlation functions are compared to that obtained by multibody Coulomb
trajectory calculations under the assumption of various decay timees of the
fragmenting system. The combined approach with the empirically modified
intranuclear cascade code followed by the statistical multifragmentation model
was used to generate the starting conditions for these calculations. The
fragment emossion time is found to be less than 40 fm/c.Comment: Accepted for publication in Bulletin of the Russian Academy of
Sciences. Physic
Investigation of large angle elastic and inelastic alpha particles scattering on Si isotopes
The distributions of differential cross sections for backward angles in
case of three (28,20,3OSi) silicon isotopes were measured for five energies
around 27 MeV. The comparison between existing data and measured
data was done. Quantitative analysis of the data was made
Elastic scattering of 27.5 MeV alpha particles on Al, Si, S, Ti and Co nuclei and the discrete ambiguity of the optical potential
Angular distributions for elastic scattering of alpha particles on Al, Si, S, Ti and Co nuclei have been measured in the angular range from about 20 to 179 (LAB). The experimental data were fitted with the optical model in full angular range. Many sets of four-parameter potentials, describing the elastic scattering, were found with the depths of the real part ranging from 40 to 450 MeV. A new discrete ambiguity in the optical model namely in was observed
On the SigmaN cusp in the pp -> pK+Lambda reaction
Measurements of the reaction at = 2.28 GeV have
been carried out at COSY-TOF. In addition to the FSI and
resonance excitation effects a pronounced narrow structure is observed in the
Dalitz plot and in its projection on the -invariant mass. The
structure appears at the N threshold and is interpreted as
N cusp effect. The observed width of 20 MeV/ is substantially
broader than anticipated from previous inclusive measurements. Angular
distributions of this cusp structure are shown to be dissimilar to those in the
residual channel, but similar to those observed in the
channel
Cross section of the reaction close to threshold
We have measured inclusive data on -meson production in collisions
at COSY J\"ulich close to the hyperon production threshold and determined the
hyperon-nucleon invariant mass spectra. The spectra were decomposed into three
parts: , and . The cross section for the
channel was found to be much smaller than a previous measurement in
that excess energy region. The data together with previous results at higher
energies are compatible with a phase space dependence.Comment: accepted by Phys. lett. B some typos correcte
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