Speaker
Description
Measurements of jet profiles in high-energy collisions are sensitive probes of
QCD parton splitting and showering. Precise understanding of the jet struc-
tures are essential for setting the baseline not only for nuclear modification of
jets in heavy-ion collisions, but also for possible semi-soft cold QCD effects such
as multi-parton interactions (MPI) that may modify jets in high-multiplicity
proton-proton collisions. We analyzed the jet radial profiles in simulations,
and defined a multiplicity-dependent characteristic jet size that is universal
in a broad range of model classes regardless of parton distributions and the
presence or absence of MPI and color-reconnection [1]. In this contribution
we demonstrate that the radial jet profiles in proton-proton collisions exhibit
scaling properties with charged-hadron event multiplicity in the full experimen-
tally accessible transverse-momentum range. Based on this we propose that
the scaling behavior stems from fundamental statistical properties of jet frag-
mentation [2]. We also study the multiplicity distributions of events with hard
jets and show that the charged-hadron multiplicity distributions scale with jet
momentum. This suggests that the Koba–Nielsen–Olesen (KNO) scaling holds
within a jet. The in-jet scaling is fulfilled without MPI, but breaks down in case
of its presence without color reconnection. Our findings imply that KNO scal-
ing is violated by parton shower or MPI in higher-energy collisions [3]. Besides
these results, newest findings on the flavor-dependence of scaling properties will
also be presented.
References
[1] Z. Varga, R. V ́ertesi and G. G ́abor Barnaf ̈oldi, Adv. High Energy Phys.
2019, 6731362 (2019) [arXiv:1805.03101 [hep-ph]].
[2] A. G ́emes, R. V ́ertesi, G. Papp and G. G. Barnaf ̈oldi, in: Gribov-90 Memo-
rial Volume: Algebraic Methods in QFT (2021) [arXiv:2008.08500 [hep-ph]].
[3] R. V ́ertesi, A. G ́emes and G. G. Barnaf ̈oldi, Phys. Rev. D 103, no.5, L051503
(2021) [arXiv:2012.01132 [hep-ph]]
