A particle classification system for the PAMELA calorimeter

Abstract In this paper we propose a particle classification system for the imaging calorimeter of the PAMELA satellite-borne experiment. The system consist of three main processing phases. First, a segmentation of the whole signal detected by the calorimeter is performed to select a Region of Interest (RoI); this step allows to retain bounded and space invariant portions of data for the following analysis. In the next step, the RoIs are characterized by means of nine discriminating variables, which measure event properties useful for the classification. The third phase (the classification step) relies on two different supervised algorithms, Artificial Neural Networks and Support Vector Machines. The system was tested with a large simulated data set, composed by 40 GeV/c momentum electrons and protons. Moreover, in order to study the classification power of the calorimeter for experimental data, we have also used biased simulated data. A proton contamination in the range 10 −4 –10 −5 at an electron efficiency greater than 95% was obtained. The results are adequate for the PAMELA imaging calorimeter and show that the approach to the classification based on soft computing techniques is complementary to the traditional analysis performed using optimized cascade cuts on different variables

Osservazione dei raggi cosmici dallo spazio

I raggi cosmici sono particelle energetiche con origine sia nel nostro sistema solare e galassia ma anche fuori della galassia. I raggi cosmici sono in gran parte protoni e nuclei di elio ma sono presenti tutti i nuclei della tavola periodica oltre ad elettroni ed antiparticelle. La loro origine, i processi di accelerazione ad alte energie come pure la propagazione verso la terra sono argomenti che stanno impegnando gli scienziati dalla loro scoperta da parte di Victor Hess nel 1912. Per studiarli adeguatamente è necessario misurarne con precisione lo spettro energetico e la composizione. Queste ricerca è stata, ed è, affrontata sperimentalmente sia con strumentazione a terra che con apparati al sommo dell'atmosfera installati su palloni stratosferici o in satelliti o stazioni spaziali. Quest'ultimo campo ha visto una significativa attività negli ultimi decenni con molti apparati equipaggiati con strumentazione all'avanguardia che hanno prodotto importanti risulti rivoluzionando la comprensione della fisica dei raggi cosmici

Osservazione dei raggi cosmici dallo spazio

I raggi cosmici sono particelle energetiche con origine sia nel nostro sistema solare e galassia ma anche fuori della galassia. I raggi cosmici sono in gran parte protoni e nuclei di elio ma sono presenti tutti i nuclei della tavola periodica oltre ad elettroni ed antiparticelle. La loro origine, i processi di accelerazione ad alte energie come pure la propagazione verso la terra sono argomenti che stanno impegnando gli scienziati dalla loro scoperta da parte di Victor Hess nel 1912. Per studiarli adeguatamente è necessario misurarne con precisione lo spettro energetico e la composizione. Queste ricerca è stata, ed è, affrontata sperimentalmente sia con strumentazione a terra che con apparati al sommo dell'atmosfera installati su palloni stratosferici o in satelliti o stazioni spaziali. Quest'ultimo campo ha visto una significativa attività negli ultimi decenni con molti apparati equipaggiati con strumentazione all'avanguardia che hanno prodotto importanti risulti rivoluzionando la comprensione della fisica dei raggi cosmici

Multi messenger astronomy and CTA: TeV cosmic rays and electrons

Cosmic rays are a sample of solar, galactic and extragalactic matter. Their origin and properties are one of the most intriguing question in modern astrophysics. The most energetic events and active objects in the Universe: supernovae explosion, pulsars, relativistic jets, active galactic nuclei, have been proposed as sources of cosmic rays although unambiguous evidences have still to be found. Electrons, while comprising ~1% of the cosmic radiation, have unique features providing important information regarding the origin and propagation of cosmic rays in the Galaxy that is not accessible from the study of the cosmic-ray nuclear components due to their differing energy-loss processes. In this paper we will analyse, discussing the experimental uncertainties and challenges, the most recent measurements on cosmic-ray nuclei and, in particular, electrons with energies from tens of GeV into the TeV region.Comment: 24 pages, 10 figure, to appear in Astroparticle Physics as a special issue on CT

A silicon imaging calorimeter prototype for antimatter search in space: experimental results

Abstract This report presents the results obtained with a prototype silicon-tungsten (Si-W) electromagnetic calorimeter, conceived as a fine-grained imaging device to carry out studies of the antimatter component in primary cosmic radiation. The calorimeter prototype contains 20 x , y sampling layers interleaved with 19 showering material planes. One sensitive layer is obtained with two silicon strip detectors (Si-D) (60 × 60) mm 2 , each divided into 16 strips, 3.6 mm wide; the two detectors are assembled back to back with perpendicular strips. This allows the transverse distributions of the shower in both coordinates at each sampling (0.5 X 0 ) to be pictured. The basic characteristics of the design and the experimental results obtained on a test beam at the CERN proton synchrotron (PS) for electrons and pions are reported. The main results presented are the response of the calorimeter to the electron at various energies (1–7 GeV), and the transverse shower profiles at different calorimeter depths as well as the patterns of the electromagnetic shower and those of the interacting and non-interacting pions. The capability of the calorimeter in measuring the direction of the incoming electromagnetic particle from the pattern of the shower has been evaluated at different energies. These results are encouraging in view of the possible use of this detector to search for high-energy γ sources in space

Silicon calorimeter for cosmic antimatter search

Abstract The silicon sampling calorimeter presented is conceived as a fine grained imaging device to carry out studies of the anti-matter component in the primary cosmic radiation; it will be used in balloon payload program starting in 1993. The first sampling layer (48×48 cm2) of this silicon calorimeter has been completed and successfully tested. We report the first results form studies performed at the CERN PS t7 beam. The complete calorimeter contains 20 xy sampling layers (strip pitch 3.6 mm) interleaved with 19 showering material planes (tungsten 0.5 X0). This allows to picture the transverse distributions of the shower in both coordinates at each sampling. The outstanding imaging capabilities reflects in high particle identification power. Preliminary results from beam tests performed with antiprotons at 3.5 GeV on a tower prototype of the calorimeter are reported

The small satellite NINA-MITA to study galactic and solar cosmic rays in low-altitude polar orbit

Abstract The satellite MITA, carrying on board the scientific payload NINA-2, was launched on July the 15th, 2000 from the cosmodrome of Plesetsk (Russia) with a Cosmos-3M rocket. The satellite and the payload are currently operating within nominal parameters. NINA-2 is the first scientific payload for the technological flight of the Italian small satellite MITA. The detector used in this mission is identical to the one already flying on the Russian satellite Resurs-O1 n.4 in a 840-km sun-synchronous orbit, but makes use of the extensive computer and telemetry capabilities of MITA bus to improve the active data acquisition time. NINA physics objectives are to study cosmic nuclei from hydrogen to iron in the energy range between 10 MeV/n and 1 GeV/n during the years 2000–2003, that is the solar maximum period. The device is capable of charge identification up to iron with isotope sensitivity up to oxigen. The 87.3 degrees, 460 km altitude polar orbit allows investigations of cosmic rays of solar and galactic origin, so to study long and short term solar transient phenomena, and the study of the trapped radiation at higher geomagnetic cutoff