R. Platt

Enhancement of hyperon production at central rapidity in 158 A GeV/c Pb–Pb collisions

Results are presented on hyperon and antihyperon production in Pb–Pb, pPb and pBe collisions at 158 GeV/c per nucleon. Λ, Ξ and Ω yields have been measured at central rapidity and medium transverse momentum as functions of the centrality of the collision. Comparing the yields in Pb–Pb to those in pBe interactions, strangeness enhancement is observed. The enhancement increases with the centrality and with the strangeness content of the hyperons, reaching a factor of about 20 for the Ω in the central Pb–Pb collisions.

Central-to-peripheral nuclear modification factors in Pb-Pb collisions at √sNN = 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.

Study of the transverse mass spectra of strange particles in Pb–Pb collisions at 158 A GeV/c

The NA57 experiment has collected high statistics, high purity samples of K0S and Λ, Ξ and Ω hyperons produced in Pb–Pb collisions at 158 A GeV/c. In this paper we present a study of the transverse mass spectra of these particles for a sample of events corresponding to the most central 53% of the inelastic Pb–Pb cross-section. We analyse the transverse mass distributions in the framework of the blast-wave model for the full sample and, for the first time at the SPS, as a function of the event centrality.

Rapidity distributions around mid-rapidity of strange particles in Pb–Pb collisions at 158 A GeV/c

The production at central rapidity of K0S, Λ, Ξ and Ω particles in Pb–Pb collisions at 158 A GeV/c has been measured by the NA57 experiment over a centrality range corresponding to the most central 53% of the inelastic Pb–Pb cross section. In this paper we present the rapidity distribution of each particle in the central rapidity unit as a function of the event centrality. The distributions are analysed based on hydrodynamical models of the collisions.

Multiplicity of charged particles in Pb–Pb collisions at SPS energies

The multiplicity of charged particles in the central rapidity region has been measured by the NA57 experiment in Pb–Pb collisions at the CERN SPS at two beam momenta: 158 A GeV/c and 40 A GeV/c. The value of dNch/dη at the maximum has been determined and its behaviour as a function of centrality has been studied in the centrality range covered by NA57 (about 50% of the inelastic cross section). The multiplicity increase is compatible with a logarithmic dependence on the centre of mass energy. The results are compared with those from other experiments and with the VENUS and RQMD models.

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 π−, measured in Pb–Pb collisions at 40 A GeV/c beam momentum. Based on these data, the collision dynamics and the spacetime 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.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.

Transverse dynamics of Pb–Pb collisions at 40 A GeV/c viewed by strange hadrons

The transverse mass spectra of K0S, Λ, Ξ and Ω particles produced in Pb–Pb collisions at 40 A GeV/c have been studied for a sample of events corresponding to the most central 53% of the inelastic Pb–Pb cross section. We analyse the distributions in the framework of a parameterized model inspired by hydrodynamics. The dependence of the freeze-out parameters on particle species and event centrality is discussed and comparisons with results at higher energy are shown.The transverse mass spectra of K0s, Lambda, Xi and Omega particles produced in Pb-Pb collisions at 40 A GeV/c have been studied for a sample of events corresponding to the most central 53% of the inelastic Pb-Pb cross-section. We analyze the distributions in the framework of a parameterized model inspired by hydrodynamics. The dependence of the freeze-out parameters on particle species and event centrality is discussed and comparisons with results at higher energy are shown.

Λ and Ω− Polarization in Pb+Pb Collisions at 160 A GeV/c

We study the transverse polarization of Λ’s and Ω−’s produced in Pb + Pb interaction at 160 A GeV/c. We also present a study of the longitudinal polarization of Λ’s produced in the weak decays of Ξ’s.

Results on strangeness production from the NA57 experiment

A review of recent NA57 results on K0S and hyperon production from Pb?Pb collisions at 40 and 158 A GeV/c is presented. An energy and centrality dependence of particle yields, strangeness enhancements as well as transverse mass spectra at mid-rapidity are discussed.A review of recent NA57 results on K 0 S and hyperon production from Pb-Pb collisions at 40 and 158 A GeV/c is presented. An energy and centrality dependence of particle yields, strangeness enhancements as well as transverse mass spectra at mid-rapidity are discussed.

LVDS tester: a systematic test of cable signal transmission at the ALICE experiment

In the ALICE experiment, the Low-Voltage Differential Signalling (LVDS) format is used for the transmission of trigger inputs from the detectors to the Central Trigger Processor (CTP), the L0 trigger outputs from Local Trigger Units (LTU) boards back to the detectors and the BUSY inputs from the sub-detectors to the CTP. ALICE has designed a set-up, called the LVDS transmission tester, that aims to measure various transmission quality parameters and the bit-error rate (BER) for long period runs in an automatic way. In this paper, this method is described and the conclusions from these tests for the ALICE LVDS cables are discussed.