Collective flow in Ar+KCl at 1.8 GeV/nucleon

Abstract

The failure of the standard sphericity tensor analysis to detect any significant collective flow ef-fect in Ar ±ICC1 at 1.8 A GeV is examined in light of the success of the transverse momentum analysis technique suggested by Danielewicz and Odyniec in exhibiting collective flow in the same system. It is argued, using a simple estimate which takes into consideration the main features of the data, that the failure of the sphericity analysis is attributable to the dominant contribution of the longitudinal momentum of the spectators which has nothing to do with the collective effects for which sphericity analysis is designed. The exclusion of the spectators from the sphericity tensor leads to a clear signal from the collective transverse flow of the participants whenever such a flow takes place.