Chiral effective theory of spin 1 dark matter direct detection
Typ
Examensarbete för masterexamen
Program
Publicerad
2021
Författare
Ernbrink, Henric
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Dark matter (DM) is the collective name for the additional mass needed to explain
the data collected from a very wide range of different astronomical observations.
Everything from the velocity dispersion of galaxies, gravitational lensing caused by
galaxies, the large scale structure of the universe as well as the structure of the
microwave background radiation all indicate the existence of DM. The exact nature
of DM is however still unknown, but it is largely believed to be new fundamental
particle, outside of the current standard model of particle physics. The elusiveness
of DM is largely due to the fact that the effects of DM never have been observed at
microscopic scales. One promising method for detecting DM particles that permeate
the galaxy is in so called direct detection experiments, in which, detectors monitor
the recoils of nuclei caused by the scattering of DM which is hitting the Earth [1].
The goal with this work is to provide new theoretical insights into the behavior of
scattering between DM and nuclei.
In this work DM is assumed to be a weakly interacting massive particle (WIMP)
and that it is non-relativistic. Further, it is also assumed to have spin 1. The cross
section for the scattering of DM against nuclei is calculated using chiral effective
theory, which has not been done before for spin 1 DM. This methodology has a
substantial advantage over non-relativistic theories where the degrees of freedom
are limited to nucleons and DM since it also includes mesons and consequently can
model the effect of meson exchange. In this work it is shown that the inclusion
of the meson exchange is crucial especially when modeling the scattering of DM
with heavier elements, e.g. xenon, which is a common choice in direct detection
experiments [2]. It is also shown that the non-relativistic operators that span the
possible DM-nucleon interactions generally cannot be studied individually in direct
detection. This is due to the fact that the interaction operators in the more general
relativistic theory match onto several DM-nucleon interaction operators. Several
DM-nucleon interaction operators consequently share common coupling constants
and must generally be studied together.
Beskrivning
Ämne/nyckelord
Dark matter , direct detection , spin 1 , chiral effective theory , EFT