BORIS Theses

BORIS Theses
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Search for Axion-Like Dark Matter and Exotic Yukawa-Like Interaction

Schulthess, Ivo (2022). Search for Axion-Like Dark Matter and Exotic Yukawa-Like Interaction. (Thesis). Universität Bern, Bern

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Despite the undoubted success of the Standard Model of particle physics, it fails to answer many longstanding questions, such as the strong CP problem, the observed effects of dark matter, and the baryon asymmetry in our universe. Many theoretical models that try to answer those questions require new particles and gauge bosons which have to be verified or excluded experimentally. Here, we present the search for two such candidates. The first candidate is an ultralight pseudo-scalar particle called axion or axion-like particle (ALP). We searched for them using a Ramsey-type apparatus for cold neutrons. A hypothetical coupling of ALPs to gluons would manifest itself in a neutron electric dipole moment signal oscillating in time. Twenty-four hours of data have been analyzed in a frequency range from 23 μHz to 1 kHz, and no significant oscillating signal has been found. The usage of present dark-matter models allows for constraining the coupling of ALPs to gluons in the mass range from 10−19 to 4 × 10−12 eV. This extends the previously tested range by over three orders of magnitude. The best limit of CG / fama = 2.7 × 1013 GeV−2 (95% C.L.) is reached in the mass range from 2 × 10−17 to 2 × 10−14 eV. Together with the results of two other laboratory experiments, a large region of the ALP-gluon coupling parameter space could be excluded. The second candidate is an axial-vector gauge boson that could mediate a Yukawalike interaction in the millimeter range between Standard Model fermions like protons, neutrons, and electrons. We built a tabletop experiment that applies Ramsey’s technique to the proton spins of hydrogen in water. We performed a proof-of-principle search for this exotic interaction for the first time using protons as probe particles. Even though we could not yet detect or constrain the existence of such an interaction with statistical arguments, developments of the apparatus are underway that will allow to do this in the near future. With the apparatus we additionally investigated radio-frequency effects like the Bloch-Siegert shift and dressed spin states. This is to our knowledge the first time that the dressed spin states of protons were measured.

Item Type: Thesis
Dissertation Type: Single
Date of Defense: 7 December 2022
Subjects: 500 Science > 530 Physics
Institute / Center: 08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC)
Depositing User: Sarah Stalder
Date Deposited: 09 Feb 2023 13:19
Last Modified: 07 Dec 2023 23:25

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