Cosmology

How do we weigh the Universe? Where is the Dark Matter? I will discuss these questions and show that several independent methods, including the observed present-day abundance of rich clusters , the evolution of cluster abundance with redshift, the baryon-fraction in clusters, the observed Mass-to-Light function from galaxies to superclusters, and other large-scale structure observations, all reveal a universe with a low mass density parameter of ~20% of the critical density. The data suggest that the mass in the Universe, including the dark-matter, approximately follows light on large scales and that most of the mass resides in huge dark halos around galaxies. I will review the combined observational evidence for dark-matter and for dark-energy in the universe and their cosmological implications.

Light hidden sectors are a generic possibility for new physics, and recent astrophysical signals motivate hidden sector dark matter. I will discuss probes of a minimal secluded U(1) hidden sector scenario with high luminosity particle physics experiments.

The XENON project pursues the goal of directly detecting nuclear recoils resulting from scattering interactions with Weakly Interacting Massive Particles (WIMPs), using a phased approach of increasingly more sensitive experiments. The detector consists of a dual-phase liquid/gas xenon time projection chamber, which can measure down to ~2 keV(ee) energy threshold and discriminates against background using both the primary scintillation light and the charge signal resulting from interactions in the noble liquid. The current exeriment XENON100 is the successor of the highly successful XENON10 detector, featuring 10 times greater sensitive mass and 100 times lower background. Its sensitivity with an ultimate exposure of 6000 kg days will be 2 times 10^{-45} cm^2 for spin-independent interactions at 100 GeV/c^2. XENON100 has been installed and is operating. I will report on the present status and discuss its physics reach along with future prospects of detectors at the ton scale.