arXiv subjects

P. Lipari

Publications and source records attributed to P. Lipari.

60 records · Page 4Linked to original sources

arXiv1999

A 3-Dimensional Calculation of Atmospheric Neutrino Flux

An extensive 3-dimensional Monte Carlo calculation of the atmospheric neutrino flux is in progress with the FLUKA Monte Carlo code. The results are compared to those obtained under the 1-dimensional approximation, where secondary particles and decay products are assumed to be collinear to the primary cosmic ray, as usually done in most of the already existing flux calculations. It is shown that the collinear approximation gives rise to a wrong angular distribution of neutrinos, essentially in the Sub-GeV region. However, the angular smearing introduced by the experimental inability of detecting recoils in neutrino interactions with nuclei is large enough to wash out, in practice, most of the differences between 3-dimensional and 1-dimensional flux calculations. Therefore, the use of the collinear approximation should have not introduced a significant bias in the determination of the flavor oscillation parameters in current experiments.

hep-ph↗

arXiv1998

Atmospheric neutrinos at Super-Kamiokande and parametric resonance in neutrino oscillations

We consider the oscillations of atmospheric neutrinos in the earth in the three-neutrino scheme with a $Δm^2$ hierarchy and a small admixture of the electron neutrino in the heavy mass eigenstate characterized by the mixing angle $θ_{13}$. We show that for $Δm^2 \simeq (0.5 - 3) \times 10^{-3}$ eV$^2$ indicated by the Super-Kamiokande data and $\sin^2 2θ_{13} \aprle 0.2$, the oscillations of multi-GeV neutrinos in the subdominant $ν_μ \leftrightarrow ν_e$ mode are enhanced by the MSW and parametric resonances. The parametric resonance, which occurs when the neutrinos cross the core of the earth, dominates for $Δm^2 \simeq (1 - 2)\times 10^{-3}$ eV$^2$, $\sin^2 2θ_{13} \aprle 0.06$. The resonance matter effects lead to an observable excess of the e-like events with a specific zenith angle dependence even for small $θ_{13}$. The up-down asymmetry of the multi-GeV e-like events can reach 15% for $|\cos Θ_e| > 0.2$ and up to 30% for $|\cos Θ_e| > 0.6$, where $Θ_e$ is the zenith angle of the electron. The resonance matter effects are relevant for the interpretation of the Super-Kamiokande data.

hep-ph↗

arXiv1998

A simulation code to assist designing space missions of the Airwatch type

The design of an Airwatch type space mission can greatly benefit from a flexible simulation code for establishing the values of the main parameters of the experiment. We present here a code written for this purpose. The cosmic ray primary spectrum at very high energies, the atmosphere modelling, the fluorescence yield, the photon propagation and the detector response are taken into account in order to optimize the fundamental design parameters of the experiment, namely orbit height, field of view, mirror radius, number of pixels of the focal plane, threshold of photo-detection. The optimization criterion will be to maximize counting rates versus mission cost, which imposes limits both on weight and power consumption. Preliminary results on signals with changing energy and zenith angle of incident particles are shown.

hep-ex↗

arXiv1998

Simulation of nuclear effects in quasi elastic and resonant neutrino interactions

The effects of nuclear re-interactions in quasi elastic and resonant neutrino interactions have been considered in the framework of the nuclear models of the DPMJET code. A preliminary investigation on the modifications induced on the final state has been performed. Some consequences affecting the experimental identification are discussed.

hep-ph↗

arXiv1993

TeV Muons in Hadronic Showers

{}From the study of the multiple muon events in deep underground detectors, it is possible to extract information about the spectrum and composition of the primary cosmic rays. In this work the number of TeV muons produced by a primary cosmic ray of a given energy and zenith angle is computed using analytic and montecarlo methods, for a family of simplified models as description of the properties of hadronic interactions. The effects of the uncertainties in our knowledge of the hadronic cross sections in the calculation of TeV muons are discussed.

hep-ph↗

arXiv1992

Matter Effects in Atmospheric Neutrino Oscillations

The Kamiokande II and IMB data on contained events induced by atmospheric neutrinos exhibit too low a ratio of muons to electrons, which has been interpreted as a possible indication of neutrino oscillations. At the same time, the recent data on upward--going muons in underground detectors have shown no evidence for neutrino oscillations, strongly limiting the allowed region of oscillation parameter space. In this paper we confront different types of neutrino oscillation hypotheses with the experimental results. The matter effects in $ν_μ\leftrightarrow ν_e$ and in $ν_μ\leftrightarrow ν_{sterile}$ oscillations are discussed and shown to affect significantly the upward--going muons.

hep-ph↗