Light Neutralino Dark Matter in the NMSSM

Neutralino dark matter is generally assumed to be relatively heavy, with a mass near the electroweak scale. This does not necessarily need to be the case, however. In the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and other supersymmetric models with an extended Higgs sector, a very light CP-odd Higgs boson can naturally arise making it possible for a very light neutralino to annihilate efficiently enough to avoid being overproduced in the early Universe. In this article, we explore the characteristics of a supersymmetric model needed to include a very light neutralino, 100 MeV < \mcnone < 20 GeV, using the NMSSM as a prototype. We discuss the most important constraints from Upsilon decays, $b \to s \gamma$, $B_s \to \mu^+ \mu^-$ and the magnetic moment of the muon, and find that a light bino or singlino neutralino is allowed, and can be generated with the appropriate relic density. It has previously been shown that the positive detection of dark matter claimed by the DAMA collaboration can be reconciled with other direct dark matter experiments such as CDMS II if the dark matter particle is rather light, between about 6 and 9 GeV. A singlino or bino-like neutralino could easily fall within this range of masses within the NMSSM. Additionally, models with sub-GeV neutralinos may be capable of generating the 511 keV gamma-ray emission observed from the galactic bulge by the INTEGRAL/SPI experiment. We also point out measurements which can be performed immediately at CLEO, BaBar and Belle using existing data to discover or significantly constrain this scenario.Comment: References updated, accepted for publication in PR

The VLBA Imaging and Polarimetry Survey at 5 GHz

We present the first results of the VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey of 1,127 sources with flat radio spectra. Through automated data reduction and imaging routines, we have produced publicly available I, Q, and U images and have detected polarized flux density from 37% of the sources. We have also developed an algorithm to use each source's I image to automatically classify it as a point-like source, a core-jet, a compact symmetric object (CSO) candidate, or a complex source. The mean ratio of the polarized to total 5 GHz flux density for VIPS sources with detected polarized flux density ranges from 1% to 20% with a median value of about 5%. We have also found significant evidence that the directions of the jets in core-jet systems tend to be perpendicular to the electric vector position angles (EVPAs). The data is consistent with a scenario in which ~24% of the polarized core-jets have EVPAs that are anti-aligned with the directions of their jet components and which have a substantial amount of Faraday rotation. In addition to these initial results, plans for future follow-up observations are discussed.Comment: 36 pages, 3 tables, 13 figures; accepted for publication in Ap

Measurement of beta_s at CDF

The latest results for the measurement of the CP violating phase beta_s in B0s -> J/psi phi decays, from 5.2 fb-1 integrated luminosity of CDF data are presented. For the first time, this measurement includes the contribution of B0s -> J/psi K+K- or B0s -> J/psi f0 events to the signal sample, where the f0 and non-resonant K+K- are S-wave states. Additional improvements to the analysis include more than doubling the signal sample, improved selection and particle ID, and fully calibrated flavour tagging for the full dataset. Additionally, the world's most precise single measurements of the B0s lifetime, tau_s, and width difference, DeltaGamma_s are given.Comment: Proceedings of FPCP 2010, 7 pages, 4 figure

The Atmospheric Muon Charge Ratio at the MINOS Near Detector

The magnetized MINOS near detector can accurately determine the charge sign of atmospheric muons, this facilitates a measurement of the atmospheric muon charge ratio. To reduce the systematic error associated with geometric bias and acceptance we have combined equal periods of data obtained with opposite magnetic field polarities. We report a charge ratio of $1.2666\pm0.0015(stat.)^{+0.0096}_{-0.0088}(syst.)$ at a mean E$_{\mu,0}cos(\theta)$=\unit[63]{GeV}. This measurement is consistent with the world average\cite{Hebbeker}\cite{Haino}\cite{Achard} but significantly lower than the earlier observation at the MINOS far detector\cite{Adamson}. This increase is shown to be consistent with the hypothesis that a greater fraction of the observed muons arise from kaon decay within the cosmic ray shower.Comment: Proceedings for the 2009, 31st International Cosmic Ray Conference in Lodz Polan

