Transcript Linden-Levy

New cold nuclear matter constraints from
J/ψ suppression in d+Au at PHENIX
L. A. Linden Levy
for the PHENIX collaboration
[email protected]
Department of Physics
390 UCB
University of Colorado
Boulder, CO 80309-0390
Why heavy quarkonia?
• J/ψ was predicted as an excellent QCD thermometer.
– Heavy quark anti-quark pairs allow potential models.
– Different states have different binding energies (radii)
as the pair is screened they dissociate.
→ Color Debye screening. (Matsui and Satz).
• Corollary: The picture of sQGP has become
even more complicated
– Cold Nuclear Matter effects
– Recombination of uncorrelated heavy flavor.
– LQCD predictions of correlations T>TC.
– Gluo-disassociation
– Detailed balance of J/ψ depletion and
restoration is necessary.
1.2 TC
A. Mocsy
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PHENIX Coordinate System
South Arm
Central Arm
North Arm
Au
d
• 200GeV d+Au collisions.
• Di-Muons recorded via MuTr and MuID in N. & S. arm.
• Di-Electrons from Central arm PC, DC, EMCal and RICH.
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Nuclear modification factor.
• Suppression due to normal density nuclear matter in d+Au 200GeV
(RHIC 2003)
• Baseline p+p 200GeV data (RHIC 2005)
Phys Rev C 77, 024912
d
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Au
Forward
d
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Mid
Backward
Au
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Quantitative comparison vs. centrality.
• Ncoll dependence of the model from a
Glauber inspired geometric model.
(R. Vogt hep-ph 0411378)
• Breakup cross section is a free param.
• CEM model for x1,x2 (R. Vogt)
• Woods-Saxon density profile for Au.
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More about fitting….
Phys Rev C 77, 024912
• Type A: point to
point uncorrelated
(bars)
• Type B: point to
point correlated
(boxes)
• Type C: global
(relative)
PRC77 064907
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Breakup cross section
NDSG σ = 0,1,2,3,4,…15
•2008 d+Au J/ψ results from PHENIX
•Systematics cancel within a run.
NDSG
EKS
EPS08
•~15X
statistics of 2003 data set.
•Expect a reduction in the Type A
error of ~1/√2.
•First look at shadowing predictions
σσ == 00 mb
mb
based on nPDF calculation
(R. Vogt private communication).
•Still interpreting the σ
data:
nomb
sigma
=
4
breakup best value yet.σ = 0 mb
•Expect a a PRL publication in the
σ = 4 mb
near future.
•Difficult to account for the forward rapidity
with a breakup cross section ~0.
•Or something completely different…
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 pA
A 
 pp

•Other physics at work?
•Note: E866 has x2 range is ~
0.01-0.1 near the crossover
from shadowing to antishadowing.
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√s=40GeV
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Quantitative Extraction
RCP
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@ Fixed y
Npart
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Rapidity dependence!
• Extract best fit to RCP
at a given rapidity
versus centrality.
• Based on predictions
from R. Vogt.
• Excellent agreement
with E866 data
versus yCM.
• Parametrizes all the
effect that shadowing
is missing.
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T. Frawley
T. Frawley
ETC,
ECT,
Trento
Trento
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Extrapolation for HI
Corollaries:
A. Suppression of excited states assumed to be the same
as J/ψ.
B. Only folded p+A not necessarily clear that CNM effects
factorize in HI collisions
• Extrapolation when σ(y) allowed (CEM - T. Frawley )
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• A long d+Au run
(with upgrades)
to answer this
quantitatively!
• Resolves SPS ε
question.(?)
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More than shadowing?
• Production Model?
– CDF puzzle still not resolved!
• Color Glass Initial State?
• Initial State energy
loss?
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Production model?
Intrinsic 2 -> 1
•Softens the result
•Does not completely describe forward suppression
RdAu(shadowing model dependent)
•What does this look like for CSM+IC? (arXiv:0908.0754)
Extrinsic 2 -> 2 & model dep.
Lansberg et al. arXiv:0912.4498
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Coherent Multiple Scattering (CGC)?
•Also calculate the backward rapidity?
(anti-shadowing as conservation of
momentum)
•How is this valid for the low energy
data at the SPS? “Due to slow energy
dependence of Qs”

σpA=Aασpp
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• We use 4 centrality bins, each
corresponding to a range of
impact parameters.
• Therefore the curve and data
on the previous slide are not
exactly comparable.
• One needs to convolute the
impact parameter distribution
with the theory.
• This should reduce the amount
of suppression.
• We need to get together and
make this plot.
“Guys this is important.”
-L. McLerran
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Energy Loss?
Data from Drell-Yan at E772
and E866 at Fermilab
Energy loss calculated in target
rest frame.
dE/dx = 2.73  0.37  0.5
GeV/fm (from hadronization)
dE/dx ~ 0.2 GeV/fm (from gluon
radiation)
“This is the first observation of a nonzero energy loss effect in such
experiments.”
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Johnson, Kopeliovich, Potashnikova, E772 et al.
Phys. Rev.C 65, 025203 (2002) hep-ph/0105195
Phys. Rev. Lett. 86, 4487 (2001) hep=ex/0010051
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Why didn’t this catch on?
•Backward shift in xF leads to a slope in rapidity
•CEM with fixed fractional
energy loss.
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(CATHIE-INT)
Is this the same as CGC?
A puzzle
• Parametrized breakup cross section has a strong
kinematic dependence on rapidity.
• It contains some physics that we have missed with
shadowing!
• Possible Explanations
– Production Mechanism?
• “Intrinsic Charm?”– S.Brodsky hep-ph/0904.3037
– Gluon Saturation (CGC) ? Tuchin hep-ph/0809.2933
– Initial State energy loss?
– Limiting Fragmentation?
• Good News:
There is more data coming RdAu(y;pT;b)
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Conclusions
• Shadowing does not contain all the physics of
d+Au collisions.
• Cold nuclear matter effects predict
the rapidity difference in HI collisions (still
onset of suppression for central collisions)
• Experiment:
– Increase statistics, reduce systematic
uncertainties in the measurements.
– Make more measurements (i.e. χC in d+Au)
• Theory:
– Think about the missing physics.
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