783 research outputs found
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
High p_T Spectra of Identified Particles Produced in Pb+Pb Collisions at 158A GeV Beam Energy
Results of the NA49 collaboration on the production of hadrons with large
transverse momentum in Pb+Pb collisions at 158A GeV beam energy are presented.
A range up to p_T = 4 GeV/c is covered. The nuclear modification factor R_CP is
extracted for pions, kaons and protons, and the baryon to meson ratios p/pi+,
pbar/pi- and Lambda/K^0_s are studied. All results are compared to other
measurements at SPS and RHIC and to theoretical calculations.Comment: Submitted to J. Phys. G (Proceedings of the 9th International
Conference on Strangeness in Quark Matter, Los Angeles, USA, March 26-31,
2006). 5 pages, 3 figure
Strangeness production at SPS energies
We present a summary of measurements of strange particles performed by the
experiment NA49 in central and minimum bias Pb+Pb collisions in the beam energy
range 20A - 158A GeV. New results on Xi production in central Pb+Pb collisions
and on Lambda, Xi production in minimum bias collisions are shown. Transverse
mass spectra and rapidity distributions of strange particles at different
energies are compared. The energy dependence of the particle yields and ratios
is discussed. NA49 measurements of the Lambda and Xi enhancement factors are
shown for the first time.Comment: Submitted to J. Phys. G (Proceedings of the 9th International
Conference on Strangeness in Quark Matter, Los Angeles, USA, March 26-31,
2006). 9 pages, 9 figure
Results on correlations and fluctuations from NA49
The large acceptance and high momentum resolution as well as the significant
particle identification capabilities of the NA49 experiment at the CERN SPS
allow for a broad study of fluctuations and correlations in hadronic
interactions. In the first part recent results on event-by-event charge and p_t
fluctuations are presented. Charge fluctuations in central Pb+Pb reactions are
investigated at three different beam energies (40, 80, and 158 AGeV), while for
the p_t fluctuations the focus is put on the system size dependence at 158
AGeV. In the second part recent results on Bose Einstein correlations of h-h-
pairs in minimum bias Pb+Pb reactions at 40 and 158 AGeV, as well as of K+K+
and K-K- pairs in central Pb+Pb collisions at 158 AGeV are shown. Additionally,
other types of two particle correlations, namely pi p, Lambda p, and Lambda
Lambda correlations, have been measured by the NA49 experiment. Finally,
results on the energy and system size dependence of deuteron coalescence are
discussed.Comment: 10 pages, 12 figures, Presented at Quark Matter 2002, Nantes, France,
Corrected error in Eq.
Event-by-Event Fluctuations of Particle Ratios in Central Pb+Pb Collisions at 20 to 158 AGeV
In the vicinity of the QCD phase transition, critical fluctuations have been
predicted to lead to non-statistical fluctuations of particle ratios, depending
on the nature of the phase transition. Recent results of the NA49 energy scan
program show a sharp maximum of the ratio of K+ to Pi+ yields in central Pb+Pb
collisions at beam energies of 20-30 AGeV. This observation has been
interpreted as an indication of a phase transition at low SPS energies. We
present first results on event-by-event fluctuations of the kaon to pion and
proton to pion ratios at beam energies close to this maximum.Comment: 4 pages, 4 figures, Quark Matter 2004 proceeding
Experimental Study of the Shortest Reset Word of Random Automata
In this paper we describe an approach to finding the shortest reset word of a
finite synchronizing automaton by using a SAT solver. We use this approach to
perform an experimental study of the length of the shortest reset word of a
finite synchronizing automaton. The largest automata we considered had 100
states. The results of the experiments allow us to formulate a hypothesis that
the length of the shortest reset word of a random finite automaton with
states and 2 input letters with high probability is sublinear with respect to
and can be estimated as $1.95 n^{0.55}.
Bose-Einstein Correlations of Charged Kaons in Central Pb+Pb Collisions at
Bose-Einstein correlations of charged kaons were measured near mid-rapidity
in central Pb+Pb collisions at 158 AGeV by the NA49 experiment at the
CERN SPS. Source radii were extracted using the Yano-Koonin-Podgoretsky and
Bertsch-Pratt parameterizations. The results are compared to published pion
data. The measured dependence for kaons and pions is consistent with
collective transverse expansion of the source and a freeze-out time of about
9.5 .Comment: 14 pages with 7 figures, submitted to Phys. Lett.
Two-proton correlations from 158 AGeV Pb+Pb central collisions
The two-proton correlation function at midrapidity from Pb+Pb central
collisions at 158 AGeV has been measured by the NA49 experiment. The results
are compared to model predictions from static thermal Gaussian proton source
distributions and transport models RQMD and VENUS. An effective proton source
size is determined by minimizing CHI-square/ndf between the correlation
functions of the data and those calculated for the Gaussian sources, yielding
3.85 +-0.15(stat.) +0.60-0.25(syst.) fm. Both the RQMD and the VENUS model are
consistent with the data within the error in the correlation peak region.Comment: RevTeX style, 6 pages, 4 figures, 1 table. More discussion are added
about the structure on the tail of the correlation function. The systematic
error is revised. To appear in Phys. Lett.
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