1. Heavy Flavor Physics at RHIC Matthias Grosse Perdekamp U of Illinois and RIKEN BNL
o Overview
Selected results from RHIC
“light quark” jet quenching
and elliptic flow
Energy loss of heavy quarks in media
as tool to study nuclear media formed in
heavy ion collisions.

2. Heavy Flavor Physics at RHIC: Overview
open heavy flavor production spectroscopy:
1) Energy loss in dense and
hot nuclear matter
2) Tomography of DHNM
3) Reference data for quarkonia
Quarkonia as “Thermometer”:
color screening depends on T
Matsui and Satz, Phy.Lett. B 178 (1986)416
QGP?
A-A
PDF(A)
p/d-A
Modification of PDFs in nuclear environment (anti-) shadowing
vs new state of matter (color glass condensate)
2) Reference data for initial state in A-A
QCD
p-p, d-A, A-A
1) Cross sections vs rapidity and √s
2) Vacuum energy loss vs media
3) Reference data
1) Hadronization mechanism
2) Reference data for quarkonia
Polarized PDFs
p-p
measure
formation process?

3. Polarized pp: ΔG from charm production
Double spin asymmetry electron
asymmetry for charm production
(I. Bojak and M. Stratmann, hep-ph/ )
Scale dependence reduced at NLO: LO
NLO

4. Relativistic Heavy Ion Collider
Design Parameters:
Performance Au + Au p+p
snn GeV GeV
L [cm-2 s -1 ] x x 1032
Cross-section barns mbarn
Interaction rates 14 kHz MHz
RHIC Capabilities
Au + Au collisions at 200 GeV/u
p + p collisions up to 500 GeV
spin polarized protons (70%)
lots of combinations in species and energy in between

5. RHIC Running 2 x design Luminosity!
Delivered 1196 (mb)-1 to Phenix [week ago : 1060] (mb)-1 last week [best week: 158]
2 x design
Luminosity!
maximum projection
physics target
minimum projection

6. Charm and J/ψ Data from RHIC
Run I, Au-Au beams at s=130 GeV
Open charm from PHENIX
Run II, Au-Au beams and p-p at s=200 GeV
Open charm and J/Y from PHENIX
Run III, d-Au, p-p at s=200 GeV
Open charm from PHENIX and STAR, J/Y from PHENIX
Run IV, Au-Au, s=200 GeV
More measurements to come

7. STAR: Large acceptance TPC+EMC

8. Au-Au Event in STAR
Das man in diesen Kollisionen ueberhaupt irgentetwas lehren kann ist ein Wunder in sich. Hier ist eine Au-Au kollision aufgezeichnet mit STAR experiment am RHIC. Sie sehen tausende von Teilchen in der Spurkammer von STAR. Und daraus gilt es nun was zu lernen.
Und mit vielen Jahren Erfahrung ist dies tatsachlich moeglich!

9. PHENIX Physics Capabilities
designed to measure rare probes: + high rate capability & granularity
+ good mass resolution and particle ID
- limited acceptance
Au-Au & p-p spin
2 central arms:
electrons, photons, hadrons
charmonium J/, ’ -> e+e-
vector meson r, w,  -> e+e-
high pT po, p+, p-
direct photons
open charm
hadron physics
2 muon arms: muons
“onium” J/, ’,  -> m+m-
vector meson  -> m+m-
combined central and muon arms:
charm production DD -> em
global detectors
forward energy and multiplicity
event characterization

10. Au-Au and d-Au events in the PHENIX Central Arms

11. Open charm in pp: Single electrons
d + Au
STAR Preliminary
charm cross sections (barely) agree!
PHENIX PRELIMINARY
=1.36 ± 0.20 ± 0.39 mb
PHENIX: three methods to subtract
photonic background
STAR: three methods to identify
electrons

12. Consistency between electron data sets
STAR slightly above PHENIX

13. Does the PYTHIA “extrapolation” work?
PYTHIA tuned to available data (sNN < 63 GeV) prior to RHIC results
1Phys. Rev. Lett. 88, (2002)
PHENIX PRELIMINARY
STAR preliminary
spectra are harder than PYTHIA extrapolation from low energies
Use parametrization for Au-Au reference
Use rapidity dependence from PYTHIA to extract cross section

14. STAR preliminary Reconstruction of D mesons in dAu Collisions
D0+D0
0 < pT < 3 GeV/c, |y| < 1.0
d+Au minbias
= 1.12 ± 0.20 ± 0.37 mb from D data
(1.36 ± 0.20 ± 0.39 mb with electrons)

15. Collision Geometry -- “Centrality”
Spectators
Participants
For a given b,
Glauber model
predicts Npart
(No. participants)
and Nbinary
(No. binary collisions)
15 fm b fm
Npart
Nbinary

16. Experimental Determination of Centrality
BBC Au
ZDC
ZDC
ZDC: zero degree
calorimeter
BBC: beam-beam
counter

17. Selected Results: Elliptic Flow
Origin: spatial anisotropy of the system when created, followed by multiple scattering of particles in the evolving system
spatial anisotropy  momentum anisotropy
v2: 2nd harmonic Fourier coefficient in azimuthal distribution of particles with respect to the reaction plane
Almond shape overlap region in coordinate space
Outgoing
particle

18. E. Shuryak

19. STAR v2 for charged particles
Large v2
STAR v2 for charged particles
Hydrodynamic limit exhausted at RHIC for low pT particles.
Large magnitude of v2 suggests highly viscous “liquid”: strongly interacting nuclear medium has been
formed!
Adler et al., nucl-ex/

