Co-chair of the Stochastic Working Group of the LIGO Scientific Collaboration (LSC) (2006-present); Member of the LSC-VIRGO Data Analysis Council (2007-present); member of the LSC Data Analysis Committee (2006-2007); co-chair of the Hardware Injections Subgroup of the LIGO Detector Characterization Group (2006-2009); member of the LIGO Detector Characterization Committee (2006-2009); member of the LIGO Calibration Review Committee (2006-present, Chair since 2009); McKnight Professorship (2010-2012).
My research focuses on the physics of the earliest stages of the Universe and of the highest energies. In particular, I am interested in experiments that probe content and properties of the Universe today, and that can shed light on the evolution of the Universe and on the physics at high energy scales. I work on two such experiments.
Laser Interferometer Gravitational-wave Observatory (LIGO) has built three multi-kilometer interferometers at two sites: Hanford, WA and Livingston Parish, LA. These interferometers are designed to search for gravitational waves that could be produced in some of the most violent events in the Universe: mergers of two neutron stars or black holes, supernova explosions, or the Big Bang. Detection of gravitational waves would therefore open a new window into astrophysics and could potentially give us a view of the early Universe, when the Universe was only a fraction-of-a-second old.
The gravitational wave detectors are sensitive to motions at the level of one ten-thousandth of the proton size. Much of my work is geared toward understanding the contributions from various noise sources that are important at such sensitivities. Currently we are focusing on the seismic noise and on the Newtonian noise (fluctuations in the local gravitational field due to the motion of nearby masses). We are investigating the advantages of the underground environment in terms of these two noise sources, for purposes of future generations of gravitational wave detectors.
I also co-chair one the of LIGO Data Analysis Groups, searching for the stochastic background of gravitational waves. The origin of such a background could be cosmological (early Universe models, cosmic strings models) or astrophysical (integrating supernovae or pulsar signals across the Universe). We have placed the most stringent bound on the energy density in gravitational waves, thereby ruling out some of the models of stochastic gravitational-wave background due to cosmic strings and superstrings. We are also developing a new search focusing on gravitational wave transients on the scale of minutes, hours, or longer.
Together with Prof. P. Cushman, I am involved in the Cryogenic Dark Matter Search (CDMS) experiment, which is designed to search for dark matter in the form of new particles, generically called Weakly Interacting Massive Particles (WIMPs). There is an overwhelming evidence today that most of the matter in the Universe is invisible (i.e. dark), and most likely non-baryonic. However, the nature of dark matter is presently unknown, turning it into one of the most pressing problems in cosmology today. WIMPs represent one possible solution to the dark matter problem. They are particularly interesting because they naturally appear in supersymmetry and large extra-dimensions models - hence, discovery of WIMPs could have very far-reaching implications for particle physics, in addition to solving the dark matter problem.
CDMS has designed detectors based on crystals of germanium or silicon, operated at very low temperatures (about 50 mK), and in very low background conditions (deep underground in Soudan mine, MN, with substantial shielding). These detectors are capable of identifying and rejecting the known particle backgrounds very efficiently, hence allowing measurement of a signal due to a new particle (WIMP). CDMS has been at the forefront of the WIMP searches over the past decade, and will remain to do so in the future, after the planned upgrade to the experiment. My research focus within CDMS is development and characterisation of detectors, mostly geared toward increasing the detector size which would simplify scaling up the total mass of the experiment. My group is also heavily involved in the analysis of CDMS data.
Hassan Chagani, Research Associate
Gwynne Crowder, Research Associate
Nafiz Jaidye, Physics Major, Science/Engineering-Intrmd Lvl, Undergrad Research Asst II
Shivaraj Kandhasamy, Fellow (Physics)
Allison Kennedy, Research Assistant/Fellow
Patrick Meyers, Teaching Assistant
Sergey Monin, Teaching Assistant
Serkay Olmez, Graduate School Fellow
Tanner Prestegard, Research Assistant
Roxanne Radpour, Research Specialist
Tania Regimbau, Visitor
Hannah Rogers, Fellow (Physics)
David Strandberg, Undergraduate Research Assistant
Eric Thrane, Research Associate
Jianjie Zhang, Research Assistant
S. Olmez, V. Mandic, and X. Siemens, Gravitational-Wave Stochastic Background from Kinks and Cusps on Cosmic Strings, Phys. Rev. D (2010)
J. Harms et al., Characterization of the seismic environment at the Sanford Underground Laboratory, South Dakota, Class. Quant. Grav. (2010)
CDMS Collaboration, Dark Matter Search Results from the CDMS II Experiment, Science (2010)
LIGO Scientific Collaboration and Virgo Collaboration, An upper limit on the stochastic gravitational-wave background of cosmological origin, Nature (2009)
CDMS Collaboration, Search for Axions with the CDMS Experiment, Phys. Rev. Lett. (2009)
CDMS Collaboration, Search for Weakly Interacting Massive Particles with the First Five-Tower Data from the Cryogenic Dark Matter Search at the Soudan Underground Laboratory, Phys. Rev. Lett.
E. Thrane et al., Probing the anisotropies of a stochastic gravitational-wave background using a network of ground-based laser interferometers, Phys. Rev. D (2009)
J. Harms et al., Simulation of underground gravity gradients from stochastic seismic fields, Phys. Rev. D (2009)
LIGO Scientific Collaboration, All-sky LIGO Search for Periodic Gravitational Waves in the Early S5 Data, Phys. Rev. Lett. (2009)
LIGO Scientific Collaboration, LIGO: The Laser Interferometer Gravitational-Wave Observatory, Rep. Prog. Phys. (2009)