Directed flow in asymmetric nucleus-nucleus collisions and the inverse Landau-Pomeranchuk-Migdal effect.

It is proposed to identify a strong electric field--created during relativistic collisions of asymmetric nuclei--via the observation of pseudorapidity and transverse momentum distributions of hadrons with the same mass but opposite charge. The results of detailed calculations within the parton-hadron string dynamics (PHSD) approach for the charge-dependent directed flow v1 are presented for semicentral Cu+Au collision at √sNN=200 GeV incorporating the inverse Landau-Pomeranchuk-Migdal (iLPM) effect, which accounts for a delay in the electromagnetic interaction with the charged degrees of freedom. By including the iLPM effect, we achieve a reasonable agreement of the PHSD results for the charge splitting in v1(pT) in line with the recent measurements by the STAR Collaboration for Cu+Au collisions at √sNN=200 GeV while an instant appearance and coupling of electric charges at the hard collision vertex overestimates the splitting by about a factor of 10. We predict that the iLPM effect should practically disappear at energies of √sNN≈9 GeV, which should lead to a significantly larger charge splitting of v1 at the future FAIR/NICA facilities. [ABSTRACT FROM AUTHOR]