experimental confirmation of the formation of dense, hot matter in nuclear collisions @ rhic
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Experimental Confirmation of Experimental Confirmation of the Formation of Dense, Hot the Formation of Dense, Hot Matter in Nuclear Collisions Matter in Nuclear Collisions
@ RHIC@ RHICProf. Brian A. Cole
Columbia University
On Sabbatical leave at KFKI, RMKI
Supported by a Fulbright grant from the US State Dept. and the Hungarian-American Commission for Educational Exchange, a NATO
Fellowship, and theHungarian National Science Fund
The Relativistic Heavy Ion The Relativistic Heavy Ion Collider Collider
STAR
Experiment @ RHICExperiment @ RHIC
Energy
Theory
Energy
PHENIX Proton-Proton Particle PHENIX Proton-Proton Particle SpectraSpectra
We have a good theoretical understanding of high energy, large-angle scattering.
Nu
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Expected*
Observed
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Energy
Au-Au Particle Spectra From Au-Au Particle Spectra From PHENIXPHENIX
Theories without energy loss
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Energy
Theories with energy loss
* — includes only trivial increase in number of particles due to the “size” of the nuclei
We observe only 20% of the expected particles.
Consistent with theories including energy loss.
PHENIX: Au-Au Final Results from PHENIX: Au-Au Final Results from 20022002
The suppression of high energy particles goes away when we create less matter.
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Energy
Submitted to Phys. Rev. Letters
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Energy
d-Au 2 independent measurements
Au-Au
PHENIX d-Au Measurement PHENIX d-Au Measurement
Control measurement shows no suppression If anything we see a modest excess
Understood theoretically (was predicted!)
Suppression of high energy particles in Au-Au is apparently caused by the created matter.
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STAR Experiment: “Jet” STAR Experiment: “Jet” Observations Observations
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Angle between high energy particles0º 180º
proton-proton jet event
In Au-Au collisions we see only one “jet” at a time !
How can this happen ? Possibly due to energy loss
Analyze by measuring angles between pairs of particles.
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STAR: Jets in d-AuSTAR: Jets in d-Au
Disappearance of jet pairs in Au-Au collisions is apparently caused by the created matter.
Angle between high energy particles
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0º 180ºq
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Experimental SummaryExperimental Summary We have shown two striking experimental observations: Consistent observations have been
obtained by all 4 experiments at RHIC (where applicable)
In both Au-Au and deuteron-gold collisions currently can only be explained as resulting
from the “quenching” of high energy particles in the hot dense medium created in Au-Au collisions.
deuteron-gold control measurements were essential to rule out alternative explanations for the observations.
Triumph of the scientific method !
My profound thanks to
Hungarian Fulbright Commission,
Dr. Bruckner and his staff
RMKI, Dept. of Theoretical Physics,
and NATO
for their outstanding support on behalf of myself
and my family.
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