The current situation concerning the
hadronic interaction simulation within our GEANT framework
is as follows:
All of this has bearing on the systemtic error estimates made
for the spectra, and thus very important. We must therefore make
a decision about which package to use. This page was created
in order to facilitate the ongoing discussion.
Prior analyses done by the spectra group used a
GHEISHA-based GEANT simulation. While analyzing
the spectra of charged hadrons, a feature a.k.a. "bump"
was discovered in both the experimental data and in the
Monte Carlo sample, roughly in the vicinity of Pt=2.0-2.5 GeV.
Some fraction of the particles contributing to this part
of the spectrum could be then traced to antinucleons
as their parents, in the simulations studies.
This is often referred to as "annihilation" peak,
however this might not be the right way to term it as
we aren't observing photons or their conversion in the
final state, and are rather dealing with charged hadrons
as products of interactions of pbars and nbars propagating
in the detector. When looking at plots of hadronic
cross sections in GEANT, it becomes clear that "annihilation"
is not considered to be a distinct process in either
There was an indication that the magnitude of this "bump"
was somewhat larger in the GHEISHA-based simulation
as compared to the data.
In the summer of year 2002, the GALOR hadronic
interactions package was put to use in the STAR
simulation runs. This was based on two facts:
at that time, there were a problem with the GSTAR/STAF
executable and GHEISHA simply didn't work -- which
since have been fixed
There had been reports (see some links below) that
GALOR may indeed be a better tool -- with the
proviso that this would of course depend on the application.
When running with GALOR, the aforementioned feature
in the Pt spectrum disappears.
GCALOR related Pages