Search for Rare b-hadron Decays at CDF

We report on searches for B^0_s to \mu^+ \mu^-, B^0_d to \mu^+ \mu^- decays and b to s \mu^+\mu^- transitions in exclusive decays of B mesons. Using 2 fb^{-1} of data collected by the CDF II detector we find upper limits on the branching fractions B(B^0_s to \mu^+ \mu^-) < 5.8 x 10^{-8} and B(B^0_d to \mu^+ \mu^-) < 1.8 x 10^{-8} at 95% confidence level. Using 924 pb^{-1} of data we measure the branching fractions B(B^+ to \mu^+ \mu^- K^+) = (0.60 \pm 0.15 \pm 0.04) x 10^{-6}, B(B^0_d to \mu^+ \mu^- K^{*0}) = (0.82 \pm 0.31 \pm 0.10) x 10^{-6} and the limit B(B^0_s to \mu^+ \mu^- phi)/B(B^0_s to J/\psi\phi) < 2.61(2.30) x 10^{-3} at 95(90)% confidence level.Comment: 3 pages, 5 figures, conference proceedings to the 2007 Europhysics Conference on High Energy Physics (Manchester, July 2007

Radiation tolerance studies of silicon microstrip sensors for the CBM Silicon Tracking System

Double-sided silicon microstrip sensors will be used in the Silicon Tracking System of the CBM experiment. During experimental run they will be exposed to a radiation field of up to 1x1014 1 MeV neq cm-2. Radiation tolerance studies were made on prototypes from two different vendors. Results from these prototype detectors before and after irradiation to twice that neutron fluence are discussed

Avoided Antiferromagnetic Order and Quantum Critical Point in CeCoIn5_5

We measured specific heat and resistivity of heavy fermion CeCoIn5 between the superconducting critical field $H_{c2} = 5 T$ and 9 T, with field in the [001] direction, and at temperatures down to 50mK. At 5T the data show Non Fermi Liquid behavior down to the lowest temperatures. At field above 8T the data exhibit crossover from the Fermi liquid to a Non Fermi Liquid behavior. We analyzed the scaling properties of the specific heat, and compared both resistivity and the specific heat with the predictions of a spin-fluctuation theory. Our analysis leads us to suggest that the NFL behavior is due to incipient antiferromagnetism (AF) in CeCoIn5, with the quantum critical point in the vicinity of the $H_{c2}$. Below $H_{c2}$ the AF phase which competes with the paramagnetic ground state is superseded by the superconducting transition.Comment: 5 pages, 3 figure