Forward onium physics from PHENIX

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Forward (onium) physics from PHENIX

• Mickey Chiu

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Why are we interested?

• High energy behavior might be universal across
  all hadrons and predicted entirely by the CGC

CGC
x lt 10-2

• Geometric Scaling
• Strongly coupled regime which becomes classical ?
  computable!

? ? 0.3
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CGC in Heavy Ion Collisions

• As Initial state for Heavy Ion Collisions
• Multiplicity Distributions
• Long range correlations from a glasma,
  explanation of the ridge

But the outstanding question is, do we see the
CGC at RHIC?
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Expectations for a color glass condensate
t related to rapidity of produced hadrons.
Kharzeev, Kovchegov, and Tuchin, hep-ph/0307037
As y grows
Iancu and Venugopalan, hep-ph/0303204
Are the forward dAu results evidence for gluon
saturation at RHIC energies? Not clear. Need
more data, and more observables.
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2?2 Hard Scattering (LO)
p3
Initial State
p2
p1
Final State
P?s/2
P
p4
Simply Elastic Scattering
Special Cases
a. y3 forward, y4 mid-rapidity (MPC-EMC)
b. y3, y4 both forward (MPC-MPC)
a. y3 forward, y4 backwards (MPC.S-MPC.N)
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PHENIX Muon Piston Calorimeter
Small cylindrical hole in Muon Magnet Piston,
Radius 22.5 cm and Depth 43.1 cm
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PHENIX Acceptance
South Muon Tracker
EMCAL Central Tracker
North Muon Tracker
0 f coverage 2p
EMCAL Central Tracker
-3 -2 -1
0 1 2
3 rapidity

• 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
  (?gt3) is covered

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PHENIX Side View
PHENIX central spectrometer magnet
Muon Piston Calorimeter (MPC)
Muon Piston
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Forward/Central Correlation
PHENIX central spectrometer magnet
Muon Piston Calorimeter (MPC)
d
p0, or clusters
Au
Backward direction (South) ?
Forward direction (North) ?
p0 or h/-
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MPC Pion/Cluster Identification

• The MPC can reliably detect pions (via p0?g g) 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 p0s for 7 GeV lt E lt 17 GeV
• Use clusters for 20 GeV lt E lt 50 GeV
• Correlation measurements are performed using p0s,
  clusters
• Use event mixing to identify pions ? form
  foreground (same event pairs) and mixed event
  background photon pair distributions

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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 (p0, h/-) with h lt 0.35
• Associate particles are p0, clusters with 3.1 lt h
  lt 3.9
• One method to quantify the correlation
• To compare pp with dA, form ratio of conditional
  yields

Peripheral d-Au Correlation Function
Npair
Df
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h/- (trigger,central)/p0 (associate,forward)
ltpTagt0.55 GeV/c
ltpTagt0.77 GeV/c
ltpTagt1.00 GeV/c
1.0 lt pTt lt 2.0 GeV/c for all plots
pp
Correlation Function
dAu 0-20
dAu 60-88
pTt, h/-
Df
pTa, p0
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p0 (trigger,central)/p0 (associate,forward)
ltpTagt0.55 GeV/c
ltpTagt0.77 GeV/c
ltpTagt1.00 GeV/c
2.0 lt pTt lt 3.0 GeV/c for all plots
pp
Correlation Function
dAu 0-20
dAu 60-88
pTt, p0
Df
pTa, p0
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p0 (trigger,central)/cluster (associate,forward)
ltpTagt1.09 GeV/c
ltpTagt2.00 GeV/c
ltpTagt3.10 GeV/c
2.0 lt pTt lt 3.0 GeV/c for all plots
pp
Correlation Function
dAu 0-20
dAu 60-88
pTt, p0
Df
pTa, cluster
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Forward/Central Correlation Widths

• No significant changes in correlation width
  between pp and dAu within experimental
  uncertainties

Trigger p0 h lt 0.35, 3.0 lt pT lt 5.0 GeV/c
Trigger p0 h lt 0.35, 2.0 lt pT lt 3.0 GeV/c
dAu 0-20
pp
dAu 40-88
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Forward/Central IdA vs Ncoll
Associate p0 3.1 lt h lt 3.9, 0.45 lt pT lt 1.59
GeV/c

• 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?

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Muon-Central IdA Widths, 2003 dAu
d
Au
Phys.Rev.Lett.96222301,2006
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dAu RCP, 1.2lt?lt2.2
PHENIX 2003 dAu
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.94082302,2005).
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Kopeliovich, hep-ph/0501260v3 Universal Sudakov
suppression (energy conservation)
Vitev, hep-ph/0405068v2 Dynamical shadowing
Vitev, hep-ph/0605200v1 CNM effects dynamical
shadowing, dE/dx, Cronin
Kharzeev, NPA 748, 727 (2005)
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Rapidity-separated hadron correlations in dAu

• At least two kinds of effects may give
  suppression in pairs that include a forward
  rapidity wrt mid-rapidity trigger hadron

shadowing (non-LT) gives suppression of pairs wrt
to singles for mid-rapidity tag but small for
forward tag Vitev, hep-ph/0405068v2
shadowing (non-LT) gives suppression of pairs wrt
to singles for mid-rapidity tag but small for
forward tag Vitev, hep-ph/0405068v2
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Shadowing the EMC effect

• depletion at small-x
• enhancement (anti-shadowing) at larger-x
• EMC effect at large x
• Fermi motion near x1
• Either from global fits to deep-inelasitic
  scattering and Drell-Yan data
• e.g. Eskola EPS09
• arXiv0902.4154
• Or from coherence models
• e.g. Vitev
• hep-ph/0309094

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• Vogt EKS
• Phys Rev C77, 024912

• Extrinsic EKS 0809.4684v1

• 2003 PHENIX dAu published J/Psi RdAu
• Production model makes a difference.

QM09 Knoxville TN
11/12/2009
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Quarkonia Production Suppression J/? in dAu

• Initial dAu J/? 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)

EKS s 0,1,2,3,4,15
EKS s 0,1,2,3,4,15

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Conclusions

• Forward Pion I_dA for Central Arm Triggered
  hadrons forward MPC pi0s
• Widths consistent between pp and dAu
• Associated Yields suppressed in dAu, 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.
• dAu is a very complicated system

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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 AuAu (x3) dAu (x30)
• data taking efficiency 52 (2007) -gt 68 (2008)
• Future
• HBD for clean low-mass dielectron measurements
  (next AuAu run)
• muon Trigger system for high-pT muon triggering
  (Ws)
• silicon detectors for new level of robustness in
  heavy-quark measurements
• continuing DAQ upgrades to maintain high speed
  and efficiency

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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

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Cold Nuclear Matter (CNM) Gluon Saturation
hep-ph/0902.4154v1
RGPb
Traditional shadowing or coherence models Gluon
saturation at small x amplified in a
nucleus Initial state energy loss multiple
scattering
Mike Leitch - PHENIX
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Experimental Method Overview

• Using azimuthal angle two-particle correlation
  technique
• dAu, 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 (p0, h/-) with h lt 0.35
• Associate particles are forward p0s and clusters
  with 3.1 lt h lt 3.9

Central Rapidity Spectrometer
p0
3.1 lt ? lt 3.9
Forward EMC
p0
x-range in Au 0.006 lt x lt 0.1
From calculation by Marco Stratmann
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Any difference between pp and dAu?
pp Di-jet
dAu Mono-jet?
Dilute parton system (deuteron)
PT is balanced by many gluons
Dense gluon field (Au)
Kharzeev, Levin, McLerran (NPA748, 627)
Color glass condensate predicts that the
back-to-back correlation from pp should be
suppressed
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Forward-midrapidity correlations in dAu
PRL 97, 152302
p0 lt?gt 4.0 h ? lt 0.75 pT gt
0.5 GeV/c

• PHENIX doesnt see any changes for ltxggt 0.015
• STAR might see suppression for ltxggt 0.006

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Cold Nuclear Structure (dAu)
Observation that structure functions are altered
in nuclei stunned much of the HEP community 25
years ago

• Regions of
• Fermi smearing
• EMC effect
• Enhancement
• Shadowing
• Saturation?
• Regions of shadowing and saturation mostly around
  Q2 1 GeV2

F2D/F2A
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Saturation picture in nuclei
Relativistic proton picture
(In rest frame of proton)
Nucleus picture

• Transverse area of a parton 1/Q2
• Cross section parton-probe s as/Q2
• Partons start to overlap when SANAs
• The parton density saturates
• Saturation scale Qs2 as(Qs2)NA/pRA2 A1/3
• At saturation Nparton is proportional to 1/as
• Qs2 is proportional to the density of
  participating nucleons larger for heavy nuclei.