Dark Sectors of Astroparticle Physics (AstroDark-2021): Axions, Neutrinos, Black Holes and Gravitational Waves

Session

Parallel 1: Axions and Other Dark Matter Particles

7 Dec 2021, 11:20

Online

43. A Measurement of Small-scale Structure with Hubble Legacy Fields

Julian B. Munoz (Harvard-Smithsonian Center for Astrophysics)

07/12/2021, 11:20

Oral

I will describe a new measurement of the small-scale matter power spectrum using UV luminosity-functions (UVLFs) from the Hubble Space Telescope. These data trace the abundance of the first galaxies forming during the epoch of reionization. Since the first galaxies were much less massive than their counterparts today, they provide us with a handle on the clustering of dark matter at smaller...

41. Ionization and Thermal Histories with Dark Matter Energy Injection

Hongwan Liu (New York University / Princeton University)

07/12/2021, 11:38

Oral

Measurements of the cosmic microwave background, the Lyman-Alpha forest and future 21-cm results can set significant constraints on dark matter annihilation or decay. To obtain such limits, a good understanding of how dark matter energy injection affects the ionization and thermal history of the universe is crucial. In this talk, I will present an open-source code package called DarkHistory,...

40. Gravitational Wave Probes of Axion Kination

Raymond Co (University of Minnesota)

07/12/2021, 11:56

Oral

We establish a paradigm where the (QCD) axion’s novel cosmological evolution, a rotation in the field space, gives rise to dark matter and the baryon asymmetry. The axion rotations also provide a natural origin for a kination era, where the total energy density is dominated by the kinetic term of the axion field, preceded by an early era of matter domination. We investigate the effects of this...

39. Friendship in the Axiverse

David Cyncynates (Stanford, SITP)

07/12/2021, 12:14

Oral

A generic low-energy prediction of string theory is the existence of a large collection of axions, commonly known as a string axiverse. In a realistic axiverse, string axions can be distributed densely over many orders of magnitude in mass, and are expected to interact with one another through their joint potential. In this talk, I will show how non-linearities in this potential can lead to a...

44. Cosmological Probes of Dark Matter Physics

Keir Rogers (University of Toronto)

07/12/2021, 12:32

Oral

Cosmology plays a central role in understanding the nature of dark matter (DM), with the power to test models which are hard to access by other means. The ultra-light axion is a compelling particle candidate that is motivated, e.g., by the string theory "axiverse" and as a possible solution to the so-called "small-scale crisis" of the cold dark matter model, if its mass is ~ 10^-22 eV. I will...

42. Axion and Dark Photon Experiments, a Translators Dictionary for the Perplexed

Alexander Millar (Stockholm University)

07/12/2021, 12:50

Oral

The dark photon is a massive hypothetical particle that interacts with the Standard Model by kinetically mixing with the visible photon. Due to the similarity with the electromagnetic signals generated by axions, many putative bounds on dark photon signals are simply reinterpretations of historical bounds set by axion haloscopes. However, the dark photon has a property that the axion does not:...

58. Seeding Supermassive Black Holes with Self-interacting Dark Matter

Yiming Zhong (Kavli Institute for Cosmological Physics)

09/12/2021, 11:20

Oral

Observations show that supermassive black holes (SMBHs) with a mass of one billion solar mass exist when the universe is just 6% of its current age. We propose a scenario where a self-interacting dark matter halo experiences gravothermal instability and its central region collapses into a seed black hole. The presence of baryons in protogalaxies could significantly accelerate the gravothermal...

86. Ion Traps as Dark Matter Detectors

Harikrishnan Ramani (Stanford University)

09/12/2021, 11:38

Oral

Millicharge particles with charge just evading accelerator bounds, possess charge large enough to accumulate on earth and cause gigantic build-up over the age of the earth. I introduce a new idea that sets exquisite bounds on millicharge particle dark matter and promises to reach interesting parameter space in the near future. The new detection concept involves the remarkable sensitivity of...

59. Cosmological Constraints on Light (but Massive) Relics

Weishuang Xu (UC Berkeley/LBL)

09/12/2021, 11:56

Oral

An intriguing possibility for the particle makeup of the dark sector is that a small fraction of the observed abundance is made up of light, feebly-interacting particle species. Neutrinos, with their yet-unresolved masses, are a concrete example in this category, but more exotic candidates readily arise from new physics scenarios. Due to their weakness of interaction but comparatively large...

60. The Companion Axion

Zachary Picker (University of Sydney)

09/12/2021, 12:14

Oral

Colored gravitational instantons, known as Eguchi-Hanson instantons, mediate vacuum-vacuum transitions in an analogous way to the well-known BPST instantons. As a result, a new source of CP-violation is present in gauge theories, described by an additional 'quantum gravity' vacuum angle. This second angle spoils the usual axion as a solution to the strong CP problem. The simplest solution to...

61. Thermal Perturbations from Cosmological Constant Relaxation

Erwin Tanin (Johns Hopkins University)

09/12/2021, 12:32

Oral

We probe the cosmological consequences of a recently proposed class of solutions to the cosmological constant problem. In these models, the universe undergoes a long period of inflation followed by a contraction and a bounce that sets the stage for the hot big bang era. A requirement of any successful early universe model is that it must reproduce the observed scale-invariant density...

57. On Microlensing of Axion Clumps

Enrico D. Schiappacasse (University of Jyväskylä)

09/12/2021, 12:50

Oral

A sizeable fraction of axion dark matter may be today in galactic halos in the form of Bose-Einstein condensate structures, which are known in the literature as “axion stars” or “axion clumps”. In this talk, I will address main astrophysical features associated with such gravitational bound objects and constraints over their abundance via gravitational microlensing, including finite lens and...

62. Recent Searches for Dark Sectors and Axion-Like Particle with BABAR

Yunxuan Li (California Institute of Technology)

09/12/2021, 13:08

Oral

Many scenarios of physics beyond the Standard Model predict new particles with masses well below the electroweak scale. Low-energy, high luminosity colliders such as BABAR are ideally suited to discover these particles. We present several recent searches for low-mass dark sector particles at BABAR, including leptophilic scalars, new gauge bosons coupling only to the second and third generation...