Two-pion femtoscopic correlations in Be plus Be collisions at ^sNN=16.84 GeV measured by the NA61/SHINE at CERN

This paper reports measurements of two-pion femtoscopic correlations in Be+Be collisions at a beam momentum of 150A GeV/c (energy available in the center of-mass system for nucleon pair root(NN)-N-s = 16.84 GeV) by the NA61/SHINE experiment at the CERN SPS accelerator. The obtained momentum space correlation functions can be well described by a Levy distributed source model. The transverse mass dependence of the Levy source parameters is presented, and their possible theoretical interpretations are discussed. The results show that the Levy exponent alpha is approximately constant as a function of mT , and far from both the Gaussian case of alpha = 2 or the conjectured value at the critical endpoint, alpha = 0.5. The radius scale parameter R shows a slight decrease in mT , which can be explained as a signature of transverse flow. Finally, an approximately constant trend of the intercept parameter lambda as a function of mT was observed, similar to previous NA44 S + Pb results (obtained with a Gaussian approximation, but unlike RHIC results).