|Ph.D Student||Yacobi Lee|
|Subject||Gamma-Ray Detector Development and Gamma-Ray Bursts Studies|
|Department||Department of Physics||Supervisor||Professor Ehud Behar|
|Full Thesis text|
The thesis reports the development of gamma-ray detectors to be flown on a NASA mission. The main goal is to use wide-field instruments to detect electromagnetic counterparts of gravitational wave sources that will enable the study of black hole and neutron star binaries in their last few orbits prior to merging. Our instrument (the GTM) aims at detecting short Gamma-Ray Bursts (GRBs) hypothesized to be associated with neutron star mergers. The GTM can measure the arrival time and energy of each detected photon and will trigger on GRBs or other transient sources, to notify other observatories. We built a breadboard model of the GTM in the laboratory.
We further built a segmented version that provides directional information when detecting a burst. The relative amount of photons detected in each segment indicates the source’s position to within a ~100 deg2 given enough (15,000) source photons. Our measurements use a 662 keV photon source, which suffers from scattering off of the surrounding materials, and which degrades the directional signal. We present simulations, which show that at lower energies, more typical of GRBs, the angular precision will be much better even for bursts with as few as 1,500 photons.
In the second part of the thesis we analyze existing data of GRBs and study their connection to cosmic neutrinos. Neutrinos are produced, e.g., in interactions of photons with hadrons, such as protons and heavier ions. The interaction of relativistic hadrons with GRB gamma-rays is considered as a possible source for ultra high energy neutrinos up to peta-electron-volts (PeV). From the absence of a temporal or directional correlation between the GRBs and the TeV-PeV neutrinos we compute an upper limit on the neutrino flux from GRBs. We also constrain the ratio of the energy carried by pions to that in electrons in the GRB jet to be fpi / fe < 0.24 at 95% confidence. For a few specific GRBs this ratio is even smaller than 0.03, as opposed to unity which is expected from equi-partition. In the last chapter of this work we show that the non-detection of neutrinos above a few PeV constrains different models of TeV-EeV neutrino generation from the interaction of cosmic rays with the cosmic-microwave-background, and put strict upper limits on the detection rate of future neutrinos telescopes for >EeV neutrinos.