797 research outputs found
CASTOR: Centauro and Strange Object Research in nucleus-nucleus collisions at LHC
We describe the CASTOR detector designed to probe the very forward,
baryon-rich rapidity region in nucleus-nucleus collisions at the LHC. We
present a phenomenological model describing the formation of a QGP fireball in
a high baryochemical potential environment, and its subsequent decay into
baryons and strangelets. The model explains Centauros and the long-penetrating
component and makes predictions for the LHC.
Simulations of Centauro-type events were done. To study the response of the
apparatus to new effects different exotic species (DCC, Centauros, strangelets
etc.) were passed through the deep calorimeter. The energy deposition pattern
in the calorimeter appears to be a new clear signature of the QGP.Comment: Talk given by E. Gladysz-Dziadus for the CASTOR group, Intern.
Workshop on Nuclear Theory, 10-15 June, 2002, Bulgaria, Rila Mountains, 15
pages, 14 figure
NA49 results on hadron production: indications of the onset of deconfinement ?
The NA49 experiment at the CERN SPS measured the energy and system size
dependence of particle production in A+A collisions. A change of the energy
dependence of several hadron production properties at low SPS energies is
observed which suggests a scenario requiring the onset of deconfinement.Comment: XXXV International Symposium on Multiparticle Dynamics 200
System-size dependence of strangeness production in nucleus-nucleus collisions at sqrt{s_{NN}}=17.3 GeV
Emission of pi, K, phi and Lambda was measured in near-central C+C and Si+Si
collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S and
Pb+Pb, the system-size dependence of relative strangeness production in
nucleus-nucleus collisions is obtained. Its fast rise and the saturation
observed at about 60 participating nucleons can be understood as onset of the
formation of coherent partonic subsystems of increasing size.Comment: Phys.Rev.Lett in print; version2: changes made according to the
request of the referee
Report from NA49
The most recent data of NA49 on hadron production in nuclear collisions at
CERN SPS energies are presented. Anomalies in the energy dependence of pion and
kaon production in central Pb+Pb collisions are observed. They suggest that the
onset of deconfinement is located at about 30 AGeV. Large multiplicity and
transverse momentum fluctuations are measured for collisions of intermediate
mass systems at 158 AGeV. The need for a new experimental programme at the CERN
SPS is underlined.Comment: invited talk presented at Quark Matter 2004, 10 page
Rapidity and transverse momentum dependence of pion-pion Bose-Einstein correlations measured at 20, 30, 40, 80, and 158 AGeV beam energy
Preliminary results on pion-pion Bose-Einstein correlations in central Pb+Pb
collisions measured by the NA49 experiment are presented. Rapidity as well as
transverse momentum dependence of the HBT-radii are shown for collisions at 20,
30, 40, 80, and 158 AGeV beam energy. Including results from AGS and RHIC
experiments only a weak energy dependence of the radii is observed. Based on
hydrodynamical models parameters like lifetime and geometrical radius of the
source are derived from the dependence of the radii on transverse momentum.Comment: 5 pages, 4 figures, contribution to the Quark Matter conference,
Oakland, USA, Jan 11-17, 200
Strange Quark Matter and Compact Stars
Astrophysicists distinguish between three different types of compact stars.
These are white dwarfs, neutron stars, and black holes. The former contain
matter in one of the densest forms found in the Universe which, together with
the unprecedented progress in observational astronomy, make such stars superb
astrophysical laboratories for a broad range of most striking physical
phenomena. These range from nuclear processes on the stellar surface to
processes in electron degenerate matter at subnuclear densities to boson
condensates and the existence of new states of baryonic matter--like color
superconducting quark matter--at supernuclear densities. More than that,
according to the strange matter hypothesis strange quark matter could be more
stable than nuclear matter, in which case neutron stars should be largely
composed of pure quark matter possibly enveloped in thin nuclear crusts.
Another remarkable implication of the hypothesis is the possible existence of a
new class of white dwarfs. This article aims at giving an overview of all these
striking physical possibilities, with an emphasis on the astrophysical
phenomenology of strange quark matter. Possible observational signatures
associated with the theoretically proposed states of matter inside compact
stars are discussed as well. They will provide most valuable information about
the phase diagram of superdense nuclear matter at high baryon number density
but low temperature, which is not accessible to relativistic heavy ion
collision experiments.Comment: 58 figures, to appear in "Progress in Particle and Nuclear Physics";
References added for sections 1,2,3,5; Equation (116) corrected; Figs. 1 and
58 update
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
Energy and centrality dependence of deuteron and proton production in Pb+Pb collisions at relativistic energies
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
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