Transcript Barannikova

Status and Implications of
PID measurements at high pT
Olga Evdokimov
University of Illinois at Chicago
Outline

The motivation:
Where we are: current picture
 High pT – What? Where? Why?


Identified particles at high pT:
The identified particle measurements
 Implications and Theoretical input
 Open questions

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WWND 2010
Summary
Olga Evdokimov
University of Illinois at Chicago
2
Jan 2- 9, 2010
Medium properties via jets
Jet Tomography: calibrated (?) probes

leading
particle
hadrons
q
Described by pQCD
Particle production in hard sector 
convolution of PDF NLO  FF
q
hadrons
leading particle

Energy loss mechanisms:

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Path length effects  non-trivial:



need discriminative measurements
need discriminative measurements
Flavor/color-charge dependence of parton-medium coupling
In-medium fragmentation/ hadronization

WWND 2010
…..
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
Define “high”
In pp: inclusive cross-section is
CDF Collaboration, PRD 65, 072005, 2002.
dominated by jet production above
~4 GeV/c
What about RHIC matter?

Quick look at intermediate pT:



WWND 2010
“Lingering” hydro flow
Baryon anomaly
Ridge
Olga Evdokimov
University of Illinois at Chicago
T.Hirano, Y.Nara,
PRC69,034908(2004)
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Jet quenching at RHIC
PHENIX p0 @ 200 GeV
Nuclear Modification Factors
Yield AA/N binary  AA
R AA 
Yield pp

coll
rad

Jet quenching evident in strong
suppression of high pT hadrons

Multiple models provide a successful
descriptions of the suppression levels

Most include radiative and collisional
energy loss
rad+coll
Fits: G. Qin et al, PRL100:072301, 2008
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
Jet quenching: Data & Models
TECHQM Collaboration:
S. Bass et al, arXiv:0808.0908
H. Caines
CATHIE/TECHQM-2009
Set to compare jet-quenching
scenarios with the same
constraints:



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* Similar results from GLV and WHDG
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same nuclear profile
same structure & fragmentation
functions
same medium (hydro)
RAA of p(h) is not very
discriminating
Need more differential
measurements
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
Medium properties and E-loss
S. Wicks et al - NPA784:426-442,2007
The real Outline:


Identified particles spectra in pp and AA
High-pT ratios and Nuclear modification
factors
Mass, Color-charge, Flavor effects


Heavy flavor studies
Correlations with identified particles
S. Albino, et ak - NPB 725 (2005) 181
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
The reference: p and p
hadrons
leading
particle
q
q
hadrons
leading
particle
p+p→p0+X
Simon, private
communication
S.S. Adler et al, PRL 91 241803
F. Simon
p+p→p0+X
KKP: B. Kniehl, G. Kramer, P¨otter, Nucl. Phys. B597, 337 (2001)
AKK: S. Albino, B Kniehl, G. Kramer, arXiv: 0803.2768v2
DSS: D. de Florian, W. Vogelsang, F. Wagner, arXiv: 0708.3060v3
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
The reference: kaons
Y. Xu
SQM09
STAR preliminary
STAR preliminary
A. Timmins
SQM09
STAR preliminary
WWND 2010
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Consistent results for K0S and K
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Extended kaon spectra – new constrains
for FF
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Direct measurements of FF: Pythia
works well for K0S , not so well for L
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
Sample of RAA in PHENIX
C. Vale, Quark Matter 09
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
Zooming in: p and p
arXiv: 0804.4760
PRELIMINARY
STAR preliminary
PHENIX QM09:
STAR QM08:
“At high pT RCP(p) approaches RCP(p)”
High pT RAA(p)>RAA(p)

The issue: pQCD predicts E-loss dependence on color-charge factors CA/CF = 9/4

Is there issue? @10 GeV/c: p(0.60q+0.40g), p (0.05q+0.95g)
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
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Jan 2- 9, 2010
Jet chemistry modifications
pQCD expectation : RAA(p) < RAA(p)
STAR Preliminary
p
k
W. Liu and R. Fries,
PRC 77, 054902 (2008)


Observation from central Au+Au collisions: RAA(r)~RAA(p) <RAA(K)<RAA(p)
K/p (AA)>K/p (pp)
Hierarchy consistent with jet flavor conversion
parton medium interactions
12
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Olga Evdokimov
University of Illinois at Chicago
Jan 2- 9, 2010
Medium-induced modifications
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Flavor-conversions q  g

HT contributions
- direct hadron production
_
S. Brodsky, A. Sickles, PLB668 111 (2008)
qqpq

W. Liu and R. Fries, PRC 77, 054902 (2008)


Reverses expected  trend /p−
ratio from pp to Au+Au to 
Boosts Kaon production ~ factor 2
due to abundance of QGP s-quarks
WWND 2010
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Describes decreasing trend pT for
v2 for (anti)protons

Centrality dependence of protontriggered correlations
d
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
Leads to RAA(p) <RAA(p)
Olga Evdokimov
University of Illinois at Chicago
13
Jan 2- 9, 2010
Energy loss for Heavy Flavor


Heavy quarks – calculable (?) probes for medium
properties
Discriminating power for energy loss scenarios
Open heavy flavor
Light flavor energy loss
Strong suppression at high pT in RAA
 Radiative vs. collisional energy loss

WWND 2010
Smaller gluon bremsstrahlung for
heavy quarks 
? Smaller suppression at high pT

Olga Evdokimov
University of Illinois at Chicago
14
Jan 2- 9, 2010
High pT suppression for HF
RAA for non-photonic electrons (from heavy flavor decays)
PHENIX QM09
STAR PRL, 98, 192301 (2007)
No decrease in suppression for non-photonic e
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
15
Jan 2- 9, 2010
Energy loss for beauty
Heavy Flavor results from non-photonic electrons:
Strong suppression of heavy-flavor at high pT in RAA ~ light mesons
 Inconsistent with radiative energy loss prediction  needs collisional too

 What
about beauty?
e –D0 correlation
using like-sign e-K pairs
mostly B


~25%B,75%C
Mid-rapidity e + forward m
Agreement on b- and c- fractions from multiple STAR & PHENIX studies
b-decays contribution to non-photonic electrons: ~50% at pT~5 GeV/c
WWND 2010
Olga Evdokimov
 strong suppressionUniversity
in AA
for both charm and beauty!
of Illinois at Chicago
16
Jan 2- 9, 2010
Summary & Outlook
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RHIC: Systematic studies of the partonic medium

Systematic studies of identified particle spectra
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New constrains of FF
Jet-chemistry modifications in AA
Jet flavor conversion / direct hadron production / ??
Ongoing challenges
- Color-charge effects and jet chemistry
- High pT suppression: both Charm and Beauty?
- …………
WWND 2010
Olga Evdokimov
University of Illinois at Chicago
17
Jan 2- 9, 2010