Quarkonium as Probe of

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Quarkonium as Probe of Hot and Cold QCD Matter
Where do we stand and where do we go?
Jamie Nagle (University of Colorado) CATHIE-TECHQM
Session on Quarkonium December 17, 2009
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Parameterizing our ignorance is good, but not
sufficient.
We have too much freedom relative to the
available experimental data.
1. We need more data that specifically addresses
the key physics. 2. We need to more critically
ask why? And what is really known within some
systematic on the theory front.
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NA50 at the CERN-SPS
Strong evidence for the formation of a
transient quark-gluon phase without color
confinement is provided by the observed
suppression of the charmonium states J/y, cc, and
y. Maurice Jacob and Ulrich Heinz
Discontinuity due to cc melting Drop due to J/y
melting Using Drell-Yan as control
15 years later, we have no measurement of the cc.
Unacceptable.
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Drell-Yan production in proton-nucleus collisions
is sensitive to parton energy loss..
m
Must carefully separate nuclear shadowing effects
and energy loss effects both of which lead to
suppression of Drell-Yan pairs.
g
m-
Dx
E772 and E866 at Fermilab dE/dx 2.73 ? 0.37 ?
0.5 GeV/fm (from hadronization due to
confinement) dE/dx 0.2 GeV/fm (from gluon
radiation due to nuclear environment) This is
the first observation of a non-zero energy loss
effect in such experiments.
Johnson, Kopeliovich, Potashnikova, E772 et
al. Phys. Rev.C 65, 025203 (2002)
hep-ph/0105195 Phys. Rev. Lett. 86, 4487 (2001)
hepex/0010051
What was wrong with this argument that it was
not broadly accepted?
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After production of the charm-anticharm pair, it
may re-interact during its traversal of the
remaining nuclear material.
These re-interactions may be of a pre-cursor to
the J/y (color octet cc-g state) or of the
physical J/y itself.1 In heavy ion reactions,
the quarkonia state may be further suppressed due
to color screening in medium.2
1Arleo, Gossiaux, Gousset, Aichelin,
hep-ph/9907286 2Matsui, Satz, Phys. Lett. B178
416 (1986). 2NA50 Phys. Lett. B521, 195 (2001)
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Some say at RHIC the physics is initial state
saturation, but that means lower energy is very
different physics.
E866 PRL 84, 3256 (2000)NA3 ZP C20, 101 (1983)
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PHENIX Preliminary
PHENIX forward rapidity data corresponds to xF
0.05 0.15
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K. Tuchin
Show us the money plot. Also, I still do not
understand Qs at such low energies.
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Mid-rapidity J/y for SPS (158, 450), E866, RHIC
Time inside Nucleus (assume 10 fm path)
(Dy) Rapidity gap between J/y and Nucleus
We need to really think about the appropriate
time scales in detail.
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One Example Long ago a calculation indicated
that s(breakup) 2 mb (singlet) and 6 mb
(octet). What was the theoretical uncertainty?
What does it mean if the data disagrees? What do
we learn?
Another Example
But, formation time can completely change the
picture. My opinion Too many knobs and not
enough critical evaluation of theory
uncertainties and other constraints.
?
Zhao HQ08
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R. Vogt We are revisiting all the issues we
thought were resolved 10 years ago.
Those who cannot remember the past are condemned
to repeat it.
George Santayana (16 December 1863 in Madrid,
Spain 26 September 1952 in Rome, Italy), was a
philosopher, essayist poet and novelist. wiki
entry