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sYajem is a wrapper for running YaJEM (T. Renk, Phys. Rev. C 78 (2008)
034908).  YaJEM itself provides a modified version of the PYSHOW
routine, but it needs several other components to produce usable
results:  

1. A source of parton-parton interactions.  For this we have
pp_pythia, which is a wrapper around PYTHIA, running p+p collisions at
a specified sqrt(s).  It runs the fastjet anti-kT algorithm on each
event for a range of jet R parameters.  It also writes out a list of
parton-parton interactions.

2. A set of back-to-back trajectories suitable for the nuclear
collision you want to study.  At the momemnt, it's assumed that the
"production points" are distributed in the transverse plan according
to T_AB(x,y).  These are provided as a ROOT file containing pairs of
TGraphs specifying (t,rho(t)).  The parameter that relates the energy
density to qhat or ehat, YAPARS(2), needs to be fit to R_AA data.

sYajem picks a parton pair and a trajectory. It chooses one branch of
the trajectory pair, set up the call to PYSHOW, and runs PYEXEC.  The
result is rotated and boosted to match the specification in the input
file. sYajem then chooses the other branch of the trajectory and
repeats the procedure.  It then swaps around parts of these two events
to get two new events, each of which has a parton following one of the
two branches of the original trajectory. The fastjet anti-kT algorithm
is run on these new events.  This procedure is repeated N_coll times
for each A+A event.

A simple macro, jet.C, divides the A+A histograms by the p+p ones
scaled by <N_coll> and the relative number of events.  The result
should be R_AA.