# Hard Probe 2016

22-27 September 2016
East Lake International Conference Center
Asia/Chongqing timezone
<a href="http://hp2016.ccnu.edu.cn">http://hp2016.ccnu.edu.cn</a>

## Time Dependent qhat from AdS/CFT

25 Sep 2016, 09:10
20m
Xiang-Yang Hall (East Lake International Conference Center)

### Xiang-Yang Hall

#### East Lake International Conference Center

Donghu Road 142, Wuchang District, Wuhan, Hubei, China

### Speaker

William Horowitz (University of Cape Town)

### Description

We present the first ever AdS/CFT calculation of $\hat{q}$ for a light quark jet as a function of position or, equivalently, time. Our result does not suffer from the gamma factor blow up of the usual time-independent AdS/CFT heavy quark setup and is qualitatively similar to, but about a factor of 2/3 larger than, the light flavor result from Liu, Rajagopal, and Wiedemann. Our findings can be immediately implemented into any $\hat{q}$-based energy loss model.

Our $\hat{q}$ derivation relies on our calculation of the average distance squared, $s^2(t)$, travelled by the endpoint of a string falling in an AdS$_3$-Schwarzschild spacetime. The early time behavior is ballistic, $s^2(t)\sim t^2$, but the late time behavior is the usual diffusive Brownian motion, $s^2(t)\sim t$. These late time dynamics are universal and depend only on the near-horizon physics, which allows us to generalize our results to arbitrary dimensions and thus make contact with the physics explored by RHIC and LHC.

Additionally, we find that AdS/CFT predicts angular ordering for radiation in medium, just as in vacuum, and in contradistinction to weak-coupling, with its anti-angular ordering prediction. Finally, our results also imply, sensibly, that AdS/CFT predicts a smooth interpolation between the angular correlations of open heavy flavor and light flavor observables.

### Summary

The content is based on the R. W. Moerman and W. A. Horowitz arXiv:1605.09285 [hep-th] manuscript (currently under review at JHEP) and is appropriate for the "Jet production and modification in QCD matter" or, possibly, the "High pT hadron spectra and correlations" stream.

Presentation type Oral

### Primary author

William Horowitz (University of Cape Town)