Pion transverse-momentum spectrum and elliptic anisotropy of partially coherent source

Abstract

In this letter, we study the pion momentum distribution of a coherent source and investigate the influences of coherent emission on the pion transverse-momentum (pT) spectrum and elliptic anisotropy. With a partially coherent source, constructed by a conventional viscous hydrodynamics model (chaotic part) and a parameterized expanding coherent source model, we reproduce the pion pT spectrum and elliptic anisotropy coefficient v2(pT) in the peripheral Pb–Pb collisions at sNN=2.76 TeV. It is found that the influences of coherent emission on the pion pT spectrum and v2(pT) are related to the initial size and shape of the coherent source, largely due to the interference effect. However, the effect of source dynamical evolution on coherent emission is relatively small. The results of the partially coherent source with 33% coherent emission and 67% chaotic emission are consistent with the experimental measurements of the pion pT spectrum, v2(pT), and especially four-pion Bose–Einstein correlations.