Presentation for NFR November 10, 2004 Trine S'Tveter

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Recent results from BRAHMS _at_ RHIC
Systems studied so far at RHIC - AuAu _at_ sNN1/2
62.4, 130, 200 GeV (heavy-ion collisions,
possible QGP formation!) - pp _at_ s1/2 200
GeV (elementary collisions) - dAu _at_ sNN1/2
200 GeV (cold nuclear matter)
Stages of a heavy-ion collision at RHIC -
Initial stage with partons inside
Lorentz-contracted nuclei - Preequilibrium stage
with hard parton-parton collisions - Phase with
deconfined (but strongly interacting) partons -
QGP? - Hadronization with subsequent chemical and
thermal freezeout
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
r_nov04_outline.txt
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The BRAHMS spectrometer
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Are we creating a QGP?
dN/dh for AuAu _at_ sNN1/2 200 GeV
Bulk properties of produced matter - Total
particle production - Relative particle yields -
Strong collective flow indicate a strongly
interacting system passing through the QGP part
of the phase diagram. More by J.I. Jørdre
Lattice QCD Critical energy density eC 0.7
GeV/fm3 for deconfinement. Bjorken's energy
estimate formula indicates energy density e
gt 5 GeV/fm3 at RHIC !
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Hard scattering and jets
Hard scattering in vacuum
STAR data pp, dAu, peripheral AuAu BTB jet
correlations Central AuAu Extended medium,
far-side jet quenched
Deconfined medium Jet energy loss from gluon
radiation
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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BRAHMS results on nuclear modification of
high-pT particles
Nuclear modification factor from comparison to
pp reference spectra Should be 1 for
superposition of NN collisions.
- Strong suppression in central AuAu
collisions, both at y0 and forward y -
Suppression strongly centrality dependent
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Initial-state or final-state effect? Jet
quenching vs parton saturation
Compare suppression in hot (AuAu) and cold
(dAu) nuclear matter, as function of h. - d-Au _at_
sNN1/2 200 GeV at h 0 Enhancement,
increasing with centrality. Indicates
final-state effect (QGP?) in AuAu. - d-Au _at_
sNN1/2 200 GeV at forward h Onset of
centrality dependent suppression, increasing
with h. Consistent with saturation picture
(Color Glass Condensate? - more by B.H.
Samset / H. Yang)
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Meson vs. baryon dependence
Nuclear modification vs. particle species
BRAHMS preliminary
BRAHMS preliminary
- Strong pion suppression at all rapidities,
increasing at higher y ? - Protons / antiprotons
not suppressed - Difference probably related to
number of quarks rather than hadron mass Possible
explanation Quark recombination involved in
hadron formation?
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Collision energy dependence
Onset of high-pT suppression effect Studied RAA
in AuAu _at_ sNN1/2 62.4 GeV Slight suppression
in central collisions, slight enhancement in
peripheral ones, but same trend with centrality
as for AuAu _at_ sNN1/2 200 GeV.
BRAHMS preliminary
Preliminary data indicate Nuclear modification
factor for high-pT hadrons shows a smooth
evolution with energy from SPS to RHIC.
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Summary and plans
Heavy-ion collisions at RHIC - observations so
far Bulk properties and suppression of high-pT
particles reveal new form of matter - Very high
energy density - Strongly interacting - Most
likely partonic Great potential for further
physics measurements at RHIC! Further
investigations - Analysis of high-statistics
AuAu _at_ sNN1/2 200 GeV data set y and pT
dependence of suppression pattern, for identified
hadrons - Run 2005 CuCu _at_ sNN1/2 200 GeV -
effect of medium extent pp
_at_ s1/2 200 GeV - improve reference spectra -
Run 2006 Test ALICE photon spectrometer PHOS in
BRAHMS?
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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PHOS in BRAHMS?
Run 2006 Possible test of PHOS module in
BRAHMS! Lead-tungstate crystals (PWO) 1 crystal
22 x 22 x 180 mm 1 module 3584 crystals Designed
for detecting high-pT photons (several tens of
GeV) Measure high-pT p0 spectra at
forward rapidity - complementary to
charged hadrons. Look for direct photons from
QGP? Useful detector test for ALICE, and also
interesting physics measurement!
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Norwegian BRAHMS participation

Present BRAHMS contingent in Norway - Dieter
Röhrich (professor, UiB) - Gunnar Løvhøiden
(professor, UiO) - Trine S. Tveter (professor,
UiO) - Jens Ivar Jørdre (Ph.D. Student, UiB) -
Bjørn H. Samset (Ph.D. Student, UiO) - Hongyan
Yang (Ph.D. Student, UiB) - Svein Lindal (master
student, UiO) - Jon Thøger (master student,
UiB) Collaborating institutions in Denmark,
France, Poland, Romania, New York, Kansas, Texas.
50 participants.
Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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Presentation for NFR - November 10, 2004 - Trine
S.Tveter
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