1. PHENIX Measurement on High pT h-h and g-h Azimuthal Correlations
Jiamin Jin
for the PHENIX collaboration
Quark Matter 2006, Shanghai
Nov. 18, 2006

2. Outline Motivation High pT p0-h correlation results (Cu+Cu/p+p)
Width and Yield
Moving on to direct g-h
Method
Results in Au+Au, how does it compare to p+p?
Conclusions

3. Motivation High pT suppression
Pattern persists up to 20GeV/c
Integral quantity, limited
sensitivity to medium properties
more differential observables needed, angular correlations!
How are inclusive spectra and jet associated yields related?
How is energy loss reflected in away side suppression?
Near side energy loss?
nucl-ex/ T

4. Construct CF, yield, various jet variables…
Correlation Function (CF)
Trigger Df
Assoc
Mixed events -- correct
PHENIX pair acceptance  

5. p0-h CF and yield: Cu+Cu vs p+p
p0: 5-10GeV/c
PHENIX Preliminary
CF(Df) [A.U.]
p0: 5-10GeV/c
PHENIX Preliminary
1/NtrigdN/dDf
0-20%
Cu+Cu
p+p
CF strength: ~ jet S/B, p+p > Cu+Cu
lines indicate flow modulated background. No flow in p+p
Per trigger Yield
away side peak seen in both systems

6. Near side jet shape: width
p0: 5-10GeV/c
Gauss width
Consistent Gauss width between Cu+Cu and p+p

7. Near side jet shape: Pout
red: Cu+Cu black: p+p
Pout
Enhancement of Pout tail in Cu+Cu (large Df), near side modified

8. Away side jet shape Gauss width
p0: 5-10GeV/c
Gauss width
Within errors, away side Gauss width shows no centrality dependence
No broadening from p+p to high trigger pT!

9. IAA: modification of yields
Red: near side
Blue: away side
IAA = Yield(Cu+Cu)
Yield(p+p) E
Near side IAA ~ unity
Away side IAA suppression ~0.6 at xE>0.4

10. Integrated IAA(0.4<xE<1.0) similar with RAA!
more suppression, as peripheral  central

11. Integrated IAA(0.4<xE<1.0) similar with RAA!
more suppression, as peripheral  central
similar to p0 RAA values!

12. Moving on to the next stage: direct g-h
Normal dijet (po-h):
Trigger bias: Ep < Ejet,, <z>~0.75
Possible surface bias
Direct g tagged jet:
No fragmentation: Eg ~ Ejet
No strong interaction, sensitive
to the whole medium
Proposed in hep-ph/
~10 years ago
hot dense medium p0 g

13. Moving on to the next stage: direct g-h
Normal dijet (po-h):
Trigger bias: Ep < Ejet,, <z>~0.75
Possible surface bias
Direct g tagged jet:
No fragmentation: Eg ~ Ejet
No strong interaction, sensitive
to the whole medium
Inclusive g-h Yield
Trigger photon is a mixture of
direct and hadron-decay photon
Need to subtract decay part
Proposed in hep-ph/
~10 years ago p0 g g g
hot dense medium
PHENIX Preliminary

14.   Method Construct inclusive g-h yield
Construct decay g-h yield via:
Pair by pair weighted summation
convolutes all p0-h pair contributions from higher pT
Weight reflects probability from kinematics for p0 at given pT to decay into photon in given pT range
Subtraction via:  

15.    Method Construct inclusive g-h yield
Construct decay g-h yield via:
Pair by pair weighted summation
convolutes all p0-h pair contributions from higher pT
Weight reflects probability from kinematics for p0 at given pT to decay into photon in given pT range
Subtraction via:   
p+p
# inclusive g
# decay g R=

16. First direct g-h yield in p+p, cmp with PYTHIA!
p+p: important baseline measurement!
PHENIX Preliminary
data
PYTHIA
PYTHIA 6.1
kT = 2.5 GeV
A nice confirmation of our method

17. First direct g-h yield in Au+Au!
Au+Au: study medium induced modification!
1/NtrigdN/dDf
1/NtrigdN/dDf
Df(rad)
Df(rad)
v2 modulated bkgd for inclusive/decay g subtracted from each corr. fn under ZYAM assumption (v2 from from single g/p measurements)
Near side yield consistent with 0
small fragmentation photon yield
Away side yield also small, suppressed!?

18. Comparison btw Au+Au and p+p
Black: Au+Au Red: p+p
1/NtrigdN/dDf
1/NtrigdN/dDf
Df(rad)
Df(rad)
Hint of away side modification in AuAu!

19. Comparison btw Au+Au and p+p
Black: Au+Au Red: p+p
1/NtrigdN/dDf
Df(rad)

20. Away side integrated yield
trigger g pT dependence
assoc. h pT dependence
centrality dependence + pp
p+p shows a systematic trend of having higher yields in the
away side than Au+Au!

21. Conclusions
Precision measurements of high pT dijets in Cu+Cu/p+p collisions
Near side modification visible in Pout distribution.
Away side yield suppressed; shape, peak width unchanged
Away side IAA quantitatively consistent with RAA
First measurements of high pT direct g-h yields in Au+Au/p+p collisions
Near side yield ~ 0
Hint of suppression of away side jets in Au+Au
Need more statistics to make conclusive statement
Upcoming Au+Au run

22. Some related posters
41 Nathan Grau Evolution of the Away-side Jet Shape and Yield From π0-h± Correlations in sqrt(sNN) = 200 GeV Au+Au collisions
43 Jiangyong Jia Study of the medium modification of the away side jet using π0-hadron correlation in AuAu/CuCu collisions in PHENIX
37 Matthew Nguyen Photon-hadron two particle correlations in sqrt(sNN) = 200GeV Au+Au collisions with the PHENIX detector
48 Hua Pei Medium Effect on Jet Correlations in Cu+Cu Collisions at sqrt(sNN) = 200 GeV at RHIC-PHENIX

23. PHENIX people

24. Backup slides

25. Per trigger yield suppressed
trigger direct g
away side jet

26. p0-h CF and yield: Cu+Cu vs p+p
p+p, trigger 5-10GeV/c
Cu+Cu, trigger 5-10GeV/c, 0-20%
CF strength: ~ jet S/B, pp > CuCu
away side peak seen above background in all systems

27. p0-h CF and yield: Cu+Cu vs p+p
p+p, trigger 5-10GeV/c
Cu+Cu, trigger 5-10GeV/c, 0-20%
CF strength: ~ jet S/B, pp > CuCu
away side peak seen above background in all systems
away side jet shape – pp: normal gaussian peak, CuCu: modified
- No dip, but extra yield ~ Df=2, conical structure?

28. Yield/IAA: for different centralities
Red: near side
Blue: away side
IAA = Yield(Cu+Cu)
Yield(p+p)
Near side IAA ~ unity
Away side yield suppressed! more suppression in central

30. Consistent width within Cu+Cu & p+p!
Near side
Away side
Near side widtht decreases with pT
Away side gauss width no centrality dependence