20. Probing the nuclear medium formed:
Jet Suppression
charm/bottom dynamics
J/Y & U
direct photons CONTROL

21. Light qs and g jets as probe of the medium
hadrons q
leading
particle
leading particle
schematic view of jet production
Jets from hard scattered
quarks observed via fast
leading particles or
azimuthal correlations
between the leading
particles
However, before they create jets, the scattered quarks radiate energy (~ GeV/fm) in the colored medium
Decreases their momentum (fewer high pT particles)
Eliminates jet partner on other side
Jet Quenching

22. Quantify Nuclear Modification of Hadron Spectra
1. Compare Au+Au to nucleon-nucleon cross sections
2. Compare Au+Au central/peripheral
Nuclear
Modification
Factor:
nucleon-nucleon
cross section
<Nbinary>/sinelp+p AA AA
If no “effects”:
R < 1 in regime of soft physics
R = 1 at high-pT where hard
scattering dominates
Suppression:
R < 1 at high-pT AA AA AA AA

23. Quantitative Agreement across Experiments
Effect is real…Final or Initial State Effect?

24. Centrality Dependence Au-Au vs d-Au
Au + Au Experiment
d + Au Control Experiment
Final Data
Preliminary Data
Significantly different and opposite centrality evolution of Au+Au experiment from d+Au control.
Jet Suppression is clearly a final state effect.

25. Heavy Quark Energy Loss in Media
Shuryak proposed that charm quarks may suffer a large energy loss
when propagating through a high opacity plasma, leading to large
suppression of D mesons. (E. V. Shuryak, Phys. Rev. C 55, 961 (1997)
Dokshitzer and Kharzeev propose the “dead cone” effect:
Reduced gluon emission at small angles in media for heavy quarks
may lead to enhancement in D meson production.
Y.L. Dokshitzer and D. E. Kharzeev, Phys. Lett. B 519, 199 (2001)
Djordjevic and Gyulassy: detailed quantitative
treatment of heavy quark energy loss in strongly
interacting media. Predict slight suppression: !
M. Djordjevic and M. Gyulassy, nucl-th/

26. Radiative heavy quark energy loss
from Magdalena Djordjevic at QM 2004
There are three important medium effects that control the
radiative energy loss at RHIC
Ter-Mikayelian effect (Djordjevic-Gyulassy Phys.Rev.C68:034914,2003)
Transition rediation (Zakharov)
Energy loss due to the interaction with the medium
Ter-Mikayelian:
QCD analog to
dielectric effect
in electrodynamics
1) ) )

27. Centrality dependence in AuAu
1/TABEdN/dp3 [mb GeV-2]
1/TABEdN/dp3 [mb GeV-2]
pp reference
pp reference
1/TAA
1/TAA
1/TABEdN/dp3 [mb GeV-2]
1/TABEdN/dp3 [mb GeV-2]
1/TABEdN/dp3 [mb GeV-2]
1/TAA
1/TAA
1/TABEdN/dp3 [mb GeV-2]
1/TAA
pp reference
pp reference
pp reference
No deviations from binary scaling within uncertainties.
Consistent with Djordjevic and Gyulassy: 10 x more data from Run 2004!

28. Centrality dependence in dAu
PHENIX PRELIMINARY
1/TAB
1/TABEdN/dp3 [mb GeV-2]
PHENIX PRELIMINARY
1/TABEdN/dp3 [mb GeV-2]
Single electron spectra in dAu are in good
agreement with the proton reference.

29. Charm flow? is partonic flow realized?
PHENIX PRELIMINARY
is partonic flow realized?
v2 of non-photonic electrons indicates non-zero charm flow in AuAu collisions
uncertainties are large
definite answer: RUN-04 AuAu data sample!

30. J/Y: Does colored medium screen cc ?
40-90%
most central
Ncoll=45
20-40%
most central
Ncoll=296
0-20%
most central
Ncoll=779
Statistics limited:
Run 2004!
R.L. Thews, M. Schroedter, J. Rafelski Phys. Rev.
C (2001): Plasma coalesence model
for T=400MeV and ycharm=1.0,2.0, 3.0 and 4.0.
L. Grandchamp, R. Rapp Nucl.
Phys. A&09, 415 (2002) and
Phys. Lett. B 523, 50 (2001):
Nuclear Absorption+ absoption
in a high temperature quark gluon
plasma
A. Andronic et. Al. Nucl-th/
Proton

31. Summary
The final state produced in central Au-Au collisions at RHIC is dense and opaque and appears to have the properties of a strongly interaction liquid.
The energy loss of heavy quarks in nuclear media is an important tool to further characterize the nature of the medium produced at RHIC.
Heavy flavor production will play an important role in studying nucleon
structure in d-A and polarized p-p collisions at RHIC. The experimental
possibilities will be greatly enhanced by silicon vertex detector upgrades
for PHENIX and STAR.
We expect a significant qualitative and quantitative advance
from run 2004 in understanding the nature of the matter
formed in central collisions at RHIC.

32. PHENIX: J/Ye+e- and m+m- from pp
s= /- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) mb
(BR*stot = 239 nb)
Central and forward rapidity measurements from Central and Muon Arms:
Rapidity shape consistent with various PDFs
√s dependence consistent with various PDFs with factorization and renormalization scales chosen to match data
Higher statistics needed to constrain PDFs

33. PHENIX: J/Ye+e- and m+m- from pp
pT shape consistent with COM over our pT range
Higher statistics needed to constrain models at high pT
Polarization measurement limited