Defining dark jets at the particle level
(2023) FYSM60 20231Particle and nuclear physics
Department of Physics
- Abstract
- One hypothesis that attempts to explain dark matter is dark QCD, which suggests that there would be a dark sector made up of dark quarks. Dark quarks would interact with each other through dark QCD similar to how Standard Model quarks interact with each other through Standard Model QCD. Dark QCD would have several QCD-like features, one of which is dark jets. If dark quarks are produced at the LHC, they would produce dark jets, which could potentially have prompt or displaced decays into Standard Model jets, either fully or partially. However, there is currently no standardized definition of which jets should be considered dark. In this thesis, we will propose such a definition at particle level, and we will test the proposed definition on... (More)
- One hypothesis that attempts to explain dark matter is dark QCD, which suggests that there would be a dark sector made up of dark quarks. Dark quarks would interact with each other through dark QCD similar to how Standard Model quarks interact with each other through Standard Model QCD. Dark QCD would have several QCD-like features, one of which is dark jets. If dark quarks are produced at the LHC, they would produce dark jets, which could potentially have prompt or displaced decays into Standard Model jets, either fully or partially. However, there is currently no standardized definition of which jets should be considered dark. In this thesis, we will propose such a definition at particle level, and we will test the proposed definition on several dark QCD models. This definition is intended to be able to be used on a wide range of theoretical models, and can be refined to target specific models. We find that a suitable baseline definition of a dark jet is a jet for which at least 80\% of its pT originates from dark particles. (Less)
- Popular Abstract
- Almost all phenomena we have studied in our universe can be explained by four forces, namely: electromagnetism, gravity, the weak force and the strong force. The latter force is of most relevance for the work presented in this thesis. The strong force, also called quantum chromodynamics or QCD, binds elementary particles called quarks together into so-called hadrons. The most common types of hadrons in nature are protons and neutrons, present in atomic nuclei, which are baryons meaning they contain three quarks. Another type of hadrons are mesons, which are made up of a quark and an antiquark. Quarks can only exist inside of hadrons, which means that attempting to knock a quark out of a hadron will produce an entire group of new hadrons... (More)
- Almost all phenomena we have studied in our universe can be explained by four forces, namely: electromagnetism, gravity, the weak force and the strong force. The latter force is of most relevance for the work presented in this thesis. The strong force, also called quantum chromodynamics or QCD, binds elementary particles called quarks together into so-called hadrons. The most common types of hadrons in nature are protons and neutrons, present in atomic nuclei, which are baryons meaning they contain three quarks. Another type of hadrons are mesons, which are made up of a quark and an antiquark. Quarks can only exist inside of hadrons, which means that attempting to knock a quark out of a hadron will produce an entire group of new hadrons called a jet.
However, some things remain unexplained, such as dark matter. This is matter that has not been observed but is still known to exist and have mass because of the gravitational force it exerts on stars and galaxies. Dark matter is one of the greatest mysteries in physics since we know almost nothing about it. This, together with other unexplained phenomena, seems to be an indication that there are more particles than those observed so far.
One hypothesis that could explain dark matter is called dark QCD, and suggests that there would be particles called dark quarks, which do not interact with everyday matter, but interact with themselves through a force similar to the strong force. Dark quarks would then be grouped together into dark hadrons, of which some would be dark matter candidates, and can be knocked out of dark hadrons and produce dark jets.
At CERN in Switzerland, there is a particle accelerator called the LHC, which has the goal to discover new particles and interactions. It has been successful in discovering the Higgs boson, which explains why particles have mass, but has so far not been able to observe dark matter. If dark QCD is true, it is however possible that dark jets are produced at the LHC but are difficult to detect.
My work focus on such dark jets, and I am making a first, generic proposal for a technical definition for a dark jet, that is suitable both for theoretical and experimental physicists. This definition can be used as a middle ground between theorists and experimentalists, for example so that theorists can more easily check if a certain dark QCD model is already excluded by experiments. It will also allow theorists to get a better idea of the experimental signature of each model, which will inform experimentalists what to look for. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9129410
- author
- Lindberg, Gustav LU
- supervisor
- organization
- course
- FYSM60 20231
- year
- 2023
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Particle physics, Dark matter, QCD
- language
- English
- id
- 9129410
- date added to LUP
- 2023-06-27 11:52:35
- date last changed
- 2023-06-27 11:52:35
@misc{9129410,
abstract = {{One hypothesis that attempts to explain dark matter is dark QCD, which suggests that there would be a dark sector made up of dark quarks. Dark quarks would interact with each other through dark QCD similar to how Standard Model quarks interact with each other through Standard Model QCD. Dark QCD would have several QCD-like features, one of which is dark jets. If dark quarks are produced at the LHC, they would produce dark jets, which could potentially have prompt or displaced decays into Standard Model jets, either fully or partially. However, there is currently no standardized definition of which jets should be considered dark. In this thesis, we will propose such a definition at particle level, and we will test the proposed definition on several dark QCD models. This definition is intended to be able to be used on a wide range of theoretical models, and can be refined to target specific models. We find that a suitable baseline definition of a dark jet is a jet for which at least 80\% of its pT originates from dark particles.}},
author = {{Lindberg, Gustav}},
language = {{eng}},
note = {{Student Paper}},
title = {{Defining dark jets at the particle level}},
year = {{2023}},
}