18,443 research outputs found

### Searches for new particles at LEP: a summary report

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

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

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

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

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

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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