Probing the interaction of semi-hard quarks and gluons with the underlying event in light- and heavy-flavor triggered proton-proton collisions

Abstract

We study underlying-event observables in inelastic proton-proton (pp) collisions at a centre-of-mass energy of $$\sqrt{s} = 13$$ s = 13 TeV with identified light and heavy-flavor triggers using the PYTHIA 8 event generator. The study is performed as a function of the transverse momentum of the leading particle ($$p_\mathrm {T}^\mathrm{trigger}$$ p T trigger ). While at high $$p_\mathrm {T}^\mathrm{trigger}$$ p T trigger ($$>10$$ > 10 GeV/c) the underlying-event activity is independent of the leading particle species, at intermediate $$p_\mathrm {T}^\mathrm{trigger}$$ p T trigger ($$2<p_\mathrm {T}^\mathrm{trigger} <8$$ 2 < p T trigger < 8 GeV/c) it is larger in pion-triggered events than in events triggered with B mesons. Moreover, the underlying event in pion-triggered events, the majority of which are initiated by gluons, shows a stronger effect of color reconnection than events triggered with B-hadrons, that are mostly initiated by quark jets. The effect is observed at both hadronic and partonic level. Given that color reconnection affects the interaction among final partons before the hadronization, and that in the string model quarks (gluons) are connected to one (two) string piece(s), we conclude that the observed effect can be attributed to differences in the interactions of gluon and quark jets with the underlying event.

Event-Shape-Dependent Analysis of Charm–Anticharm Azimuthal Correlations in Simulations

“…Heavy quarks are mostly created in the early stages of the collision, in perturbatively accessible quantum chromodynamics (QCD) processes; a heavy quark can be created from a pair of gluons or light quarks by flavour creation (FLC), a gluon splitting into the quark-antiquark pair (GSP), or through flavour excitation (FLX) [7,8]. Moreover, they may interact in semi-hard processes and participate in the formation of the underlying event [9]. Further insight to the connection of the hard process and the underlying event can be gained by the differential exploration of events with respect to event-shape variables.…”

Defining the underlying-event activity in the presence of heavy-flavour processes

“…Measuring and modelling the creation of heavy flavour at the semi-soft boundary can help with differentiating between colour-charge and mass effects. While heavy-flavour leading processes have been modelled in terms of the UE [18], a systematic study of identified heavy-flavour production in association with a hard process (in a similar fashion to that in [13] for light flavour) has not yet been done.…”

Defining the Underlying-Event Activity in the Presence of Heavy-Flavour Processes in Proton-Proton Collisions at LHC Energies

“…Measuring and modelling the creation of heavy flavour at the semi-soft boundary can help with differentiating between colour-charge and mass effects. While heavy-flavour leading processes have been modelled in terms of the UE [19], a systematic study of identified heavy-flavour production in association with a hard process (in a similar fashion to that in [14] for light flavour) has not yet been done.…”