Measurements of Lambda, Lambda-bar and K-short from Pb-Pb collisions at 158 GeV per nucleon in a large acceptance experiment

[摘要] The main reason for studying relativistic heavy-ion collisions is to discover the phase transition from nuclear matter to the Quark-Gluon Plasma. Such a transition is predicted to occur under conditions of high temperature and density. The predicted state features deconfined quarks and gluons as the relevant degrees of freedom instead of colour-singlet hadrons. These new degrees of freedom should lead to an enhanced production of strange quarks which has directly observable consequences on the composition of the final state hadrons detected in such a collision. The NA49 experiment is able to measure hadronic production in central Pb+Pb collisions. It uses a Pb beam, of energy 158 GeV per nucleon, from the CERN SPS with a fixed Pb target. The experiment features four large tracking detectors which can measure the trajectories of charged particles. In this thesis the method of reconstructing neutral strange particles, Lambda, Lambda-bar and K-short from their charged decay products is described. The procedure for correcting the raw yields for losses due to the limited experimental acceptance and efficiency in reconstruction is explained. An estimate of some systematic errors is made. The resulting rapidity distributions, which span either side of mid-rapidity are peaked (with the possible exception of Lambda) and the transverse momentum spectra fit the Hagedorn distribution. The inverse slope parameters, T_Lambda = 274 ± 5 MeV, T_Lambda-bar = 279 ± 10 MeV and T_K = 238 ± 5 MeV are consistent with the picture of transverse flow observed in these collisions. These results are compared with other measurements.

[发布机构] University:University of Birmingham;Department:Physics

[关键词] Q Science;QC Physics