1. Results on deuteron – gold collision at forward rapidity in PHENIX
IhnJea Choi
(UIUC)
For the PHENIX collaboration
01/04/2012
1/4/12

2. Outline d+Au collision Experiment
Nuclear Modification Factor
Competing models
CGC, Shadowing, Energy Loss, Absorption
Experiment
RHIC
RHIC luminosity, PHENIX experiment
MPC ( Muon Piston Calorimeter in PHENIX )
Hadron RdA , RCP results at different rapidity ranges
Hadron and decay muon
Single electron and single muon
J/ψ, Υ
Light vector meson (ϕ, ρ, ω)
Di-hadron azimuthal angle correlation results
CY, IdA, JdA
Mid-forward rapidity correlation
Forward-forward rapidity correlation
Summary
1/4/12

3. d+A Collision
RHIC experiments have made an amazing array of measurements in d+Au
 to understand cold nuclear matter
   Initial state effects vital to interpreting results from heavy
     ion collisions
  Are effects at forward rapidity due to gluon saturation effects (have we
reached a regime of QCD where non-linear effects are important)?
Backward rapidity
(Au going direction)
x_Au > x_d
Deutron
Parton x_d Au
Parton x_Au
Deutron
Parton x_d Au
Parton x_Au
Forward rapidity
(Deutron going direction)
x_d > x_Au (Low x in Au)
1/4/12

4. Why hadron production suppressed at forward rapidity !
Nuclear Modification factor
Cold Nuclear Matter(CNM) effect
STAR, BRAHMS Forward h
PRL 97 (2006),
p0 meson
PHENIX |h| < 0.35
RdA
RdA ~ 1 at mid rapidity
PRL 98 (2007),
STAR BRAHMS results show RdA < 1
Compelling theory models to explain this suppression at forward rapidity.
Gluon saturation(or CGC)
Nuclear shadowing/ E_loss
Parton recombination
Multi Parton Interaction (MPI)
Momentum imbalance (recent paper)
etc.
1/4/12

5. Color Glass Condensate & Effect
Y is related to rapidity
of produced hadron
Kharzeev, Kovchegov, and Tuchin, hep-ph/
Gluon density saturates for
large denisites at small x
As y, energy grows
Phase diagram of QCD evolution
Mechanism for gluon saturation
RpA suppressed at all values of pT as
rapidity / energy grows.
1/4/12

6. Nuclear Shadowing / Energy Loss / Absorption
Shadowing can arise from coherence
- Small-x wavefunction spans large longitudinal
distances
λ ~ 1/pparton ~ 1/x
i.e. the probe interacts with multiple target nucleons coherently
Energy loss of incident gluon shifts effective xF and produces nuclear suppression which increases with xF
R(A/p)
R=1 xF A p
Absorption (or dissociation) of into two D mesons by nucleus or co-movers
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7. RHIC
Completed as of 2006
STAR
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8. RHIC Luminosity Run3 d+Au 2.74 nb-1 MB triggered
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9. PHENIX Detector Central Arms | η | < 0.35 Charged hadrons
Neutral pions / η-mesons
Heavy Flavor electrons
Direct Photon
J/Psi
Muon Piston Calorimeter (MPC)
3.1 < | η | < 3.8
Neutral pions / η-mesons
Muon Arms < | η | < 2.4
Heavy Flavor muons
J/Psi
Charged hadrons
Installed
2005-7
1/4/12

10. PHENIX Muon Piston Calorimeter (MPC)
Technology  ALICE(PHOS)
PbWO4
avalanche photo diode readout
2.20 x 2.2 x 18 cm3 crystals
Acceptance:
3.1 < η < 3.9, 0 < φ < 2π
-3.7 < η < -3.1, 0 < φ < 2π
Both detectors built, installed
Usable for 2008 d+Au run.
MPC
p0gg
Merged p0gg
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11. Single hadron results
1/4/12

12. Punch Through Hadron & Hadron Decay Muon RCP
Phys. Rev. Lett. 94, (2005)
Mostly π+-,Κ+- and their decay into μ+-
Forward rapidity suppression
No backward rapidity suppression (slightly enhanced)
Consistent result with
BRAHMS results ( η = 2.2 )
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13. Heavy quarks RdAu Single muons from open charm & beauty:
at forward rapidity suppressed
at backward rapidity enhanced
y = 1.6
y = -1.6
Forward/Backward rapidity
Single muon
1/4/12 13

14. CNM effects in J/ψ production
PHENIX arXiv: v1
Reasonable agreement with EPS09 nPDF + br=4 mb for central collisions but not peripheral
EPS09 with linear thickness dependence fails to describe centrality dependence of forward rapidity region.
Gluon saturation model is good agreement with data at forward rapidity.
1/4/12

15. Y(1S + 2S + 3S) RdA PHENIX Preliminary STAR Preliminary
Shows suppression at forward rapidity
RdAu = 0.84±0.34(stat.)±0.20(sys.), backward rapidity
RdAu = 0.53±0.20(stat.)±0.16(sys.), forward rapidity
Y access different low x range to J/Ψ : Y(x~0.01), J/ψ (x ~ 0.003)
1/4/12

16. Light vector meson RCP
Comparing Nuclear Modification Factor RCP for ϕ, ρ, ω.
Backward rapidity
forward rapidity
Significant suppression in forward rapidity
Stronger suppression for r/w than f and J/Y
( Due to lighter quark content, and/or different production mechanisms? )
1/4/12

17. Forward π0 results for RdA
PHENIX MPC
Suppression increase with increasing rapidity and centrality
1/4/12

18. Forward π0 RdA, Model Comparison
R. B. Neufeld, I. Vitev, and B-W Zhang arXiv:
STAR forward RdA vs.
Cronin + Shadowing + E_loss Model
 good agreement with data
PHENIX MPC
Shadowing Model
overperdicted RdA of central collision data
1/4/12

19. Di-hadron correlation
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20. Accessing Low-x with Di-Hadrons
Guzey, Strikman, Vogelsang, PL B603, 173
Single Hadrons
However, x covered by single inclusive measurement is over wide range
Includes shadowing, anti-shadowing, (EMC effect)
Di-Hadrons from Di-Jets
 Narrow x-range
Smaller mean x, Constrain x-range !
1/4/12

21. Di-hadron azimuthal angle correlation
Measure Df of all particle pairs
trigger particle (usually leading pT)
associate particle (lower pT)
trigger
associate Df
Beam view
or transverse plane
p+p, d+Au di-hadron correlations are similar at mid rapidity
Dh=0 is similar for d+Au (closed) and p+p (open)
S.S Adler et al, Phys. Rev. C 73:054903,2006.
Away-side
Near-side Df
Nearside peak
Beam View Df
Awayside Peak
1/4/12

22. CY / IdA / JdA Df CY ( Conditional Yield )
CORRELATED Npair
CY ( Conditional Yield )
Number of particle pairs per trigger particle after corrections for efficiencies, combinatoric background, and subtracting off pedestal. Df
Trigger comparison of d+Au jet associated
counts relative to pp
Di-Hadron pair Nuclear Modification factor
Single hadron Nuclear Modification Factor
1/4/12

23. Di-hadron, CGC signature
D. Kharzeev, E. Levin, and L. McLerran Nucl. Phys. A748 (2005) 627–640
Mid-forward di-hadron correlation
Strength of correlation -> CGC phase or still in pQCD
Expected large suppression in dAu than pp
Expected angle broadening of away side peak
Later, not reached low enough low x to see CGC effect
J. L. Albacete and C. Marquet, PRL105 (2010)
J.L Albacete and C.Marquet, PRL105 (2010)
Fwd-Fwd di-hadron correlation
Access lower x region than mid-forward cor.
CGC predicts significant b-dependence to suppression expected
Width broadening expected at away side peak
High pt of jet balanced by many gluons, Monojet
Fwd di-hadron correlation measurements provide a good testing of CGC theory model
1/4/12

