Oscar A. Sampayo

Precession of neutrino-cooled accretion disks in gamma-ray burst engines

Aims. We study the precession of accretion disks in the context of gamma-ray burst inner engines. Methods. With an accretion disk model that allows for neutrino cooling, we evaluate the possible periods of disk precession and nutation due to the Lense-Thirring effect. Results. Assuming jet ejection perpendicular to the disk midplane and a typical intrinsic time dependence for the burst, we find possible gamma-ray light curves with a temporal microstructure similar to what is observed in some subsamples. Conclusions. We conclude that the precession and nutation of a neutrino-cooled accretion disk in the burst engine might be responsible for some events, especially those with a slow rise and a fast decay.

On neutrino absorption tomography of the Earth

Abstract We study the passage of UHE neutrinos through the Earth in order to perform an absorption tomography of its inner structure. The aim of this work is to study the extraction methods of the Earths density, in this conditions, we do not need to implement a realistic Monte Carlo simulation, as we are only interested in comparing the goodness of a standard method [Astropart. Phys. 12 (1999) 193] with the one we propose. The Earths density is reconstructed using the 2-d Radon transform and we compare the density obtained considering neutral current regeneration through the complete transport equation, with the one obtained making use of the effective cross section approximation (standard method). We see that the effective cross section leads in general to inaccurate results, especially for flat initial neutrino fluxes, while the full transport equation method works regardless of the initial flux. Finally, an error propagation analysis made for different uncertainties in the surviving neutrino flux shows that the recovered density presents a percentage uncertainty less than two times the uncertainty in the flux.

Majorana neutrino decay in an Effective Approach

The search strategy or the finding of new effects for heavy neutrinos often relies on their different decay channels to detectable particles. In particular in this work we study the decay of a Majorana neutrino with interactions obtained from an effective general theory modeling new physics at the scale

Majorana Neutrinos Production at NLC in an Effective Approach

\Lambda

Effective Majorana neutrino decay

. The results obtained are general because they are based in an effective theory and not in specific models. We are interested in relatively light heavy Majorana neutrinos, with masses lower than the

New physics with IceCube

W

Bilepton and exotic quark mass limits in 331 models from Z → b b decay

mass (

Majorana neutrinos in an effective field theory approach

m_N<m_W

Not-that-heavy Majorana neutrino signals at the LHC

). This mass range simplifies the study by reducing the possible decay modes. Moreover, we found that for

Propagation of high-energy neutrinos in a background of ultralight scalar dark matter

\Lambda\sim 1