Understanding Energy Loss of Heavy Quarks

1
Understanding Energy Loss of Heavy Quarks
William Horowitz The Ohio State University June
2, 2009
With many thanks to Brian Cole, Yuri Kovchegov,
and Ulrich Heinz
2
Outline

• Introduction
• pQCD
• AdS/CFT
• pQCD Again
• Conclusions

3
The Heavy Flavor Data
STAR, Phys. Rev. Lett. 98, 192301 (2007)
PHENIX, Phys. Rev. Lett. 98, 172301 (2007)
4
Simultaneous Understanding?
Y. Akiba for the PHENIX collaboration,
hep-ex/0510008
STAR, Phys. Rev. Lett. 98, 192301 (2007)
WHDG
PHENIX, Phys. Rev. Lett. 98, 172301 (2007)
C. Vale, QM09 Plenary (analysis by R. Wei)
5
RAA vs. v2 Anti-correlation
WH, Acta Phys.Hung.A27221-225,2006
p0
CuCu
PHENIX, arXiv0903.4886
6
pQCD
7
Hard Spectra
PHENIX, 0903.4851 hep-ex
A Dion, Quark Matter 2009
J Dunlop, QM09
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pQCD Uncertainty (I)

• E-loss Mechanisms

• Initial Spectra

S Wicks, et al., NPA784426-442,2007
N Armesto, et al., Phys.Lett.B637362-366,2006
S Wicks, Ph. D. Thesis
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pQCD Uncertainty (II)

• kT int. cutoff (UV)

• mg/IR kT cutoff

B Cole and WH
M Djordjevic, 0903.4591
B Cole and WH, not-yet-published
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Initial State Effects

• Cronin for e-?

• Coal. K

P.B. Gossiaux, QM09 P.B. Gossiaux, R. Bierkandt,
J. Aichelin, arXiv0901.0946
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Out-of-Medium Hadronization Effects

• Addl Channels

• Coalescence

R Rapp and H van Hees, arXiv0903.1096
H. van Hees, M. Mannarelli, V. Greco, and R.
Rapp, Phys.Rev.Lett.100192301,2008
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In-Medium Hadronization Effects

• Coll. Diss.

• In-medium Frag.

A Adil, I Vitev, Phys.Lett.B649139-146,2007
A Adil and I Vitev, Phys.Lett.B649139-146,2007
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AdS/CFT
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Motivation for High-pT AdS

• Why study AdS E-loss models?
• Many calculations vastly simpler
• Complicated in unusual ways
• Data difficult to reconcile with pQCD
• pQCD quasiparticle picture leads to dominant q
  m .5 GeV mom. transfers
• gt Nonperturbatively large as
• Use data to learn about E-loss mechanism, plasma
  properties
• Domains of self-consistency crucial for
  understanding

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AdS/CFT Energy Loss Models I

• Langevin Diffusion
• Collisional energy loss for heavy quarks
• Restricted to low pT
• pQCD vs. AdS/CFT computation of D, the diffusion
  coefficient
• ASW/LRW model
• Radiative energy loss model for all parton
  species
• pQCD vs. AdS/CFT computation of
• Debate over its predicted magnitude

Moore and Teaney, Phys.Rev.C71064904,2005 Casalde
rrey-Solana and Teaney, Phys.Rev.D74085012,2006
JHEP 0704039,2007
BDMPS, Nucl.Phys.B484265-282,1997 Armesto,
Salgado, and Wiedemann, Phys. Rev. D69 (2004)
114003 Liu, Ragagopal, Wiedemann, PRL
97182301,2006 JHEP 0703066,2007
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AdS/CFT Energy Loss Models II

• String Drag calculations
• Embed string rep. quark/gluon in AdS geom.
• Includes all E-loss modes (difficult to
  interpret)
• Gluons and light quarks
• Empty space HQ calculation
• Previous HQ thermalized QGP plasma, temp. T
• HQ in Shock hot and cold nuclear matter

Gubser, Gulotta, Pufu, Rocha, JHEP 0810052,
2008 Chesler, Jensen, Karch, Yaffe,
arXiv0810.1985 hep-th
Kharzeev, arXiv0806.0358 hep-ph
Gubser, Phys.Rev.D74126005,2006 Herzog, Karch,
Kovtun, Kozcaz, Yaffe, JHEP 0607013, 2006
WH and Y Kovchegov, arXiv0904.2536
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AdS Thermal Drag
P Chesler, Quark Matter 2009

• AdS/CFT Drag
• dpT/dt -(T2/Mq) pT

WH, Ph. D. Thesis
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Shocking Loss

• HQ Drag in Hot and Cold nuclear matter

• Recall for BH
• Shock gives exactly the same drag as BH for L p
  T

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Future RHIC Measurements
WH, J.Phys.G35044025,2008
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Hard to Beat
S S Gubser, Quark Matter 2009
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pQCD Again
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pQCD as Consistent Picture?

• v2 Sensitivity to IC

A Drees, H Feng, J Jia, Phys.Rev.C71034909,2005
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High e and pQCD h/s?
T Hirano, et al., Phys.Lett.B636299-304,2006
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pQCD p and e- Consistency?

• Coll. fluctuations

• Dyn. scat. centers

M Djordjevic, QM09 M Djordjevic and U Heinz,
PRL101022302,2008
S Wicks, Ph. D. Thesis
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Conclusions and Outlook

• Exciting years ahead!
• Initial state effects
• Higher momenta
• Reduce hadronization effects
• Individual c and b contributions
• Disambiguate E-loss mechanisms
• HQ correlations
• Disambiguate E redistribution mechanisms
• Rehabilitation for pQCD?

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Supplements
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LHC RcAA(pT)/RbAA(pT) Prediction

• Individual c and b RAA(pT) predictions

WH and M. Gyulassy, Phys. Lett. B 666, 320 (2008)
WH and M. Gyulassy, Phys. Lett. B 666, 320 (2008)
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S Wicks, WH, M Djordjevic, and M Gyulassy,
Nucl.Phys.A784426-442,2007
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Energy Loss Comparison
D7 Probe Brane
t
x
z 0
v
Q, m

• AdS/CFT Drag
• dpT/dt -(T2/Mq) pT

31D Brane Boundary
zm l1/2/2pm
D3 Black Brane (horizon)
zh 1/pT
Black Hole
z

• Similar to Bethe-Heitler
• dpT/dt -(T3/Mq2) pT
• Very different from LPM
• dpT/dt -LT3 log(pT/Mq)

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New Geometries
Constant T Thermal Black Brane
Shock Geometries
J Friess, et al., PRD75106003, 2007
Nucleus as Shock
DIS
Embedded String in Shock
Before
After
Albacete, Kovchegov, Taliotis, JHEP 0807, 074
(2008)
Bjorken-Expanding Medium
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