Northwestern Events Calendar


Physics and Astronomy Brown Bag Lunch Seminar Series: Rocco Coppejans and Aprajita Hajela

When: Wednesday, November 6, 2019
12:00 PM - 1:00 PM Central

Where: Technological Institute, F160, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Bud Robinson   (847) 491-3644

Group: Physics and Astronomy Brown Bag Lunch Seminars

Category: Academic


Designing and Building Two Scintillating LAr Bubble Chamber for WIMPs and reactor CEvNS

Rocco Coppejans, Postdoctoral Researcher

The Scintillating Bubble Chamber (SBC) is a rapidly developing new technology for sub-keV nuclear recoil detection.  Demonstrations in liquid xenon at the few-gram scale have confirmed that this technique combines the event-by-event energy resolution of a liquid-noble scintillation detector with the world-leading electron-recoil discrimination capability of the bubble chamber, and in fact maintains that discrimination capability at much lower thresholds than traditional Freon-based bubble chambers.  The promise of unambiguous identification of sub-keV nuclear recoils in a scalable detector makes this an ideal technology for both GeV-mass WIMP searches and CEvNS detection at reactor sites.  We will present progress from the SBC Collaboration towards the construction of two 10-kg argon bubble chamber with SiPM-based scintillation readout to test the low-threshold performance of this technique in a physics-scale device.


Two years of non-thermal emission from GW170817

Aprajita Hajela, Doctoral Student

GW170817 marked the beginning of the era of multi-messenger astronomy on August 17, 2017, and for the first time connected the origin of short gamma-ray burst to binary neutron star mergers. Two years later we still have detection of the non-thermal emission from the interaction of the relativistic blast-wave driven by the merger with the ambient medium. Even though there is a consensus on a model with a structured jet that is viewed off-axis that best describes the evolution of the light curve of GW170817 across multiple wavelengths, the energetics and microphysical parameters of the outflow have a broad distribution. The lack of evidence of any spectral evolution in the GRB afterglow motivates us to find new ways to break the degeneracy between the afterglow model parameters, like the energy of the jet and the density of the surrounding medium. I will present a new method we developed to independently constrain the ambient density of the medium in which the outflow is expanding, to get tighter constraints on the energetics of the outflow. I will further show the inferences we draw from the two years of extensive X-ray and Radio observations of GW170817 and how we used them to put the first-ever constraints on the fastest moving Kilonova ejecta. I will also present a temporal analysis we performed to test short time-scale variability to constrain the nature of the end product of the merger.

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