PAMELA Satellite-borne Experiment Research Articles

Relationship between the Longitude Distribution of the Heliospheric Characteristics and the GCR Intensity in 2007–2008 and 2014–2015

On the basis of the temporal behavior of the galactic cosmic rays and the heliospheric factors observed in 2007–2008 and 2014–2015, their average heliolongitude distributions are formed and compared. In addition to the neutron monitor data, the provisional database of daily average galactic cosmic ray proton intensities measured by the PAMELA satellite-borne experiment in 2006–2015 is used. It is shown that the properties of the heliolongitude distributions in the above periods are substantially different.

Strategies of Searches of the Angular Anisotropy of Fluxes of Galactic Electrons and Positrons by Means of the PAMELA Experiment Calorimeter

The possibility of studying the anisotropy of the total fluxes of electrons and positrons of high-energy (10 GeV to 1 TeV) cosmic rays in the PAMELA satellite-borne experiment by means of a calorimeter is considered. The procedure developed with aim of performing searches for this anisotropy is described along with the results of applying it to a test data sample.

Solar Modulation of 2H/1H and 3He/4He according to Data Obtained in the PAMELA Satellite-Borne Experiment between 2006 and 2014

Preliminary results of measurements of the solar modulation of the isotopic hydrogen and helium content in galactic cosmic rays are presented for the first time. These data were obtained between 2006 and 2014 in the PAMELA international orbital experiment via measuring the time of flight of nuclei in the Pamela scintillation telescope and via analyzing, in the multilayered calorimeter of the PAMELA magnetic spectrometer, ionization losses of nuclei whose rigidity was known from trajectory measurements and which traversed the instrument without undergoing nuclear interactions. The results of these measurements are compared with existing experimental and calculated data, which are quite scanty.

H, He, Li and Be Isotopes in the PAMELA-Experiment

On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anti-coincidence system, a shower tail counter scintillator and a neutron detector. The scientific objectives addressed by the mission are the measurement of the antiprotons and positrons spectra in cosmic rays, the hunt for antinuclei as well as the determination of light nuclei fluxes from hydrogen to oxygen in a wide energy range and with very high statistics. In this paper the identification capability for light nuclei isotopes using two different detector systems (Time-of-Flight and multiple dE/dx measurements in the calorimeter) and preliminary results of the isotopic ratios will be presented.

Identification reliability for hydrogen isotopes detected in cosmic ray fluxes

A technique for identifying hydrogen isotopes based on experimental data obtained in the PAMELA satellite-borne experiment is analyzed. Discrimination of cosmic-ray deuteron fluxes from the background of proton fluxes with a significantly higher intensity using information from the magnetic spectrometer and the time-of-flight system is discussed. Selection of smooth functions for fitting experimentally measured distributions of the inverse particle velocity is considered. Criteria for verifying the correctness of detected particle counting are developed.

Measurement of the total spectrum of electrons and positrons in the energy range of 300–1500 GeV in the PAMELA experiment with the aid of a sampling calorimeter and a neutron detector

A method based on the use of a sampling calorimeter was developed for measuring the total energy spectrum of electrons and positrons from high-energy cosmic rays in the PAMELA satellite-borne experiment. This made it possible to extend the range of energies accessible to measurements by the magnetic system of the PAMELA spectrometer. Themethod involves a procedure for selecting electrons on the basis of features of a secondary-particle shower in the calorimeter. The results obtained by measuring the total spectrum of cosmic-ray electrons and positrons in the energy range of 300–1500 GeV by the method in question are presented on the basis of data accumulated over a period spanning 2006 and 2013.

The PAMELA experiment and antimatter in the universe

On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The primary scientific goal is the measurement of the antiproton and positron energy spectra. Antiparticles are a natural component of the cosmic radiation being produced in the interaction between cosmic rays and the interstellar matter. They have been shown to be extremely interesting for understanding the propagation mechanisms of cosmic rays. Furthermore, novel sources of primary cosmic-ray antiparticles of either astrophysical or exotic origin (e.g. annihilation of dark matter particles) can also be probed. In this paper we review the PAMELA antiparticle results and their significance for the field of astroparticle physics.

North-south asymmetry for high-energy cosmic-ray electrons measured with the PAMELA experiment

The north-south asymmetry for cosmic-ray particles was measured with one instrument of the PAMELA satellite-borne experiment in the period June 2006-May 2009. The analysis has been performed by two ...

Measurement of the deflection of cosmic-ray electrons in the energy range 75–250 GeV by the Earth’s magnetic field with the PAMELA experiment

The deflection of electrons in the Earth’s magnetic field in the energy range 75–250 GeV (the so-called east-west effect) has been measured with the PAMELA satellite-borne experiment. The results are presented for various L-shells. The data obtained can be used to construct mathematical models that describe the structure of the Earth’s magnetic field and to refine the already existing models. These data can also be directly applied to estimate the positron fraction in cosmic-ray electron fluxes both in the PAMELA experiment and in other satellite-borne experiments.

