Between the years 2012 and 2014, I have been working on my PhD thesis, in the LPNHE (Laboratoire de Physique Nucléaire et de Hautes Énergies), Paris, in collaboration with the Pierre Auger Observatory, in the PhD program of the UPMC (Université Pierre et Marie Curie).

Title: Different approaches to determine the composition of the ultra-high energy cosmic rays in the Pierre Auger Observatory.

Advisor: Antoine Letessier-Selvon. Defended on December 12th, 2014.

Complete text (pdf) available clicking this link.

Presentation (keynote) available clicking this link.


The motivation of this PhD thesis is to improve the capabilities to determine the mass composition of the ultra-high energy cosmic rays in the Pierre Auger Observatory. The measure of their mass composition is done with the fluorescence technique, that needs special luminosity conditions that reduce the exposure time to about 10% of the time. Three different approaches are proposed.

The first approach is a new analysis. Muons in the horizontal showers are deviated by the magnetic field of the Earth. This deflection is related with different characteristics of the extensive air shower that allow the construction of an estimator to obtain an alternative measure of Xμmax, an observable sensitive to the mass of the primary.

The second approach is to explore the detection of the radio emission produced in the extensive air showers, a technique similar to the fluorescente one, but without the limitations in the duty cycle. The detection of the Molecular Bremsstrahlung Radiation emission is revised and investigated from different points of view.
The third approach is to propose a new surface detector that obtains different responses to the different components of the extensive air shower: electromagnetic and muonic. The access to the muonic component is another way to access to the composition of the primary particle.

The new method of analysis proposed appears as a promising tool to be applied in any data set. The technique of the radio detection did not show clear indications of being an alternative to traditional techniques. The new detector represents a promising alternative to be considered in any future ultra-high energy cosmic rays experiment.

Some images of the text and videos of the presentation:

Multivariate analysis applied to the composition of cosmic rays:

EAS in atmosphere:

Layered Surface Detector:

Radio emissions of the Extensive Air Showers:

Profiles of the Extensive Air Showers: