Measurement of pseudorapidity distributions of charged particles in proton-proton collisions at root s=8 TeV by the CMS and TOTEM experiments

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Neutrino mixing effects on the tau-neutrino mass limit

We point out that the usual experimental upper bounds on the ''tau-neutrino mass'' do not apply if neutrino mixing is considered. The suppression of the population of the tau decay spectrum near the end point, caused by mixing, may be compensated by an enhancement because of a resonant mechanism of hadronization. It is necessary therefore to analyze the whole spectrum to infer some limit to the '' tau-neutrino mass.'' We argue that, consequently, neutrino mixing evades the objection to interpret the KARMEN anomaly as a heavy sequential neutrino.

On the question of neutrino spin precession in a magnetic field

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 νL→νR 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.

Soft color enhancement of the production of J/psi's by neutrinos

We calculate the production of J/ψ mesons by neutrino-nucleon collisions in fixed target experiments. Soft color, often referred to as color evaporation effects, enhances production cross sections due to the contribution of color octet states. Though still small, J/ψ production may be observable in present and future experiments such as NuTeV and μ colliders. ©2001 The American Physical Society.

O setor leptônico neutro e a violação de CP

Pós-graduação em Física - IFT