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

Light quark jet quenching in AdS/CFTAndrej Ficnar

Columbia University

Hot Quarks 2012October 15, 2012

Summary

❶ Energy loss linear in time

❷ RAA has the right shape

❸ 1/Nc corrections can increase RAA

Light quark jet quenching in AdS/CFT | Andrej Ficnar | Hot Quarks 2012 2/15

❶ AdS/CFT, light quarks and energy loss

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) quarks and finite temperatures(boundary)

Witten, 1998black hole

D7-brane

Karch & Katz, 2002

Introduce ‘quarks’:

Finite temperatures:Light ‘quarks’:


Light quarks as falling strings

Open strings on a D7 brane = dressed pairs

Chesler et al., 2009

stopping distance Δx

Falling strings


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.


Instantaneous energy loss Related to the spacetime momentum

currents on the string worldsheet

To make this relation, define a jet

For non-stationary strings detailsof the worldsheet geometrybecome important:

This correction does not affect the maximum stopping distance

Ficnar, 2012

jet


Instantaneous energy loss - numerics

(uncorrected)

‘Bragg peak’


Instantaneous energy loss - numerics Varying initial conditions, keeping the energy constant:

suggests


❷ Computing the light quark RAA

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


Correct shape, but jet quenchingis too strong

Computing RAA Dynamical, expanding plasma with Glauber initial conditions:

CMS, 2012

For and we have:


❸ Higher derivative corrections

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


RAA with higher derivative corrections

~100% increase


Conclusions & prospects

Conclusions Formalism for computing the energy loss in arbitrary string

configurations Light quark energy loss linear in time

Phenomenological model for calculating RAA

Qualitative agreement, but the quenching is too strong Higher derivative corrections

RAA is sensitive, but they are not enough


Prospects

conformal

non-conformal

❶ non-conformal effects

❷ generalized initial conditions

❸ expanding geometry

❹ massless momentum at endpoints


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

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