results on deuteron – gold collision at forward rapidity in phenix ihnjea choi (uiuc) for the...
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Results on deuteron – gold collision at forward rapidity in PHENIX
IhnJea Choi
(UIUC)
For the PHENIX collaboration
01/04/2012
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Outline
• d+Au collision– 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
• Summary1/4/12 HEP2012@Chile
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d+A Collision
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DeutronParton x_d
AuParton x_Au
DeutronParton x_d
AuParton x_Au
Forward rapidity(Deutron going direction)x_d > x_Au (Low x in Au)
Backward rapidity(Au going direction)x_Au > x_d
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)?
Why hadron production suppressed at forward rapidity !
p0 meson
PHENIX |h| < 0.35
RdA
RdA ~ 1 at mid rapidity
PRL 98 (2007), 172302
STAR, BRAHMS Forward hPRL 97 (2006), 152302
Nuclear Modification factor Cold Nuclear Matter(CNM) effect
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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.
STAR BRAHMS results show RdA < 1
As y, energy grows
Color Glass Condensate & Effect
Kharzeev, Kovchegov, and Tuchin, hep-ph/0307037
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Phase diagram of QCD evolution
RpA suppressed at all values of pT as rapidity / energy grows.
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Gluon density saturates for large denisites at small x
Mechanism for gluon saturation
Y is related to rapidity of produced hadron
Nuclear Shadowing / Energy Loss / Absorption
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Energy loss of incident gluon shifts effective xF and produces nuclear suppression which increases with xF
R(A/p)
R=1 xF
pA
D
Dccmoversco-
Absorption (or dissociation) of into two D mesons by nucleus or co-movers
cc
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Shadowing can arise from coherence - Small-x wavefunction spans large longitudinal distances
λ ~ 1/pparton ~ 1/xi.e. the probe interacts with multiple target nucleons coherently
STAR
RHIC
Completed as of 2006
Completed as of 2006
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Run3 d+Au 2.74 nb-1 MB triggered
Run8 d+Au 85 nb-1 MB triggered
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RHIC Luminosity
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PHENIX Detector
Muon Arms 1.2 < | η | < 2.4• Heavy Flavor muons• J/Psi• Charged hadrons
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
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Installed2005-7
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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 2005-2007Usable for 2008 d+Au run.
MPC
p0gg
Merged p0gg
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Single hadron results
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Phys. Rev. Lett. 94, 082302 (2005)
•Forward rapidity suppression •No backward rapidity suppression (slightly enhanced)
• Consistent result with BRAHMS results ( η = 2.2 )
Punch Through Hadron & Hadron Decay Muon RCP
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Mostly π+-,Κ+- and their decay into μ+-
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Heavy quarks RdAu
y = 1.6
Single muons from open charm & beauty:• at forward rapidity suppressed • at backward rapidity enhanced
y = -1.6
Forward/Backward rapiditySingle muon
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CNM effects in J/ψ production
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.
PHENIX arXiv:1010.1246v1
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Gluon saturation model is good agreement with data at forward rapidity.
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Y(1S + 2S + 3S) RdA
RdAu = 0.84±0.34(stat.)±0.20(sys.), backward rapidityRdAu = 0.53±0.20(stat.)±0.16(sys.), forward rapidity
• Shows suppression at forward rapidity
STAR Preliminary
PHENIX Preliminary
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Y access different low x range to J/Ψ : Y(x~0.01), J/ψ (x ~ 0.003)
Light vector meson RCP
Comparing Nuclear Modification Factor RCP for ϕ, ρ, ω.
forward rapidityBackward rapidity
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• 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? )
Forward π0 results for RdA
Suppression increase with increasing rapidity and centrality
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PHENIX MPC
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Forward π0 RdA, Model Comparison
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PHENIX MPCShadowing Model overperdicted RdA of central collision data
STAR forward RdA vs. Cronin + Shadowing + E_loss Model good agreement with data
R. B. Neufeld, I. Vitev, and B-W Zhang arXiv:1010.3708
Di-hadron correlation
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Accessing Low-x with Di-Hadrons
Guzey, Strikman, Vogelsang, PL B603, 173
Di-Hadrons from Di-Jets Narrow x-rangeSmaller mean x, Constrain x-range !
Single Hadrons
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•However, x covered by single inclusive measurement is over wide range
• Includes shadowing, anti-shadowing, (EMC effect)
Measure Df of all particle pairs trigger particle (usually leading pT) associate particle (lower pT)
trigger
associate
Df
Beam viewor 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
Df
Awayside Peak
Beam View
Di-hadron azimuthal angle correlation
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Df
CORRELATED NpairCY ( Conditional Yield ) Number of particle pairs per
trigger particle after corrections for efficiencies, combinatoric background, and subtracting off pedestal.
Di-Hadron pair Nuclear Modification factor
pppairpp
dApairdA
colldA NJ
/
/1
ppsglpp
dAsgldA
colldA NR
/
/1
CY / IdA / JdA
Trigger comparison of d+Au jet associated
counts relative to pp
d
dN
NN
NCY
assoc
trigassoctrig
pair 1
Single hadron Nuclear Modification Factor
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J. L. Albacete and C. Marquet, PRL105 (2010) 162301
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)
• 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
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No significant broadening mid-forward rapidity azimuthal correlations (FMS-BEMC/FMS-TPC) Significant broadening for forward di-pion correlations (FMS-FMS)
Strong suppression of away side peak for central forward-forward correlationwith CGC prediction
Di-hadron azimuthal correlation STAR
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arXiv:1008.3989v1
Multiple soft scatterings de-correlate the away side peak
dynamical shadowing, Energy Loss, Cronin
Dihadron, Shadowing
•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)
(Qiu, Vitev PLB632:507,2006)
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Dihadron, Multi Parton Interaction(MPI)
At large forward rapidity range,
azimuthal-angular independent pedestal component
−> expected significant enhancement at central dAu collision
STAR PRL 97, 152302π0: |<η>| = 4.0, h±: |η| < 0.75, pT > 0.5 GeV/c
PRD 83, 034029M. Strikman, W. Vogelsang
Forward (Muon) – Mid rapdity, IdA
Phys.Rev.Lett.96:222301,2006
dAu 1.4< η <2.0
η < | 0.35|
No significant suppression or widening seen within large uncertainties!
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-2 < η < -1.4
Only away side peak seen due to rapidity gap
Mid-Forward Correlations
dAu
PHENIX central spectrometer magnet
Backward direction (South)
Forward direction (North)
Muon Piston Calorimeter (MPC)
Side View
dAu
p0s
p0 or h+/-
xgluon ~ 10-2 (0.008,0.04)
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Di-hadron Correlation, Mid-Fwd • Mid-rapidity triggered
|hmid| < 0.35, hfwd = 3.0-3.8
• Normalized by pi0 triggers and subtracted uncorrelated background (b0)• Due to large rapidity separation, only away side peak is seen.
PRL107, 172301 (2011)
• Central d+Au collision shows suppression of away side peak• No away side peak width broadening apparent
|hmid| < 0.35, hfwd = 3.0-3.8
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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%
ppdAu 40-88%
•Widths are consistent between p+p and d+Au (all centralities) within large statistical and systematic errors•No broadening seen (within errors)
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Forward-Forward Correlations h1,2 = 3.4
dAu
PHENIX central spectrometer magnet
Backward direction (South)
Forward direction (North)
Muon Piston Calorimeter (MPC)
Side View
dAu
Mostly Merged p0s
clusters
p0
xgluon ~ 10-4-10-3 (0.001, 0.005)
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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 = 3.0-3.8
PRL107, 172301 (2011)
• Normalized by pi0 triggers and subtracted uncorrelated background (b0, ZYAM)• Minimum cluster separation cut decrease amount of near side peak
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JdA (Mid-Fwd, Fwd-Fwd)
Suppression of JdA increases withNcoll increasePT mid decreasePT fwd decrease
Suppression Larger in fwd-fwd than mid-fwd
Centrality dependent suppression
Suppression of JdA increases withNcoll increase
Note: points offset from true <Ncoll> to show pT dependence
PRL107, 172301 (2011)
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dcdab
pbpp
ap
d
cdab
AubAud
ad
pppairsppcoll
dAupairsdAu
dA
zzDxfxf
zzDxfxf
NJ
c
c
,)()(
,)()(
/
/
JdA versus RGAu ?
Low x, mostly gluons JdA High x, mostly quarksWeak effects expected ~ RG
Au
b=0-100%Q2 = 4 GeV2
xAu
EPS09 NLO gluonsEskola , Paukkunen, Salgado, JHP04 (2009)065
RGAu
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Forward-Forward Mid-Forward
s
epepx TTfragAu
21
21
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arXiv:1109.2133v1
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“ 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)
This model explains both suppression and broadening of away side peak well.
PHENIX JdA with model STAR Δϕ correlation with model
Recent model predict
Zhong-Bo Kang, Ivan Vitev, Hongxi Xing et al, arXiv(1112.6021)
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dAu
Summary
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• 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 ~ RG
AU
• Recent model calculation for both JdA and away side peak width
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Backup slide
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Nuclear Shadowing models
N. Armesto Hep-ph/0604108v2
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.
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4040
PHENIX Muon Piston Calorimeter
Small cylindrical holes in Muon Magnet Pistons, Radius 22.5 cm and Depth 43.1 cm
SOUTH
PbWO4
North
)( 43 yyTd ee
s
px )( 43 yyT
Au ees
px
•Fwd-Fwd, x~(0.001,0.005)•Mid-Fwd, x~(0.008,0.040)•Mid-Bwd, x~(0.050,0.100)
d(forward) Au(backward)
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MPC PerformanceNorth MPC
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)
“Trigger”NearFar
Jet1
Jet2
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RCP and RdAu show strong rapidity dependence
Brahms data
Strong suppression at large rapidity (small-x)
More central, larger rapidity range 1/4/12 HEP2012@Chile
Quarkonia Suppression in A+A Collisions
Recent Gluon Saturation (CGC) calculations (arXiv:1109.1250v1) 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
PHENIX y=1.7
PHENIX y=0
ALICE y~3.2
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J/ψ in d+Au – learning about CNM thickness dependence
Nuclear effects are dependent on the density weighted longitudinal thickness of Au
0
1( ) ( , )T Tr dz z r
The forward rapidity points suggest a quadratic geometry dependence.
Circle : Sys err.
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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)
Smaller fitting range:0.5-2.5 GeVLarger parameter range
Estimated background
r f w
r f w
y>0, Centrality: 40-60 y>0, Centrality: 40-60
Larger fitting range:0.4-2.6GeVSmaller parameter range
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