6,589 research outputs found

    Prospects for Measurements of Rare BB Decays and Other Heavy Flavour Physics at CMS

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    The Compact Muon Solenoid (CMS) is a multi-purpose detector operating at the Large Hadron Collider at CERN. Its excellent tracking system, combined with low momentum muon trigger capabilities, allows for precise studies of heavy flavour physics. The capabilities of the CMS experiment in this field have been studied in several benchmark processes. These studies are based on a full detector simulation and show the capability of CMS to identify, select and reconstruct heavy flavour decays, which present a significant challenge due to the high backgrounds and relatively low particle momenta. After a description of the detector, the trigger system, and the trigger strategy for BB physics, four heavy flavour analyses in CMS are presented: exclusive Bs0B^0_s decays to J ⁣/ ⁣ψϕJ\!/\!\psi\phi and to μ+μ\mu^+\mu^-; a study of the Bc+B^+_c meson; and the decay τμμμ+\tau^-\rightarrow\mu^-\mu^-\mu^+

    X-ray Observations of Distant Optically Selected Cluster

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    We have measured fluxes or flux limits for 31 of the 79 cluster candidates in the Palomar Distant Cluster Survey (PDCS) using archival ROSAT/PSPC pointed observations. Our X-ray survey reaches a flux limit of 3×1014\simeq 3 \times 10^{-14} erg s1^{-1} cm2^{-2} (0.4 - 2.0 keV), which corresponds to luminosities of Lx5×1043L_x\simeq 5 \times 10^{43} erg s1^{-1} (HoH_o = 50 km s1^{-1} Mpc1^{-1}, qoq_o = 1/2{1/2}), if we assume the PDCS estimated redshifts. Of the 31 cluster candidates, we detect six at a signal-to-noise greater than three. We estimate that 2.91.4+3.32.9^{+3.3}_{-1.4} (90% confidence limits) of these six detections are a result of X-ray emission from objects unrelated to the PDCS cluster candidates. The net surface density of X-ray emitting cluster candidates in our survey, 1.712.19+0.911.71^{+0.91}_{-2.19} clusters deg2^{-2}, agrees with that of other, X-ray selected, surveys. It is possible, given the large error on our contamination rate, that we have not detected X-ray emission from any of our observed PDCS cluster candidates. We find no statistically significant difference between the X-ray luminosities of PDCS cluster candidates and those of Abell clusters of similar optical richness. This suggests that the PDCS contains objects at high redshift similar to the low redshift clusters in the Abell catalogs. We show that the PDCS cluster candidates are not bright X-ray sources, the average luminosity of the six detected candidates is only Lxˉ=0.9×1044\bar{L_x}=0.9\times10^{44} erg s1^{-1} (0.4-2.0 keV). This finding is in agreement with previous X-ray studies of high redshift, optically selected, rich clusters of galaxies.Comment: 19 pages, LaTeX with AAS Preprint Macros (v. 4), 3 embedded postscript figures, 3 Seperate Tables using aj_pt4.sty, Accepted by the Astronomical Journal for November 199

    Observation of Spin Flips with a Single Trapped Proton

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    Radio-frequency induced spin transitions of one individual proton are observed for the first time. The spin quantum jumps are detected via the continuous Stern-Gerlach effect, which is used in an experiment with a single proton stored in a cryogenic Penning trap. This is an important milestone towards a direct high-precision measurement of the magnetic moment of the proton and a new test of the matter-antimatter symmetry in the baryon sector

    Resolution of Single Spin-Flips of a Single Proton

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    The spin magnetic moment of a single proton in a cryogenic Penning trap was coupled to the particle's axial motion with a superimposed magnetic bottle. Jumps in the oscillation frequency indicate spin-flips and were identified using a Bayesian analysis.Comment: accepted for publication by Phys. Rev. Lett., submitted 6.June.201

    A Turn-over in the Galaxy Luminosity Function of the Coma Cluster Core?

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    Our previous study of the faint end (R\leq21.5) of the galaxy luminosity function (GLF) was based on spectroscopic data in a small region near the Coma cluster center. In this previous study Adami et al. (1998) suggested, with moderate statistical significance, that the number of galaxies actually belonging to the cluster was much smaller than expected. This led us to increase our spectroscopic sample. Here, we have improved the statistical significance of the results of the Coma GLF faint end study (R\leq22.5) by using a sample of 85 redshifts. This includes both new spectroscopic data and a literature compilation. The relatively small number of faint galaxies belonging to Coma that was suggested by Adami et al. (1998) and Secker et al. (1998) has been confirmed with these new observations. We also confirm that the color-magnitude relation is not well suited for finding the galaxies inside the Coma cluster core, close to the center at magnitudes fainter than R\sim19. We show that there is an enhancement in the Coma line of sight of field galaxies compared to classical field counts. This can be explained by the contribution of groups and of a distant z0.5z\sim 0.5 cluster along the line of sight. The result is that the Coma GLF appears to turn-over or at least to become flat for the faint galaxies. We suggest that this is due to environmental effects.Comment: 8 pages, 6 postscript figures, accepted in A&A, new table 1, updated figure

    L-functions with large analytic rank and abelian varieties with large algebraic rank over function fields

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    The goal of this paper is to explain how a simple but apparently new fact of linear algebra together with the cohomological interpretation of L-functions allows one to produce many examples of L-functions over function fields vanishing to high order at the center point of their functional equation. The main application is that for every prime p and every integer g>0 there are absolutely simple abelian varieties of dimension g over Fp(t) for which the BSD conjecture holds and which have arbitrarily large rank.Comment: To appear in Inventiones Mathematica
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