Laser Interferometer Gravitational-wave Observatory (LIGO) has built three multi-km interferometers, designed to search for gravitational waves. One of the targets of this search is the stochastic background of gravitational waves, which is expected to exist both due to cosmological and due to astrophysical sources. The search for stochastic background radiation is conducted by examining cross-correlations between different interferometers. I will discuss the current status of the LIGO interferometers and the most recent results of the search for stochastic gravitational-wave background. I will also discuss the implications of these results on theoretical models for stochastic background of gravitational waves.
Cryogenic Dark Matter Search (CDMS) experiment is designed to search for Dark Matter in the form of Weakly Interacting Massive Particles (WIMPs). To achieve low radioactive background levels, CDMS is operated at a deep site at the Soudan Underground Laboratory, with agressive active and passive shielding. Furthermore, CDMS detectors are based on Ge or Si substrates with ionization and phonon sensors, allowing for a very effective event-by-event rejection of the dominant photon and electron background. The data CDMS acquired in 2003/2004 has led to the world’s most sensitive upper limit on the WIMP-nucleon elastic scattering cross-section. I will discuss the current status of the CDMS experiment and its most recent results.
The Laser Interferometer Gravitational-wave Observatory is the largest component in a worldwide effort to detect gravitational waves reaching the Earth. After several years of commissioning, the three LIGO detectors have essentially reached their sensitivity goals and are beginning long-term observing. Many searches for gravitational waves have already been carried out using data from a series of short "science runs". A number of the searches have used LIGO data in combination with data from other detectors. I will highlight a recently completed search for short gravitational wave bursts of arbitrary form using LIGO data from the fourth science run.
In November of 2005, the Laser Interferometer Gravitational-wave Observatory (LIGO) began a year long science run at its designed strain sensitivity (~10^{-21}). Over the past five years students and scientists have worked to increase the sensitivity by several orders of magnitude. I will describe how these high-power, 4 km long interferometers work, how their sensitivities have been improved over the past few years and describe the upgrades which, in the near future, will increase the event rates by a factor of 1000.
Current experimental limits allow for new forces in nature millions of times stronger than gravity at distances resolvable to the unaided eye, and trillions of times stronger than gravity at ranges accessible to scanning probe microscopy. Recent theoretical work has led to specific predictions of new physics in these regimes. I will describe an ongoing experiment designed to attain gravitational sensitivity in the range of about 10 microns. The experiment uses high-frequency (kHz) oscillators as test masses with a stiff conducting shield between them to suppress backgrounds. Proposed scanning probe experiments using some of the same techniques might attain sensitivities a few million times gravitational strength at 100 nm, if backgrounds due to Casimir forces can be controlled. Finally, I will briefly mention a new search for a permanent electric dipole moment of the neutron that will provide a significant challenge to proposed extensions to the Standard Model of particle physics, and will also have implications for the parameter space probed by the gravity tests.
The Laser Interferometer Gravitational-wave Observatory (LIGO) aims to make the first direct observation of gravitational waves. To achieve this goal, LIGO uses three interferometers of km-scale length, two in Hanford, WA, and one in Livingston, LA, measuring differences in length of one part in 1021, or 10-18 m, one thousand times smaller than the nuclear diameter. The detectors have now reached their design sensitivity and the LIGO Scientific Collaboration is actively searching for gravitational wave signatures in the interferometers’ data. In this talk I will present one of these ongoing efforts, the "eye-wide-open" search for unmodeled bursts of gravitational waves. I will describe its challenges and the methods used to optimize the detection efficiency and to suppress the false alarm rate with minimal assumptions on the signal's morphology. I will present the most recent upper limit results and discuss possible future directions for the LIGO burst analysis.