825 research outputs found

    CP violation and mass hierarchy at medium baselines in the large theta(13) era

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    The large value of theta(13) recently measured by rector and accelerator experiments opens unprecedented opportunities for precision oscillation physics. In this paper, we reconsider the physics reach of medium baseline superbeams. For theta(13) ~ 9 degree we show that facilities at medium baselines -- i.e. L ~ O(1000 km) -- remain optimal for the study of CP violation in the leptonic sector, although their ultimate precision strongly depends on experimental systematics. This is demonstrated in particular for facilities of practical interest in Europe: a CERN to Gran Sasso and CERN to Phyasalmi nu_mu beam based on the present SPS and on new high power 50 GeV proton driver. Due to the large value of theta(13), spectral information can be employed at medium baselines to resolve the sign ambiguity and determine the neutrino mass hierarchy. However, longer baselines, where matter effects dominate the nu_mu->nu_e transition, can achieve much stronger sensitivity to sign(Delta m^2) even at moderate exposures.Comment: 14 pages, 14 figures, version to appear in EPJ

    Searching the Higgs with the Neurochip TOTEM

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    We show that neural network classifiers can be helpful in discriminating Higgs production events from the huge background at LHC, assuming the case of a mass value MH∌200M_H \sim 200 GeV. We use the high performance neurochip TOTEM, trained by the Reactive Tabu Search algorithm (RTS), which could be used for on-line purposes. Two different sets of input variables are compared.Comment: 4 pages,1 figure, requres espcrc2.sty and epsfig.sty. Work prsented in The 5th Topical Seminar on ``The irresistible rise of the Standard Model'', San Miniato, Tuscany, Italy, April 21-25 199

    Investigation of in the full hadronic final state at CDF with a neural network approach

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    Abstract In this work we present the results of a neural network (NN) approach to the measurement of the t t production cross-section and top mass in the all-hadronic channel, analyzing data collected at the Collider Detector at Fermilab (CDF) experiment. We have used a hardware implementation of a feed forward neural network, TOTEM , the product of a collaboration of INFN (Istituto Nazionale Fisica Nucleare)—IRST (Istituto per la Ricerca Scientifica e Tecnologica)—University of Trento, Italy. Particular attention has been payed to the evaluation of the systematics specifically related to the NN approach. The results are consistent with those obtained at CDF by conventional data selection techniques

    The OPERA magnetic spectrometer

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    The OPERA neutrino oscillation experiment foresees the construction of two magnetized iron spectrometers located after the lead-nuclear emulsion targets. The magnet is made up of two vertical walls of rectangular cross section connected by return yokes. The particle trajectories are measured by high precision drift tubes located before and after the arms of the magnet. Moreover, the magnet steel is instrumented with Resistive Plate Chambers that ease pattern recognition and allow a calorimetric measurement of the hadronic showers. In this paper we review the construction of the spectrometers. In particular, we describe the results obtained from the magnet and RPC prototypes and the installation of the final apparatus at the Gran Sasso laboratories. We discuss the mechanical and magnetic properties of the steel and the techniques employed to calibrate the field in the bulk of the magnet. Moreover, results of the tests and issues concerning the mass production of the Resistive Plate Chambers are reported. Finally, the expected physics performance of the detector is described; estimates rely on numerical simulations and the outcome of the tests described above.Comment: 6 pages, 10 figures, presented at the 2003 IEEE-NSS conference, Portland, OR, USA, October 20-24, 200

    Prospect for Charge Current Neutrino Interactions Measurements at the CERN-PS

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    Tensions in several phenomenological models grew with experimental results on neutrino/antineutrino oscillations at Short-Baseline (SBL) and with the recent, carefully recomputed, antineutrino fluxes from nuclear reactors. At a refurbished SBL CERN-PS facility an experiment aimed to address the open issues has been proposed [1], based on the technology of imaging in ultra-pure cryogenic Liquid Argon (LAr). Motivated by this scenario a detailed study of the physics case was performed. We tackled specific physics models and we optimized the neutrino beam through a full simulation. Experimental aspects not fully covered by the LAr detection, i.e. the measurements of the lepton charge on event-by-event basis and their energy over a wide range, were also investigated. Indeed the muon leptons from Charged Current (CC) (anti-)neutrino interactions play an important role in disentangling different phenomenological scenarios provided their charge state is determined. Also, the study of muon appearance/disappearance can benefit of the large statistics of CC muon events from the primary neutrino beam. Results of our study are reported in detail in this proposal. We aim to design, construct and install two Spectrometers at "NEAR" and "FAR" sites of the SBL CERN-PS, compatible with the already proposed LAr detectors. Profiting of the large mass of the two Spectrometers their stand-alone performances have also been exploited.Comment: 70 pages, 38 figures. Proposal submitted to SPS-C, CER

    Glass resistive plate chambers in the OPERA experiment

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    Abstract OPERA is an underground neutrino oscillation experiment to search for Îœ τ appearance from a pure Îœ ÎŒ beam produced at CERN. To flag the events due to the neutrino interactions with the rock surrounding the OPERA detector, a large VETO system, based on the use of Glass Resistive Plate Chambers (GRPC) has been realized. We describe the detectors, the tests performed before the installation in the underground laboratories and the monitor system for the water pollution in the GRPC gas mixture

    Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment

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    The OPERA long-baseline neutrino-oscillation experiment has observed the direct appearance of Μτ\nu_\tau in the CNGS ΜΌ\nu_\mu beam. Two large muon magnetic spectrometers are used to identify muons produced in the τ\tau leptonic decay and in ΜΌCC\nu_\mu^{CC} interactions by measuring their charge and momentum. Besides the kinematic analysis of the τ\tau decays, background resulting from the decay of charmed particles produced in ΜΌCC\nu_\mu^{CC} interactions is reduced by efficiently identifying the muon track. A new method for the charge sign determination has been applied, via a weighted angular matching of the straight track-segments reconstructed in the different parts of the dipole magnets. Results obtained for Monte Carlo and real data are presented. Comparison with a method where no matching is used shows a significant reduction of up to 40\% of the fraction of wrongly determined charges.Comment: 10 pages. Improvements in the tex

    Observation of nu_tau appearance in the CNGS beam with the OPERA experiment

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    The OPERA experiment is searching for nu_mu -> nu_tau oscillations in appearance mode i.e. via the direct detection of tau leptons in nu_tau charged current interactions. The evidence of nu_mu -> nu_tau appearance has been previously reported with three nu_tau candidate events using a sub-sample of data from the 2008-2012 runs. We report here a fourth nu_tau candidate event, with the tau decaying into a hadron, found after adding the 2012 run events without any muon in the final state to the data sample. Given the number of analysed events and the low background, nu_mu -> nu_tau oscillations are established with a significance of 4.2sigma.Comment: Submitted to Progress of Theoretical and Experimental Physics (PTEP
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