Anisotropic collective flow of Lambda-hyperons produced in C plus C collisions at 4.2 A GeV/c

摘要

Features of anisotropic collective flow and spectral temperatures have been determined for Lambda hyperons emitted from C + C collisions, at incident momentum of 4.2 A GeV/c, measured using the Propane Bubble Chamber of JINR at Dubna. Moreover, characteristics of protons and of negative pions, emitted from those collisions, have been determined and provided for comparison. The directed and elliptic flows of Lambda s both agree in sign with the corresponding flows of protons. Parameters of the directed and elliptic flows for Lambda s agree further, within errors, with the corresponding parameters for the co-produced protons. This contrasts an earlier finding by the E895 Collaboration of the directed flow being significantly weaker for Lambda s than protons, in the much heavier Au + Au system, at comparable incident momentum. Particle spectral temperatures in the C+C collisions have been determined focusing independently on either center-of-mass energy, transverse energy or transverse momentum distributions. For either protons or negative pions, the temperatures were found to be approximately the same, no matter whether the emission of those particles was associated with Lambda production or not. Results of the measurements have been compared to the results of simulations within the Quark-Gluon String Model.