Measuring bremsstrahlung photons in pp collisions update

1
Measuring bremsstrahlung photons in pp collisions
(update)

• Ali Hanks
• Group Meeting
• Oct. 16, 2006

2
Method

• Fragmentation photons are correlated with high pT
  jets
• Use h-? correlations to select photons associated
  with jets
• Tagging method for estimating decay photon
  background
• Tag photons from ?0 using invariant mass
  distribution
• Estimate tagging efficiency with fastmc

3
Method (contd)

• Associated ??0-decay per trigger yield
• Include contribution from other hadronic decays
• Associated ?frag per trigger yield

4
h-ginc per trigger yield
5
h-gtagged per trigger yield
6
Tagging efficiency

• Simulation generates p0s in a guassian
  distribution around a trigger hadron
• distribution is pT dependant
• determined from real data
• Let these p0s decay and compare resulting h-g Df
  distribution for single photon acceptance and
  pair acceptance

?
p0
trigger
hadron-? ?? distribution
two particle acceptance
three particle acceptance
??
7
?0 distribution from data
8
?0 distribution from data

• Use sigma values from fit as input for
  distributions generated in same pT bins

9
Tagging efficiency estimates

• Study tagging efficiency as a function of Df in
  same pT bins as data
• Still need to do this with input p0 spectrum from
  pp

10
h-gtagged per trigger yield

• With estimated tagging efficiency included

11
h-gsubtracted per trigger yield

• h-ginc h-gtagged with tagging efficiency
  included

12
To Do

• Complete work on subtraction of h-gdecay
• Study tagging to check for possible over-tagging
• Check esitmate of tagging efficiency for errors
• contribution from other hadronic decays
• Still not clear if shape is same as for g?0

13
Hot tower Maps

• hot towers for cluster with pT from 1-2 GeV/c

14
Hot tower Maps

• hot towers for cluster with pT from 2-3 GeV/c

15
Hot tower Maps

• hot towers for cluster with pT from 3-20 GeV/c

16
Tagging efficiency