Separation of the electron and proton cosmic-ray components by means of a calorimeter in the PAMELA satellite-borne experiment for the case of particle detection within a large aperture

The PAMELA satellite-borne experiment is designed to study cosmic rays over a broad energy range. The apparatus has been in near-Earth cosmic space from June 2006 to the present time. It is equipped with a magnetic spectrometer for determining the sign of the particle charge and rigidity. In solving some problems, however, information from the magnetic spectrometer becomes inaccessible, so that it is necessary to employ a calorimeter to separate the electron and nuclear cosmic-ray components. A procedure for separating these components for particles arriving off the magnetic-spectrometer aperture is considered.

H, He, Li and Be Isotopes in the PAMELA-Experiment

On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anti-coincidence system, a shower tail counter scintillator and a neutron detector. The scientific objectives addressed by the mission are the measurement of the antiprotons and positrons spectra in cosmic rays, the hunt for antinuclei as well as the determination of light nuclei fluxes from hydrogen to oxygen in a wide energy range and with very high statistics. In this paper the identification capability for light nuclei isotopes (especially lithium and beryllium) using multiple dE/dx measurements in the calorimeter and first results of the isotopic ratio will be presented.

A method for identifying deuterons in the PAMELA satellite-borne experiment

The procedure of deuteron identification against the background of other particles in cosmic-ray measurements is described. The algorithm is based on measuring and comprehensively analyzing the particle rigidity, velocity, and ionization losses and allows discrimination of deuterons with an admixture of other particles of a few percent or less. This method has been developed in the course of the PAMELA experiment [1] with the magnetic spectrometer and the time-of-flight system.

Measurements of He isotopic ratio in cosmic rays in the 100 MeV – 1 GeV range with the PAMELA experiment

The PAMELA satellite-borne experiment was launched on 15 June 2006 from the Baikonur cosmod- rome and it has been collecting data since then. The apparatus comprises a time-of-flight system, a silicon- microstrip magnetic spectrometer, a silicon-tungsten electro- magnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The com- bination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide en- ergy range (100 MeV 1 TeV) with high statistics, with par- ticular focus on the antiparticle component. In this work we present 3 He/ 4 He isotopic ratio in the energy range from 100 MeV nucleon -1 to 1 GeV nucleon -1 . The mea- sured abundances are compared with different interstel- lar/heliospheric propagation calculations which are tuned on previous proton and helium measurements.

The PAMELA space mission for antimatter and dark matter searches in space

The PAMELA satellite-borne experiment has presented new results on cosmic-ray antiparticles that can be interpreted in terms of DM annihilation or pulsar contribution. The instrument was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The combination of a permanent magnet silicon strip spectrometer and a silicon-tungsten imaging calorimeter allows precision studies of the charged cosmic radiation to be conducted over a wide energy range with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. This talk illustrates the most recent scientific results obtained by the PAMELA experiment.

The PAMELA space experiment

On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus is comprised of a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100MeV to 100’sGeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectra in order to search for exotic sources, such as dark matter particle annihilations. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. Moreover, PAMELA is investigating phenomena connected with solar and earth physics. After 4years of operation in flight, PAMELA is now delivering coherent results about spectra and chemical composition of the charged cosmic radiation, allowing scenarios of production and propagation of cosmic rays to be fully established and understood.

PAMELA and electrons

The 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon–tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV–100's GeV) with high statistics. The measurement of the positron to electron fraction and of the electron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations, are within the PAMELA primary scientific goal.

Determining the parameters of a particle shower initiated in an position-sensitive calorimeter by electrons and protons

Several methods of reconstructing a shower axis and methods of searching for the starting point of the shower are presented. They were developed for “thin“ sampling position-sensitive calorimeters. For this purpose we used a Monte Carlo simulation of the interaction of electrons and protons with the silicon-tungsten calorimeter of the PAMELA satellite-borne experiment. After some adaptation, these methods could be applied for different types of calorimeters.

Dark Matter research with the PAMELA Mission

The PAMELA satellite-borne experiment was launched from the Baikonur launch site on the 15th of June 2006. Since July 2006 it is daily delivering to ground 16 GBytes of data. The instrument is composed by a magnetic spectrometer, a time-of-flight system, a silicon-tungsten electromagnetic calorimeter, a neutron detector and anticoincidence scintillators. The primary scientific goal is to searching for evidence of dark matter particle annihilations studying antiparticles fluxes. Preliminary results concerning antiproton-proton and positron-electron ratios are presented.

The electron–hadron separation performance of the PAMELA electromagnetic calorimeter

A silicon-tungsten sampling imaging calorimeter has been designed and built for the PAMELA satellite-borne experiment. The main physics goals of the experiment are the measurement of the flux of antiprotons (80 MeV–190 GeV) and positrons (50 MeV–270 GeV) in the cosmic radiation. The calorimeter has been designed to identify antiprotons from an electron background and positrons in a background of protons with a high efficiency and rejection power. This work presents the electron–hadron separation capabilities of the calorimeter as obtained using both Monte Carlo and test beam data. The calorimeter is found to have sufficient performance to reach the primary scientific objectives of PAMELA, providing a proton rejection factor of ∼10 5 while keeping a ∼90% efficiency in selecting electrons and positrons. From simulations, an electron rejection factor of ∼10 5 in antiproton measurements (∼90% antiproton identification efficiency) is demonstrated.

A particle classification system for the PAMELA calorimeter

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 40GeV/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.