Geometries in Hadronic Calorimeter at LDMX

Abstract

A cornerstone in particle physics is that of simulation. The ability
to test the components of a larger experiment in a safe and cheap
digital environment allows modern experiments to have an optimised
setup before testing it in an expensive to use particle accelerator.
In this study, variations in the configuration of the main Hadronic
Calorimeter (HCal) at the Light Dark Matter eXperiment (LDMX)
are investigated using modern simulation tools for the purpose of
improving neutron veto inefficiencies while also reducing production
costs.

The neutron veto inefficiency is the value used to determine the
optimal configurations of the HCal. It is a measure of how many
events in the detector pass a veto on the maximum signal seen in
any channel. For a veto which only passes events with a registered
amount of five or less Photoelectrons (PEs) in the scintillator bars
that form the active medium, the inefficiency is calculated and compared
to previously established inefficiencies. Finding that another
configuration improves performance and possibly reduces costs would
benefit the experiment greatly.

The study presented here found that the veto inefficiencies for
the tested geometries are on similar levels to the default geometry.

Popular Abstract

Consider the world around you; when doing so you might observe a
number of things such as a chair, a tree, birds flying by, or the cup of
coffee you just poured for yourself. You can confirm the existence of
these by the touch, albeit birds might fly away or the cup might prove
too hot to touch. Furthermore you can try and move these objects,
again the tree might prove difficult to dislodge. We can conclude that
your observations exist by the properties they all share: interaction
with light, mass and the ability to interact with other objects by the
touch; all your observations consist of matter, the collective term for
all constellations of particles we can observe.

Astonishingly, astronomical observations conclude that only about
5% of the universe consists of matter, implying that 95% is not conventionally
observable. Theoretical models predict that around 27%
of the universe consist of Dark Matter (DM). What sets DM apart
from regular matter ties in with what we considered before; the only
property we can ascribe dark matter is that of mass, meaning that we
cannot observe it visually nor interact with it directly. The property
of mass in DM was already suggested in 1930 by Knut Lundmark at
Lund University[1], where the movement of celestial bodies implied
that something massive but "invisible" exists due to the presence of
gravitational interactions with the objects we can observe.
However, we cannot conclude what DM is without closer obervations. The project I am involved in, the Light Dark Matter eXperiment
(LDMX), aims to produce DM on Earth. My part of the
project is to look at how the layout of the detector used can improve
results.

The experiment hopes that in bombarding a small piece of matter
with particles, DM would be produced in the process following the
impact on the target. The process is similar to the discovery of the
Higgs boson, where particle collisions could provide evidence for its
existence. LDMX looks for missing momentum between its input
and output. Analogous to this would be the following; imagine you
are bouncing a ball off a wall. As it returns you instinctively know
what path it is going to take because your brain knows about the
conservation of momentum and how it will move on the return. Were
it to bounce unexpectedly, a very interesting phenomena has occurred
where some of the momentum has "disappeared". In this analogy, the
loss of recorded momentum is that of the dark matter produced. In
keeping with the analogy, my project would be fine-tuning our senses
to be able to observe the missing momentum of the ball.
Finding DM would not only be the largest scientific discovery
made in our lifetime, it would literally be the largest find. Hopefully
it will uncover an entire realm of new science to further our
understanding of the enigmatic universe we live in.

• author: Sjöström Strobel, Jesper
• supervisor: Ruth Pöttgen; Torsten Åkesson
• organization: Department of Physics
• course: FYSK02 20221
• year: 2022
• type: M2 - Bachelor Degree
• subject: Physics and Astronomy
• keywords: Hadronic calorimeter, HCal, Light Dark Matter eXperiment, LDMX, Calorimetry
• language: English
• id: 9097881
• date added to LUP: 2022-08-22 08:57:07
• date last changed: 2022-08-22 08:57:07