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Production of φ Mesons as a Function of Multiplicity & Spherocity

Nassirpour, Adrian LU (2017) FYSM60 20171
Department of Physics
Particle Physics
Abstract
The purpose of this project is to further investigate whether the collective behavior observed in
high energy proton-proton (p-p) collision can be attributed to the formation of Quark-Gluon Plasma
(QGP). This is done by measuring the production rate of the strange φ meson in high multiplicity
p-p collisions at √sNN = 13 TeV. The high multiplicity p-p events are then divided into different
transverse spherocity bins, in order to gauge whether the φ production is dominated by events that
are geometrically characterized as jet-like or isotropic. The results, although leaving some questions to
be asked regarding the simulated detector efficiency, present a pronounced enhancement of φ mesons
in high multiplicity collisions, and further... (More)
The purpose of this project is to further investigate whether the collective behavior observed in
high energy proton-proton (p-p) collision can be attributed to the formation of Quark-Gluon Plasma
(QGP). This is done by measuring the production rate of the strange φ meson in high multiplicity
p-p collisions at √sNN = 13 TeV. The high multiplicity p-p events are then divided into different
transverse spherocity bins, in order to gauge whether the φ production is dominated by events that
are geometrically characterized as jet-like or isotropic. The results, although leaving some questions to
be asked regarding the simulated detector efficiency, present a pronounced enhancement of φ mesons
in high multiplicity collisions, and further state that the strangeness enhancement is dominated by
events with an overall isotropic shape. These findings suggest that Lund string-like models might
be inadequate at fully describing high multiplicity p-p collisions. It also gives further support to the
idea that the preferred mechanism of φ particle production might follow a statistical, hydrodynamical
model, through the formation of a QGP phase. (Less)
Popular Abstract (Swedish)
Under detta projekt s˚a analyserades h¨ogenergetiska proton-proton kollisioner i syftet f¨or att b¨attre f¨orst˚a
hur den starka v¨axelverkan med hj¨alp av gluoner h˚aller ihop kvarkar, en av materians fundamentalpartiklar,
f¨or att bilda hadroner. Dessa h¨ogenergetiska protoner accelereras upp till 99 % av ljusets
hastighet med hj¨alp av partikelacceleratorn ”Large Hadron Collider” (LHC), innan de till slut kolliderar
mot varandra i speciellt kontruerade partikeldeteckorer. Kollisionerna ¨ar tillr¨ackligt kraftfulla f¨or att
kvarkarna momentant frig¨ors fr˚an sina hadroner, vilket g¨or det m¨ojligt att studera hur gluonerna och
kvarkarna interagerar med varandra.
Om kollisionen ¨ar tillr¨ackligt kraftfull s˚a kan en Kvark-Gluon... (More)
Under detta projekt s˚a analyserades h¨ogenergetiska proton-proton kollisioner i syftet f¨or att b¨attre f¨orst˚a
hur den starka v¨axelverkan med hj¨alp av gluoner h˚aller ihop kvarkar, en av materians fundamentalpartiklar,
f¨or att bilda hadroner. Dessa h¨ogenergetiska protoner accelereras upp till 99 % av ljusets
hastighet med hj¨alp av partikelacceleratorn ”Large Hadron Collider” (LHC), innan de till slut kolliderar
mot varandra i speciellt kontruerade partikeldeteckorer. Kollisionerna ¨ar tillr¨ackligt kraftfulla f¨or att
kvarkarna momentant frig¨ors fr˚an sina hadroner, vilket g¨or det m¨ojligt att studera hur gluonerna och
kvarkarna interagerar med varandra.
Om kollisionen ¨ar tillr¨ackligt kraftfull s˚a kan en Kvark-Gluon Plasma bildas. Kvark-gluon plasman
¨ar ett v¨aldigt kompakt och varmt materietillst˚and som f¨orh˚aller sig i termiskt och kemiskt ekvilibrium.
I en kvark-gluon plasma s˚a ¨ar kvarkarna och gluonerna inte bunda innuti hadroner, utan ist¨allet beter
sig som en kollektiv, perfekt (n¨astintill ingen viskositet) v¨atska. Plasman bildas bara under en v¨aldigt
kort tidstund innan det kyls ner. Efter nedkylningen s˚a ¨ar kvarkarna ˚aterigen bunda inom individuella
hadroner. Att kontinuerligt h˚alla kvark-gluon plasman vid korrekt tryck och temperatur skulle kr¨ava
enorma resurser, vilket g¨or det praktiskt om¨ojligt att direkt verifiera om plasman har bildats. Ist¨allet s˚a
unders¨oks hur andra producerade partiklar interagerar med kvark-gluon plasman, f¨or att b¨attre f¨orst˚a
hur den fungerar. Tecken p˚a att kvark-gluon plasma har bildats brukar vara att partiklarna i kollisionen
har ett kollektivt beteende, en ¨okad produktion av vissa parikelsorter och andra fenomen.

Ett problem uppstod dock n¨ar man m¨arkte att n˚agra av de fenomen som ans˚ags vara signaturer
av kvark-gluon plasman ¨aven hittades i kollisioner som man inte trodde var energetiska nog f¨or att
kunna bilda kvar-gluon plasma. D¨arefter ifr˚agasattes id´en om huruvida kvark-gluon plasma faktiskt
n˚agonsin bildats i en kontrollerad partikelkollision. Huvudsyftet med detta projekt ¨ar att unders¨oka hur
produktionen av φ mesonen, en partikel som tros har en ¨okad produktionshalt i en eventuell kvark-gluon
plasma, beter sig f¨or varierande proton-proton kollisioner av olika energigrader. (Less)
Please use this url to cite or link to this publication:
author
Nassirpour, Adrian LU
supervisor
organization
course
FYSM60 20171
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8921900
date added to LUP
2017-07-18 22:56:16
date last changed
2017-07-18 22:56:16
@misc{8921900,
  abstract     = {The purpose of this project is to further investigate whether the collective behavior observed in
high energy proton-proton (p-p) collision can be attributed to the formation of Quark-Gluon Plasma
(QGP). This is done by measuring the production rate of the strange φ meson in high multiplicity
p-p collisions at √sNN = 13 TeV. The high multiplicity p-p events are then divided into different
transverse spherocity bins, in order to gauge whether the φ production is dominated by events that
are geometrically characterized as jet-like or isotropic. The results, although leaving some questions to
be asked regarding the simulated detector efficiency, present a pronounced enhancement of φ mesons
in high multiplicity collisions, and further state that the strangeness enhancement is dominated by
events with an overall isotropic shape. These findings suggest that Lund string-like models might
be inadequate at fully describing high multiplicity p-p collisions. It also gives further support to the
idea that the preferred mechanism of φ particle production might follow a statistical, hydrodynamical
model, through the formation of a QGP phase.},
  author       = {Nassirpour, Adrian},
  language     = {eng},
  note         = {Student Paper},
  title        = {Production of φ Mesons as a Function of Multiplicity & Spherocity},
  year         = {2017},
}