J. Bellandi

On the question of neutrino spin precession in a magnetic field

Abstract Using the Feynman procedure of ordered exponential operators we solve the evolution equations for a two-neutrino system considering arbitrarily varying matter density and magnetic field along the neutrino trajectory. We show that a large geometrical phase velocity suppresses vL→vR transitions unless some stationary trajectory is found along the neutrino path. Concerning the solar neutrino case, if we admit the standard solar model matter distribution, no such trajectory can be found.

On the question of the energy dependence of inelasticity

Abstract We discuss the question of the energy dependence of inelasticity in very-high-energy hadronic interactions. From existing extensive-air-shower data, a definite conclusion cannot yet be reached. However, Glauber model realistic calculations and recent results from Tevatron suggest a slow increase of the mean inelasticity with energy.

Diffractive contribution to the elasticity and to the nucleonic flux in the atmosphere

We perform an analysis of the nucleonic and hadronic fluxes in the atmosphere by considering two components for the nucleon scattering, namely non-diffractive and diffractive interactions. It is shown that, albeit small, the diffractive component is really necessary to get good agreement with data. An analysis of the proton - proton total cross section and proton - air inelastic cross section, both extracted from cosmic-ray data, is also presented.

The Feynman-like procedure of ordered exponential operators applied to solar neutrinos

Abstract An analytic resonant solution to the solar neutrino problem induced by small solar magnetic field phase velocity is derived using the Feynman-like procedure of ordered exponential operators. We assume the standard solar model matter distribution inside the Sun and the model proposed by Akhmedov and Bychuk for the solar magnetic field to conclude that a neutrino magnetic moment of order (5–8)×10 −13 μ B is sufficient to explain the experimentally observed solar neutrino deficit, an improvement by a factor (2–4) relative to the conventional resonant spin-precession solution induced by neutrino squared mass difference when the same solar characteristics are considered.

The energy dependence of the inelasticity and the nucleonic cascade

The authors obtain a simple solution for the one-dimensional nucleonic diffusion equation in the atmosphere assuming that both the interaction mean free path and inelasticity are energy dependent. They also show that a fairly accurate description of nucleonic fluxes is obtained by using the average inelasticity as an increasing function of energy.

On the behaviour of the total cross section at superhigh energies from cosmic-ray data

Abstract We have performed a reanalysis of the Akeno data on absorption cross section by using different scenarios for the average inelasticity wherein it can alternatively be an increasing or a decreasing function of energy. The proton-proton total cross section and the proton-air inelastic cross section were calculated up to LHC energy scale.

Three-dimensional nucleonic cascade induced by one single nucleon in the atmosphere

Using a Feynman-like procedure of ordered exponential operators the authors solve the three-dimensional diffusion equation for the nucleonic cascade induced by one single nucleon in the atmosphere.

Analysis of the hadronic energy spectrum in high‐energy cosmic‐ray families detected by emulsion chambers

We analyze the hadronic energy spectrum for cosmic‐ray families detected by emulsion chambers in the high‐energy region, by means of the solution of diffusion equations for the hadronic cascade induced by one single nucleon in the atmosphere, assuming three different models for the energy distribution function in multiple pion production. We describe the experimental data for the energy of three high‐energy families detected in emulsion chamber of Brazil‐Japan Colloboration (BJC) at Mt. Chacaltaya and of two families detected by Pamir Collaboration (PC). We look also for consistency of the rapidity‐density distribution, obtained for the different hypotheses for multiple pion production above, with accelerator data in the ISR and Collider regions. Finally, the Models are analysed with respect to the energy dependence of the mean inelasticity.

Leading nucleon and inelasticity in hadron-nucleus interactions

We present in this paper a calculation of the average proton-nucleus inelasticity. Using an iterative leading particle model and the Glauber model we relate the leading particle distribution in nucleon-nucleus interactions with the respective one in nucleon-proton collisions. To describe the leading particle distribution in nucleon-proton collisions we use the Regge-Mueller formalism.

Universality tests for total cross sections

Starting directly from data we test the universality of the decomposition of total cross-sections in an asymptotically dominant term, the Pomeron, and a non dominant one, the Reggeon. Without assuming Regge pole model behaviour or additive quark model relations we show that data are compatible with both models. Support is not found for models predicting asymptotical equality of total cross-sections.