arXiv subjects

Robert Vertesi

Publications and source records attributed to Robert Vertesi.

At least 19 recordsLinked to original sources

arXiv2026

Baryon enhancement in jets

The enhancement of the baryon production relative to mesons in small-collision systems is considered a breakthrough result of the Large Hadron Collider since a similar effect in heavy-ion collisions is understood by invoking the formation of the strongly-interacting quark--gluon plasma. In this letter, a baryon enhancement is reported for $p_{\rm T}^{\rm ch,\, jet}>15$\,GeV/$c$ jets produced in pp collisions at $\sqrt{s}=13$\,TeV simulated with PYTHIA8. The effect can be explained as a transition between quark-initiated jets (low jet multiplicities) to gluon-initiated jets (high jet multiplicities). The present result challenges the interpretation about the multiplicity dependence of the baryon enhancement in terms of collective expansion of the medium and quark recombination.

hep-ph↗

arXiv2026

Effect of event classification on the Tsallis-thermometer

We analyze identified hadron spectra in pp collisions at $\sqrt{s} = 13$ TeV measured by ALICE within a non-extensive statistical framework. Spectra classified by multiplicity, flattenicity, and spherocity were fitted with the Tsallis-Pareto distribution, and the parameters were studied on the Tsallis-thermometer. Multiplicity and flattenicity classes follow a previously observed scaling, while the non-extensivity parameter shows a distinct sensitivity to the spherocity. A data-driven parametrization confirms a proportionality between the Tsallis temperature and mean transverse momentum, offering a simple estimate of the effective temperature. These results highlight the ability of the Tsallis-thermometer to capture both multiplicity and event-shape effects, linking soft and hard processes in small systems.

hep-ph↗

arXiv2025

ML-based muon identification using a FNAL-NICADD scintillator chamber for the MID subsystem of ALICE 3

The ALICE Collaboration is planning to construct a new detector (ALICE 3) aiming at exploiting the potential of the high-luminosity Large Hadron Collider (LHC). The new detector will allow ALICE to participate in LHC Run 5 scheduled from 2036 to 2041. The muon-identifier subsystem (MID) is part of the ALICE 3 reference detector layout. The MID will consist of a standard magnetic iron absorber ($\approx4$ nuclear interaction lengths) followed by muon chambers. The baseline option for the MID chambers considers plastic scintillation bars equipped with wave-length shifting fibers and readout with silicon photomultipliers. This paper reports on the performance of a MID chamber prototype using 3 GeV/$c$ pion- and muon-enriched beams delivered by the CERN Proton Synchrotron (PS). The prototype was built using extruded plastic scintillator produced by FNAL-NICADD (Fermi National Accelerator Laboratory - Northern Illinois Center for Accelerator and Detector Development). The prototype was experimentally evaluated using varying absorber thicknesses (60, 70, 80, 90, and 100 cm) to assess its performance. The analysis was performed using Machine Learning techniques and the performance was validated with GEANT 4 simulations. Potential improvements in both hardware and data analysis are discussed.

physics.ins-det↗

arXiv2025

Event-activity dependence of heavy-flavor production at the ALICE experiment

Heavy-flavor production at the LHC offers valuable tests of quantum-chromodynamics calculations, owing to the large masses of heavy quarks. Measurements of charm production as a function of event activity reveal new features of charm production and fragmentation, providing insights to the interplay between soft and hard processes. In addition, charm production in heavy-ion collisions addresses flavor-dependent quark transport properties in both hot and cold nuclear matter, helping to clarify the roles of coalescence and fragmentation in heavy-flavor hadron formation. This contribution summarizes recent measurements from the ALICE experiment on charm production as a function of charged-particle multiplicity in pp collisions at various energies, including the measurements of charm baryon-to-meson production yield ratios in pp, p--Pb and Pb--Pb collisions. New results on ${\rm D}^0$ production in pp collisions as a function of the transverse spherocity of the event, as well as of the transverse event-activity classifier $R_{\rm T}$, are also presented.

nucl-ex↗

arXiv2024

The ALICE 3 detector concept for LHC Runs 5 and 6 and its physics performance

The LHC Run 5 and 6 data taking phases will bring unprecedented luminosity in high-energy proton-proton and in heavy-ion collisions. The ALICE Collaboration proposes a next-generation experiment, ALICE 3, specifically designed to operate with the future LHC. ALICE 3 will feature a large pixel-based tracking system covering eight units of pseudorapidity, complemented by advanced particle identification systems. These include silicon time-of-flight layers, a ring-imaging Cherenkov detector, a muon identification system, and an electromagnetic calorimeter. By placing the vertex detector on a retractable plate inside the beam pipe, a track pointing resolution better than 10 microns can be achieved for the transverse momentum range $p_T$>200 MeV/c. ALICE 3 will be capable of innovative measurements of the quark-gluon plasma (QGP) and explore new frontiers in quantum chromodynamics (QCD). The detailed study of thermal and dynamical properties of QGP will be made possible by measuring low-$p_T$ heavy-flavour production, including beauty hadrons, multi-charm baryons, and charm-charm correlations. Precise multi-differential measurements of dielectron emission will allow for the exploration of chiral-symmetry restoration and the time-evolution of QGP temperature. In addition to QGP studies, ALICE 3 will make unique contributions to the physics of the hadronic phase, through femtoscopic studies of charm meson interaction potentials and searches for nuclei containing charm. This contribution covers the detector design, expected physics performance, and the current status of detector research and development.

physics.ins-det↗

arXiv2024

Thermodynamical string fragmentation and string density effects in jets

It has been proposed to search for thermal and collective properties arising from parton-fragmentation processes by examining high jet charged-constituent multiplicities ($N_{\rm j,ch}$) in proton-proton (pp) collisions. This proposal was initially tested using the PYTHIA~8 event generator with the Monash tune, which incorporates multiparton interactions (MPI) and the MPI-based colour reconnection (CR) model. These studies did not reveal any conclusive evidence for the presence of radial flow. In this paper, we expand upon the proposed Monte Carlo study by eliminating selection biases associated with triggering on charged particle multiplicities. Furthermore, MPI are disabled to focus exclusively on jet fragments. We analyse pp collisions at $\sqrt{s}$=13 TeV simulated with PYTHIA~8, exploring different implementations of the generator: thermodynamical string fragmentation and the standard Lund fragmentation model. The impact of colour-string juctions was also explored. Surprisingly, the thermodynamical string fragmentation together with the close-packing of strings mechanism predicts a hint of baryon enhancement in jets. Additionally, the light-flavor baryon-to-meson ratios as a function of $j_{\rm T}$ exhibit similarities across all PYTHIA~8 implementations, and hint at radial flow-like effects. In contrast, the ratio of heavy-flavor hadrons (\LcToDz) at low $j_{\rm T}$ as a function of $N_{\rm j,ch}$ shows a trend similar to that observed as a function of charged-particle multiplicity in minimum-bias data, suggesting that colour-string junctions may play a crucial role in heavy baryon production in jets. The same mechanism also predicts a $j_{\rm T}$-integrated \LcToDz ratio that increases with increasing $N_{\rm j,ch}$.

hep-ph↗

arXiv2024

Jet substructure measurements in heavy-ion collisions

Jet substructure in heavy-ion collisions is a rapidly evolving area with lots of intriguing new measurements. This contribution presents a selection of recent jet-substructure measurements from experiments at the LHC, in particular, soft-drop groomed radii of jets and reclustered large-radius jets from ATLAS, jet axis difference and generalized jet angularities from ALICE, as well as dijet shapes and b-jet shapes from the CMS experiment.

nucl-ex↗

arXiv2024

How far can we see back in time in high-energy collisions using charm hadrons?

We use open charm production to estimate how far we can see back in time in high-energy hadron-hadron collisions. We analyze the transverse momentum distributions of the identified D mesons from pp, p--Pb and A--A collisions at the ALICE and STAR experiments covering the energy range from $\sqrt{s_{\rm NN}} = 200$~GeV up to 7~TeV. Within a non-extensive statistical framework, the common Tsallis parameters for D mesons represent higher temperature and more degrees of freedom than that of light-flavour hadrons. Assuming Bjorken-expansion, the production of D mesons corresponds to a significantly earlier proper time, $\tau_{\rm D} = (0.18 \pm 0.06) \tau_{\rm LF}$.

hep-ph↗

arXiv2023

Event-shape-dependent analysis of charm-anticharm azimuthal correlations in simulations

In high-energy collisions of small systems, by high-enough final-state multiplicities, a collective behaviour is present that is similar to the flow patterns observed in heavy-ion collisions. Recent studies connect this collectivity to semi-soft vacuum-QCD processes. Here we explore QCD production mechanisms using angular correlations of heavy flavour using simulated proton-proton collisions at $\sqrt{s} = 13$~TeV with the PYTHIA8 Monte Carlo event generator. We demonstrate that the event shape is strongly connected to the production mechanisms. Flattenicity, a novel event descriptor, can be used to separate events containing the final-state radiation from the rest of the events.

hep-ph↗

arXiv2022

Charm and beauty production and hadronization with the ALICE experiment

This contribution summarizes a selection of recent results from the ALICE experiment. We show the cross-section of beauty jets in pp collisions, as well as the charmed baryon-to-meson production ratios, down to unprecedentedly low momenta, at $\sqrt{s_{\rm NN}} = 5.02$ and 13 TeV collision energies. We present the nuclear modification of ${\rm D}^0$-jets and the $v_2$ of non-prompt ${\rm D}^0$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. We also discuss the implications and constraints from comparing these data to some of the most recent theoretical models.

