26 research outputs found

    Spin alignment of leading K(892)0K^{*}(892)^{0} mesons in hadronic Z0Z^0 decays

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    Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.Helicity density matrix elements for inclusive K ∗ (892) 0 mesons from hadronic Z 0 decays have been measured over the full range of K ∗ 0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x p values above 0.3, with the matrix element ϱ 00 rising to 0.66 ± 0.11 for x p > 0.7. The values of the real part of the off-diagonal element ϱ 1 - 1 are negative at large x p , with a weighted average value of −0.09 ± 0.03 for x p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the q q system from the Z 0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x p range. The K ∗ 0 fragmentation function has also been measured and the total rate determined to be 0.74 ± 0.02 ± 0.02 K ∗ (892) 0 mesons per hadronic Z 0 decay

    The performance of the jet trigger for the ATLAS detector during 2011 data taking

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    The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton–proton collisions with a centre-of-mass energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon–nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40 MHz nominal maximum bunch crossing rate to the approximate 400 Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25 GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60 GeV. Jets reconstructed in the final trigger level and corresponding to offline jets with transverse energy greater than 60 GeV, are reconstructed with a resolution in transverse energy with respect to offline jets, of better than 4 % in the central region and better than 2.5 % in the forward direction

    Topological search for the production of neutralinos and scalar particles

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    Contains fulltext : 124609pre.pdf (preprint version ) (Open Access) Contains fulltext : 124609pub.pdf (publisher's version ) (Open Access

    Test of QCD analytic predictions for the multiplicity ratio between gluon and quark jets

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    Contains fulltext : 124606pub.pdf (publisher's version ) (Open Access) Contains fulltext : 124606pre.pdf (preprint version ) (Open Access

    Electroweak measurements in electron–positron collisions at w-boson-pair energies at lep

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    Contains fulltext : 121524.pdf (preprint version ) (Open Access

    Epigraphic evidence for a ‘Porridge-and-Pot’ tradition on the ancient Middle Nile

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    An Upper limit on the branching ratio for tau decays into seven charged particles

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    We have searched for decays of the tau lepton into seven or more charged particles, using data collected with the OPAL detector from 1990 to 1995 in e^+e^- collisions at sqrt(s) ~ M_Z. No candidate events were found and an upper limit on the branching ratio for tau decays into seven charged particles of 1.8 x 10^-5 at the 95% confidence level was determined.Comment: 13 pages LaTeX, uses a4p.sty, 4 eps figures included, accepted by Physics Letters

    An Improved measurement of the B(s)0 lifetime

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    Contains fulltext : 124533.pdf (preprint version ) (Open Access

    A Study of b quark fragmentation into B0 and B+ mesons at LEP

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    Contains fulltext : 124531.pdf (preprint version ) (Open Access
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