Cosmic muon simulation with a new HCal prototype geometry at LDMX
(2026) FYSK04 20261Particle and nuclear physics
Department of Physics
- Abstract
- The light dark matter experiment (LDMX) is a planned experiment to search for dark matter (DM) in the partly unexplored lower region of the mass range motivated by the thermal freeze-out mechanism. Electrons will be accelerated toward a tungsten target, and as they scatter off a nucleus, production of DM may occur, which will be inferred from a significant amount of missing energy in the detector. Therefore, a detector capable of detecting and measuring all incoming and outgoing particles, together with a thorough understanding of its performance, is necessary. Measurements, as well as simulations, of cosmic muon interactions with prototypes of the detector's different subsystems is one approach that will contribute to a deeper... (More)
- The light dark matter experiment (LDMX) is a planned experiment to search for dark matter (DM) in the partly unexplored lower region of the mass range motivated by the thermal freeze-out mechanism. Electrons will be accelerated toward a tungsten target, and as they scatter off a nucleus, production of DM may occur, which will be inferred from a significant amount of missing energy in the detector. Therefore, a detector capable of detecting and measuring all incoming and outgoing particles, together with a thorough understanding of its performance, is necessary. Measurements, as well as simulations, of cosmic muon interactions with prototypes of the detector's different subsystems is one approach that will contribute to a deeper understanding.
The aim of this thesis is to create a geometry description of the hadronic calorimeter (HCal) components of a test-stand that will be used for cosmic-muon measurements, integrate it into the LDMX software framework, and simulate cosmic muons passing through it. The work carried out in this project includes the description of the HCal prototype geometry in a GDML file, adaptation of a Python file that supplies detector information to the software, and modifications of the employed cosmic muon generator. Data obtained directly from simulation and after mimicking real data acquisition are analyzed. When the new geometry is incorporated into the software, data received directly from simulation provide reasonable results, while issues appear to arise in the digitization or reconstruction process. In addition, different parts of the detector are observed to receive an unequal amount of hits. Most likely, more changes must be made to the software to successfully digitize and reconstruct the simulated data obtained when using the new geometry. (Less) - Popular Abstract
- Have you ever looked into the night sky and felt a little lightheaded from all the stars staring back at you? You are one small human, in this seemingly endless sea of planets, stars, and galaxies. Well, let me tell you something that is even more unsettling: even if you were to visit every planet, every star, and count every single atom you come across, you would only have observed about 20% of the matter of the universe. The rest is made up of something we have not yet discovered, so-called dark matter (DM). Detecting this unknown matter is what the light dark matter experiment (LDMX) plans to do.
When astronomers study the dynamics of galaxies and galaxy clusters, some things do not add up. They move and rotate much faster than what... (More) - Have you ever looked into the night sky and felt a little lightheaded from all the stars staring back at you? You are one small human, in this seemingly endless sea of planets, stars, and galaxies. Well, let me tell you something that is even more unsettling: even if you were to visit every planet, every star, and count every single atom you come across, you would only have observed about 20% of the matter of the universe. The rest is made up of something we have not yet discovered, so-called dark matter (DM). Detecting this unknown matter is what the light dark matter experiment (LDMX) plans to do.
When astronomers study the dynamics of galaxies and galaxy clusters, some things do not add up. They move and rotate much faster than what the gravitational pull of the visible mass should be able to handle. The only explanation for the structures remaining bound together is some additional dark matter. The most accepted theory is that DM is some undiscovered particle that does not interact with light. Many searches for DM have been carried out throughout the years, but no discovery has yet been made. However, the lower mass range of approximately a MeV - a GeV is still largely unexplored and is what LDMX is designed to unravel.
By shooting electrons at a dense fixed target, LDMX will attempt to create a DM and anti-DM pair via dark bremsstrahlung – a process in which an electron scatters of a nucleus, resulting in the emission of a DM mediator. As DM is invisible to the detector, it will be detected by missing momentum. Therefore, it is important to precisely measure all particles that enter and leave the detector. This is achieved with detector components such as trackers, an electromagnetic calorimeter, and a hadronic calorimeter (HCal).
Another particle that is important for LDMX is the muon, specifically cosmic muons. Unlike the mysterious DM particle, cosmic muons are not interesting because of any enigmatic properties, but rather the opposite – their very well-known behavior. Most cosmic muons that reach the surface of the earth are minimally ionizing particles, which means that they will deposit nearly the same energy in the detector. Therefore, in addition to being a free and continuous source, they are great for calibration and testing of detectors. By measuring cosmic muons in a setup of prototypes of the detectors various subsystems, LDMX will get further insight on how to optimize, understand, and operate the detector.
The focus of this project is to implement a geometry description of the HCal prototype in the LDMX software, based on a provided design, and to simulate cosmic muons passing through it. I find that the geometry description works well in direct simulation, while some errors occur as the data is handled by the software. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9246704
- author
- Hedin, Wilde LU
- supervisor
-
- Ruth Pöttgen LU
- Lene Bryngemark LU
- organization
- course
- FYSK04 20261
- year
- 2026
- type
- M2 - Bachelor Degree
- subject
- language
- English
- id
- 9246704
- date added to LUP
- 2026-07-13 09:41:18
- date last changed
- 2026-07-13 09:41:18
@misc{9246704,
abstract = {{The light dark matter experiment (LDMX) is a planned experiment to search for dark matter (DM) in the partly unexplored lower region of the mass range motivated by the thermal freeze-out mechanism. Electrons will be accelerated toward a tungsten target, and as they scatter off a nucleus, production of DM may occur, which will be inferred from a significant amount of missing energy in the detector. Therefore, a detector capable of detecting and measuring all incoming and outgoing particles, together with a thorough understanding of its performance, is necessary. Measurements, as well as simulations, of cosmic muon interactions with prototypes of the detector's different subsystems is one approach that will contribute to a deeper understanding.
The aim of this thesis is to create a geometry description of the hadronic calorimeter (HCal) components of a test-stand that will be used for cosmic-muon measurements, integrate it into the LDMX software framework, and simulate cosmic muons passing through it. The work carried out in this project includes the description of the HCal prototype geometry in a GDML file, adaptation of a Python file that supplies detector information to the software, and modifications of the employed cosmic muon generator. Data obtained directly from simulation and after mimicking real data acquisition are analyzed. When the new geometry is incorporated into the software, data received directly from simulation provide reasonable results, while issues appear to arise in the digitization or reconstruction process. In addition, different parts of the detector are observed to receive an unequal amount of hits. Most likely, more changes must be made to the software to successfully digitize and reconstruct the simulated data obtained when using the new geometry.}},
author = {{Hedin, Wilde}},
language = {{eng}},
note = {{Student Paper}},
title = {{Cosmic muon simulation with a new HCal prototype geometry at LDMX}},
year = {{2026}},
}