Roberta Sparvoli

The cosmic-ray electron and positron spectra measured at 1 Au during solar minimum activity

We report on a new measurement of the cosmic-ray electron and positron spectra. The data were collected by the balloon-borne experiment CAPRICE94, which was —own from Lynn Lake, Canada, on 1994 August 8¨9 at an altitude corresponding to 3.9 g cm~2 of average residual atmosphere. The experi- ment used the NMSU-WIZARD/CAPRICE94 balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cerenkov (RICH) detector, a time-of-—ight system, a tracking device consisting of drift chambers and multiwire proportional chambers, and a silicon-tungsten calorimeter. This was the —rst time a RICH detector was used together with an imaging calorimeter in a balloon-borne experi- ment. A total of 3211 electrons, with a rigidity at the spectrometer between 0.3 and 30 GV, and 734 positrons, between 0.3 and 10 GV, were identi—ed with small backgrounds from other particles. The absolute energy spectra were determined in the energy region at the top of the atmosphere between 0.46 and 43.6 GeV for electrons and between 0.46 and 14.6 GeV for positrons. We found that the observed positron spectrum and the positron fraction are consistent with a pure secondary origin. A comparison of the theoretically predicted interstellar spectrum of electrons shows that the injection spectrum of primary electrons is steeper than that of the nucleonic components of cosmic rays. Furthermore, the observed electron and positron spectra can be reproduced from the interstellar spectra by a spherically symmetric model for solar modulation; hence, the modulation is independent of the sign of the particle charge. Subject headings: balloonscosmic rayselementary particlesSun: activity

THE COSMIC-RAY PROTON AND HELIUM SPECTRA BETWEEN 0.4 AND 200 GV

We report on the hydrogen nuclei (protons and deuterons) spectrum from 0.15 to 200 GeV and on the helium nuclei spectrum over the energy range from 0.2 to 100 GeV nucleon~1 at the top of the atmo- sphere measured by the balloon-borne experiment Cosmic Antiparticle Ring-Imaging Cerenkov Experi- ment (CAPRICE), which was —own from Lynn Lake, Manitoba, Canada, on 1994 August 8¨9. We also report on the proton spectrum over the energy range from 0.15 to 4.2 GeV. The experiment used the NMSU-WiZard/CAPRICE balloon-borne magnet spectrometer equipped with a solid radiator Ring- Imaging Cerenkov (RICH) detector and a silicon-tungsten calorimeter for particle identi—cation. This was the —rst time a RICH was used together with an imaging calorimeter in a balloon-borne experiment. These detectors allowed for clear particle identi—cation, as well as excellent control of the detector effi- ciencies. The data were collected during 18 hr at a residual mean atmospheric depth of 3.9 g cm~2. With this apparatus 516,463 hydrogen and 32,457 helium nuclei were identi—ed in the rigidity range 0.4 to 200 GV and 1.2 to 200 GV, respectively. The observed energy spectrum at the top of the atmosphere can be represented by (1.1 ^ 0.1) ) 104 E~2.73B0.06 particles (m2 GeV sr s)~1 for hydrogen (E in GeV) between 20 and 200 GeV and (4.3 ^ 0.9) ) 102 E~2.65B0.07 particles (m2 GeV nucleon~1 sr s)~1 for helium nuclei (E in GeV nucleon~1) between 10 and 100 GeV nucleon~1. These spectra are in good agreement with other recent measurements above 10 GeV. The observed spectra —atten below 10 GeV due to solar modulation and are consistent with earlier measurements when solar modulation is taken into account. Between 5 and 200 GV the hydrogen to helium ratio as a function of rigidity was found to be approx- imately constant at 6.1 ^ 0.1. Subject headings: cosmic rayselementary particles

The Cosmic-Ray Antiproton Flux between 0.62 and 3.19 GeV Measured Near Solar Minimum Activity

We report on the absolute antiproton Nux and the antiproton to proton ratio in the energy range 0.62E3.19 GeV at the top of the atmosphere, measured by the balloon-borne experiment CAPRICE Nown from Lynn Lake, Manitoba, Canada, on 1994 August 8E9. The experiment used the New Mexico State University WiZard/CAPRICE balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cherenkov (RICH) detector and a silicon-tungsten calorimeter for particle identi-cation. This is the -rst time a RICH is used together with an imaging calorimeter in a balloon experiment, and it allows antiprotons to be clearly identi-ed over the rigidity range 1.2E4 GV. Nine antiprotons were identi-ed in the energy range 0.62E3.19 GeV at the top of the atmosphere. The data were collected over 18 hr at a mean residual atmosphere of 3.9 g cm~2. The absolute antiproton Nux is consistent with a pure secondary production of antiprotons during the propagation of cosmic rays in the Galaxy. Subject headings: balloons E cosmic rays E elementary particles E Sun: activity

