2nd International Conference on Hard and Electromagnetic

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High (and intermediate) pT Physics in PHENIX
Wolf Gerrit Holzmann for the
Collaboration
2nd International Conference on Hard and
Electromagnetic Probes of High-Energy Nuclear
Collisions, June 9 16, 2006
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The Big Picture
Can we learn about the history of the universe
from Heavy Ion Collisions?
Todays Cold Universe
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Strongly Interacting Matter at RHIC
Evidence for strongly interacting high energy
density matter is compelling!
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Strongly Interacting Matter at RHIC
How can we probe the properties of strongly
interacting partonic matter at RHIC?

• Jets are remarkable probe
• for medium
• Auto-generated early
• Calculable (pQCD)
• Calibrated
• Accessible statistically
• at RHIC via correlations

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The Game Plan
Operational Strategy
AA
pp
dA
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Jet Correlations well Calibrated
pp and dAu jet correlations
Clear (di)jet peaks observed in correlation
function Jet properties in pp and dAu very
similar
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Jet Modification in AuAu
Jets via Nuclear Modification Factor
Jets via Two Particle Correlations
Phys. Rev. Lett. 96, 202301 (2006)
Strong jet modification observed in AuAu
What are the next steps?
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The Next Steps, .
It is time to become quantitative!
Prerequisite Better experimental insights into
mechanistic details of jet
modification
Need to address issues

• new and reliable jet extraction methodologies
• interactions of jets with medium
• particle species dependence of jet modification
• system size dependence of jet modification
• energy calibration (direct g)-jet correlations

Status report of PHENIX efforts follows
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The Need for Decomposition
Asymmetries and Anisotropies present in AuAu
Correlation Functions
Need to Reliably Decompose Flow and Jet Signals!
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Decomposition of Flow and Jet Signals
N.N. Ajitanand et al. Phys. Rev. C 72, 011902
(2005)
Subtraction
Extinction
Two source model Flow (H) Jet (J)
High pt particle constrained perpendicular to RP
a0 is obtained without putting any
constraint on the Jet shape by requiring
Constraint byte
i.e. Zero Yield At Minimum (ZYAM)
Reliable Decomposition of Flow and Jet Signals
via two separate Methods
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Test of Ansatz
Simulation
Phys. Rev. C 72, 011902 (2005)
Strong Away-Side Modification in AuAu Revealed
via Both Methods
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Possible Modification of Jet Topology
Can we use jets to probe the equation of state at
RHIC?
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Three Particle Correlation Method
p2n, p3n
Same Side
Away Side
Associated particles are viewed in the frame
where the high pT direction is the z-axis
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Three Particle Correlations
Df 0
See N.N. Ajitanands talk
Cent0-5
3-particle Correlation Function
PHENIX Acceptance
Uncorrected, NO v2 subtraction
PHENIX Preliminary
Indication of abnormal jets without harmonic
removal
Further study needed to distinguish between cone
or deflected jets
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Particle Species Dependent Jet Modification?
Protons appear to scale with Ncoll Mesons are
suppressed
Large p/p ratio
Phys.Rev.Lett. 91, 172301 (2003)
Phys. Rev. C 72, 014903 (2005)
Are jet associated baryons modified by the medium?
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Jet Associated Identified Partner Particles
Meson vs. Baryon associated partner (for fixed
Hadron trigger)
Yes, jet associated baryons are modified by the
medium
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Jet Associated Identified Conditional Yields
Meson vs. Baryon associated partner (for fixed
Hadron trigger)
Different pT trends of associated meson and
baryon yields
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Jet Associated Baryon to Meson Ratio
Meson vs. Baryon associated partner (for fixed
Hadron trigger)
Does the medium modify the chemistry within the
jet?
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Fully Identified Jet Functions
Meson vs. Baryon trigger (for fixed Meson partner)
Trigger particle species dependent jet
modification at intermediate pT ?
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What about Higher pT Range,
Trigger 2.5ltpTlt4 GeV/c Associated
1.7ltpTlt2.5 GeV/c
see A. Sickles talk
At higher pT the story seems different ?
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Mechanistic Details of Jet Modification
nucl-ex/0409015
What are the relative influences
of Energy-density Path-length (L, L2, La)
Need to look at problem in several different
ways to pin down mechanistic details!
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Complementary Approach Varying System Size
nucl-ex/0409015
dNch/dh very similar for AuAu and CuCu at the
same Npart ! At RHIC almost all transverse energy
goes into particle production Complementary
opportunity for jet-tomography -gt fix energy
density -gt vary path length
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Jet Modification in AuAu and CuCu
Jets via Nuclear Modification Factor
Jets via Two Particle Correlations
p0
No striking difference in modification pattern
observed for AuAu and CuCu at the same Npart!
Energy density major actor!
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Jet Modification in CuCu at higher pT
J. Jia, PANIC2005
30-40 AuAu Npart 114
0-10 CuCu Npart 98
At higher pT still striking similarities between
jet functions for AuAu and CuCu at the same
Npart!
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Particle Production in AuAu and CuCu
C.M. Vale, WWND2006
Similarity between CuCu and AuAu for equivalent
Npart also seen for production of several other
identified particles
It will be interesting to see the identified jet
correlations in CuCu
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En Route for g-jet Correlations,
(inclusive! g)-jet correlations
For new results on single particle (!) direct
g see T. Isobes talk
Need to decompose correlations to disentangle
(direct g)-jet correlations,
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Summary
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13 Countries 62 Institutions 550
Participants
as of March 2005
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Backup
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• Away-side peak consistent
• with mach-cone scenario
• nucl-th/0406018 Stoecker
• hep-ph/0411315 Casalderrey-Solana, et al
• Not the only explanation

nucl-ex/0507004
Strong centrality dependent modification of
away-side jet in AuAu
Cherenkov gluon radiation nucl-th/0507063 Koch,
Majumder, X.-N. Wang
What is (are) the mechanism(s) for modification ?
Jets and Flow couple hep-ph/0411341
Armesto,Salgado,Wiedemann
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DELPHI
Baryon yield dependence consistent with jet
physics in e-e collisions
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TOF timing resolution 120 ps
Analysis performed with the PHENIX detector
PHENIX EMC (PbSc)
New PID results for

• PID analysis is an extension
• of PRL. 91, 182301, 2003 (TOF)
• Differences
• PID analysis with EMCAL (PbSc)
• (6 sectors) TOF detector
• High statistics
• detailed centrality and pT results

EMC timing resolution 400 ps
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Two Source Model
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PHENIX Preliminary
Broadening of away-side jet observed in
central/semicentral CuCu collisions
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