10/20/06Hard/Photon Analysis Fest

1

Measuring bremsstrahlung photons in pp

collisions (update)

Ali Hanks

Group Meeting

Oct. 16, 2006

10/20/06Hard/Photon Analysis Fest

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

10/20/06Hard/Photon Analysis Fest

3

Method (cont’d)

• Associated 0-decay per trigger yield:

• Include contribution from other hadronic decays:

• Associated frag per trigger yield:

10/20/06Hard/Photon Analysis Fest

4

h-inc

per trigger yield

10/20/06Hard/Photon Analysis Fest

5

h-tagged

per trigger yield

10/20/06Hard/Photon Analysis Fest

6

Tagging efficiency

• Simulation generates 0s in a

guassian distribution around a

“trigger” hadron

– distribution is pT dependant

– determined from real data

• Let these 0s decay and compare

resulting h- distribution for

single photon acceptance and pair

acceptance

0

trigger

∆

hadron- ∆ distribution

two particle acceptance

three particle acceptance

10/20/06Hard/Photon Analysis Fest

7

0 distribution from data

10/20/06Hard/Photon Analysis Fest

8

0 distribution from data

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

10/20/06Hard/Photon Analysis Fest

9

Tagging efficiency estimates

• Study tagging efficiency as a function of in same pT bins as data

• Still need to do this with input 0 spectrum from pp

10/20/06Hard/Photon Analysis Fest

10

h-tagged

per trigger yield• With estimated tagging efficiency included

10/20/06Hard/Photon Analysis Fest

11

h-subtracted

per trigger yield• h-

inc – h-

tagged with tagging efficiency included

10/20/06Hard/Photon Analysis Fest

12

To Do

• Complete work on subtraction of h-decay

– 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 0

10/20/06Hard/Photon Analysis Fest

13

Hot tower Maps

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

10/20/06Hard/Photon Analysis Fest

14

Hot tower Maps

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

10/20/06Hard/Photon Analysis Fest

15

Hot tower Maps

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

10/20/06Hard/Photon Analysis Fest

16

Tagging efficiency