Azimuthal Anisotropy of $η$ and $π^{0}$ Mesons in Heavy-Ion Collisions at 2 AGeV

Taranenko, A.; Kugler, A.; Pleskac, R.; Tlusty, P.; Wagner, V.; Lohner, H.; Ostendorf, R. W.; Siemssen, R. H.; Vogt, P. H.; Wilschut, H. W.; Averbeck, R.; Hlavac, S.; Holzmann, R.; Schubert, A.; Simon, R. S.; Stratmann, R.; Wissmann, F.; Charbonnier, Y.; Martinez, G.; Schutz, Y.; Diaz, J.; Marin, A.; Doppenschmidt, A.; Appenheimer, M.; Hejny, V.; Metag, V.; Novotny, R.; Stroher, H.; Weiss, J.; Wolf, A. R.; Wolf, M.; Collaboration, TAPS

Azimuthal Anisotropy of $η$ and $π^{0}$ Mesons in Heavy-Ion Collisions at 2 AGeV

Authors

Description

Azimuthal distributions of $η$ and $π^{0}$ mesons emitted at midrapidity in collisions of 1.9 AGeV $^{58}$Ni+$^{58}$Ni and 2 AGeV $^{40}$Ca+$^{nat}$Ca are studied as a function of the number of projectile-like spectator nucleons. The observed anisotropy corresponds to a negative elliptic flow signal for $η$ mesons, indicating a preferred emission perpendicular to the reaction plane. The effect is smallest in peripheral Ni+Ni collisions. In contrast, for $π^{0}$ mesons, elliptic flow is observed only in peripheral Ni+Ni collisions, changing from positive to negative sign with increasing pion transverse momentum.
4 pages, 2 figures, Submitted to Phys. Rev. Lett