Abstract
Jet shape measurements are employed to explore the microscopic evolution mechanisms of parton-medium interaction in ultra-relativistic heavy-ion collisions. In this study, jet shape modifications are quantified in terms of the fragmentation function , relative momentum , density of charged particles , jet angularity , jet momentum dispersion , and for proton-proton (pp) collisions at 0.9, 2.76, 5.02, 7, and 13 TeV, as well as for lead-lead collisions at 2.76 TeV and 5.02 TeV by JEWEL. A differential jet shape parameter is proposed and studied at a smaller jet radius . The results indicate that the medium has the dominant effect on jet shape modification, which also has a weak dependence on the center-of-mass energy. Jet fragmentation is enhanced significantly at very low , and fragmented jet constituents are linearly spread to larger jet-radii for . The waveform attenuation phenomena is observed in , , and distributions. The results obtained for from to , where the wave-like distribution in collision is ahead of collisions at small jet-radii, indicates a strong medium effect.
Highlights
One goal of jet physics is to explore the microscopic properties of hot-dense QCD matter, quark-gluon plasma (QGP), created in ultra-relativistic heavy-ion collisions [1,2,3]
For pp collisions and P b + P b collisions without recoil effect, the enhancement or reduction on F (z) depend on collisional energy and participant nucleus. ρ(r) indicate the same performance that jet constituents spread to large jet-radius with the increase of center of mass energy of collisions, and the medium effect is significant for the modification at relative large angles. ρ(r) distribution is exponential decrease with jet-radius. f distribution shows an independent of collisional energy, but strongly modified by QCD medium and present an obvious enhancement at about 0.3 < r < 1.0
It concludes that the medium effect is dominant for jet shape modifications, which has weak dependence on center of mass energy
Summary
One goal of jet physics is to explore the microscopic properties of hot-dense QCD matter, quark-gluon plasma (QGP), created in ultra-relativistic heavy-ion collisions [1,2,3]. The jet structure modifications from proton-proton collisions to heavy-ion collisions could be investigated by a set of jet shape quantities and will shed light on understanding of jet energy loss mechanism in medium, color coherence and fundamental medium properties. In [12], the jet shapes modifications are studied at small jet cone size (r < 0.2) and found an inconsistent with a fully coherent energy loss picture. Those results supply rich inputs for theoretical calculations and phenomena modeling on jet-medium interactions. One additional differential jet shape parameter of Dgirth is proposed and studied at r < 0.3 to investigate the jet shape evolution
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