Particle identification with the AMS-02 RICH detector: search for dark matter with antideuterons

The Alpha Magnetic Spectrometer (AMS), whose final version AMS-02 is to be installed on the International Space Station (ISS) for at least 3 years, is a detector designed to measure charged cosmic ray spectra with energies up to the TeV region and with high energy photon detection capability up to a few hundred GeV, using state-of-the art particle identification techniques. It is equipped with several subsystems, one of which is a proximity focusing Ring Imaging Cherenkov (RICH) detector equipped with a dual radiator (aerogel+NaF), a lateral conical mirror and a detection plane made of 680 photomultipliers and light guides, enabling precise measurements of particle electric charge and velocity (Delta beta / beta ~ 10^-3 and 10^-4 for Z=1 and Z=10-20, respectively) at kinetic energies of a few GeV/nucleon. Combining velocity measurements with data on particle rigidity from the AMS-02 Tracker (Delta R / R ~ 2% for R=1-10 GV) it is possible to obtain a reliable measurement for particle mass. One of the main topics of the AMS-02 physics program is the search for indirect signatures of dark matter. Experimental data indicate that dark, non-baryonic matter of unknown composition is much more abundant than baryonic matter, accounting for a large fraction of the energy content of the Universe. Apart from antideuterons produced in cosmic-ray propagation, the annihilation of dark matter will produce additional antideuteron fluxes. Detailed Monte Carlo simulations of AMS-02 have been used to evaluate the detector's performance for mass separation, a key issue for anti-D/anti-p separation. Results of these studies are presented.Comment: 5 pages. Contribution to the 20th European Cosmic Ray Symposium (Lisbon 2006). Presenter: Rui Pereir

Particle identification with the AMS-02 RICH detector: D/p and anti-D/anti-p separation

The Alpha Magnetic Spectrometer (AMS), whose final version AMS-02 is to be installed on the International Space Station (ISS) for at least 3 years, is a detector designed to measure charged cosmic ray spectra with energies up to the TeV region and with high energy photon detection capability up to a few hundred GeV, using state-of-the art particle identification techniques. Among several detector subsystems, AMS includes a proximity focusing RICH enabling precise measurements of particle electric charge and velocity. The combination of both these measurements together with the particle rigidity measured on the silicon tracker endows a reliable measurement of the particle mass. The main topics of the AMS-02 physics program include detailed measurements of the nuclear component of the cosmic-ray spectrum and the search for indirect signatures of dark matter. Mass separation of singly charged particles, and in particular the separation of deuterons and antideuterons from massive backgrounds of protons and antiprotons respectively, is essential in this context. Detailed Monte Carlo simulations of AMS-02 have been used to evaluate the detector's performance for mass separation at different energies. The obtained results and physics prospects are presented.Comment: 5 pages. Contribution to the Sixth International Workshop on New Worlds in Astroparticle Physics (Faro 2007). Presenter: Rui Pereir

Drinking patterns among Portuguese university students: gender differences and association with self-perception of mental health

Alcohol abuse is one of the most concerning risk behaviours in higher education. Therefore, this study aims to: characterize alcohol consumption among Portuguese university students; investigate gender differences; analyse the association between alcohol use and the perception of mental health. 174 Portuguese students completed a questionnaire about risk behaviours and rated their self-perceptions of mental health. Results show that 17.3% of the students haven’t consumed any alcohol during the last month, while, on the opposite side, 11% of those who drank, reported having binge episodes at least twice a week. Men drank significantly more often; more drinks at a time and had more risk behaviours associated with alcohol, than women. A significant, yet very weak, positive correlation was found between the amount of alcohol consumed and the self-perception of mental health. Results are debated in light of relevant literature and suggestions for prevention are discussed.This investigation was supported by a FCT scholarship (SFRH/BD30085/2006

Portuguese media discourse on nuclear energy before and after Fukushima: prepared for the EFDA Workprogramme 2012 WP12-SER-ACIF-1

