Summer Seminar: Rebecca Leane and Radek Poleski

November 14, 2016
Tuesday, June 28, 2016 - 11:30am to 12:30pm
4138 PRB
Oval

"Dark Forces in the Sky: Signals from Z' and the Dark Higgs"

Rebecca Leane (Melbourne/Physics)

In this talk I will discuss the indirect detection signals for a self-consistent hidden U(1) model containing a fermionic dark matter candidate, dark Z' gauge boson and a dark Higgs. Compared with a model containing only a dark matter candidate and Z' mediator, the presence of an additional scalar provides a mass generation mechanism for the dark sector particles and can be required in order to avoid unitarity violation at high energies. I will show that the inclusion of the additional scalar opens up a new two-body s-wave annihilation channel, providing rich phenomenology for indirect detection searches. This phenomenology is missed in the usual simplified model approaches. This new process allows indirect searches to explore regions of parameter space not accessible with other commonly considered s-wave annihilation processes, and enables both the Z' and scalar couplings to be probed. I will discuss the phenomenology of the sector with a focus on this new process, and determine the limits on the model parameter space from Fermi data on Dwarf Spheriodal Galaxies and other relevant experiments.

 

"Ice Giant Exoplanets"

Radek Poleski (Astronomy)

Among possible analogues of planets observed in the Solar System, objects similar to Uranus and Neptune are hardest to detect. Their long orbital periods make transits and radial velocities signals very hard to detect, even the planets are common. It turns out that microlensing is the only technique that can detect analogues of Uranus or Neptune. I will present a few examples of ice giant exoplanets detected using existing microlensing experiments. I will show that planet properties can be derived using Nested Sampling algorithm (useful also for other optimization problems), even if a standard MCMC run on the same data fails badly. Finally, I will show that deriving properties of microlensing ice giants is harder than it is for microlensing planets lying closer to their host stars.

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