3,357 research outputs found

    Quarkonia and open Beauty production in ATLAS

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    When the LHC starts up in the second half of 2008 and beginning of 2009, ATLAS will have unique opportunities to study beauty production from central pppp collisions at 14 TeV making use of first data. In the initial phase of the LHC operation at lower luminosity several Standard Model physics analyses have to be performed to contribute to the commissioning and validation of the ATLAS detector and trigger system. One of the crucial initial measurements is that of the inclusive bbar production cross section, quarkonium spectroscopy and polarization. Furthermore, the B+ -> J/psi K+ channel will be an important reference channel for the search for di-muons from rare BB decays and a control channel for the CP violation measurement used to estimate systematic uncertainties and tagging efficiencies. Due to the huge bbar cross section and the expected high rates of the corresponding triggers, the data collection for beauty measurements can be done easily during the low luminosity phase. We describe the ATLAS expectations and strategies for open and hidden b-quark production where we expect to have first results already in the first few data

    B and Onia production in ATLAS

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    When the LHC starts up later this year ATLAS will have unique opportunities to study beauty production from central p-p collisions at ~14 TeV. This talk gives an overview of the ATLAS plans for initial measurements of inclusive and exclusive B cross sections, and of charm and beauty resonances. In the latter case we also show our sensitivity estimations for J/psi and Upsilon polarization measurements

    A New Scintillator Tile/Fiber Preshower Detector for the CDF Central Calorimeter

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    A detector designed to measure early particle showers has been installed in front of the central CDF calorimeter at the Tevatron. This new preshower detector is based on scintillator tiles coupled to wavelength-shifting fibers read out by multi-anode photomultipliers and has a total of 3,072 readout channels. The replacement of the old gas detector was required due to an expected increase in instantaneous luminosity of the Tevatron collider in the next few years. Calorimeter coverage, jet energy resolution, and electron and photon identification are among the expected improvements. The final detector design, together with the R&D studies that led to the choice of scintillator and fiber, mechanical assembly, and quality control are presented. The detector was installed in the fall 2004 Tevatron shutdown and started collecting colliding beam data by the end of the same year. First measurements indicate a light yield of 12 photoelectrons/MIP, a more than two-fold increase over the design goals.Comment: 5 pages, 10 figures (changes are minor; this is the final version published in IEEE-Trans.Nucl.Sci.

    Search for the Higgs boson in events with missing transverse energy and b quark jets produced in proton-antiproton collisions at s**(1/2)=1.96 TeV

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    We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1 integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model prediction.Comment: 8 pages, 2 figures, submitted to Phys. Rev. Let

    Search for a High-Mass Diphoton State and Limits on Randall-Sundrum Gravitons at CDF

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    We have performed a search for new particles which decay to two photons using 1.2/fb of integrated luminosity from p-pbar collisions at sqrt(s) = 1.96 TeV collected using the CDF II Detector at the Fermilab Tevatron. We find the diphoton mass spectrum to be in agreement with the standard model expectation, and set limits on the cross section times branching ratio for the Randall-Sundrum graviton, as a function of diphoton mass. We subsequently derive lower limits for the graviton mass of 230 GeV/c2 and 850 GeV/c2, at the 95% confidence level, for coupling parameters (k/M_Pl) of 0.01 and 0.1 respectively.Comment: submitted to Phys. Rev. Let

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector