Abstract
We propose a novel definition of a holographic light hadron jet and consider the phenomenological consequences, including the very first fully self-consistent, completely strong-coupling calculation of the jet nuclear modification factor $R_{AA}$, which we find compares surprisingly well with recent preliminary data from LHC. We show that the thermalization distance for light parton jets is an extremely sensitive function of the \emph{a priori} unspecified string initial conditions and that worldsheets corresponding to non-asymptotic energy jets are not well approximated by a collection of null geodesics. Our new string jet prescription, which is defined by a separation of scales from plasma to jet, leads to the re-emergence of the late-time Bragg peak in the instantaneous jet energy loss rate; unlike heavy quarks, the energy loss rate is unusually sensitive to the very definition of the string theory object itself. A straightforward application of the new jet definition leads to significant jet quenching, even in the absence of plasma. By renormalizing the in-medium suppression by that in the vacuum we find qualitative agreement with preliminary CMS $R_{AA}^{jet}(p_T)$ data in our simple plasma brick model. We close with comments on our results and an outlook on future work.
Highlights
JHEP11(2014)017 and LHC [5, 9, 15]
The dynamics of the earliest times in heavy ion collisions is given by weak-coupling physics, not that of strong-coupling physics. perturbative QCD (pQCD)-based energy loss models that incorporate the effects of the QGP medium on the evolution of jets [47, 48] agree quantitatively with preliminary data [45]
The main result of this paper is that we find an agreement between our simple jet suppression model predictions and recent preliminary jet measurements from the CMS collaboration [46], suggesting that the single conceptual framework of a strongly-coupled plasma described by the AdS/CFT correspondence might be capable of characterizing the physics of quark-gluon plasma produced in heavy ion collisions
Summary
Fundamental representation quarks added to the N = 4 SYM theory are dual to open strings moving in the 10d geometry [57] attached to D7 branes [58]. These branes fill the whole 4D Minkowski space and extend along the radial coordinate from the boundary at u = 0 down to a maximum coordinate at u = um. The bare mass M of the quark is proportional to 1/um [59], so for massless quarks the D7 brane fills the whole radial direction Open strings with both endpoints attached to the D7 brane are dual to quarkanti-quark pairs on the field theory side.
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