1. Measuring Bremsstrahlung Photons in s = 200GeV p-p Collisions
Columbia University, for the PHENIX Collaboration
Ali Hanks,
Zakharov hep-ph/
no quenching
with quenching
Just bremsstrahlung photons
Motivation
Photons radiated will not interact with the medium - make a good probe
In heavy ion collisions as jets propogate through the medium they lose energy through gluon radiation
Radiated gluons are lost through interaction with the medium
Provide direct measure of radiation spectrum
Expect strong final state interaction effects on bremsstrahlung photon cross-section
Gluon radiation spectrum cannot be measured directly
RAA predictions show significant enhancement for pT<10GeV/c
p-p reference
In pp collisions the "bremsstrahlung" photons are produced as the jets fragment
At next-to-leading-order pQCD describes the proton-proton photon cross-section well
Includes fragmentation component ≥ 20%
The distinction between direct and fragmentation photons blurs
Isolation cuts can be used to distinguish direct photons experimentally
however it is difficult to incorporate these cuts into the theory calculations
A direct measurement of the fragmentation component will provide a good test of the theory
INCNLO(v1.4):
J. Ph. Guillet, M. Werlen et al
trigger hadrons are detected using DC-PC1 tracks and PC3 projections
photons are detected using the the EMC
Method
two particle acceptance - all  in accpetance
three particle acceptance -  pair in acceptence
Tagging efficiency calculated from fastmc
 and pT dependent input distribution taken from data to simulate 0's correlated with high pT hadrons
Fragmentation photons are picked out by selecting photons associated with a high pT hadron
Hadron trigger from 2-20 GeV/c, assoc from GeV/c
Inclusive yield contains both fragmentation photons and the hadronic decay background p0
trigger 
 for all accepted  vs
 when sister  falls in acceptence as well
0 tagging method to calculate decay background
photons that fall in the 0 mass peak window are tagged
This gives us the corrected 0 decay yield:
Assuming a similar shape for other hadronic decays, the 0 decay yield can be used to calculate total decay yield:
The yield for tagged photons now needs to be corrected for efficiency
h-frag per trigger yield calculated using fully corrected decay per trigger yield
The tagged  yield, including corrections, can be subtracted from the inclusive yield, leaving only the fragmentation photons remaining
19thInternational Conference on Ultra-Relativistic Nucleus-Nucleus Collisions: November, 2006; Shanghai, China