This report presents the results of the analysis of nuclear related content in Portuguese print media. The report is submitted to the first step of the research task untitled Public Discourse about Nuclear Fusion before and after the Fukushima accident, as part of the Socio-Economic Research on Fusion under the general coordination of EFDA Workprogramme 2012

Cosmic ray velocity and electric charge measurements with the AMS/RICH detector: prototype results

The Alpha Magnetic Spectrometer (AMS) to be installed on the International Space Station (ISS) will measure charged cosmic ray spectra of elements up to iron, in the rigidity range from 1 GV to 1 TV, for at least three years. AMS is a large angular spectrometer composed of different subdetectors, including a proximity focusing Ring Imaging CHerenkov (RICH) detector. This will be equipped with a mixed radiator made of aerogel and sodium fluoride (NaF), a lateral conical mirror and a detection plane made of 680 photomultipliers coupled to light guides. The RICH detector allows measurements of particle's electric charge up to iron, and particle's velocity. Two possible methods for reconstructing the Cherenkov angle and the electric charge with the RICH will be discussed. A RICH prototype consisting of a detection matrix with 96 photomultipliers, a segment of a conical mirror and samples of the radiator materials was built and its performance was evaluated using ion beam data. Results from the last test beam performed with ion fragments resulting from the collision of a 158 GeV/c/nucleon primary beam of indium ions (CERN SPS) on a lead target are reported. The large amount of collected data allowed to test and characterize different aerogel samples and the NaF radiator. In addition, the reflectivity of the mirror was evaluated. The data analysis confirms the design goals.Comment: 5 pages. Contribution to the 20th European Cosmic Ray Symposium in Lisbon, Portugal. September 5th-8th 2006. Presenter: Luisa Arrud

Comparative Analysis of the public discourse about fusion and nuclear energy before and after Fukushima: WP12-SER-ACIF-1 Final Report

This report presents a comparative analysis of media coverage of fusion and fission energy before and after the accident in the nuclear reactors of Fukushima, Japan. The analysis is based on research conducted under the EFDA Workprogramme 2012, addressing three national-based print media – Germany, Spain and Portugal as well as English-language print media addressing transnational elite

Do risco no alpinismo de alta montanha

This paper emerges after the lost of one Portuguese climber, who died in his descent from Shishapangma, one of the 14 mountains in Himalayas. Taking into account this climber’s death and all the others that are not reported, the issue of risk in sport and physical activities, like climbing, is noteworthy. This paper attempts to redress this imbalance through an approach to voluntary risk-taking in high-altitude climbing, where risk can be seen as part of the activity or even as an end. For this intent it is crucial to consider what does this activity signifies to its adherents, analysing the ways in which this activity is invested with and how these meanings may change. After a brief characterization of high-altitude climbing as a risky activity, our paper it is divided in the following sections: i) Control of risk vs. control of life; ii) Risk-taking as a form of transgression; iii) Adventure in high-altitude climbing; iv) Risk as an aestheticization of the experience; v) High-altitude climbing as a form of transcendence and self-overcoming and vi) Social recognition and distinction. This enumeration did not have the goal to isolate meanings; however our re?ection allowed perceiving that they are all linke

An LP-Based Approach for Goal Recognition as Planning

Goal recognition aims to recognize the set of candidate goals that are compatible with the observed behavior of an agent. In this paper, we develop a method based on the operator-counting framework that efficiently computes solutions that satisfy the observations and uses the information generated to solve goal recognition tasks. Our method reasons explicitly about both partial and noisy observations: estimating uncertainty for the former, and satisfying observations given the unreliability of the sensor for the latter. We evaluate our approach empirically over a large data set, analyzing its components on how each can impact the quality of the solutions. In general, our approach is superior to previous methods in terms of agreement ratio, accuracy, and spread. Finally, our approach paves the way for new research on combinatorial optimization to solve goal recognition tasks.Comment: 8 pages, 4 tables, 3 figures. Published in AAAI 2021. Updated final authorship and tex