HighpT , Jets, Direct Photon From RHIC to LHC

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High-pT , Jets, Direct Photon From RHIC to LHC
Jan Rak for the PHENIX collaboration Jyväskylä
University Helsinki Institute of Physics,
Finland
DIFFRACTION 2008, La Londe-les-Maures, France,
September 9 - 14, 2008
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Outline

• ALICE/LHC (CERN)
• pp _at_ vs14 TeV
• PbPb _at_ vs5.5 TeV

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1st big step Friday Aug 8th beam through ALICE
http//www.bnl.gov/rhic/news/081208/e-log.asp
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2nd step September 10th full injection

• RF capture working
• number of turns per injected bunch is increasing.
  Beam-2 held for 20 min.
• Data taking
• Beam-gas, screen collisions, cosmic events

Si-Pixel tracker inj Aug 24th
Beam-gas event, coasting Sep 11
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3rd step collision _at_ vs900 GeV next week?
10 September 2008 first (successful) attempt to
circulate beam in front of 300 journalists on
site, Google news found over 3500 press cuttings
on the day, not to mention featuring the LHC on
the Google logo. Around 450 television stations
picked up our broadcast signal. Eurovision has
reported that it was broadcast over 2100 times.
CERN websites strained under the pressure of over
100 million hits. In our Member States and around
the world, CERN was the lead news story on
television news, even demoting the US elections
to second place. Particle physics has never had
such a high profile, and it gives us an
opportunity over the coming years to get basic
science back into the mainstream. Robert
Aymar CERN Director General

• Most frequent questions asked by journalists
• What we are going to learn from protein-protein
  collisions ?
• How danger Black Holes really are ?

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Hard Probes - Nuclear Modification Factor RAA
AA
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Nuclear Geometry and Hydrodynamic flow
FRP
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RHIC 2004 first paradigm shift
Au Au Experiment
d Au Control
Preliminary Data
Final Data

• Dramatically different and opposite centrality
  evolution of AuAu experiment from dAu control.
• Jet Suppression is clearly a final state effect.
  Initial state ala Color Glass Condensate ruled
  out at midrapidity (at RHIC)

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Flowing Quarks ?
Assumption all bulk particles are coming from
recombination of flowing partons
v2

• Universal scaling
• flow parameters scaled by quark content nq
  resolves meson-baryon separation of final state
  hadrons. Works for strange and even charm quarks.
  
• Suggests the early thermalization and quark
  degree of freedom.

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RHIC 2006 second paradigm shift String Theory
test bench for string theory (AdS/CFT)
AdS/CFT Correspondence (Maldacena 1998)
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RHIC 2008

• Successes many discoveries, evidences for sQGP
  - perfect liquid.
• Failures Arrogance by some in thinking that we
  understand everything when we are far from
  understanding, e.g. the many effects observed,
  the underlying physics of QCD in a medium, and
  the properties of the medium (Mike Tannenbaum
  HP08)
• Open questions
• Light and heavy quarks suppression looks so
  similar
• Quarks and gluons suppression looks similar
• Direct photon suppression at high pT looks
  similar
• J/? suppression same at RHIC as at SPS
  (vs17GeV)
• Mach cone same at RHIC as at SPS (vs17GeV)

New paradigm shift on the horizon?
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Some open questions

• Standard LO pQCD (AKK)
• Protons gluons jets fragmentation
• Pions Quarks jets fragmentation
• Where is CA /CF ?

Mark Thomas Heinz
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The biggest result at QM2006?
pp?p0X reference From FNAL, SPS, ISR
extrapolation our own measurement
If R?AA RpAA the whole concept of energy loss
changes perhaps no effect for pTgt20 GeV. New
physics on the horizon?
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J/? Suppression--RAA
PHENIX mid-rapidity (ee-) the same as
NA50!
Suppression increases at more forward rapidity
PHENIX PRL 98, 232301 (2007)
NA50 at SPS (0ltylt1) PHENIX at RHIC (ylt0.35)
This was CERN-Heavy Ions main claim to fame in
the infamous press conference of 2000 claiming
observations consistent with the predicted
signatures of a QGP. Will have to wait for LHC
to find out whether J/? merely act like ordinary
hadrons at low pT or whether they are actually
probes of deconfinement as predicted by Matsui
and Satz PLB178(1986)416.
More dense medium
Less dense medium
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More Exclusive observ. - modification of D(z)
Wang, X.N., Nucl. Phys. A, 702 (1) 2002
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D(z) measurement without jet reconstruction
Assumption Leading particle fixes the energy
scale of the trigger assoc. jet gt
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Azimuthal correlation function in pp _at_ ?s200 GeV
dAu

