Abstract
I develop an Effective Field Theory (EFT) framework to compute jet substructure observables for heavy ion collision experiments. As an example, I consider dijet events that accompany the formation of a weakly coupled long lived Quark Gluon Plasma (QGP) medium in a heavy ion collision and look at an observable insensitive to jet selection bias: the simultaneous measurement of jet mass along with the transverse momentum imbalance between the jets that are groomed to remove soft radiation. Treating the jet as an open quantum system, I write down a factorization formula within the SCET (Soft Collinear Effective Theory) framework in the forward scattering regime. The physics of the medium is encoded in a universal soft field correlator while the jet-medium interaction is captured by a medium induced jet function. The factorization formula leads to a Lindblad type equation for the evolution of the reduced density matrix of the jet in the Markovian approximation. The solution for this equation allows a resummation of large logarithms that arise due to the final state measurements imposed while simultaneously summing over multiple incoherent interactions of the jet with the medium.
Highlights
Energy collision of nuclei both at Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) creates sufficiently energetic partons that can escape confinement from color neutral hadrons and give rise to a strongly/weakly coupled soup of quarks and gluons known as the Quark Gluon Plasma medium which, in thermal equilibrium is mainly characterized by its temperature
Energy collision of nuclei both at RHIC and the LHC creates sufficiently energetic partons that can escape confinement from color neutral hadrons and give rise to a strongly/weakly coupled soup of quarks and gluons known as the Quark Gluon Plasma medium which, in thermal equilibrium is mainly characterized by its temperature
This has been recently observed in experiments at both Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) [21,22,23,24,25,26,27,28,29,30].The suppression mechanism happens through the mechanism of energy loss when jets travel through the hot medium
Summary
I want to a consider final state dijet event produced in a HIC in the background of a QGP medium. The measurement we wish to impose is the transverse momentum imbalance between the two jets qT ∼ T While this fixes the scaling of all radiation modes that fail grooming, this does not necessarily guarantee collinear scaling inside the jet. For most jet observables in vacuum, and, in particular the one which we are considering, these modes are redundant in that their effect is already captured by the Soft and collinear physics. The collinear mode is sensitive to the grooming parameter zc so that it may either pass or fail grooming When it fails grooming, it will contribute to the transverse momentum imbalance while when it passes, it will contribute to the cumulative jet mass. There will be jet substructure modification within the jet without changing its radius and pT so that it becomes possible to compare the jet substructure modification for the same hard events in pp and HIC even while working in the same pT , R bin
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