18,443 research outputs found

    Searches for new particles at LEP: a summary report

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    We review the progress made at LEP in the quest for new particles.Comment: 10 pages, latex, 1 figure, summary talk given at `13th Convegno sulla Fisica al LEP (LEPTRE 2001)', Rome, Italy, 18-20 April 200

    The flat X-ray spectrum of the LINER NGC1052

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    We report on ROSAT and ASCA observations of the LINER NGC1052, which is the first one where broad optical lines in polarized light have been observed. The 2-10 keV spectrum is very flat, with an observed photon index (Gamma) ~0.1. A model where a nuclear source is - partly or totally - obscured by a screen of matter with column density ~10^23 atom/cm/cm is the most convincing explanation for the observed flatness. This agrees with the hypothesis that the LINERs are a population of low-luminosity AGN, to which the Seyfert unification scenario applies. The intrinsic spectral index is still rather flat (1.0-1.4), as observed in a few type-2 Seyferts so far or predicted if the accretion occurs in an advection-dominated flow.Comment: 5 pages, Latex, 2 Postscript figures, accepted for publication in MNRA

    Neutrino oscillations and Lorentz Invariance Violation in a Finslerian Geometrical model

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    Neutrino oscillations are one of the first evidences of physics beyond the Standard Model (SM). Since Lorentz Invariance is a fundamental symmetry of the SM, recently also neutrino physics has been explored to verify the eventual modification of this symmetry and its potential magnitude. In this work we study the consequences of the introduction of Lorentz Invariance Violation (LIV) in the high energy neutrinos propagation and evaluate the impact of this eventual violation on the oscillation predictions. An effective theory explaining these physical effects is introduced via Modified Dispersion Relations. This approach, originally introduced by Coleman and Glashow, corresponds in our model to a modification of the special relativity geometry. Moreover, the generalization of this perspective leads to the introduction of a maximum attainable velocity which is specific of the particle. This can be formalized in Finsler geometry, a more general theory of space-time. In the present paper the impact of this kind of LIV on neutrino phenomenology is studied, in particular by analyzing the corrections introduced in neutrino oscillation probabilities for different values of neutrino energies and baselines of experimental interest. The possibility of further improving the present constraints on CPT-even LIV coefficients by means of our analysis is also discussed.Comment: Accepted for publication with minor revisions, will appear on European Physics Journal

    Full QCD on APE100 Machines

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    We present the first tests and results from a study of QCD with two flavours of dynamical Wilson fermions using the Hybrid Monte Carlo Algorithm (HMCA) on APE100 machines.Comment: 23 pages, LaTeX, 13 PS figures not include

    The Neutrino mass matrix after Kamland and SNO salt enhanced results

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    An updated analysis of all available neutrino oscillation evidence in Solar experiments including the latest SNO ES,CC and NC data (254d live time, NaCL enhanced efficiency) is presented. We obtain, for the fraction of active oscillating neutrinos: sin^2alpha=(\Phi_{NC}-\Phi_{CC})/(\Phi_{SSM}-\Phi_{CC})=0.94^{+0.0.065}_{-0.060} nearly 20\sigma from the pure sterile oscillation case. The fraction of oscillating sterile neutrinos cos^2\alpha \lsim 0.12 (1 sigma CL). At face value, these results might slightly favour the existence of a small sterile oscillating sector. In the framework of two active neutrino oscillations we determine individual neutrino mixing parameters and their errors we obtain Delta m^2= 7.01\pm 0.08 \times 10^{-5} eV^2, tan^2 theta=0.42^{+0.12}_{-0.07}. The main difference with previous analysis is a better resolution in parameter space. In particular the secondary region at larger mass differences (LMAII) is now excluded at 95% CL. The combined analysis of solar and Kamland data concludes that maximal mixing is not favoured at 4-5 sigma. This is not supported by the antineutrino reactor results alone. We estimate the individual elements of the two neutrino mass matrix, writing M^2=m^2 I+M_0^2, we obtain (1 sigma errors): M_0^2=10^{-5} eV^2\pmatrix{ 2.06^{+0.29}_{-0.31} & 3.15^{+0.29}_{-0.35} \cr 3.15^{+0.29}_{-0.35} & 4.60^{+0.56}_{-0.44} }

    Hamevol1.0: a C++ code for differential equations based on Runge-Kutta algorithm. An application to matter enhanced neutrino oscillation

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    We present a C++ implementation of a fifth order semi-implicit Runge-Kutta algorithm for solving Ordinary Differential Equations. This algorithm can be used for studying many different problems and in particular it can be applied for computing the evolution of any system whose Hamiltonian is known. We consider in particular the problem of calculating the neutrino oscillation probabilities in presence of matter interactions. The time performance and the accuracy of this implementation is competitive with respect to the other analytical and numerical techniques used in literature. The algorithm design and the salient features of the code are presented and discussed and some explicit examples of code application are given.Comment: 18 pages, Late
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