• sN ltjTgt jet fragmentation transverse
  momentum
• sA ltkTgt parton transverse momentum
• YA folding of D(z) and final state parton
  dist.

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Jet shape evolution with trigger and assoc. pT
AuAu / pp vs 200 GeV

• Flat region
• celebrated b2b disappearance
• Punch through region (HR)
• reappearance at high-pT
• Shoulder region (SR)
• Medium induced Mach cone

• Low pT
• Enhancement in SR suppression in HS
• High pT
• Reappearance of away-side jet not due to merging
  of side peaks

Per-trigger yield vs. Df for various trigger and
partner pT (pAT ? pBT), arranged by increasing
pair momentum (pAT pBT)
arXiv0705.3238 nucl-ex
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Soft hard QCD radiation kT phenomenology
Back-to-back balanced
Compton photo-production
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Correl. fcn width - kT and acoplanarity
Lorentz boost gt pT,pair kT,t kT,a
colinearity
Lab frame
Hard scattering rest frame
hadronic
partonic
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Associated yield
Assumption (Phys.Rev.D74072002,2006 for details)
Invariant mass of mass-less partons in hard
scattering CMS and in LAB is the same -gt
non-Gaussian kT-smearing.
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High pT ref. for HI, resummation, detailed
NLO tests
PHENIX measured ltpTgtpair3.360.090.43GeV/c
extrapolation to LHC vltk2Tgt6.1 GeV/c,
ltpTgtpair7.6 GeV/c
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PHENIX vs200 GeV p0 and dir-? assoc.
distributions
Exponential slopes still vary with trigger pT.
If dN/dxEdN/dz then the local slope should be
pT independent.
Arbitrary Normalization
Arbitrary Normalization
Run 5 pp _at_ 200 GeV
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??-h correlation and kT bias
Can one extract the Fragmentation Function from
?-h associated distribution despite the kT bias?
Solve for net-pair momentum
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Fragmentation function from ?-h (PHENIX pp) and
jets (STAR AuAu)
Modulo kT, the xE distribution opposite the
direct-? IS the fragmentation function of a jet
of pT-pT?
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Away-side correlations to a particle which is a
fragment of a jet do NOT measure the
fragmentation function!!!
Let me refer to this meeting talks T. Trainor
Probing parton-medium interactions in heavy ion
collisions with STAR. A. Kaidalov Anisotropic
flows in Reggeon theory
MJT Moriond 2008.
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Summary

• RHIC provided us the high precision data which
  indicate
• High density deconfined matter is produced
• Quark DOFs observed (v2 scaling)
• Fast thermalization
• Small viscosity (strongly coupled matter)
• Open questions
• Heavy and light quark suppression similarity
• Prompt photon suppression at high-pT
• J/? suppression similar at RHIC (?s200GeV) and
  SPS (?s17GeV)
• J/? suppression at RHIC larger at forward
  rapidity
• LHC half of all magnets cooled, first beam in
  June-July, collisions in August, first run 3
  month _at_ 10 TeV October December!

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p p _at_ s1/2 14 TeV
K.J. Eskola and T. Renk, private
communication
THEORY

• Main principles as in PRC75 (2007) 054910
• Quenching in hydro medium with dNch/dh 100
• ? large, effect might be overestimated
• Only large DR case in hydro evolution
• Uncertainties especially from hydro evolution
  are expected, magnitude needs to be studied

Charged hadrons
VERY PRELIMINARY
How does one select events?

• No separate reference measurement
• What is bulk in pp ? soft production vs.
  multiplicity from fragmenting hard jets

events with high associated soft production ?
with hydro medium
RAA
events with low associated soft production ?
without hydro medium