6,865 research outputs found

    New results from an extensive aging test on bakelite Resistive Plate Chambers

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    We present recent results of an extensive aging test, performed at the CERN Gamma Irradiation Facility on two single--gap RPC prototypes, developed for the LHCb Muon System. With a method based on a model describing the behaviour of an RPC under high particle flux conditions, we have periodically measured the electrode resistance R of the two RPC prototypes over three years: we observe a large spontaneous increase of R with time, from the initial value of about 2 MOhm to more than 250 MOhm. A corresponding degradation of the RPC rate capabilities, from more than 3 kHz/cm2 to less than 0.15 kHz/cm2 is also found.Comment: 6 pages, 7 figures, presented at Siena 2002, 8th Topical Seminar on Innovative Particle and Radiation Detectors 21-24 October 2002, Siena, Ital

    Precision Measurement of KS Meson Lifetime with the KLOE detector

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    Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DaFne, we have measured the KS lifetime. From a fit to the proper time distribution we find tau = (89.562 +- 0.029_stat +- 0.043_syst) ps. This is the most precise measurement today in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the Ks.Comment: 5 pages, 7 figure

    A direct search for the CP-violating decay Ks->3p^0 with the KLOE detector at DAFNE

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    We have searched for the decay Ks->3p^0 with the KLOE experiment at DAFNE using data from e^+ e^- collisions at a center of mass energy W= m(phi) for an integrated luminosity L=450 pb^-1. The search has been performed with a pure Ks beam obtained by tagging with Kl interactions in the calorimeter and detecting six photons. We find an upper limit for the branching ratio of 1.2x10^-7 at 90% C.L.Comment: 15 pages, 6 figures. To be submitted to Physics Letter

    Follicular dynamics in synchronized Italian Mediterranean buffalo cows

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    The aim of this study was to evaluate the length and the characteristics of the oestrous cycle in Italian Mediterranean buffalo cows, undergone synchronization of ovulation. The trial was performed on 32 buffaloes synchronized by the Ovsynch Program, which consists of an injection of GnRH on day 0, PGF2α on day 7 and GnRH on day 9. Starting on day 10 (Day 0 of the new cycle). Buffaloes undergone ultrasound examination of the ovaries on alternate days until the following heat. Follicular growth and corpus luteum formation and dimensions were recorded as well as the number of follicular waves. Statistical analysis was performed by ANOVA. Four animals (12.5%) did not show signs of oestrous and were excluded from the trial. The mean length of the oestrous cycle was 23.7±3.4 days. In particular, 1 animal (3.6%) showed an oestrous cycle characterized by 1 follicular wave with a length of 16 days, 17 subjects (60.7%) showed 2 follicular waves with a cycle length of 22.4±2.3 days and 10 buffaloes (35.7%) showed 3 follicular waves with a cycle of 26.8±2.0 days. These results confirm previous reports performed in buffalo species, although the cycle resulted longer in the 3-waves group

    Measurement of the η3π0\eta\to 3\pi^{0} slope parameter α\alpha with the KLOE detector

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    We present a measurement of the slope parameter α\alpha for the η3π0\eta\to 3\pi^{0} decay, with the KLOE experiment at the DAΦ\PhiNE ϕ\phi-factory, based on a background free sample of \sim 17 millions η\eta mesons produced in ϕ\phi radiative decays. By fitting the event density in the Dalitz plot we determine α=0.0301±0.0035stat  0.0035+0.0022syst\alpha = -0.0301 \pm 0.0035\,stat\;_{-0.0035}^{+0.0022}\,syst\,. The result is in agreement with recent measurements from hadro- and photo-production experiments.Comment: 14 pages, 11 figure

    A Study of the Radiative Ke3 Decay and Search for Direct Photon Emission with the KLOE Detector

