Corona effect in AA collisions at LHC
V. S. Pantuev
Institute for Nuclear Research RAS, 117312 Moscow, Russia
Abstract
Following our earlier finding based on RHIC data on the dominant
jet production from nucleus corona region, we reconsider this effect in
nucleus-nucleus collisions at LHC energies. Our hypothesis was based on
experimental data, which raised the idea of a finite formation time for the
produced medium. At RHIC energy and in low density corona region this time
reaches about 2 fm/c. Following this hypothesis, the nuclear modification
factor RAA at high pt should be independent on particle momentum, and
the azimuthal anisotropy of high pt particles, v2, should be finite. A
separate prediction held that, at LHC energy, the formation time in the
corona region should be about 1 fm/c. New data at LHC show that RAA is
not flat and is rising with pt. We add to our original hypothesis an
assumption that a fast parton traversing the produced medium loses the fixed
portion of its energy. A shift of about 7 GeV from the original power law
p-6 production cross section in pp
explains well all the observed RAA dependencies. The shift of about
7 GeV is also valid at RHIC energy. We also show that the observed at LHC
dependence of v2 at high pt and our previous predictions agree.