131 research outputs found

    High energy cosmic ray physics with underground muons in MACRO. I. Analysis methods and experimental results

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    In this paper, the first of a two-part work, we present the reconstruction and measurement of muon events detected underground by the MACRO experiment at Gran Sasso (E у 1.3 TeV in atmosphere͒. The main aim of this work is to discuss the muon multiplicity distribution as measured in the detector. The data sample analyzed consists of 4.4ϫ10 6 muon events, of which ϳ 263 000 are multiple muons, corresponding to a total live time of 5850 h. In this sample, the observed multiplicities extend above N ϭ35, with intermuon separations up to 50 m and beyond. Additional complementing measurements, such as the inclusive muon flux, the angular distribution, and the muon separation distribution ͑decoherence͒, are also included. The physical interpretation of the results presented here is reported in the following companion paper. ͓S0556-2821͑97͒00615-2͔ PACS number͑s͒: 13.85. Tp, 96.40.De, 96.40.Tv, 98.70.S

    MACRO results on atmospheric neutrinos

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    We discuss the final results of the MACRO experiment on atmospheric neutrino oscillations. The data concern event topologies with average neutrino energies of ∼ 3 and ∼ 50 GeV. Multiple Coulomb Scattering of the high energy muons was used to estimate the neutrino energy event by event. The angular distributions, the L/Eν distribution, the particle ratios and the absolute fluxes all favor νμ → ντ oscillations with maximal mixing and Δm2 ≃ 0.0023 eV2. Emphasis is given to measured ratios which are not affected by Monte Carlo (MC) absolute normalization; a discussion is made on MC uncertainties. A preliminary search for possible Lorentz invariance violation contributions to atmospheric neutrino oscillations is presented and discussed. © 2005 Elsevier B.V. All rights reserved

    MACRO results on atmospheric neutrino oscillations

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    The final results of the MACRO experiment on atmospheric neutrino oscillations are presented. The data concern different event topologies with average neutrino energies of ∼ 3 and ∼ 50 GeV. Multiple Coulomb Scattering of the high energy muons was used to estimate the neutrino energy of each event. The angular distributions, the L/Eν distribution, the particle ratios and the absolute fluxes all favour νμ → ντ oscillations with maximal mixing and Δm2 = 0.0023 eV2. A discussion is made on the Monte Carlos used for the atmospheric neutrino flux

    The cosmic ray proton, helium and CNO fluxes in the 100 TeV energy region from TeV muons and EAS atmospheric Cherenkov light observations of MACRO and EAS-TOP

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    The primary cosmic ray (CR) proton, helium and CNO fluxes in the energy range 80-300 TeV are studied at the National Gran Sasso Laboratories by means of EAS-TOP (Campo Imperatore, 2005 m a.s.l.) and MACRO (deep underground, 3100 m w.e., the surface energy threshold for a muon reaching the detector being Eμth~1.3 TeV). The measurement is based on: (a) the selection of primaries based on their energy/nucleon (i.e., with energy/nucleon sufficient to produce a muon with energy larger than 1.3 TeV) and the reconstruction of the shower geometry by means of the muons recorded by MACRO in the deep underground laboratories; (b) the detection of the associated atmospheric Cherenkov light (C.l.) signals by means of the C.l. detector of EAS-TOP. The C.l. density at core distance r>100 m is directly related to the total primary energy E0. Proton and helium (``p+He'') and proton, helium and CNO (``p+He+CNO'') primaries are thus selected at E0~=80 TeV, and at E0~=250 TeV, respectively. Their flux is measured: Jp+He(80TeV)=(1.8+/-0.4)×10-6 m-2s-1sr-1TeV-1, and Jp+He+CNO(250TeV)=(1.1+/-0.3)×10-7 m-2s-1sr-1TeV-1, their relative weights being: Jp+He/Jp+He+CNO(250TeV)=0.78+/-0.17. By using the measurements of the proton spectrum obtained from the direct experiments and hadron flux data in the atmosphere, we obtain for the relative weights of the three components at 250 TeV: Jp:JHe:JCNO=(0.20+/-0.08):(0.58+/-0.19):(0.22+/-0.17). This corresponds to the dominance of helium over proton primaries at 100-1000 TeV, and a possible non-negligible contribution from CNO. The lateral distribution of Cherenkov light in Extensive Air Showers (EASs), which is related to the rate of energy deposit of the primary in the atmosphere, is measured for a selected proton and helium primary beam, and good agreement is found when compared with the one calculated with the CORSIKA/QGSJET simulation model

    Search for stellar gravitational collapses with the MACRO detector

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    We present the final results of the search for stellar gravitational collapses obtained by the MACRO experiment. The detector was active for a stellar collapse search for more than 11 years and it was sensitive to collapses occurring all over in our galaxy for 8.6 years. A real time system for a prompt recognition of neutrino bursts was developed and was operating on-line for almost the whole life of the experiment. No signal compatible with a neutrino burst from a galactic supernova was observed

    Measurements of atmospheric muon neutrino oscillations, global analysis of the data collected with MACRO detector

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    The final analysis of atmospheric neutrino events collected with the MACRO detector is presented. Three different classes of events, generated by neutrinos in different energy ranges, are studied looking at rates, angular distributions and estimated energies. The results are consistent for all the subsamples and indicate a flux deficit that depends on energy and path - length of neutrinos. The no - oscillation hypothesis is excluded at similar to 5sigma, while the hypothesis of nu(mu) --> nu(tau) oscillation gives a satisfactory description of all data. The parameters with highest probability in a two flavor scenario are sin(2) 2theta(m) = 1 and Deltam(2) = 0.0023 eV(2). This result is independent of the absolute normalization of the atmospheric neutrino fluxes. The data can also be used to put experimental constrain on this normalization

    Measurements of atmospheric muon neutrino oscillations,global analysis of the data collected with MACRO detector

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    The final analysis of atmospheric neutrino events collected with the MACRO detector is presented. Three different classes of events, generated by neutrinos in different energy ranges, are studied looking at rates, angular distributions and estimated energies. The results are consistent for all the subsamples and indicate a flux deficit that depends on energy and path-length of neutrinos. The no-oscillation hypothesis is excluded at ∼ 5σ, while the hypothesis of νμ → ντ oscillation gives a satisfactory description of all data. The parameters with highest probability in a two flavor scenario are sin2 2θm= 1 and Δm2 = 0.0023 eV2. This result is independent of the absolute normalization of the atmospheric neutrino fluxes. The data can also be used to put experimental constrain on this normalization

    Measurements of atmospheric muon neutrino oscillations, global analysis of the data collected with MACRO detector

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    The final analysis of atmospheric neutrino events collected with the MACRO detector is presented. Three different classes of events, generated by neutrinos in different energy ranges, are studied looking at rates, angular distributions and estimated energies. The results are consistent for all the subsamples and indicate a flux deficit that depends on energy and path-length of neutrinos. The no-oscillation hypothesis is excluded at 5 , while the hypothesis of oscillation gives a satisfactory description of all data. The parameters with highest probability in a two flavor scenario are sin22m=1 and m2=00023eV2 . This result is independent of the absolute normalization of the atmospheric neutrino fluxes. The data can also be used to put experimental constrain on this normalization
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