291 research outputs found
Strong polarization of the residual nucleus in a heavy-ion induced transfer reaction
A strong polarization of 20Ne levels has been observed in the 16O(16O, 12C)20Ne* reaction along an axis perpendicular to the reaction plane. This polarization differs from that reported in the (7Li, t) reaction, when the same nuclear levels were populated. D.W.B.A. calculations which fitted both angular distributions and polarization in the (7Li, t) reaction and which can also describe the (16O, 12C) angular distributions fail to reproduce the associated 20Ne* polarization
Lambda^0 polarization as a probe for production of deconfined matter in ultra-relativistic heavy-ion collisions
We study the polarization change of Lambda^0's produced in ultra-relativistic
heavy-ion collisions with respect to the polarization observed in proton-proton
collisions as a signal for the formation of a Quark-Gluon Plasma (QGP).
Assuming that, when the density of participants in the collision is larger than
the critical density for QGP formation, the Lambda^0 production mechanism
changes from recombination type processes to the coalescence of free valence
quarks, we find that the Lambda^0 polarization depends on the relative
contribution of each process to the total number of Lambda^0's produced in the
collision. To describe the polarization of Lambda^0's in nuclear collisions for
densities below the critical density for the QGP formation, we use the
DeGrand-Miettinen model corrected for the effects introduced by multiple
scattering of the produced Lambda^0 within the nuclear environment.Comment: 9 pages, 6 figures, uses ReVTeX and epsfig.st
First performance studies of a prototype for the CASTOR forward calorimeter at the CMS experiment
We present results on the performance of the first prototype of the CASTOR quartz-tungsten sampling calorimeter, to be installed in the very forward region of the CMS experiment at the LHC. This study includes GEANT Monte Carlo simulations of the Cherenkov light transmission efficiency of different types of air-core light guides, as well as analysis of the calorimeter linearity and resolution as a function of energy and impact-point, obtained with 20-200 GeV electron beams from CERN/SPS tests in 2003. Several configurations of the calorimeter have been tested and compared, including different combinations of (i) structures for the active material of the calorimeter (quartz plates and fibres), (ii) various light-guide reflecting materials (glass and foil reflectors) and (iii) photodetector devices (photomultipliers and avalanche photodiodes)
Information entropy in fragmenting systems
The possibility of facing critical phenomena in nuclear fragmentation is a
topic of great interest. Different observables have been proposed to identify
such a behavior, in particular, some related to the use of information entropy
as a possible signal of critical behavior. In this work we critically examine
some of the most widespread used ones comparing its performance in bond
percolation and in the analysis of fragmenting Lennard Jones Drops.Comment: 3 pages, 3 figure
CASTOR: The ALICE forward detector for identification of Centauros and Strangelets in Nucleus-Nucleus Collisions at the LHC
The physics motivation for a very forward detector for the ALICE heavy ion
experiment at the CERN LHC is discussed. A phenomenological model describing
the formation and decay of a Centauro fireball in nucleus-nucleus collisions is
presented. The CASTOR detector which is aimed to measure the hadronic and
photonic content of an interaction and to identify deeply penetrating objects
in the very forward, baryon-rich phase space 5.6 < eta < 7.2 in an
event-by-event mode is described. Results of simulations of the expected
response of the calorimeter, and in particular to the passage of strangelets,
are presented.Comment: Presented at XXVIII Int. Symp. on Multiparticle Dynamics, Delphi,
6-11 Sept. 1998. 9 pages, 11 figure
CASTOR detector: model, objectives and simulated performance
We present a phenomenological model describing the formation and evolution of a Centauro fireball in the baryon-rich region in nucleus-nucleus interactions in the upper atmosphere and at the LHC. The small particle multiplicity and imbalance of electromagnetic and hadronic content characterizing a Centauro event and also the strongly penetrating particles (assumed to be strangelets) frequently accompanying them can be naturally explained. We describe the CASTOR calorimeter, a subdetector of the ALICE experiment dedicated to the search for Centauro in the very forward, baryon-rich region of central Pb+Pb collisions at the LHC. The basic characteristics and simulated performance of the calorimeter are presented
Transverse polarization in inclusive quasi-real photoproduction at the current fragmentation
It is shown that the recent HERMES data on the transverse
polarization in the inclusive quasi-real photoproduction at can be
accommodated by the strange quark scattering model. Relations with the quark
recombination approach are discussed.Comment: 5 pages, 3 figures, accepted by Eur. Phys. J.
Antideuteron and deuteron production in mid-central Pb+Pb collisions at 158 GeV
Production of deuterons and antideuterons was studied by the NA49 experiment
in the 23.5% most central Pb+Pb collisions at the top SPS energy of
=17.3 GeV. Invariant yields for and were measured
as a function of centrality in the center-of-mass rapidity range .
Results for together with previously published
measurements are discussed in the context of the coalescence model. The
coalescence parameters were deduced as a function of transverse momentum
and collision centrality.Comment: 9 figure
Inclusive production of charged pions in p+C collisions at 158 GeV/c beam momentum
The production of charged pions in minimum bias p+C interactions is studied
using a sample of 377000 inelastic events obtained with the NA49 detector at
the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area
ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in
Feynman x. Inclusive invariant cross sections are given on a grid of 270 bins
per charge thus offering for the first time a dense coverage of the projectile
hemisphere and of the cross-over region into the target fragmentation zone.Comment: 31 pages, 30 figures, submitted to European Journal of Physic
High p_T Spectra of Identified Particles Produced in Pb+Pb Collisions at 158GeV/nucleon Beam Energy
Transverse momentum spectra of pi^{+/-}, p, pbar, K^{+/-}, K^0_s and Lambda
at midrapidity were measured at high p_T in Pb+Pb collisions at 158GeV/nucleon
beam energy by the NA49 experiment. Particle yield ratios (p/pi, K/pi and
Lambda/K^0_s) show an enhancement of the baryon/meson ratio for p_T>2GeV/c. The
nuclear modification factor R_{CP} is extracted and compared to RHIC
measurements and pQCD calculations.Comment: Quark Matter 2005 parallel section proceeding
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