1. Light quark jet quenching in AdS/CFT Andrej Ficnar Columbia University Hot Quarks 2012 October 15, 2012

2. Summary ❶ Energy loss linear in time ❷ R AA has the right shape ❸ 1/Nc corrections can increase R AA Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 2/15

3. ❶ AdS/CFT, light quarks and energy loss

4. AdS/CFT in a nutshell  AdS/CFT conjecture:  Holographic dictionary:  Take the ‘t Hooft limit:  one can study strongly coupled gauge theories by doing classical, two-derivative (super)gravity calculations  Here: use SYM as a model for sQGP  medium properties encoded in the metric (3+1)-dim. SYM Type IIB string theory on Maldacena, 1998 Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 3/15

5. (Light) quarks and finite temperatures (boundary) Witten, 1998 black hole D7-brane Karch & Katz, 2002 Introduce ‘quarks’: Finite temperatures: Light ‘quarks’: Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 4/15

6. Light quarks as falling strings Open strings on a D7 brane = dressed pairs Chesler et al., 2009 stopping distance Δx Falling strings Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 5/15

7. Stopping distance of light quarks  Maximum stopping distance in  Numerically:  Analytical model (prelim.):  Cannot be used for extracting instantaneous energy loss Chesler et al., 2009 Gubser et al., 2008 Ficnar, in prep. Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 6/15

8. Instantaneous energy loss  Related to the spacetime momentum currents on the string worldsheet  To make this relation, define a jet  For non-stationary strings details of the worldsheet geometry become important:  This correction does not affect the maximum stopping distance Ficnar, 2012 jet Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 7/15

9. Instantaneous energy loss - numerics (uncorrected) ‘Bragg peak’ Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 8/15

10. Instantaneous energy loss - numerics  Varying initial conditions, keeping the energy constant: suggests Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 9/15

11. ❷ Computing the light quark R AA

12. Phenomenological model  Model phenomenologically relevant part of the energy loss as:  Use the energy scaling of stopping distance:  This gives:  Effective coupling: Ficnar, Noronha, Gyulassy, 2012 Looks like pQCD Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 10/15

13. Correct shape, but jet quenching is too strong Computing RAA  Dynamical, expanding plasma with Glauber initial conditions: CMS, 2012 For and we have: Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 11/15

14. ❸ Higher derivative corrections

15. Gauss-Bonnet gravity  Leading order corrections come from the higher derivative -terms  Causality & energy positivity:  Falling strings stopping distance up to linear order in gives Gauss-Bonnet term Myers et al., 2008 Hofman & Maldacena, 2008 Ficnar, Noronha, Gyulassy, 2012 ~ 40% increase in effective Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 12/15

16. R AA with higher derivative corrections ~100% increase Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 13/15

17. Conclusions & prospects

18. Conclusions  Formalism for computing the energy loss in arbitrary string configurations  Light quark energy loss linear in time  Phenomenological model for calculating R AA  Qualitative agreement, but the quenching is too strong  Higher derivative corrections  R AA is sensitive, but they are not enough Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 14/15

19. Prospects conformal non-conformal ❶ non-conformal effects ❷ generalized initial conditions ❹ massless momentum at endpoints Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 15/15