Recent femtoscopy results from NA49: evidence for a non-Gaussian tail in the 3-dimensional two-pion emission source at SPS

Abstract

The NA49 experiment at CERN SPS has acquired a huge data set of Pb+Pb events over a broad range of energy and centrality during the last several years. This high statistics data set, coupled with a state-of-the-art analysis technique, allows for the first model-independent extraction and energy scan of 3D emission sources for pion pairs at SPS energies. These 3D two-pion emission sources provide new insights into the nature of a long-range source previously reported by PHENIX at RHIC. The new results indicate that the two-pion source function is essentially Gaussian from 20 AGeV to 80 AGeV but it displays significant non-Gaussian tails at 158 AGeV.

Summary talk for ISMD 06

“…Chung presented an analysis which suggest that the nonGaussian tail of the distribution measured at RHIC may, as was the case at LEP, provide non-trivial information on the decoupling surface [39]. This has the potential to modify conclusions drawn from a Gaussian analysis.…”