24. Di-hadron azimuthal correlation STAR
No significant broadening mid-forward rapidity azimuthal correlations (FMS-BEMC/FMS-TPC)
Significant broadening for forward di-pion correlations (FMS-FMS)
arXiv: v1
Strong suppression of away side peak for central forward-forward correlation
with CGC prediction
Multiple soft scatterings de-correlate the away side peak
1/4/12

25. Dihadron, Shadowing
dynamical shadowing, Energy Loss, Cronin
(Qiu, Vitev PLB632:507,2006)
Di-Hadron Correlations allow one to select out the di-jet from the underlying event
Constrains x range (probe one region at a time)
Probe predicted angular decorrelation of di-jets (width broadening)
1/4/12

26. Dihadron, Multi Parton Interaction(MPI)
PRD 83,
M. Strikman, W. Vogelsang
STAR
PRL 97,
π0: |<η>| = 4.0, h±: |η| < 0.75, pT > 0.5 GeV/c
At large forward rapidity range,
azimuthal-angular independent pedestal component
−> expected significant enhancement at central dAu collision
1/4/12

27. Forward (Muon) – Mid rapdity, IdAAu d
-2 < η < -1.4
1.4< η <2.0
η < | 0.35|
Phys.Rev.Lett.96:222301,2006
No significant suppression or widening seen within large uncertainties!
Only away side peak seen due to rapidity gap
1/4/12

28. Mid-Forward Correlations
p0s
p0 or h+/-
PHENIX central spectrometer magnet
Muon Piston Calorimeter (MPC) d Au d Au
xgluon ~ 10-2 (0.008,0.04)
Forward direction (North) 
Backward direction (South) 
Side View
1/4/12

29. Di-hadron Correlation, Mid-Fwd
Mid-rapidity triggered
Central d+Au collision shows suppression of away side peak
No away side peak width broadening apparent
|hmid| < 0.35, hfwd =
|hmid| < 0.35, hfwd =
Normalized by pi0 triggers and subtracted uncorrelated background (b0)
Due to large rapidity separation, only away side peak is seen.
PRL107, (2011)
1/4/12

30. Away side peak widths broadening ?
Trigger p0: |h| < 0.35, 2.0 < pT < 3.0 GeV
Trigger p0: |h| < 0.35, 3.0 < pT < 5.0 GeV
dAu 0-20% pp
dAu 40-88%
Widths are consistent between p+p and d+Au (all centralities) within large statistical and systematic errors
No broadening seen (within errors)
1/4/12

31. Forward-Forward Correlations h1,2 = 3.4
Mostly Merged p0s
clusters p0
PHENIX central spectrometer magnet
Muon Piston Calorimeter (MPC) d Au d Au
xgluon ~ (0.001, 0.005)
Forward direction (North) 
Backward direction (South) 
Side View
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32. Di-hadron Correlation, Fwd-Fwd
Forward rapidity triggered
Central d+Au appears to show significant suppression
Angular broadening possible in central d+Au
hclus,p0 =
PRL107, (2011)
Normalized by pi0 triggers and subtracted uncorrelated background (b0, ZYAM)
Minimum cluster separation cut decrease amount of near side peak
1/4/12

33. JdA (Mid-Fwd, Fwd-Fwd) PRL107, 172301 (2011)
Note: points offset from true <Ncoll> to show pT dependence
Suppression of JdA increases with
Ncoll increase
PT mid decrease
PT fwd decrease
Suppression of JdA increases with
Ncoll increase
Suppression Larger in fwd-fwd than mid-fwd
Centrality dependent suppression
1/4/12

