Detector Characterization to Enable Discovery of Gravitational Waves with Advanced LIGO

Syracuse University, Syracuse NY

Investigators

Abstract

The General Theory of Relativity discovered by Einstein tells us that the familiar, everyday force of gravity is a manifestation of something much stranger: the bending of the geometry of space-time by matter. Among the key predictions of the theory, which includes the expanding Universe and the existence of black holes, is the existence of gravitational waves (GW): ripples moving at the speed of light in the geometry of space-time caused by the fast motion of large masses. Although well tested in terms of their indirect effects on binary systems of compact stars, the direct detection of gravitational waves incident on Earth poses an outstanding challenge. The scientific rewards from achieving this ability would be enormous - ranging from probing the extreme dynamics of exploding stars to gleaning information about the state of the Universe almost at the moment of the Big Bang itself. The effort to enable this new window on the universe has occupied several decades of experimental and technological developments that have pushed the boundaries across diverse fields in the physical sciences. The year 2015 will mark a highly-anticipated watershed moment for gravitational-wave physics: The two advanced Laser Interferomenter Gravitational Wave Observatory (aLIGO) detectors will start their initial data taking runs, followed by the commissioning of the advanced Virgo gravitational wave observatory in Europe. The sensitivity of the aLIGO detector will be ramped up to become about ten times better than that of the first-generation detectors, opening up a spatial volume for observing GW sources that will be 1000 times larger than before. The Syracuse group will support the LIGO Scientific Collaboration's search for gravitational wave signals from binary star systems consisting of neutron stars and/or black holes (called compact binary coalescences, or "CBC's"). Its special focus will be to study the ways in which instrumental artifacts (called "glitches") can mimic genuine signals, and to develop new tools to distinguish glitches from genuine signals. Because the gravitational waveforms from binaries can be very well predicted, some special techniques have already been developed that help make the distinction. However, these methods do not suffice for the full range of binaries expected to be seen with Advanced LIGO. The Syracuse group will develop new tools that will work on these more vulnerable kinds of signals. The Syracuse group will support the search with Advanced LIGO ("aLIGO") for CBC signals in its first observing run (called "O1") with three basic approaches. Firstly, they will tune, run, and apply the special diagnostic tool called "Daily CBC", which gives rapid feedback to commissioners on any departures of aLIGO data from Gaussianity. Secondly, they will develop a new specially-focused version of LIGO's standard tool for investigating the statistical correlation between glitches and candidate signals, hveto; because of the long duration of CBC signals, it is necessary to implement a tuned time-shift method before asking if a glitch is coincident in time with a CBC signal. Finally, they will use related technology to implement a new statistical test that measures whether the data yielding a candidate signal looks more like a true signal or like a glitch. These techniques will enable searches for CBC signals in O1 (and beyond) to live up to their potential, making it substantially more likely that aLIGO will be succeed in detecting signals from these fascinating objects.