Search for Direct Photon Production at Large P/sub T/ in Proton-proton Collisions At. Sqrt. S PDF Download
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Languages : en
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Preliminary results from the CCOR Group, Experiment R-108, at the CERN ISR are reported. In addition, previously published results from the Rome-Brookhaven-CERN Group at the ISR will be reviewed.
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Languages : en
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Preliminary results from the CCOR Group, Experiment R-108, at the CERN ISR are reported. In addition, previously published results from the Rome-Brookhaven-CERN Group at the ISR will be reviewed.
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Languages : en
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As part of a study of large p/sub T/ phenomena in proton-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon production and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is .gamma./all = 0.074 +- 0.012 for 6 GeV/c = 0.26 +- 0.04 for p/sub T/> 10 GeV/c, with an additional systematic uncertainty of +- 0.05 for both values. It is found that single photons are produced preferentially with no accompanying particles on the same side. The ratio of positive to negative particles on the away side is found to be 3.7 +- 1.2 at high x/sub E/ and p/sub T/ for the single photon events.
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Category : Aeronautics
Languages : en
Pages : 704
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Category : Power resources
Languages : en
Pages : 992
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Languages : en
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A search for the resonant production of high-mass photon pairs is presented. The analysis is based on samples of proton-proton collision data collected by the CMS experiment at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 3.3 inverse femtobarns, respectively. The search focuses on spin-0 and spin-2 resonances with masses between 0.5 and 4 TeV and with widths, relative to the mass, between 1.4E-4 and 5.6E-2. Limits are set on scalar resonances produced through gluon-gluon fusion, and on Randall--Sundrum gravitons. A modest excess of events compatible with a narrow resonance with a mass of about 750 GeV is observed. The local significance of the excess is approximately 3.4 standard deviations. The significance is reduced to 1.6 standard deviations once the effect of searching under multiple signal hypotheses is considered. More data are required to determine the origin of this excess.
Author: You-Hao Chang
Publisher: Springer
ISBN: 9811038244
Category : Science
Languages : en
Pages : 107
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This book mainly focuses on the study of photon + 3 jets final state in Proton-Proton Collisions at √s = 7TeV, searching for patterns of two (or more) distinct hard scatterings in the same collision, i.e the so-called Double Parton Scattering (DPS). A new method by using Monte Carlo generators was performed and provides higher order corrections to the description of the Single Parton Scattering (SPS) background. Further it is investigated whether additional contributions from DPS can improve the agreement between the measured data and the Monte Carlo predictions. The current theoretical uncertainties related to the SPS background are found to be larger than expectation. At the same time a rich set of DPS-sensitive measurements is reported for possible further interpretation.
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Category :
Languages : en
Pages : 1082
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Languages : en
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A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at √s = 7 TeV, pp → p??−p, is reported using data corresponding to an integrated luminosity of 40 pb−1. For muon pairs with invariant mass greater than 11.5 GeV, transverse momentum p{sub T} > 4 GeV and pseudorapidity.
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Languages : en
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We report a measurement of high-p{sub T} inclusive [pi]°, [eta], and direct photon production in p + p and d + Au collisions at √s{sub NN} = 200 GeV at midrapidity (0
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Languages : en
Pages : 96
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Inclusive transverse momentum spectra of photons and [pi]°s at mid-rapidity are studied as a function of collision centrality for 197Au+ 197Au collisions at √s{sub NN} = 130 GeV. Photon pair conversions have been reconstructed from charged tracks measured by the main Time Project Chamber of the STAR experiment at the RHIC heavy ion facility. The transverse momentum resolution of photons with this method is estimated to be [Delta]p{sub t}/p{sub t} = 2% at 0.125 GeV/c and 5% at 2.5 GeV/c. Photon spectra were measured up to a transverse momentum of 2.4 GeV/c between ± 0.5 units of rapidity. The dominant photon production mechanism, the [pi]° → [gamma][gamma] decay, was measured between 0.25-2.5 GeV/c and ± 1 units of rapidity. Spectra are reported for the top 11%, 11-34% and 34-85% centrality classes. It was observed that in mid-central and central collisions the relative contribution of the [pi]° → [gamma][gamma] decay to the inclusive photon spectrum decreases above a transverse momentum of 1.65 GeV/c. In central collisions the magnitude of the decrease from p{sub t} = 1.65 GeV/c to 2.4 GeV/c is 20%. It is unlikely that contributions from other [pi]° decay channels and other particle decays fully explain this decrease. The centrality dependence on the shapes of the [pi]° spectra was analyzed with Boltmann and Bose-Einstein functions. In the transverse momentum windows of the spectra, the extracted temperatures are near 0.295 GeV. These temperatures are substantially higher than those extracted from [pi]{sup {+-}} spectra in a lower range of transverse momentum. This is an indication that the shapes of the pion spectra deviate from purely exponential shapes.
