Forward (onium) physics from
PHENIX
Mickey Chiu
Why are we interested?•High energy behavior might be universal across all hadrons and predicted entirely by the CGC E2ln~ Eas
CGC: )/(ln~~~ 222QCDT Eyb
•Geometric Scaling
•Strongly coupled regime which becomes classical computable!
0.3
x < 10-2
CGC in Heavy Ion Collisions •As Initial state for Heavy Ion Collisions
•Multiplicity Distributions
•Long range correlations from a “glasma”, explanation of the ridge
PHOBOS W=200 GeV
But the outstanding question is, do we see the CGC at RHIC?
ln 1x related to rapidity of
produced hadrons.
As y grows
Expectations for a color glass condensate
Kharzeev, Kovchegov, and Tuchin, hep-ph/0307037
Iancu and Venugopalan, hep-ph/0303204
Are the forward d+Au results evidence for gluon saturation at RHIC energies?Not clear. Need more data, and more observables.
22 Hard Scattering (LO)
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a. y3 forward, y4 backwards (MPC.S-MPC.N)
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yT es
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p1p2
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Initial State:
Final State:
Special Cases:
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 6
PHENIX Muon Piston Calorimeter
Small cylindrical hole in Muon Magnet Piston, Radius 22.5 cm and Depth 43.1 cm
SOUTH NORTH
2.16Refractive Index
420-440, 500 nmMain Emission Lines
1000 GyRadiation Hardness
-2% / CTemp. Coefficient
~10 p.e./MeV @ 25 CLight Yield
22.4 cmInteraction Length
0.89 cmRadiation Length
2.0 cmMoliere radius
721.3 gWeight
20 X0, 0.92 Length
2.2x2.2x18 cm3Size
8.28 g/cm3Density
PbWO4
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 7
-3 -2 -1 0 1 2 3 rapidity
cove
rage
2
EM
CA
L +
Ce
ntr
al
Tra
ck
er
PHENIX Acceptance
MP
C
MP
C
•Addition of MPC increases PHENIX acceptance for calorimetry by a factor of 4 (with a detector more than 10 times smaller)•Especially important that the very forward region (>3) is covered
EM
CA
L +
Ce
ntr
al
Tra
ck
er
Sou
th M
uon
Tra
cker
North M
uon T
racker
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 8
PHENIX Side View
Muon Piston
Muon Piston Calorimeter (MPC)
PHENIX central spectrometer magnet
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 9
Forward/Central Correlation
dAu0, or
clusters
PHENIX central spectrometer magnet
Backward direction (South) Forward direction
(North)
Muon Piston Calorimeter (MPC)
0 or h+/-
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 10
• The MPC can reliably detect pions (via 0) up to 17 GeV in energy– Limitations are the tower separation and merging effects
pT max ~ 1.7 GeV/c
• To go to higher pT, use single clusters in the calorimeter
– Use 0s for 7 GeV < E < 17 GeV
– Use clusters for 20 GeV < E < 50 GeV
• Correlation measurements are performed using 0s, clusters
• Use event mixing to identify pions form foreground (same event pairs) and mixed event background photon pair distributions
MPC Pion/Cluster IdentificationNorth MPC
Minv (GeV/c2)
12 < E < 15Foreground
Background
Yield
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 11
Correlation Measurements sNN = 200 GeV d-Au, pp collisions from 2008 at RHIC
– No flow contribution
– Rapidity separated jets produce no nearside peak
Constant background + Gaussian signal
• Trigger particles are (0, h+/-) with || < 0.35• Associate particles are 0, clusters with 3.1 < < 3.9• One method to quantify the correlation:
– To compare pp with dA, form ratio of conditional yields
)Acceptance
/
Acceptance
/(6.1/2
Acceptance
/ 2
8.02
8.0
0
FGFGFGpair
ddNd
ddNd
ddNN
assoctrig
pair
N
NCY
Npair
pp
dAdA CY
CYI
Peripheral d-Au Correlation Function
Acceptance
/ FGddN
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 12
h+/- (trigger,central)/0 (associate,forward)
<pTa>=0.55 GeV/c
pp
Cor
rela
tion
Fu
nct
ion
dAu 0-20%
dAu 60-88%
<pTa>=0.77 GeV/c <pT
a>=1.00 GeV/c
pTt,
h+/-
pTa, 0
1.0 < pTt < 2.0 GeV/c
for all plots
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 13
0 (trigger,central)/0 (associate,forward)
<pTa>=0.55 GeV/c
pp
Cor
rela
tion
Fu
nct
ion
dAu 0-20%
dAu 60-88%
<pTa>=0.77 GeV/c <pT
a>=1.00 GeV/c2.0 < pTt < 3.0 GeV/c
for all plots
pTt, 0
pTa, 0
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 14
0 (trigger,central)/cluster (associate,forward)
<pTa>=1.09 GeV/c
pp
Cor
rela
tion
Fu
nct
ion
dAu 0-20%
dAu 60-88%
<pTa>=2.00 GeV/c <pT
a>=3.10 GeV/c2.0 < pTt < 3.0 GeV/c
for all plots
pTt, 0
pTa,
cluster
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 15
Forward/Central Correlation Widths
• No significant changes in correlation width between pp and dAu within experimental uncertainties
Trigger 0: |< 0.35, 2.0 < pT < 3.0 GeV/c Trigger 0: |< 0.35, 3.0 < pT < 5.0 GeV/c
dAu 0-20%
ppdAu 40-88%
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 16
Forward/Central IdA vs Ncoll
• Increasing suppression of IdA reaches a factor 2 for central events
• Model calculations are needed to distinguish between different models– Saturation (Color
Glass Condensate)
– Shadowing– Cronin– Others?
Associate 0: 3.1 < < 3.9, 0.45 < pT < 1.59 GeV/c
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Muon-Central IdA & Widths, 2003 d+Au
Phys.Rev.Lett.96:222301,2006
dAu
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
d+Au RCP, 1.2<||<2.2
RHIC experiments have observed a suppression of hadron production relative to binary collision scaling in deuteron-gold reaction at forward rapidity sensitive to low x partons in the gold nucleus, Phys.Rev.Lett.94:082302,2005).
PHENIX 2003 d+Au
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Kopeliovich, hep-ph/0501260v3Universal Sudakov suppression(energy conservation)
Vitev, hep-ph/0605200v1CNM effects: dynamical shadowing, dE/dx, Cronin
Vitev, hep-ph/0405068v2Dynamical shadowing
Kharzeev, NPA 748, 727 (2005)
19
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
•At least two kinds of effects may give suppression in pairs that include a forward rapidity wrt mid-rapidity trigger hadron
Mono-jets in the gluon saturation (CGC) picture give suppression of pairs per trigger and some broadening of correlationKharzeev, NPA 748, 727 (2005)
PT is balanced by many gluons
Dilute parton system
(deuteron)
Dense gluon
field (Au)
Rapidity-separated hadron correlations in d+Au
shadowing (non-LT) gives suppression of pairs wrt to singles for mid-rapidity tag – but small for forward tagVitev, hep-ph/0405068v2
shadowing (non-LT) gives suppression of pairs wrt to singles for mid-rapidity tag – but small for forward tagVitev, hep-ph/0405068v2
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
• depletion at small-x• enhancement (anti-shadowing) at larger-x• EMC effect at large x• Fermi motion near x~1
Either from global fits to deep-inelasitic scattering and Drell-Yan data• e.g. Eskola – EPS09 arXiv:0902.4154
Or from coherence models • e.g. Vitev hep-ph/0309094
Shadowing & the EMC effect
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 200904/21/23 QM09 Knoxville TN 22
Vogt EKS
Phys Rev C77, 024912Extrinsic EKS 0809.4684v1
•2003 PHENIX d+Au published J/Psi RdAu•Production model makes a difference.
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
23Quarkonia Production & Suppression – J/Ψ in d+Au
Initial d+Au J/Ψ update from new 2008 data (~30x 2003)
• RCP pretty flat vs centrality at backward rapidity; but falls at forward rapidity (small-x)
• more soon – precision statistics requires precision systematics & careful analysis
• starting to study constraints on CNM models (thanks R. Vogt)
%8860%8860
%200%200
%200
collinv
collinv
CPNN
NNR
EKS σ = 0,1,2,3,4,…15EKS σ = 0,1,2,3,4,…15
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Conclusions•Forward Pion I_dA for Central Arm Triggered hadrons – forward MPC pi0’s
•Widths ~ consistent between p+p and d+Au•Associated Yields suppressed in d+Au, and stronger with more central collisions•Working on triggered MPC data and Au going MPC side•Can then map out x dependence
•Less forward muon arm triggered (2-5 GeV pT) hadrons – central arm hadron correlations show small I_dAu difference
•R_dAu of those muon arm hadrons shows suppression pattern •New data from run08 on the way
•Some of the more “ordinary” cold nuclear effects can be mapped out with complementary measurements, like J/Psi.
