Modification of $K^{0}_{s}$ and $\Lambda (\overline{\Lambda})$ transverse momentum spectra in Pb-Pb collisions at $\sqrt{^{s}NN}$ = 2.76 TeV with ALICE

Measurements of the transverse momentum (pt) spectra of K0s and Lambda(Anti-Lambda) in Pb-Pb and pp collisions at sqrt(sNN) = 2.76 TeV with the ALICE detector at the LHC at CERN up to pT = 20GeV/c and pT = 16GeV/c, respectively, are presented in this thesis. In addition, the particle rapidity densities at mid-rapidity and nuclear modification factors of K0s and Lambda(Anti-Lambda) are discussed. Regarding the rapidity density, a suppression of the strange particle production in pp as compared to Pb–Pb collisions is observed at all centralities, whereas the production per pion rapidity density stays constant as a function of mean particle production including both systems. Furthermore, the relative increase of the individual particle species in pp and AA collisions is compatible for non- and single-strange particles when going from RHIC (sqrt(sNN) = 0.2 TeV) to LHC energies. On the other hand, in case of multi-strange baryons, a stronger increase in the particle production in pp is seen. The Lambda and Anti-Lambda production in Pb–Pb and pp collisions is found to be equal. Concerning the nuclear modification factors, the ratio of pT spectra in Pb-Pb collisions to the corresponding spectra in pp scaled with the number of binary collisions in Pb-Pb, at high pT (pT > 8 GeV/c), a strong suppression in central Pb–Pb collisions with respect to pp collisions is observed for K0s and Lambda(Anti-Lambda). This nuclear modification is similar to the modification of charged hadrons and mesons with charm quark content at high pT.