Some of the most important probes of the quark-gluon plasma (QGP) produced inheavy ion collisions come from the analysis of how the shape and energy of jetsare modified by passage through QGP. We model an ensemble of back-to-backdijets to gain a qualitative understanding of how the shapes of the individualjets and the asymmetry in the energy of the pairs of jets are modified bypassage through an expanding droplet of strongly coupled plasma, as modeled ina holographic gauge theory. We do so by constructing an ensemble of strings inthe gravitational description of the gauge theory. We model QCD jets in vacuumusing strings whose endpoints move "downward" into the gravitational bulkspacetime with some fixed small angle that represents the opening angle (ratioof jet mass to jet energy) that the QCD jet would have in vacuum. Such stringsmust be moving through the gravitational bulk at (close to) the speed of light;they must be (close to) null. This condition does not specify the energydistribution along the string, meaning that it does not specify the shape ofthe jet being modeled. We study the dynamics of strings that are initially notnull and show that strings with a wide range of initial conditions rapidlyaccelerate and become null and, as they do, develop a similar distribution oftheir energy density. We use this distribution of the energy density along thestring, choose an ensemble of strings whose opening angles and energies aredistributed as in perturbative QCD, and show that we can then fix one modelparameter such that the mean jet shape in our ensemble matches that measured inp-p collisions reasonably well. We send our strings through the plasma,choosing the second model parameter to get a reasonable suppression in thenumber of jets, and study how the mean jet shape and the dijet asymmetry aremodified, comparing both to data from LHC heavy ion collisions.
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