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    We present a measurement of the ratio R = \Gamma(\keg;\Estar>30\mev,\qstar>20^\circ)//\Gamma(\kegf)andafirstmeasurementofthedirectemissioncontributioninKLsemileptonicdecays.ThemeasurementisdoneattheDAFNEphifactoryselectingphi>KLKSdecayswiththeKLOEdetector.Weuse328pb1 and a first measurement of the direct emission contribution in KL semileptonic decays. The measurement is done at the DAFNE phi-factory selecting phi->KL KS decays with the KLOE detector. We use 328 pb^{-1} of data corresponding to about 3.5 million Ke3(g) events and about 9000 radiative events. Our result is R=(924 +/- 23(stat) +/-16(syst)10^{-5} for the branching ratio and X=-2.3 +/- 1.3(stat) +/- 1.4(syst) for the parameter describing direct emission.Comment: 8 pages, 7 figure

    Precision measurement of the ηπ+ππ0\eta\to\pi^+\pi^-\pi^0 Dalitz plot distribution with the KLOE detector

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    Using 1.61.6 fb1^{-1} of e+eϕηγe^+ e^-\to\phi\to\eta\gamma data collected with the KLOE detector at DAΦ\PhiNE, the Dalitz plot distribution for the ηπ+ππ0\eta \to \pi^+ \pi^- \pi^0 decay is studied with the world's largest sample of 4.7106\sim 4.7 \cdot 10^6 events. The Dalitz plot density is parametrized as a polynomial expansion up to cubic terms in the normalized dimensionless variables XX and YY. The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a gX2YgX^2Y term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.Comment: 11 pages, 9 figures, supplement: an ascii tabl

    Measurement of the pseudoscalar mixing angle and η\eta^{\prime} gluonium content with KLOE detector

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    We have measured the ratio Rϕ=BR(ϕηγ)/BR(ϕηγ)R_{\phi}=BR(\phi \to \eta^{\prime} \gamma)/BR(\phi \to \eta \gamma) by looking for the radiative decays ϕηγ\phi \to \eta^{\prime} \gamma and ϕηγ\phi \to \eta \gamma in the final states π+π\pi^+\pi^- 7 γ\gamma's and 7 γ\gamma's respectively, in a sample of 1.3109\sim 1.3\cdot 10^{9} ϕ\phi mesons produced at the Frascati ϕ\phi-factory. We obtain Rϕ=(4.77±0.09stat±0.19sys)103R_{\phi}=(4.77\pm0.09_{stat}\pm0.19_{sys})\cdot 10^{-3} from which we derive BR(ϕηγ)=(6.20±0.11stat±0.25sys)105BR(\phi \to \eta^{\prime} \gamma)=(6.20\pm0.11_{stat}\pm0.25_{sys})\cdot 10^{-5}. In the hypothesis of no gluonium content we extract the pseudoscalar mixing angle in the quark-flavor basis ϕP=(41.4±0.3stat±0.7sys±0.6th)\phi_P=(41.4\pm0.3_{stat}\pm0.7_{sys}\pm0.6_{th})^{\circ}. Combining the value of RϕR_{\phi} with other constraints, we estimate the gluonium fractional content of η\eta^{\prime} meson as Z2=0.14±0.04Z^2 = 0.14\pm0.04 and the mixing angle ϕP=(39.7±0.7)\phi_P = (39.7\pm0.7)^{\circ}.Comment: 13 pages, 8 figure

    First observation of quantum interference in the process phi -> KS KL ->pi+pi-pi+pi-: a test of quantum mechanics and CPT symmetry

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    We present the first observation of quantum interference in the process phi -> KS KL ->pi+pi-pi+pi-. This analysis is based on data collected with the KLOE detector at the e^+e^- collider DAFNE in 2001--2002 for an integrated luminosity of about 380pb^-1. Fits to the distribution of Delta t, the difference between the two kaon decay times, allow tests of the validity of quantum mechanics and CPT symmetry. No deviations from the expectations of quantum mechanics and CPT symmetry have been observed. New or improved limits on various decoherence and CPT violation parameters have been obtainedComment: submitted to Physics Letter B one number changed old:gamma=(1.1+2.9-2.4)10^-21 GeV new:(1.3+2.8-2.4)10^-21GeV corrected typo
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