Study of the production of π, K and p in pp collisions at √s = 13 TeV as a function of the Transverse Spherocity and the Relative Transverse Activity

Vazquez Rueda, Omar

Study of the production of π, K and p in pp collisions at √s = 13 TeV as a function of the Transverse Spherocity and the Relative Transverse Activity

Mark

Vazquez Rueda, Omar ^LU (2022)

Abstract: High-energy heavy-ion collisions allow the Quark-Gluon Plasma (QGP) production and study, a state of high-density QCD matter in which quarks and gluons are no longer confined inside hadrons for a very short time. Different observables reveal an enhanced production of strange hadrons, signatures of collective effects and opacity to jets due to the QGP formation. However, collective effects and strangeness enhancement are also observed in pp and p-Pb collisions (small systems) with high charged-particle multiplicity. These observations in small systems are very puzzling since the QGP is not expected to be formed since the small systems are considered too dilute and too short-lived.

In this thesis, I present a study on the production... (More); High-energy heavy-ion collisions allow the Quark-Gluon Plasma (QGP) production and study, a state of high-density QCD matter in which quarks and gluons are no longer confined inside hadrons for a very short time. Different observables reveal an enhanced production of strange hadrons, signatures of collective effects and opacity to jets due to the QGP formation. However, collective effects and strangeness enhancement are also observed in pp and p-Pb collisions (small systems) with high charged-particle multiplicity. These observations in small systems are very puzzling since the QGP is not expected to be formed since the small systems are considered too dilute and too short-lived.

In this thesis, I present a study on the production of π, K and p in pp collisions at √s = 13 TeV using data recorded by the ALICE experiment. To investigate the origins of collective effects and strangeness enhancement, I measure the particle production as a function of the Relative Transverse Activity (R_T) and the Transverse Spherocity (S₀). In the R_T analysis, particle production is measured in different topological regions (toward, away, and transverse) with respect to the leading charged track per event. The toward and away regions mainly contain the fragmentation products of the jet, while the Underlying Event dominates the transverse. The transverse momentum spectra and K/π and p/π ratios are measured as a function of R_T = N_T/⟨N_T⟩, where N_T is the charged-particle multiplicity in the transverse region. It is observed that the K/π and p/π ratios increase with increasing R_T in the toward region, while little R_T dependence is observed in the transverse. Models tuned to e⁺e^- results describe the low-R_T particle ratios qualitatively.
The transverse spherocity is an event shape observable that can disentangle jet-like from isotropic topologies. I studied particle production in high-multiplicity events as a function of spherocity. I contrast the results obtained using a forward and a mid-pseudorapidity multiplicity estimator. The results show that the mid-pseudorapidity estimator combined with the spherocity selection allows selecting events with more significant variations in the average transverse momentum (⟨p_T⟩) than the forward estimator. I present the p_T spectra and particle ratios as a function of S₀. Finally, all the data results are contrasted with microscopic models.
(Less)

Please use this url to cite or link to this publication: https://lup.lub.lu.se/record/4c05fd1b-a3fd-4fd6-bcb1-5fb99c51fc7f

author

Vazquez Rueda, Omar ^LU

supervisor

opponent

Professor Calderon de la Barca Sanchez, Manuel, Department of Physics and Astronomy, UC Davis, USA

organization

Particle and nuclear physics

publishing date

2022

type

Thesis

publication status

published

subject

Physical Sciences

keywords

LHC, ALICE, Quark-Gluon Plasma, Small Systems, pp Collisions, Underlying Event, Transverse Spherocity, Relative Transverse Activity, Fysicumarkivet A:2022:Vázquez Rueda

pages

198 pages

publisher

Lund

defense location

Rydbergsalen, Fysiska Institutionen, Professorsgatan 1, Lund.

defense date

2022-06-10 13:15:00

ISBN

978-91-8039-282-2

978-91-8039-281-5

language

English

LU publication?

yes

id

4c05fd1b-a3fd-4fd6-bcb1-5fb99c51fc7f

date added to LUP

2022-05-12 09:28:11

date last changed

2024-02-02 10:07:48

@phdthesis{4c05fd1b-a3fd-4fd6-bcb1-5fb99c51fc7f,
  abstract     = {{High-energy heavy-ion collisions allow the Quark-Gluon Plasma (QGP) production and study, a state of high-density QCD matter in which quarks and gluons are no longer confined inside hadrons for a very short time. Different observables reveal an enhanced production of strange hadrons, signatures of collective effects and opacity to jets due to the QGP formation. However, collective effects and strangeness enhancement are also observed in pp and p-Pb collisions (small systems) with high charged-particle multiplicity. These observations in small systems are very puzzling since the QGP is not expected to be formed since the small systems are considered too dilute and too short-lived.<br/><br/>In this thesis, I present a study on the production of π, K and p in pp collisions at √s = 13 TeV using data recorded by the ALICE experiment. To investigate the origins of collective effects and strangeness enhancement, I measure the particle production as a function of the Relative Transverse Activity (<i>R</i><sub>T</sub>) and the Transverse Spherocity (<i>S</i><sub>0</sub>). In the <i>R</i><sub>T</sub> analysis, particle production is measured in different topological regions (toward, away, and transverse) with respect to the leading charged track per event. The toward and away regions mainly contain the fragmentation products of the jet, while the Underlying Event dominates the transverse. The transverse momentum spectra and K/π and p/π ratios are measured as a function of <i>R</i><sub>T</sub> = <i>N</i><sub>T</sub>/⟨<i>N</i><sub>T⟩</sub>, where <i>N</i><sub>T</sub> is the charged-particle multiplicity in the transverse region. It is observed that the K/π and p/π ratios increase with increasing <i>R</i><sub>T</sub> in the toward region, while little <i>R</i><sub>T</sub> dependence is observed in the transverse. Models tuned to <i>e</i><sup>+</sup><i>e</i><sup>-</sup> results describe the low-<i>R</i><sub>T</sub> particle ratios qualitatively.<br/>The transverse spherocity is an event shape observable that can disentangle jet-like from isotropic topologies. I studied particle production in high-multiplicity events as a function of spherocity. I contrast the results obtained using a forward and a mid-pseudorapidity multiplicity estimator. The results show that the mid-pseudorapidity estimator combined with the spherocity selection allows selecting events with more significant variations in the average transverse momentum (⟨<i>p</i><sub>T</sub>⟩) than the forward estimator. I present the <i>p</i><sub>T</sub> spectra and particle ratios as a function of <i>S</i><sub>0</sub>. Finally, all the data results are contrasted with microscopic models.<br/>}},
  author       = {{Vazquez Rueda, Omar}},
  isbn         = {{978-91-8039-282-2}},
  keywords     = {{LHC; ALICE; Quark-Gluon Plasma; Small Systems; pp Collisions; Underlying Event; Transverse Spherocity; Relative Transverse Activity; Fysicumarkivet A:2022:Vázquez Rueda}},
  language     = {{eng}},
  publisher    = {{Lund}},
  school       = {{Lund University}},
  title        = {{Study of the production of π, K and p in pp collisions at √s = 13 TeV as a function of the Transverse Spherocity and the Relative Transverse Activity}},
  url          = {{https://lup.lub.lu.se/search/files/118013005/Doctoral_Thesis_OmarVazquezRueda.pdf}},
  year         = {{2022}},
}

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Study of the production of π, K and p in pp collisions at √s = 13 TeV as a function of the Transverse Spherocity and the Relative Transverse Activity