183 research outputs found
New results from the NA57 experiment
We report results from the experiment NA57 at CERN SPS on hyperon production
at midrapidity in Pb-Pb collisions at 158 GeV/ and 40 GeV/.
, and yields are compared with those from the STAR
experiment at the higher energy of the BNL RHIC. , , \
and preliminary transverse mass spectra are presented and interpreted
within the framework of a hydro-dynamical blast wave model.Comment: 8 pages, 3 figures, contribution to the proceedings of The XXXVIIIth
Rencontres de Moriond "QCD and High Energy Hadronic Interactions
Expansion dynamics of Pb-Pb collisions at 40 A GeV/c viewed by negatively charged hadrons
In this paper we present results on transverse mass spectra and Hanbury-Brown
and Twiss correlation functions of negatively charged hadrons, which are
expected to be mostly negative pions, measured in Pb-Pb collisions at 40 A
GeV/c beam momentum. Based on these data, the collision dynamics and the
space-time extent of the system at the thermal freeze-out are studied over a
centrality range corresponding to the most central 53% of the Pb--Pb inelastic
cross section. Comparisons with freeze-out conditions of strange particles and
HBT results from other experiments are discussed.Comment: 29 pages, 18 figure
Results on hyperon production from the NA57 experiment
Recent results on hyperon production in Pb--Pb collisions from the NA57
experiment are reported. Strangeness enhancement and the transverse mass
spectra properties at 158 GeV per nucleon are described.Comment: submitted to Acta Phys. Hung. A (Heavy Ion Physics
Strange particle production in 158 and 40 GeV/ Pb-Pb and p-Be collisions
Results on strange particle production in Pb-Pb collisions at 158 and 40
GeV/ beam momentum from the NA57 experiment at CERN SPS are presented.
Particle yields and ratios are compared with those measured at RHIC.
Strangeness enhancements with respect to p-Be reactions at the same beam
momenta have been also measured: results about their dependence on centrality
and collision energy are reported and discussed.Comment: Contribution to the proceedings of the "Hot Quarks 2004" Conference,
July 18-24 2004, New Mexico, USA, submitted to Journal of Physics G 7 pages,
5 figure
Cosmological distance indicators
We review three distance measurement techniques beyond the local universe:
(1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and
(3) HI intensity mapping. We describe the principles and theory behind each
method, the ingredients needed for measuring such distances, the current
observational results, and future prospects. Time delays from strongly lensed
quasars currently provide constraints on with < 4% uncertainty, and with
1% within reach from ongoing surveys and efforts. Recent exciting discoveries
of strongly lensed supernovae hold great promise for time-delay cosmography.
BAO features have been detected in redshift surveys up to z <~ 0.8 with
galaxies and z ~ 2 with Ly- forest, providing precise distance
measurements and with < 2% uncertainty in flat CDM. Future BAO
surveys will probe the distance scale with percent-level precision. HI
intensity mapping has great potential to map BAO distances at z ~ 0.8 and
beyond with precisions of a few percent. The next years ahead will be exciting
as various cosmological probes reach 1% uncertainty in determining , to
assess the current tension in measurements that could indicate new
physics.Comment: Review article accepted for publication in Space Science Reviews
(Springer), 45 pages, 10 figures. Chapter of a special collection resulting
from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in
the Space Ag
Rapid turnover of Plasmodium falciparum var gene transcripts and genotypes during natural non-symptomatic infections
OcorrĂŞncia de Cryptosporidium spp. em pequenos mamĂferos silvestres de trĂŞs áreas serranas do Sudeste brasileiro
Results on cascade production in lead-lead interactions from the NA57 experiment
The NA57 experiment has been designed to study the production of strange and multi-strange particles in Pb-Pb and p-Be collisions at the CERN SPS. The predecessor experiment WA97 has measured an enhanced abundance of strange particles in Pb-Pb collisions relative to p-A reactions at 160 GeV/c per nucleon beam momentum. NA57 has extended the WA97 measurements to investigate the evolution of the strangeness enhancement pattern as a function of the beam energy and over a wider centrality range. In this paper, we report results on cascade production for about the 60% most central collisions at 160 GeV/c per nucleon
Central-to-peripheral nuclear modification factors in Pb-Pb collisions at sqrt{s_NN} = 17.3 GeV
We present central-to-peripheral nuclear modification factors, R_CP, for the
p_T distributions of K^0_S, Lambda, Anti-Lambda, and negatively charged
particles, measured at central rapidity in Pb-Pb collisions at top SPS energy.
The data cover the 55% most central fraction of the inelastic cross section.
The K^0_S and Lambda R_CP(p_T) are similar in shape to those measured at
sqrt{s_NN} = 200 GeV at RHIC, though they are larger in absolute value. We have
compared our K^0_S R_CP data to a theoretical calculation. The prediction
overestimates the data at p_T \approx 3-4 GeV/c, unless sizeable parton energy
loss is included in the calculation.Comment: 13 pages, 5 figures, submitted to Physics Letters
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