34. JdA versus RGAu ? EPS09 NLO gluons RGAu xAu  JdA  ~ RGAu b=0-100%
Forward-Forward
Mid-Forward
b=0-100%
Q2 = 4 GeV2
xAu
EPS09 NLO gluons
Eskola , Paukkunen, Salgado, JHP04 (2009)065
RGAu
arXiv: v1
Low x, mostly gluons
 JdA 
High x, mostly quarks
Weak effects expected
~ RGAu
1/4/12

35. Recent model predict
“ Dihadron momentum imbalance and correlations in d+Au collisions”
Initial- and final-state multiple interactions can affect dijet(dihadron ) production in p+A(d+A)
Zhong-Bo Kang, Ivan Vitev, Hongxi Xing et al, arXiv( )
dAu
PHENIX JdA with model
STAR Δϕ correlation with model
This model explains both suppression and broadening of away side peak well.
1/4/12

36. Summary
d+Au collision at forward rapidity range enables us to study low-x physics
PHENIX RdA , RCP of single hadron results showed suppression and consistent with STAR and BRAHMS data
Di-hadron azimuthal angle correlation measurement
Large suppression of away side peak seen in forward-forward correlation in d+Au relative to p+p (Jda)
More suppressed in most central collision
Angular Broadening of away side peak
Mid-forward rapidity, no increase seen within errors
Fwd-Fwd, increase seen in STAR data, currently inconclusive in PHENIX data
Measurements of JdA ~ RGAU
Recent model calculation for both JdA and away side peak width
1/4/12

37. Backup slide
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38. Nuclear Shadowing models
N. Armesto Hep-ph/ v2
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39. Centrality Selection Charged particle track distribution representing
92% (+/- 2% systematic)
of the 7.2 barn total Au+Au cross section.
We then select event classes based on geometry (number of participating nucleons) using the Zero Degree Calorimeter and Beam-Beam Counter.
1/4/12

40. PHENIX Muon Piston Calorimeter
d(forward)
Au(backward)
North
SOUTH
Add d, Au cartoon, define forward, mid, backward
Fwd-Fwd, x~(0.001,0.005)
Mid-Fwd, x~(0.008,0.040)
Mid-Bwd, x~(0.050,0.100)
PbWO4
Small cylindrical holes in Muon Magnet Pistons, Radius 22.5 cm and Depth 43.1 cm
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41. MPC Performance North MPC
“Trigger”
Near
North MPC
Far
Jet1
Jet2
Decay photon impact positions for low and high energy p0s. The decay photons from high energy p0s merge into a single cluster
Sometimes use (EM) clusters, but always corrected to 0 energy
Clusters  80% 0 (PYTHIA)
MPC Performance Proof, Explanation of merging at “low” pt
1/4/12

42. RCP and RdAu show strong rapidity dependence
Brahms data
Strong suppression at large rapidity (small-x)
More central, larger rapidity range
1/4/12

43. Quarkonia Suppression in A+A Collisions
Recent Gluon Saturation (CGC) calculations (arXiv: v1) also leave room for QGP effects in A+A collisions
However, they do not help explain the stronger suppression at forward rapidity in A+A
y=-1.7
y=0
y=1.7
ALICE y~3.2
PHENIX y=0
PHENIX y=1.7
1/4/12

44. J/ψ in d+Au – learning about CNM thickness dependence
Nuclear effects are dependent on the density
weighted longitudinal thickness of Au
Circle : Sys err.
The forward rapidity points suggest a quadratic geometry dependence.
1/4/12

45. Yield Extraction Examples
Fitting function: Two Gaussian (f/w) + One Relativistc BW (r) +Background (Defined by estimated shape)
f yields stable when fitting procedure changes
r+w yields using background subtraction (large uncertainty)
y>0, Centrality: 40-60
y>0, Centrality: 40-60
Estimated background
r f w
r f w
Larger fitting range: GeV
Smaller parameter range
Smaller fitting range: GeV
Larger parameter range
1/4/12