JETS IN HOLOGRAPHY AN OVERVIEW. Wilke van der Schee. JET collaboration Satelite meeting, Montreal, June 26, 2015

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1 JETS IN HOLOGRAPHY AN OVERVIEW Work in progress in this talk is with Krishna Rajagopal and Andrey Sadofyev Wilke van der Schee JET collaboration Satelite meeting, Montreal, June 26, 2015

2 2/12 OUTLINE Early work Jets as strings and stopping distance Recent progress Defining energy loss: shooting string through a slab Lund model in AdS: strings with finite endpoint momentum Experimental comparisons? Too much energy loss? Outlook AdS: more about broadening then about energy loss? What about initial string conditions? Fit to pp data. quenching??

3 3/12 ACTIVE FIELD OF RESEARCH J. Casalderrey, D. Can Gulhan, J. Guilherme Milhano, D. Pablos and K. Rajagopal, A Hybrid Strong/Weak Coupling Approach to Jet Quenching R. Morad, W.A. Horowitz, Strong-coupling Jet Energy Loss from AdS/CFT (2014) A. Ficnar, S.S. Gubser and M. Gyulassy, Shooting String Holography of Jet Quenching at RHIC and LHC (2013)

4 4/12 EARLY WORK Drag force Force required for stationary moving string: Radiative loss through Wilson loop: Stopping distance for light quarks:

5 5/12 JET PRODUCTION Typical philosophy: Jet is result of hard event, as prescribed in pqcd Energy loss, through soft modes, and non-perturbative In AdS/CFT: jet = (classical) string Collisions within AdS will also lead to `jet-like (shooting) strings finite N c and l corrections can in principle be computed: Current status: Create string (quark-antiquark pair) with `jet-like properties Problem: initial condition string is 2 functions (position, velocity) Z. Zhang, D. Houa and H. Ren, The finite t Hooft coupling correction on the jet quenching parameter in a N = 4 SYM plasma (2012)

6 6/12 ENERGY LOSS BY A SLAB OF PLASMA Long standing problem: how to define energy jet in terms of string? In particular, how much energy has jet lost? Natural definition: size black hole = size QGP, shoot jet through Model evolution more realistically Part of string falls in black hole: dissipates into hydro modes Part of string can exit Here: static plasma with constant T (straightforward to improve) Attractive: final string in vacuum AdS is well understood Angle in AdS jet angle P.M. Chesler and K. Rajagopal, Jet quenching in strongly coupled plasma (2014)

7 7/12 A LUND MODEL IN ADS Put all initial energy/momentum at endpoint ( quark) Natural from Lund model perspective. Also: minimal energy loss EOM: endpoint follows null geodesic, losing energy gradually Energy loss does not depend on energy jet Attractive: removes functional freedom of initial conditions Create string near horizon? (shooting strings) Natural place for original `nuclei to collide (perhaps not akin to pqcd?) Easier to have less energy loss/smaller opening angles A. Ficnar and S. Gubser, Finite momentum at string endpoints (2013)

8 8/12 REVISITING STOPPING DISTANCE Assumptions behind numerics identified: String shape in UV quickly in regime of (stationary) drag force calculation Endpoint moves along null geodesic Possible to do better Endpoint strings are not well described by stationary shape Possible to go about 19% further (already 11% in ) Shooting strings go about 88% further (but lot of fine-tuning!) A. Ficnar and S. Gubser, Finite momentum at string endpoints (2013) P.M. Chesler, K. Jensen, A. Karch and L.G. Yaffe, Light quark energy loss in strongly-coupled N = 4 supersymmetric Yang-Mills plasma (2008)

9 9/12 A TYPICAL EXAMPLE Try simulate `normal string, with most energy at endpoint: Shoot through slab of plasma (or dynamic spacetime) Naïve: constant 300 MeV plasma, length 4fm, create at 1fm Little bit of freedom: start at 5% from boundary-horizon distance Naïve: `t Hooft coupling 5.5, gives jet energy of 1 TeV

10 10/12 STRING EVOLUTION Black hole String endpoint (blue) follows null trajectory initially (red dashed) String endpoints change direction when energy vanishes `Snapback : especially relevant when string is moving upwards Can use geometric optics approximation at early and late times

11 11/12 JET ANGULAR SPECTRUM At late times string falls into AdS, straight lines for each s. Stress-energy on boundary due to `collection of AdS point particles : energy e, angle to center q, AdS angle a Left: 876 GeV (7% loss) angle ~ 0.01 Right: 462 GeV (52% loss) angle ~ 0.04 Y. Hatta, E. Iancu, A. Mueller and D. Triantafyllopoulos, Aspects of the UV/IR correspondence: energy broadening and string fluctuations (2010)

12 12/12 DISCUSSION Significant recent progress String through slab, jet broadening essential part of jets (in AdS) Lund-type model bring closer connection with (p)qcd How to compare N=4 SYM to QCD Compare at constant energy density or constant temperature? Problematic: energy loss does not scale with entropy density/dof! Naïve comparison with l 5.5 seems to fail (?) Initial conditions Reasonable progress: from two functions to a few parameters? Idea: fix initial conditions with pp collisions and see what happens Jet created in pqcd? Near boundary or near horizon? Outlook More quantitative comparisons with experiment, e.g. improved hybrid models Match to pp? through plasma? Finite coupling corrections in more realistic settings?