Speaker
Description
We report here measurements of correlations between Lambda0-anti-Lambda0, Lambda0-Lambda0, and anti-Lambda-anti-Lambda0 hyperon pairs produced inclusively at the LHC. The analysis is based on hyperon pairs selected using the muon and minimum bias sample collected at the ATLAS experiment from proton-proton collisions at a center-of-mass energy of 7 TeV in 2010. Dynamical correlations between the hyperon pairs have been explored through a correlation function defined as the ratio of two-particle to single-particle densities. Positive correlation is observed for Lambda0-anti-Lambda0 events and anticorrelation is observed for Lambda0-Lambda0 and anti-Lambda-anti-Lambda0 events for Q in [0,2] GeV. The structure replicates similar correlations in ppbar, pp, and pbarpbar events in PYTHIA generator as predicted by the string model. Parameters of the ''popcorn'' mechanism implemented in the PYTHIA generator are tuned and are found to have little impact on the structure observed. The spin composition of the sample is extracted using a data-driven reference sample built by event mixing. Appropriate correction is made to the kinematic distributions in the reference sample by kinematic weighting to make sure that the detector effects are well modeled. The Pearson's chi-squared test statistics is calculated for the decay angle distributions to determine the best-fitted value of spin correlation parameter for data. The results are consistent with zero for both like-type and unlike-type hyperon pairs for Q in [0,10] GeV and [1,10] GeV respectively. Data statistics for Q in [0,1] GeV is too low for the estimation of the emitter size for Fermi-Dirac correlation.