nucl-ex↗

arXiv2021

The role of the underlying event in the $\Lambda_c^{+}$ enhancement in high-energy pp collisions

We study the enhanced production of charmed baryons relative to charmed mesons in proton--proton collisions at LHC energies. Utilizing PYTHIA 8 simulations with enhanced color-reconnection we propose methods based on the comparative use of several event-activity classifiers to identify the source of the charmed-baryon enhancement. We also conclude that in the scenario under investigation the excess $\Lambda_c^{+}$ production is primarily linked to the underlying event activity and not to the production of jets.

hep-ph↗

arXiv2021

Jet substructure measurements with ALICE

A selection of new jet substructure measurements are reported from the ALICE experiment at the CERN LHC in both proton-proton and heavy-ion collisions. These include the first fully corrected inclusive measurements of the groomed jet momentum fraction and the groomed jet radius, as well as the $N$-subjettiness distribution and the fragmentation distribution of reclustered subjets. We also report on the measurement of several groomed substructure observables of heavy-flavor jets in pp collisions, fragmentation functions and the new measurements of the radial distributions of D$^0$ mesons or $\Lambda^+_c$ baryons in jets. The measurements are compared to theoretical calculations and provide new constraints on the physics underlying parton fragmentation and jet quenching.

nucl-ex↗

arXiv2021

Azimuthal correlations of D mesons with charged particles in simulations with the ALICE experiment

In this manuscript, results of a component-level analysis with Monte Carlo simulations are presented, that aid the interpretation of recent ALICE results on the azimuthal correlation distribution of prompt D mesons with charged hadrons in pp and p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. Parton-level contributions and fragmentation properties are evaluated. Charm and beauty contributions are compared in order to identify the observables that serve as sensitive probes of the production and hadronization of heavy quarks.

nucl-ex↗

arXiv2020

KNO-like scaling within a jet in proton--proton collisions at LHC energies

We study the multiplicity distributions of events with hard jets in proton-proton collisions at LHC energies using PYTHIA 8 Monte-Carlo simulations. We demonstrate 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 multiple-parton interactions (MPI), but breaks down in case MPI is present without color reconnection. Our findings imply that KNO scaling is violated by parton shower or multiple-parton interactions in higher-energy collisions.

hep-ph↗

arXiv2020

Jet measurements with ALICE: substructure, dead cone, charm jets

A selection of recent jet measurements are presented from the ALICE experiment at the CERN LHC in proton-proton collisions at $\sqrt{s}=13$ TeV, focusing on substructure results for inclusive and charmed jets. The groomed jet momentum fractions ($z_g$) of inclusive full jets are shown for various jet resolution parameters, and $z_g$, the groomed splitting radius ($\theta_g$) as well as the number of soft drops ($n_{\rm SD}$) of inclusive and charmed charged-particle jets are compared. The first direct measurement of the dead cone in heavy-flavor jets is also presented. Furthermore, the parallel momentum fractions of charmed D$^0$ mesons and $\Lambda_\mathrm{c}^+$ baryons are shown. Besides serving as a reference for jet structure modification measurements in heavy-ion collisions, these results provide new insight to QCD parton shower properties and flavor-dependent fragmentation processes.

hep-ex↗

arXiv2020

Scaling properties of jet-momentum profiles with multiplicity

We study the structure of jets in proton-proton collisions at LHC energies using \textsc{Pythia} 8 Monte Carlo simulations. We demonstrate that the radial jet profiles exhibit scaling properties with charged-hadron event multiplicity over a broad transverse-momentum range. We also provide parametrizations of the jet profiles based on different statistically-motivated analytical distributions. Based on this we propose that the scaling behavior stems from fundamental statistical properties of jet fragmentation.

hep-ph↗

arXiv2019

Overview of Recent ALICE Results

A selection of recent ALICE results from pp, p--Pb, Pb--Pb and Xe--Xe collisions taken during the Run 1 and Run 2 phases are summarized in this contribution, and the prospects for the upcoming Run 3 phase are outlined.

nucl-ex↗

arXiv2019

Heavy flavour measurements with the ALICE experiment at the LHC

Heavy quarks (charm and beauty) are produced early in the nucleus-nucleus collisions, and heavy flavor survives throughout the later stages. Measurements of heavy-flavor quarks thus provide us with means to understand the properties of the Quark-Gluon Plasma, a hot and dense state of matter created in heavy-ion collisions. Production of heavy-flavor in small collision systems, on the other hand, can be used to test Quantum-chromodynamics models. After a successful completion of the Run-I data taking period, the increased luminosity from the LHC and an upgraded ALICE detector system in the Run-II data taking period allows for an unprecedented precision in the study of heavy quarks. In this article we give an overview of selected recent results on heavy-flavor measurements with ALICE experiment at the LHC.

nucl-ex↗