Abstract
We compute the color coherence effects for soft gluon radiation off antennas containing heavy quarks in the presence of a QCD medium – the actual calculations is made for a triplet configuration and then generalize to both color singlet and octet ones. This work completes the studies of antenna radiation inside a medium which provide a useful picture of the relevance of interference effects in jet parton showers for the jet quenching phenomenon observed in high-energy nuclear collisions. The analysis is performed resumming the multiple scatterings of the partonic system with the medium. The main conclusion is that decorrelation due to color rotation is more effective in the case in which at least one of the emitters of the antenna is a heavy quark. This effect, present both for a heavy-quark–antiquark or a heavy-quark–gluon antenna is more relevant for the later or for the case in which the energies of the quark and antiquark are very different. The parameter controlling these effects involves the dead-cone angle. We find that interferences are cancelled, spoiling the color correlation of the pair, when θDC≡M/E≫1/ωL where E and ω are the energies of the heavy quark and the radiated gluon and L is the medium length. In the case of a heavy-quark–antiquark antenna tform, defined as the difference in splitting times in amplitude and complex conjugate of the amplitude, appears instead of L if the original splitting is symmetric. The presence or absence of interferences modifies the energy loss pattern.
Highlights
Jets traversing QCD matter created in high-energy nuclear collisions have been experimentally studied for the last ten years, first at the RHIC at BNL [1] and at the LHC at CERN [2,3,4]
The main result in the paper is the reduction o√f the color coherence when the dead-cone angle θDC ≡ M/E 1/ ωL where E and ω are the energies of the heavy quark and the radiated gluon and L is the medium length
(where we have used the multiple soft scattering approximation for the last expression, qbeing the transport coefficient known as jet quenching parameter) and the dead-cone phase: ΔDC
Summary
Jets traversing QCD matter created in high-energy nuclear collisions have been experimentally studied for the last ten years, first at the RHIC at BNL [1] and at the LHC at CERN [2,3,4]. Interesting results exist for the case of b-quark jets [42] which study a region of much larger transverse momentum, where the effects of the mass are expected to be small – some coherence effects as the ones studied here are, expected to be of relevance there Motivated by these theoretical and experimental findings we present here a calculation of the color coherence effects in a set up which includes a heavy-quark and a gluon antenna radiating a soft gluon in the presence of a medium. The present publication completes the study of the in-medium antenna radiation spectrum [24,25,26,27,28,29,30] and provides the way to encode heavy quark effects in the new picture of jet quenching being developed
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