Speaker:

Chris (UCI)

Nolan Smyth (UCSC)

Logan Morrison (UCSC)

Date:

Wednesday, April 29, 2020

Time:

3:00 pm

Location:

Online

Three seminars (1 hr in total). Speakers and talk titles/abstracts are below:

**Chris (UCI): Neutral Naturalness and pNGB Dark Matter (30min)**

**Abstract:**While both Higgs naturalness and the WIMP dark matter favor new particles with weak scale masses and couplings, such particles have yet to be discovered. I outline a new realization of neutral naturalness (which address the hierarchy problem without new light colored states), in which both the Higgs and a complex scalar dark matter candidate arise as the pseudo-Nambu-Goldstone bosons of a broken global symmetry. The comparatively weak bounds on the symmetry partners allow the induced potential between the Higgs and the dark matter to be small. Thus, in this case more natural models, those with lighter top partners, lead to a WIMP dark matter that has not yet been probed by experiment. I then outline both the collider and dark matter phenomenology of these models, showing how they can be conclusively discovered by existing and upcoming experiments.

**Nolan Smyth (UCSC): Asteroid-Mass Primordial Black Holes as Dark Matter (15 min)**

Microlensing of stars places significant constraints on sub-planetary mass compact objects, including primordial black holes, as dark matter candidates. However, when the Einstein radius of the lens in the source plane is smaller than the size of the light source, amplification is strongly suppressed, making it difficult to constrain lenses with a mass below ~10^-10 solar masses, i.e. asteroid-mass objects. Current constraints,using Subaru HSC observations of M31, assume a fixed source size of one solar radius. We correct the HSC constraints by constructing a source size distribution based on the M31 PHAT survey and on a synthetic stellar catalogue, and by correspondingly weighing the finite-size source effects. We find that the actual HSC constraints are weaker by up to almost three orders of magnitude in some cases, broadening the range of masses for which primordial black holes can be the totality of the cosmological dark matter by almost one order of magnitude.

**Logan Morrison (UCSC): Dark Matter from a secluded Dark SU(N) Theory with a Single Quark Flavor (15 min)**

In this talk, we analyze the viability of dark matter candidates arising from a secluded, confining, large-N SU(N) gauge theory with a single quark flavor. In a SU(N) gauge theory with a single quark flavor, the low-energy bound states consist of a delta-like baryon and an eta-prime meson. By solving coupled Boltzmann equations, we demonstrate that there are ample regions of parameter space in which either delta (via freeze-in) or eta-prime (via freeze-out) dark matter is possible. Limits on dark matter self-interaction and delta-N-effective are applied to constrain the available parameter space of the theory. We find that eta-prime dark matter is generically allowed, while delta dark matter is tightly constrained by self-interaction constraints.

Host:

Arvind Rajaraman