Single crystal of superconducting SmFeAsO1-xFy grown at high pressure

Single crystals of SmFeAsO1-xFy of a size up to 120 micrometers have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K.Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO1-xFy at 1302 C.Comment: 12 pages, 3 tables, 6 figure

Sterile neutrino oscillations in MINOS and hadron production in pC collisions

MINOS is a long baseline neutrino oscillation experiment, starting with a muon-neutrino beam, for the precise measurement of the atmospheric neutrino oscillation parameters |{Delta}m{sup 2}| and {theta}{sub 23}. The Near Detector measures the neutrino flux and spectra before oscillations. The beam propagates for 735 km to the Far Detector, which measures the depleted spectrum after oscillations. The depletion can be interpreted as {nu}{sub {mu}} {yields} {nu}{sub {tau}} oscillations. Subdominant {nu}{sub {mu}} {yields} {nu}{sub e} oscillations may be allowed if the mixing angle {theta}{sub 13} {ne} 0. The two detectors are functionally identical in order to cancel systematic errors when using the Near Detector data to constrain the Far Detector prediction. A crucial part of the analysis is the relative calibration between the two detectors, which is known at the 2% level. A calibration procedure to remove the time and temperature dependence of the detector response using through-going cosmic muons is presented here. Although the two-detector approach reduces the systematic uncertainties related to the neutrino flux, a cross check on the neutrino parent meson ratios is performed in this thesis. The cross sections of mesons produced in proton-carbon interactions from the NA49 experiment have been measured and the results have been compared to the MINOS expectations. A neutrino oscillation analysis allowing mixing to a sterile neutrino is performed, under the assumption that the additional mass splitting is {Omicron}(1 eV{sup 2}). The analysis uses the energy spectrum of the neutral current interaction products, as neutral current interactions are sensitive to sterile neutrino mixing but not to the active flavour neutrino mixing. The neutrino oscillation parameters have been found to be: |{Delta}m{sup 2}| = 2.43{sub -0.18}{sup +0.21} x 10{sup -3} eV{sup 2}, {theta}{sub 23} = 40.27{sup o}{sub -5.17}{sup +14.64}, {theta}{sub 24} = 0.00{sup o}{sup +5.99} and {theta}{sub 34} = 0.00{sup o}{sup +24.57} under the assumption that {theta}{sub 13} = 12{sup o} (limited by the CHOOZ experiment) or |{Delta}m{sup 2}| = 2.43{sub -0.18}{sup +0.20} x 10{sup -3} eV{sup 2}, {theta}{sub 23} = 39.09{sup o}{sub -4.89}{sup +16.71}, {theta}{sub 24} = 0.00{sup o}{sup +4.79} and {theta}{sub 34} = 0.00{sup o}{sup +17.39} if {theta}{sub 13} is assumed to be zero

B^0_s mixing at D0 experiment

In this report, we present a report on B{sub s}{sup 0} mixing studies at the D0 experiment. New results based on use of two additional decay modes are discussed and limits are given on the B{sub s}{sup 0} mixing parameter

Enacting the Soft Automaton: Empirical Ontologies of Two Soft Robots from Technical Research and Media Art

This paper examines two soft robots from technical research and media art respectively and the practices through which they come into being. Departing from a juxtaposition of video presentations of the two robots, the empirical ontologies of a soft robot enacted in practice are analysed. The paper argues that two different versions of softness are being done and that the two sets of practices concomitantly respecify “knowledge” and “autonomy” as concepts, with different ethical and political implications.This paper examines two soft robots from technical research and media art respectively and the practices through which they come into being. Departing from a juxtaposition of video presentations of the two robots, the empirical ontologies of a soft robot enacted in practice are analysed. The paper argues that two different versions of softness are being done and that the two sets of practices concomitantly respecify “knowledge” and “autonomy” as concepts, with different ethical and political implications