18 research outputs found
Strange Particle Production in p+p, p+Pb and Pb+Pb Interactions from NA49
Recent NA49 results on Lambda, Antilambda, Xi- and Antixi+ production in
minimum bias p+p and centrality selected p+Pb collisions at 158 GeV/c, and the
results on Lambda, Antilambda, K+ and K- production in central Pb+Pb collisions
at 40, 80 and 158 A GeV are discussed and compared with other available data.
By comparing the energy dependence of Lambda and Antilambda production at
mid-rapidity a striking similarity is observed between p+p and A+A data. This
is also seen in the energy dependence of the Lambda/pi ratio. K+/pi at
mid-rapidity is affected in a similar way, due to the associated production of
K+ together with Lambda particles. The observed yields increase faster than the
number of wounded nucleons when comparing p+Pb to p+p. As already observed in
A+A collisions, the increase is larger for multistrange than for strange
baryons and for baryons than for anti-baryons.Comment: 8 pages, 10 figures, To appear in proceedings of Strange Quark in
Matter 2001-A Flavourspace Odyssey, Frankfurt am Main, Germany, 24-29. Sept.
200
Energy dependence of kaon production in central Pb+Pb collisions
Recent results from the NA49 experiment on the energy dependence of charged
kaon production in central Pb+Pb collisions are presented. First results from
the new data at 80 AGeV beam energy are compared with those from lower and
higher energies. A difference in the energy dependence of the /
and / ratios is observed. The / ratio shows a
non-monotonic behaviour with a maximum near 40 AGeV.Comment: 8 pages, 7 figures, proceedings of talk at SQM2001, Frankfurt,
Germany, to appear in J. Phys.
Strangeness from 20 AGeV to 158 AGeV
New results from the energy scan programme of NA49, in particular kaon
production at 30 AGeV and phi production at 40 and 80 AGeV are presented. The
K+/pi+ ratio shows a pronounced maximum at 30 AGeV; the kaon slope parameters
are constant at SPS energies. Both findings support the scenario of a phase
transition at about 30 AGeV beam energy. The phi/pi ratio increases smoothly
with beam energy, showing an energy dependence similar to K-/pi-. The measured
particle yields can be reproduced by a hadron gas model, with chemical
freeze-out parameters on a smooth curve in the T-muB plane. The transverse
spectra can be understood as resulting from a rapidly expanding, locally
equilibrated source. No evidence for an earlier kinetic decoupling of heavy
hyperons is found.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003"
(March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics
G. 11 pages, 14 figure
Lambda production in central Pb+Pb collisions at CERN-SPS energies
In this paper we present recent results from the NA49 experiment for
and hyperons produced in central Pb+Pb collisions at
40, 80 and 158 AGeV. Transverse mass spectra and rapidity distributions
for are shown for all three energies. The shape of the rapidity
distribution becomes flatter with increasing beam energy. The multiplicities at
mid-rapidity as well as the total yields are studied as a function of collision
energy including AGS measurements. The ratio at mid-rapidity and
in 4 has a maximum around 40 AGeV. In addition,
rapidity distributions have been measured at 40 and 80 AGeV, which
allows to study the / ratio.Comment: SQM proceedings. J. Phys. G: Nucl. Part. Phys.: submitte
Energy and centrality dependence of deuteron and proton production in Pb + Pb collisions at relativistic energies
The transverse mass mt distributions for deuterons and protons are measured in Pb + Pb reactions near midrapidity and in the range 0<mt-m<1.0 (1.5) GeV/c2 for minimum bias collisions at 158A GeV and for central collisions at 40 and 80 A GeV beam energies. The rapidity density dn/dy, inverse slope parameter T and mean transverse mass mt derived from mt distributions as well as the coalescence parameter B2 are studied as a function of the incident energy and the collision centrality. The deuteron mt spectra are significantly harder than those of protons, especially in central collisions. The coalescence factor B2 shows three systematic trends. First, it decreases strongly with increasing centrality reflecting an enlargement of the deuteron coalescence volume in central Pb + Pb collisions. Second, it increases with mt. Finally, B2 shows an increase with decreasing incident beam energy even within the SPS energy range. The results are discussed and compared to the predictions of models that include the collective expansion of the source created in Pb + Pb collision
Energy dependence of transverse momentum fluctuations in Pb plus Pb collisions at the CERN Super Proton Synchrotron (SPS) at 20A to 158A GeV
Results are presented on event-by-event fluctuations of transverse
momenta p(T) in central Pb + Pb interactions at 20A, 30A, 40A, 80A, and
158A GeV. The analysis was performed for charged particles at forward
center-of-mass rapidity (1.1 < y(pi)* < 2.6). Three fluctuation
measures were studied: the distribution of average transverse momentum
M(p(T)) in the event, the Phi p(T) fluctuation measure, and two-particle
transverse momentum correlations. Fluctuations of p(T) are small and
show no significant energy dependence in the energy range of the CERN
Super Proton Synchrotron. Results are compared with QCD-inspired
predictions for the critical point, and with the UrQMD model. Transverse
momentum fluctuations, similar to multiplicity fluctuations, do not show
the increase expected for freeze-out near the critical point of QCD
System size and centrality dependence of the balance function in A+A collisions at root S-NN=17.2 GeV
Electric charge correlations were studied for p+p, C+C, Si+Si, and
centrality selected Pb+Pb collisions at root s(NN) = 17.2 GeV with the
NA49 large acceptance detector at the CERN SPS. In particular,
long-range pseudorapidity correlations of oppositely charged particles
were measured using the balance function method. The width of the
balance function decreases with increasing system size and centrality of
the reactions. This decrease could be related to an increasing delay of
hadronization in central Pb+Pb collisions