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
2009 RHIC and AGS Users’ Meeting

2. 2009 RHIC and AGS Users’ Meeting
Outline
Introduction
pQCD
AdS/CFT
pQCD Again
Conclusions
2009 RHIC and AGS Users’ Meeting

3. 2009 RHIC and AGS Users’ Meeting
The Heavy Flavor Data
STAR, Phys. Rev. Lett. 98, (2007)
PHENIX, Phys. Rev. Lett. 98, (2007)
2009 RHIC and AGS Users’ Meeting

4. Simultaneous Understanding?
Y. Akiba for the PHENIX collaboration, hep-ex/
STAR, Phys. Rev. Lett. 98, (2007)
WHDG
C. Vale, QM09 Plenary (analysis by R. Wei)
PHENIX, Phys. Rev. Lett. 98, (2007)
2009 RHIC and AGS Users’ Meeting

5. RAA vs. v2 Anti-correlation
WH, Acta Phys.Hung.A27: ,2006 p0
Cu+Cu
PHENIX, arXiv:
2009 RHIC and AGS Users’ Meeting

6. 2009 RHIC and AGS Users’ Meeting
pQCD
2009 RHIC and AGS Users’ Meeting

7. 2009 RHIC and AGS Users’ Meeting
Hard Spectra
PHENIX, [hep-ex]
A Dion, Quark Matter 2009
pT [GeV/C] 1 9
J Dunlop, QM09
2009 RHIC and AGS Users’ Meeting

8. 2009 RHIC and AGS Users’ Meeting
pQCD Uncertainty (I)
E-loss Mechanisms
Initial Spectra
S Wicks, et al.,
NPA784: ,2007
N Armesto, et al.,
Phys.Lett.B637: ,2006
S Wicks, Ph. D. Thesis
2009 RHIC and AGS Users’ Meeting

9. 2009 RHIC and AGS Users’ Meeting
pQCD Uncertainty (II)
kT int. cutoff (UV)
mg/IR kT cutoff
B Cole and WH
M Djordjevic,
B Cole and WH, not-yet-published
2009 RHIC and AGS Users’ Meeting

10. 2009 RHIC and AGS Users’ Meeting
Initial State Effects
Cronin for e-?
Coal. + K
P.B. Gossiaux, QM09; P.B. Gossiaux, R. Bierkandt, J. Aichelin, arXiv:
2009 RHIC and AGS Users’ Meeting

11. Out-of-Medium Hadronization Effects
Add’l Channels
Coalescence
R Rapp and H van Hees, arXiv:
H. van Hees, M. Mannarelli, V. Greco, and R. Rapp,
Phys.Rev.Lett.100:192301,2008
2009 RHIC and AGS Users’ Meeting

12. In-Medium Hadronization Effects
Coll. Diss.
In-medium Frag.
A Adil, I Vitev, Phys.Lett.B649: ,2007
A Adil and I Vitev, Phys.Lett.B649: ,2007
2009 RHIC and AGS Users’ Meeting

13. 2009 RHIC and AGS Users’ Meeting
AdS/CFT
2009 RHIC and AGS Users’ Meeting

14. 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
=> Nonperturbatively large as
Use data to learn about E-loss mechanism, plasma properties
Domains of self-consistency crucial for understanding
2009 RHIC and AGS Users’ Meeting

15. 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.C71:064904,2005
Casalderrey-Solana and Teaney, Phys.Rev.D74:085012,2006; JHEP 0704:039,2007
BDMPS, Nucl.Phys.B484: ,1997
Armesto, Salgado, and Wiedemann, Phys. Rev. D69 (2004)
Liu, Ragagopal, Wiedemann, PRL 97:182301,2006; JHEP 0703:066,2007
2009 RHIC and AGS Users’ Meeting

16. 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 0810:052, 2008
Chesler, Jensen, Karch, Yaffe, arXiv: [hep-th]
Kharzeev, arXiv: [hep-ph]
Gubser, Phys.Rev.D74:126005,2006
Herzog, Karch, Kovtun, Kozcaz, Yaffe, JHEP 0607:013, 2006
WH and Y Kovchegov, arXiv:
2009 RHIC and AGS Users’ Meeting

17. 2009 RHIC and AGS Users’ Meeting
AdS Thermal Drag
P Chesler, Quark Matter 2009
AdS/CFT Drag:
dpT/dt ~ -(T2/Mq) pT
WH, Ph. D. Thesis
2009 RHIC and AGS Users’ Meeting

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Shocking Loss
HQ Drag in Hot and Cold nuclear matter
Embedded String in Shock Q
vshock x z
Before
After
Recall for BH:
Shock gives exactly the same drag as BH for L = p T
2009 RHIC and AGS Users’ Meeting

19. Future RHIC Measurements
In-Medium Frag
WH, J.Phys.G35:044025,2008
2009 RHIC and AGS Users’ Meeting

20. 2009 RHIC and AGS Users’ Meeting
Hard to Beat
PHENIX, Phys. Rev. Lett. 98, (2007)
S S Gubser, Quark Matter 2009
2009 RHIC and AGS Users’ Meeting

21. 2009 RHIC and AGS Users’ Meeting
pQCD Again
2009 RHIC and AGS Users’ Meeting

22. pQCD as Consistent Picture?
v2 Sensitivity to IC
A Drees, H Feng, J Jia, Phys.Rev.C71:034909,2005
2009 RHIC and AGS Users’ Meeting

23. 2009 RHIC and AGS Users’ Meeting
High e and pQCD h/s?
T Hirano, et al., Phys.Lett.B636: ,2006
2009 RHIC and AGS Users’ Meeting

24. pQCD p and e- Consistency?
Coll. fluctuations
Dyn. scat. centers
M Djordjevic, QM09;
M Djordjevic and U Heinz, PRL101:022302,2008
S Wicks, Ph. D. Thesis
2009 RHIC and AGS Users’ Meeting

25. 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?
2009 RHIC and AGS Users’ Meeting

26. 2009 RHIC and AGS Users’ Meeting
Supplements
2009 RHIC and AGS Users’ Meeting

27. 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)
2009 RHIC and AGS Users’ Meeting

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S Wicks, WH, M Djordjevic, and M Gyulassy, Nucl.Phys.A784: ,2007
2009 RHIC and AGS Users’ Meeting

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30. Energy Loss Comparison
D7 Probe Brane t
z = 0 x v
AdS/CFT Drag:
dpT/dt ~ -(T2/Mq) pT
Q, m
zm = l1/2/2pm
3+1D Brane
Boundary
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)
2009 RHIC and AGS Users’ Meeting

31. 2009 RHIC and AGS Users’ Meeting
New Geometries
Constant T Thermal Black Brane
Shock Geometries
Nucleus as Shock
J Friess, et al., PRD75:106003, 2007
DIS
Embedded String in Shock
Before
After
Albacete, Kovchegov, Taliotis,
JHEP 0807, 074 (2008) Q
vshock x z
vshock x z Q
Bjorken-Expanding Medium
2009 RHIC and AGS Users’ Meeting

32. 2009 RHIC and AGS Users’ Meeting