•d+Au is a very complicated system
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Backup Slides
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Figure 2: The ratio of gluon distributions in lead relative to deuterium as determined from projected measurements with an EIC, as a function of gluon momentum fraction x. HKM and FGS represent QCD parameterizations of existing data extrapolated linearly to small x. The curve labeled Color Glass Condensate is a saturation model prediction. Domains relevant to nucleus-nucleus collisions at RHIC and the LHC are shown.
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
27
Brief PHENIX Status & Future
Recent detector improvements:• large, more accurate reaction plane detector• higher-pT PID (TOF-West)• forward (MPC) calorimeters• Hadron blind detector (HBD)
Operations improvements:• integrated luminosity: Au+Au (x3); d+Au (x30)• data taking efficiency: 52% (2007) -> 68% (2008)
Future:• HBD for clean low-mass dielectron measurements (next AuAu run)• muon Trigger system for high-pT muon triggering (W’s)• silicon detectors for new level of robustness in heavy-quark measurements• continuing DAQ upgrades to maintain high speed and efficiency
VTX/FVTX
HBD
MPC
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
LHC: extending the low-x reach
• RHIC as opened the low-x frontier finding indications for new physics (CGC?)
• LHC will lower the x- frontier by another factor ~30 at the same rapidities
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Cold Nuclear Matter (CNM) & Gluon Saturation
Mike Leitch - PHENIX
29
Traditional shadowing or coherence models
Gluon saturation at small x; amplified in a nucleus
Initial state energy loss & multiple scattering
hep-ph/0902.4154v1
RG
Pb
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009 30
Experimental Method: Overview• Using azimuthal angle two-particle correlation technique
– d+Au, pp collisions at sNN = 200 GeV from RHIC Run8
– Rapidity separated particles with one particle in the forward direction allows one to probe the gluon distribution at lower x
– Trigger particles are (0, h+/-) with || < 0.35– Associate particles are forward 0s and clusters with 3.1 < < 3.9
Central Rapidity Spectrometer
3.1 < η < 3.9π0
π0
x-range in Au: 0.006 < x < 0.1
Forw
ard
EM
C
From calculation by Marco Stratmann
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Any difference between p+p and d+Au?
Kharzeev, Levin, McLerran (NPA748, 627)
d+Au: Mono-jet?
PT is balanced by many gluons
Dilute parton system
(deuteron)
Dense gluon
field (Au)
Color glass condensate predicts that the back-to-back correlation from p+p should be suppressed
p+p: Di-jet
2 Jun 2009 Color Glass Condensate Workshop, RHIC-AGS 2009
Forward-midrapidity correlations in d+Au
• PHENIX doesn’t see any changes for <xg> ~ 0.015
• STAR might see suppression for <xg> ~ 0.006
PRL 96, 222301
STARSTAR PRL 97, 152302
π0: |<η>| = 4.0h±: |η| < 0.75 pT > 0.5 GeV/c
PRL 94, 082302
Regions of:• Fermi smearing• EMC effect• Enhancement• Shadowing• Saturation?
Regions of shadowing and saturation mostly around Q2 ~1 GeV2
F2D/F2A
Observation that structure functions are altered in nuclei stunned much of the HEP community ~25 years
ago
Cold Nuclear Structure (d+Au)
Saturation picture in nuclei
•Transverse area of a parton ~ 1/Q2
• Cross section parton-probe : ~ s/Q2
• Partons start to overlap when SA~NA• The parton density saturates
• Saturation scale : Qs2 ~ s(Qs
2)NA/RA2 ~A1/3
• At saturation Nparton is proportional to 1/s
• Qs2 is proportional to the density of participating nucleons; larger for
heavy nuclei.
Relativistic proton picture
Nucleus picture
NBjBjcoh mxpxkl
1~
1~
1~
(In rest frame of proton)