3,248 research outputs found

    Overview of Charm Physics at RHIC

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    Heavy-quark production provides a sensitive probe of the gluon structure of nucleons and its modication in nuclei. It is also a key probe of the hot-dense matter created in heavy-ion collisions. We will discuss the physics issues involved, as seen in quarkonia and open heavy-quark production, starting with those observed in proton-proton collisions. Then cold nuclear matter effects on heavy-quark production including shadowing, gluon saturation, energy loss and absorption will be reviewed in the context of recent proton-nucleus and deuteron-nucleus measurements. Next we survey the most recent measurements of open-charm and J/Psi's in heavy-ion collisions at RHIC and their interpretation. We discuss the high-pT suppression and flow of open charm in terms of energy loss and thermalization and, for J/Psi, contrast explanations in terms of screening in a deconfined medium vs. recombination models.Comment: 6 pages, 12 figures, proceedings for Quark Confinement and Hadron Spectrum VI

    Intravenous conscious sedation in patients under 16 years of age. Fact or fiction?

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    Recently published guidelines on the use of conscious sedation in dentistry have published varying recommendations on the lower age limit for the use of intravenous conscious sedation. There are a large number of dentists currently providing dental treatment for paediatric patients under intravenous conscious sedation. The 18 cases reported here (age range 11-15 years), were successfully managed with intravenous conscious sedation. The experience in this paper is not sufficient evidence to recommend the wholesale use of intravenous conscious sedation in patients who are under 16 years. The fact that a range of operators can use these techniques on paediatric patients would suggest that further study should be carried out in this population. The guidance should be modified to say there is insufficient evidence to support the use of intravenous conscious sedation in children, rather than arbitrarily selecting a cut off point at age 16 years

    Optical Observations of the Binary Millisecond Pulsars J2145-0750 and J0034-0534

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    We report on optical observations of the low-mass binary millisecond pulsar systems J0034-0534 and J2145-0750. A faint (I=23.5) object was found to be coincident with the timing position of PSR J2145-0750. While a galaxy or distant main-sequence star cannot be ruled out, its magnitude is consistent with an ancient white dwarf, as expected from evolutionary models. For PSR J0034-0534 no objects were detected to a limiting magnitude of R=25.0, suggesting that the white dwarf in this system is cold. Using white dwarf cooling models, the limit on the magnitude of the PSR J0034-0534 companion suggests that at birth the pulsar in this system may have rotated with a period as short as 0.6 ms. These observations provide further evidence that the magnetic fields of millisecond pulsars do not decay on time scales shorter than 1 Gyr.Comment: 6 pages, uuencoded, gz -9 compressed postscript, accepted by ApJ

    A Sunyaev-Zel'dovich Effect Survey for High Redshift Clusters

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    Interferometric observations of the Sunyaev-Zel'dovich Effect (SZE) toward clusters of galaxies provide sensitive cosmological probes. We present results from 1 cm observations (at BIMA and OVRO) of a large, intermediate redshift cluster sample. In addition, we describe a proposed, higher sensitivity array which will enable us to survey large portions of the sky. Simulated observations indicate that we will be able to survey one square degree of sky per month to sufficient depth that we will detect all galaxy clusters more massive than 2x10^{14} h^{-1}_{50}M_\odot, regardless of their redshift. We describe the cluster yield and resulting cosmological constraints from such a survey.Comment: 7 pages, 6 figures, latex, contribution to VLT Opening Symposiu

    DASI Three-Year Cosmic Microwave Background Polarization Results

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    We present the analysis of the complete 3-year data set obtained with the Degree Angular Scale Interferometer (DASI) polarization experiment, operating from the Amundsen-Scott South Pole research station. Additional data obtained at the end of the 2002 Austral winter and throughout the 2003 season were added to the data from which the first detection of polarization of the cosmic microwave background radiation was reported. The analysis of the combined data supports, with increased statistical power, all of the conclusions drawn from the initial data set. In particular, the detection of E-mode polarization is increased to 6.3 sigma confidence level, TE cross-polarization is detected at 2.9 sigma, and B-mode polarization is consistent with zero, with an upper limit well below the level of the detected E-mode polarization. The results are in excellent agreement with the predictions of the cosmological model that has emerged from CMB temperature measurements. The analysis also demonstrates that contamination of the data by known sources of foreground emission is insignificant.Comment: 13 pages Latex, 10 figures, submitted to Ap

    Cosmological Parameter Extraction from the First Season of Observations with DASI

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    The Degree Angular Scale Interferometer (\dasi) has measured the power spectrum of the Cosmic Microwave Background anisotropy over the range of spherical harmonic multipoles 100<l<900. We compare this data, in combination with the COBE-DMR results, to a seven dimensional grid of adiabatic CDM models. Adopting the priors h>0.45 and 0.0<=tau_c<=0.4, we find that the total density of the Universe Omega_tot=1.04+/-0.06, and the spectral index of the initial scalar fluctuations n_s=1.01+0.08-0.06, in accordance with the predictions of inflationary theory. In addition we find that the physical density of baryons Omega_b.h^2=0.022+0.004-0.003, and the physical density of cold dark matter Omega_cdm.h^2=0.14+/-0.04. This value of Omega_b.h^2 is consistent with that derived from measurements of the primordial abundance ratios of the light elements combined with big bang nucleosynthesis theory. Using the result of the HST Key Project h=0.72+/-0.08 we find that Omega_t=1.00+/-0.04, the matter density Omega_m=0.40+/-0.15, and the vacuum energy density Omega_lambda=0.60+/-0.15. (All 68% confidence limits.)Comment: 7 pages, 4 figures, minor changes in response to referee comment
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