The Search for Neutrinos from Gamma-Ray Bursts with the AMANDA Detector

Rellen Hardtke, University of Wisconsin

Photo of Rellen Hardtke

In the 1960s, the United States deployed a network of satellites to monitor the earth for violations of the nuclear test ban treaty. These satellites did not detect terrestrial explosions but, perhaps more surprisingly, did detect short bursts of very high energy gamma rays from space. Due to a lack of observational data, these powerful gamma-ray bursts (GRBs) remained an enigma for over two decades. We learned some important facts about GRBs in the 1990s, but the fundamental nature of these phenomena remains a mystery. I seek to understand the inner workings of GRBs by searching for neutrinos that may carry information to us from the depths of these explosions. Neutrinos are neutral and nearly massless. In fact, they barely interact with matter at all. Though these characteristics make them difficult to detect -- and drive the need for massive detectors -- neutrinos can reach us from environments where photons and charged particles may not, like the centers of GRBs. I work with the Antarctic Muon and Neutrino Detector Array (AMANDA), a neutrino telescope embedded deep in the ice shelf near the geographic South Pole. I've been culling four years of AMANDA data for a GRB neutrino signal. The computational challenges of such a search are numerous. I am searching for a tiny signal (1 or 2 events) among several billion background events induced by cosmic rays. I will explain how we use the entire earth as a filter to locate neutrino candidates, how we transport and filter large data sets for multiple scientific goals, and how we use many-parameter maximum likelihood fits to reduce errors in reconstruction of event paths. The detection or absence of neutrinos in GRB emission will have a major impact on the theories of GRB and cosmic ray origins, two of the most important and hotly debated issues in high energy astrophysics today.

Abstract Author(s): Rellen Hardtke