Measurement of the flux of atmospheric muons with the CAPRICE94 apparatus

A new measurement of the momentum spectra of both positive and negative muons as function of atmospheric depth was made by the balloon-borne experiment CAPRICE94. The data were collected during ground runs in Lynn Lake on the 19-20th of July 1994 and during the balloon flight on the 8-9th of August 1994. We present results that cover the momentum intervals 0.3-40 GeV/c for negative muons and 0.3-2 GeV/c for positive muons, for atmospheric depths from 3.3 to 1000 g/cm**2, respectively. Good agreement is found with previous measurements for high momenta, while at momenta below 1 GeV/c we find latitude dependent geomagnetic effects. These measurements are important cross-checks for the simulations carried out to calculate the atmospheric neutrino fluxes and to understand the observed atmospheric neutrino anomaly.

Eye light flashes on the mir space station

The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer.

The Wizard/CAPRICE silicon-tungsten calorimeter

A silicon-tungsten calorimeter has been developed to be flown in the Wizard/CAPRICE balloon borne experiment to measure the flux of antiprotons, positrons and light nuclei in the cosmic radiation. The calorimeter is composed of 8 .r. .v silicon sampling planes [active area (48 X 48) cm’] interleaved with 7 tungsten absorbers (7 radiation lengths): it provides the topology of the interacting events together with an independent measurement of the deposited energy. Details of the front-end electronics and of the read-out system are given and the overall performances during pre-flight ground operations are described as well.

Performance of the CAPRICE RICH detector during the 1994 balloon flight

A RICH detector capable of detecting unit charged particles, e.g. antiprotons and positrons, has been used successfully for the first time in a balloon-borne magnet spectrometer. The thin and compact CAPRICE RICH detector uses a NaF solid radiator, TMAE vapour as photo converter and cathode pad readout in the photosensitive MWPC operated at low gain. 15 photoelectrons are detected per ring for β = 1, perpendicular incidence particles giving a resolution on the Cherenkov angle of 8 mrad, increasing to 14 mrad at 20°C incidence angle. Besides particle identification on an event-by-event basis it efficiently rejects multiparticle events and albedo particles.

Two years of flight of the Pamela experiment: results and perspectives.

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of 10 −8 ). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15 th 2006 in a 350 × 600 km orbit with an inclination of 70 degrees. In this work we describe the scientific objectives and the performance of PAMELA in its first two years of operation. Data on protons of trapped, secondary and galactic nature - as well as measurements of the December 13 th 2006 Solar Particle Event - are also provided.

GAMMA-RAY ENERGY DETERMINATION USING NEURAL NETWORK ALGORITHMS FOR AN IMAGING SILICON CALORIMETER

Abstract A neural network technique, based on multi-layer perceptrons, is used to fully exploit the performances of a sampling silicon calorimeter in energy identification of gamma rays. The results obtained on simulated data are significantly better than those coming from a classic method analysis.

High-energy gamma-ray studying with GAMMA-400

Extraterrestrial gamma-ray astronomy is now a source of new knowledge in the fields of astrophysics, cosmic-ray physics, and the nature of dark matter. The next absolutely necessary step in the development of extraterrestrial high-energy gamma-ray astronomy is the improvement of the physical and technical characteristics of gamma-ray telescopes, especially the angular and energy resolutions. Such a new generation telescope will be GAMMA-400. GAMMA-400, currently developing gamma-ray telescope, together with X-ray telescope will precisely and detailed observe in the energy range of ~20 MeV to ~1000 GeV and 3-30 keV the Galactic plane, especially, Galactic Center, Fermi Bubbles, Crab, Cygnus, etc. The GAMMA- 400 will operate in the highly elliptic orbit continuously for a long time with the unprecedented angular (~0.01{\deg} at E{\gamma} = 100 GeV) and energy (~1% at E{\gamma} = 100 GeV) resolutions better than the Fermi-LAT, as well as ground gamma-ray telescopes, by a factor of 5-10. GAMMA-400 will permit to resolve gamma rays from annihilation or decay of dark matter particles, identify many discrete sources (many of which are variable), to clarify the structure of extended sources, to specify the data on the diffuse emission.