FNAL E866NuSea

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A measurement of
Anti-quark asymmetry in the Nucleon Sea
FNAL E866/NuSea
ACU, ANL, FNAL, GSU, IIT, LANL, LSU, NMSU, UNM,
ORNL, TAMU, Valpo
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From Draft NSAC Long Range Plan The Structure
of the Nuclear Building Blocks
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Nuclear modification of parton level structure
dynamics
Drell-Yan
Ratio(W/Be)
Drell-Yan Process
1.0
0.9
0.8
NMC DIS
E772 R(W/D)
E866 R(W/Be)
0.7

• Modification of parton momentum distributions of
  nucleons embedded in nuclei
• e.g. shadowing depletion of low-momentum
  partons. Process dependent?
• Nuclear effects on parton dynamics
• energy loss of partons as they propagate through
  nuclei
• and (associated?) multiple scattering effects

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• Nuclear Dependence for heavy vector mesons, e.g.
  J/?, ? ', ?
• production color singlet or octet ( )
  and color neutralization timescale
• hadronization time
• Coherence length for cc fluctuations
• absorption on nucleons or co-movers
• feed-down from higher mass resonances, e.g. ?c

E789
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• J/? suppression an effective signature of
  Quark-gluon plasma (QGP) formation?
• Color screening in a QGP would destroy
  pairs before they can hadronize into charmonium
• But ordinary nuclear effects also absorb or
  modify J/?s
• We need a comprehensive understanding of
  charmonium production in nuclei
• Competing effects may be identified in p-A
  collisions by their strong kinematic
  dependencies, together with complementary studies
  of Drell-Yan scattering and open-charm production

NA50 -- Anomalous J/? suppression. Evidence for
QGP??
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E866/NuSea 800 GeV p-A (Fermilab) PRL 84, 3256
(2000)
PT Broadening at 800 GeV
open charm no A-dep at mid-rapidity
Hadronized J/Y?

• J/? and ? similar at large xF where they both
  correspond to a traversing the nucleus
• but ? absorbed more strongly than J/? near
  mid-rapidity (xF 0) where the resonances are
  beginning to be hadronized in nucleus.

a(pT) shape is independent of xF same for NA3
at a lower energy
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PT Broadening in Drell-Yan and associated
Radiative Energy Loss
Baier et al. NP B484, 265 (1987)
E866 Preliminary
or
So energy loss associated with observed pT
broadening is tiny, e.g. for W
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Quark energy loss in nuclear matter
Johnson, Kopeliovich et al., PRL 86, 4483 (2001)
Shadowing
dE/dx 0
dE/dx Shadowing
dE/dx 0.25
Charged hadron and p0 production at PHENIX versus
pT for central collisions which, when compared to
pQCD models that work well for peripheral
collisions, suggests that jet-quenching or
energy-loss may be present.
Analysis of our p-A Drell-Yan data (E772 - PRL
64, 2479 (1990) using the Kopeliovich model.
Dashed lines with shadowing only solid lines
with parton energy loss of, dE/dz 2.32 0.52
0.5 GeV/fm
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J.C.Peng, LANL
Eskola, Kolhinen, Vogt hep-ph/0104124
PHENIX µµ-
E866/NuSea
ee-
PHENIX µ PHENIX e E866 (mid-rapidity) NA50
Kopeliovich, Tarasov, Hufner hep-ph/0104256
Expected statistical errors from a 2-week d-A run
at PHENIX and measurements form E866/NuSea
Gluon Shadowing for J/?s predictions?

• In PHENIX µ acceptance for Au-Au collisions?
• Eskola 0.8
• Kopeliovich 0.4
• Strikman hep-ph/9812322 0.4

PHENIX µµ- (Au)
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Theoretical Models for PT Broadening

• Predicts a different dominant mechanism for pT
  broadening in DY at RHIC LHC energies
• For lower energy fixed target measurements
  initial-state multiple scattering is most
  important
• But at RHIC LHC color filtering preserves small
  dipole configurations which have high-pT
  and therefore give larger pT broadening

Kopeliovich et al, hep-ph/0110221 Light Cone
Dipole approach
(full)
RHIC
LHC
R(Au/H)
(longitudinal only)
DY as bremsstrahlung in the target rest frame
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J/? Polarization

• NRQCD based predictions (color octet model)
  necessary to explain CDF charm cross sections
• E866 J/Y measurement not in agreement with NRQCD
  based predictions Beneke Rothstein, PRD 54,
  2005 (1996) which give
• 0.31
• Complicated by feedown (40) from higher mass
  states.

E866/NuSea
E866/NuSea PRL 86, 2529 (2001).
However U(2S3S), which should not suffer from
feeddown, have maximal polarization consistent
with the Octet model!
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Charmonium at PHENIX - Coming soon!
mm-

• PHENIX South Muon Electrons taking first data
  now (Au-Au over p-p in progress)
• North Muon in 2003 (after shutdown)
• d-A collisions strong consensus building
  hopefully coming soon.

Simulated
ee-
Simulated
Min-bias/RHIC-year for a .92 (Nagle
Brooks) E866 nuclear dependence data only
Upsilons from E772
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m Physics Program - High-pT Single ms

• High-pT single-ms come from heavy mesons, i.e.
  Ds or Bs
• These mesons are produced primarily through gluon
  fusion and thus are sensitive to the gluon
  structure functions.
• In p-A collisions the shadowing of gluons can be
  studied

Simulated

• With polarized beams the gluon polarization, ?G,
  can be studied.
• W ? m ?m can be identified by high-pT
  single-ms and W/W- can be used to measure the
  flavor asymmetry in the nucleon sea including its
  spin decomposition

Simulated
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From Draft NSAC Long Range Plan The Structure
of the Nuclear Building Blocks
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The North-m Arm

• North-m arm advantages
• Superior arm with more kick, better momentum
  resolution better mass resolution than South
  (for ?s sNorth 190 MeV compared to sSouth
  240 MeV )
• While J/?s should melt in a QGP, ?s are smaller
  and should not, so a well separated ? peak
  (separation of ?1S ?2S is 563 MeV) is critical
• ? mesons may be broadened, shifted in mass or
  even enhanced in a QGP. With its 10o (as opposed
  to 12o for South) minimum theta, the North-m arm
  has much larger acceptance for ?s which tend to
  decay into ms are small angles.
• The mID is directly behind the tracking volume
  (in contrast with the South-m arm which has a
  large gap). This should help reduce backgrounds
  and improve matching between tracking and mID.

• Two m-arms
• Doubles the counting rate
• Allows measuring forward and backward mm-
  simultaneously, i.e. negative positive rapidity
  at the same time. Important for the study of
  formation-time effects in p-A.
• Allows for events with one m in each arm, e.g.
  mid-rapidity ?s
• Required for W ? m ?m spin measurements since
  the Z0 ? mm- backgrounds can be determined
  only using two arms.

North m arm
South m arm
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PHENIX Silicon Vertex Upgrade

• Matching tracklets in silicon to tracks in m-arms
• Momentum measurement
• displaced vertex
• And also detect h in silicon

LANL LDRD supporting RD for us (250K/yr)

• Gluon polarization in proton
• Nuclear dependence of open charm
• Gluon shadowing
• Charm cross section
• To understand J/Y in A-A collisions

Accurate projection to collision vertex close,
thin detector