Firstly, let's take a look at the yields from central collisions (b=0-3 fm).
To do this, you have to decode RQMD's PID scheme to LUND scheme, and then I go to
GEANT scheme (thanks to Dieter, Heng and Roy for getting me going). However, GEANT
does not have PID's as far as I know for phi mesons or delta baryons or some
others (which ARE still around at the end of the calculation), so I "extended"
this scheme a bit. By the way, the LUND scheme (JETSET 6.2) is not what is on the
cern pages; I guess it is an old scheme. To find the new one, go to CPC39, 347 (1986).
What?-- You don't know what is CPC? Neither did I-- it is Computer Physics Communications.
Anyway, the code runs for 50 fm/c, and plotted in the following pictures on top is the
particle yield at the end of the calculation. So, most of the delta's have decayed, but
there are a few around still. Also phi's and stuff.
At the bottom panel is shown, for the pions at the end of the calculation, the "nature of the
last collision", which could actually be a decay. There are plenty of pions from collisions,
strings, "high mass decays" (that's what RQMD says-- I don't know more), and deltas. Even
a couple of pions from ropes, and some from cascades and Sigma*'s and etaprime's.
(NB: If a pion comes from Delta decay, RQMD does not specify what type of Delta it was, so
all are plotted in the Delta++ bin.)
So here are the plots. These yields are the sum of 100 events at b=0-3 fm.
The histogram is the results of running RQMD in cascade mode, and the red stars are when the
meanfield is on.
It can be hard to read the x-axis (which labels the particles),
so a postscript version of each is available too.
What do we see? Just a preliminary glance says:
- At the end of the calculation, meanfield has less strange particles (lambda's sigmas)
than cascade, but always more deltas still around at the end. Not sure if this makes sense
about the deltas.
- Although there are less pions created in meanfield mode, there are more from those
mysterious "high mass decays."
Back to E895 HBT and RQMD