Electron Production in Pythia Simulation of p+p
Collisions
Sam Pagel
One of the goals of the PHENIX experiment is
detection and characterization of the quarkgluon plasma.
One probe for confirming the
production of the qgp is the suppression of J/Ψ
production.
J/Ψ is characterized by the
momenta of the electrons produced from its
decay; however, electrons from the decay of
light mesons cloud the data and must be
accounted for.
1
Introduction
The Relativistic Heavy Ion Collider (RHIC) at Brookhaven
National Laboratory offers an opportunity for detecting and
characterizing the quark gluon plasma produced in Au+Au
collisions.
PHENIX is one of four detectors at RHIC
currently set for detecting and characterizing the quarkgluon plasma.
It is particularly well suited for detecting
photons, electrons, and muons produced in the decay of
mesons produced from the quark-gluon plasma.
Of particular
interest is the suppression of J/ψ production due to quark
deconfinement in the quark-gluon plasma.
J/ψ suppression
is one probe in determining whether the quark-gluon plasma
is being produced.
2
J/ψ
ψ Suppression
J/ψ is one of a class of mesons composed of a charm and
anticharm quarks.
It is produced in nuclear collisions
with sufficient energy for producing charm quarks.
In the
quark-gluon plasma, the density of nuclear matter increases
to the point where deconfinement sets in.
Formation of J/ψ
and other heavy mesons is prevented because the high
density of quarks and gluons in the plasma screens the
strong force.
Color screening does not, however affect the
production of light mesons (such as π0) because
they are more tightly bound then heavier mesons, and so the
meson radius is less than the screening radius of the
plasma.
3
Pythia Data
I am currently looking at simulation data generated by
Pythia for p+p collisions, with 10000 events.
The data
does not currently contain information for J/ψ production,
but it does provide an opportunity to analyze data similar
to what will be generated by PHENIX, if not of the same
scale.
The majority (about 95%) of electrons come from light
mesons, mostly π0.
I want to find a way to filter most of
these out of the data so that I can concentrate on the
heavier mesons.
To do this, I looked at the distribution
of momenta of the electrons as well as electron rapidity,
y, versus the transverse momentum, pT.
Looking at the light
mesons, a large proportion have a small transverse momentum
and a correspondingly large rapidity.
The detector
geometry eliminates many of these particles because it
selects for |y| < 0.35.
This cut has a much smaller effect
on the heavier charm and bottom meson classes because they
have larger transverse momenta.
Therefore, in addition to
the angle cuts of the detector, introducing a cut in
transverse momentum of approximately 1-2 GeV/c would
eliminate most of the light mesons from the data while
leaving a majority of the charm and bottom mesons.
4
Summary
I would like to incorporate J/ψ into the data to see how
the proposed cuts affect the signal. This will require a
larger sample of data from Pythia.
I would also like to
begin to work with data coming in from PHENIX when there is
a reasonable sample size to work with.
Fig. 1 Momentum distributions of neutral pions, charm mesons, and
bottom mesons, with and without the detector geometry angle cuts.
Fig 2. Rapidity versus pT for light, charm, and bottom mesons.
detector angle cuts restrict rapidity to |y|<0.35.
The