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Studies of Dark Matter Signals at the LHC

Angelsmark, Martin LU (2017) FYSK02 20171
Department of Physics
Particle Physics
Abstract
Standard matter, the matter that we can see, only make up about 6% of the universe. Astronomical observations have found that there exist other matter, which is non-luminous, called dark matter. This matter can interact gravitationally with standard matter, but it is unknown if it can interact weakly with the help of some other force as well. If such interactions were possible, events between dark matter and standard matter could be created in a particle accelerator.

This thesis has studied simulations of dark matter events possible in the ATLAS detector at the Large Hadron Collider. Our theoretical models include a mediator, a particle carrying the force between interacting particles, that can interact with both the standard matter... (More)
Standard matter, the matter that we can see, only make up about 6% of the universe. Astronomical observations have found that there exist other matter, which is non-luminous, called dark matter. This matter can interact gravitationally with standard matter, but it is unknown if it can interact weakly with the help of some other force as well. If such interactions were possible, events between dark matter and standard matter could be created in a particle accelerator.

This thesis has studied simulations of dark matter events possible in the ATLAS detector at the Large Hadron Collider. Our theoretical models include a mediator, a particle carrying the force between interacting particles, that can interact with both the standard matter particles called quarks and dark matter. When two quarks collide, it is now possible for them to decay into the mediator particle. This mediator can decay back into two quarks, which will be detected as jets. The invariant mass of the two jets will be equal to the mass of the mediator. Such events, called di-jet, have been examined in this thesis.

The simulated events were generated in MadGraph5. The simulations are divided into different levels. At parton level only the interaction between quarks is considered. At particle level the creation of jets is simulated and will introduce a smearing to the energy values. The last level includes how the particles interact with the detector, which will add further smearing. At the end the measured energies will have a certain resolution caused by the smearing. This thesis compares the resolution at particle level and detector level. Furthermore, the energies at particle level were smeared using a simple formula to approximate the effects of the detector. These smeared values were compared to the values at detector level and seem to suggest that it is a good approximation. The detector level is more involved than particle level and parameterization of the detector resolution will thus save time for future di-jet event simulations. (Less)
Popular Abstract (Swedish)
Astronomiska observationer på 1900-talet visade att det saknas lysande materia i vårt universum. Materian som inte syntes fick namnet mörk materia. Efter denna upptäckt har olika teoretiska modeller och experiment skapats för att förklara mörk materias egenskaper. På CERN sker forskning för att upptäcka mörk materia i ATLAS detektorn. Simuleringar av sådana händelser har blivit undersökta i detta arbete.

Astronomiska observationer har lett till att vi nu vet att mörk materia består av något annat än det som utgör den synliga lysande materia, som vi kallar standardmateria. Det är också känt att mörk materia kan interagera med standardmateria med hjälp av gravitation. Nya teoretiska modeller för mörk materia måste överensstämma med dessa... (More)
Astronomiska observationer på 1900-talet visade att det saknas lysande materia i vårt universum. Materian som inte syntes fick namnet mörk materia. Efter denna upptäckt har olika teoretiska modeller och experiment skapats för att förklara mörk materias egenskaper. På CERN sker forskning för att upptäcka mörk materia i ATLAS detektorn. Simuleringar av sådana händelser har blivit undersökta i detta arbete.

Astronomiska observationer har lett till att vi nu vet att mörk materia består av något annat än det som utgör den synliga lysande materia, som vi kallar standardmateria. Det är också känt att mörk materia kan interagera med standardmateria med hjälp av gravitation. Nya teoretiska modeller för mörk materia måste överensstämma med dessa astronomiska observationer. Trotts brist på bevis så finns det teoretiska modeller som inkluderar en ytterliggare svag växelverkan mellan mörk och standardmateria. Vissa av dessa modeller har haft stor framgång med att förutspå rätt mängd mörk materia i universum. En sådan modell skulle kunna bli upptäckt av ATLAS-detektorn.

Partikelfysik försöker beskriva de minsta beståndsdelarna som bygger upp vårt universum. Energin av dessa partiklar kan mätas av en partikeldetektor, så som ATLAS-detektorn. I detektorn krockar protoner som är uppbygda av partiklarna kvarkar. En kraft mellan två partiklar bärs av en partikel som kallas för mediatorpartikel. Om det finns en svag interaktion mellan mörk och standardmateria så kan det även finnas en mediator för denna kraft. Denna mediator kan skapas i kollisionen och sedan brytas ner till två kvarkar. För att testa modellen så måste en mängd simuleringar göras.

Simuleringarna genereras nivåvis. Först generas interaktionen mellan kvarkarna, sedan kvarkarnas väg till detektorn och till slut hur detektorn upptäcker partiklarna. Kvarkarna kommer skapa fler partiklar på väg till detektorn. Denna grupp av partiklar kallas för jet och skapar en osäkerhet av energin som mäts. Detektorn kommer ge en ytterligare osäkerhet. Osäkerheterna introducerade av jets och av detektorn har här jämförts. Energin vid jetnivån har förskjutits för att approximera detektorns osäkerhet. Vårt resultat visar att dessa förskjutningar verkar vara en bra approximation för detektorns osäkerhet och detta kan effektivisera framtida simuleringar. (Less)
Please use this url to cite or link to this publication:
author
Angelsmark, Martin LU
supervisor
organization
course
FYSK02 20171
year
type
M2 - Bachelor Degree
subject
keywords
Large Hadron Collider, resolution, detector, ATLAS, physics, particle, dark, matter, Martin, Angelsmark, di-jet, CERN
language
English
id
8909051
date added to LUP
2017-05-30 09:40:17
date last changed
2017-05-30 09:40:17
@misc{8909051,
  abstract     = {Standard matter, the matter that we can see, only make up about 6% of the universe. Astronomical observations have found that there exist other matter, which is non-luminous, called dark matter. This matter can interact gravitationally with standard matter, but it is unknown if it can interact weakly with the help of some other force as well. If such interactions were possible, events between dark matter and standard matter could be created in a particle accelerator.

This thesis has studied simulations of dark matter events possible in the ATLAS detector at the Large Hadron Collider. Our theoretical models include a mediator, a particle carrying the force between interacting particles, that can interact with both the standard matter particles called quarks and dark matter. When two quarks collide, it is now possible for them to decay into the mediator particle. This mediator can decay back into two quarks, which will be detected as jets. The invariant mass of the two jets will be equal to the mass of the mediator. Such events, called di-jet, have been examined in this thesis. 

The simulated events were generated in MadGraph5. The simulations are divided into different levels. At parton level only the interaction between quarks is considered. At particle level the creation of jets is simulated and will introduce a smearing to the energy values. The last level includes how the particles interact with the detector, which will add further smearing. At the end the measured energies will have a certain resolution caused by the smearing. This thesis compares the resolution at particle level and detector level. Furthermore, the energies at particle level were smeared using a simple formula to approximate the effects of the detector. These smeared values were compared to the values at detector level and seem to suggest that it is a good approximation. The detector level is more involved than particle level and parameterization of the detector resolution will thus save time for future di-jet event simulations.},
  author       = {Angelsmark, Martin},
  keyword      = {Large Hadron Collider,resolution,detector,ATLAS,physics,particle,dark,matter,Martin,Angelsmark,di-jet,CERN},
  language     = {eng},
  note         = {Student Paper},
  title        = {Studies of Dark Matter Signals at the LHC},
  year         = {2017},
}