Nov. 8, 2022 at 2 p.m. in Lorentz room (Staudingerweg 7, 5th floor) and via Zoom

Mathias Becker

Sebastian Schenk

Yong Xu

ALP Dark Matter from Kinetic Fragmentation: Opening up the parameter window and Observational Consequences
Cem Eröncel (DESY)

Axion-like-particle (ALP) is a well-motivated candidate for dark matter, and it has been subject to extensive theoretical and experimental research in recent years. The most popular ALP production mechanism studied in the literature is the misalignment mechanism, where the ALP field initially has negligible kinetic energy and starts oscillating when its mass becomes comparable to the Hubble scale. Recently, a new mechanism called Kinetic Misalignment has been proposed where the ALP field receives large kinetic energy at early times due to the explicit breaking of the Peccei-Quinn symmetry. This causes a delay in the onset of oscillations so that the ALP dark matter parameter space can be expanded to lower values of the axion decay constant. At the same time, the ALP fluctuations grow exponentially via parametric resonance in this setup, and most of the energy in the homogeneous mode is converted to ALP particles. This process is known as fragmentation. In this talk, I will discuss the observational consequences of fragmentation for the axion mini-clusters and show that a sizable region of the ALP parameter space can be tested by future experiments that probe the small-scale structure.