1. |
- Adriani, O., et al.
(author)
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Cosmic-Ray Electron Flux Measured by the PAMELA Experiment between 1 and 625 GeV
- 2011
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:20, s. 201101-
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Journal article (peer-reviewed)abstract
- Precision measurements of the electron component in the cosmic radiation provide important information about the origin and propagation of cosmic rays in the Galaxy. Here we present new results regarding negatively charged electrons between 1 and 625 GeV performed by the satellite-borne experiment PAMELA. This is the first time that cosmic-ray e(-) have been identified above 50 GeV. The electron spectrum can be described with a single power-law energy dependence with spectral index -3.18 +/- 0.05 above the energy region influenced by the solar wind (> 30 GeV). No significant spectral features are observed and the data can be interpreted in terms of conventional diffusive propagation models. However, the data are also consistent with models including new cosmic-ray sources that could explain the rise in the positron fraction.
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2. |
- Adriani, O., et al.
(author)
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Measurement of the flux of primary cosmic ray antiprotons with energies of 60 MeV to 350 GeV in the PAMELA experiment
- 2013
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In: JETP Letters. - 0021-3640 .- 1090-6487. ; 96:10, s. 621-627
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Journal article (peer-reviewed)abstract
- It is interesting to measure the antiproton galactic component in cosmic rays in order to study the mechanisms by which particles and antiparticles are generated and propagate in the Galaxy and to search for new sources of, e.g., annihilation or decay of dark matter hypothetical particles. The antiproton spectrum and the ratio of the fluxes of primary cosmic ray antiprotons to protons with energies of 60 MeV to 350 GeV found from the data obtained from June 2006 to January 2010 in the PAMELA experiment are presented. The usage of the advanced data processing method based on the data classification mathematical model made it possible to increase statistics and analyze the region of higher energies than in the earlier works.
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3. |
- Adriani, O., et al.
(author)
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Measurements of cosmic-ray proton and helium spectra with the PAMELA calorimeter
- 2013
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In: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 51:2, s. 219-226
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Journal article (peer-reviewed)abstract
- We present a new measurement of the cosmic ray proton and helium spectra by the PAMELA experiment performed using the "thin" (in terms of nuclei interactions) sampling electromagnetic calorimeter. The described method, optimized by using Monte Carlo simulation, beam test and experimental data, allows the spectra to be measured up to 10 TeV, thus extending the PAMELA observational range based on the magnetic spectrometer measurement.
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4. |
- Adriani, O., et al.
(author)
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Measurements of quasi-trapped electron and positron fluxes with PAMELA
- 2009
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114, s. A12218-
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Journal article (peer-reviewed)abstract
- This paper presents precise measurements of the differential energy spectra of quasi-trapped secondary electrons and positrons and their ratio between 80 MeV and 10 GeV in the near-equatorial region (altitudes between 350 km and 600 km). Latitudinal dependences of the spectra are analyzed in detail. The results were obtained from July until November 2006 onboard the Resurs-DK satellite by the PAMELA spectrometer, a general purpose cosmic ray detector system built around a permanent magnet spectrometer and a silicon-tungsten calorimeter.
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5. |
- Adriani, O., et al.
(author)
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OBSERVATIONS OF THE 2006 DECEMBER 13 AND 14 SOLAR PARTICLE EVENTS IN THE 80 MeV n(-1)-3 GeV n(-1) RANGE FROM SPACE WITH THE PAMELA DETECTOR
- 2011
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In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 742:2, s. 102-
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Journal article (peer-reviewed)abstract
- We present the space spectrometer PAMELA observations of proton and helium fluxes during the 2006 December 13 and 14 solar particle events. This is the first direct measurement of the solar energetic particles in space with a single instrument in the energy range from similar to 80 MeV n(-1) up to similar to 3 GeV n(-1). For the December 13 event, measured energy spectra of solar protons and helium are compared with results obtained by neutron monitors and other detectors. Our measurements show a spectral behavior different from those derived from the neutron monitor network. No satisfactory analytical fitting was found for the energy spectra. During the first hours of the December 13 event, solar energetic particles spectra were close to the exponential form, demonstrating rather significant temporal evolution. Solar He with energy up to 1 GeV n(-1) was recorded on December 13. For the December 14 event, energy of solar protons reached 600 MeV, whereas the maximum energy of He was below 100 MeV n(-1). The spectra were slightly bent in the lower energy range and preserved their form during the second event. Differences in the particle flux appearance and temporal evolution of these two events may argue for special conditions leading to the acceleration of solar particles up to relativistic energies.
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6. |
- Adriani, O., et al.
(author)
-
PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra
- 2011
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 332:6025, s. 69-72
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Journal article (peer-reviewed)abstract
- Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.
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7. |
- Adriani, O., et al.
(author)
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PAMELA Results on the Cosmic-Ray Antiproton Flux from 60 MeV to 180 GeV in Kinetic Energy
- 2010
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:12, s. 121101-
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Journal article (peer-reviewed)abstract
- The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the Galaxy. More precise secondary production models are required for a complete interpretation of the results.
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8. |
- Adriani, O., et al.
(author)
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The discovery of geomagnetically trapped cosmic-ray antiprotons
- 2011
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In: Astrophysical Journal Letters. - 2041-8205. ; 737:2, s. L29-
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Journal article (peer-reviewed)abstract
- The existence of a significant flux of antiprotons confined to Earth's magnetosphere has been considered in several theoretical works. These antiparticles are produced in nuclear interactions of energetic cosmic rays with the terrestrial atmosphere and accumulate in the geomagnetic field at altitudes of several hundred kilometers. A contribution from the decay of albedo antineutrons has been hypothesized in analogy to proton production by neutron decay, which constitutes the main source of trapped protons at energies above some tens of MeV. This Letter reports the discovery of an antiproton radiation belt around the Earth. The trapped antiproton energy spectrum in the South Atlantic Anomaly (SAA) region has been measured by the PAMELA experiment for the kinetic energy range 60-750 MeV. A measurement of the atmospheric sub-cutoff antiproton spectrum outside the radiation belts is also reported. PAMELA data show that the magnetospheric antiproton flux in the SAA exceeds the cosmic-ray antiproton flux by three orders of magnitude at the present solar minimum, and exceeds the sub-cutoff antiproton flux outside radiation belts by four orders of magnitude, constituting the most abundant source of antiprotons near the Earth.
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9. |
- Adriani, O., et al.
(author)
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The PAMELA Space Mission for Antimatter and Dark Matter Searches in Cosmic Rays
- 2010
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In: SCIENCE WITH THE NEW GENERATION OF HIGH-ENERGY GAMMA-RAY EXPERIMENTS. - : AIP. - 9780735407671 ; , s. 33-42
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Conference paper (peer-reviewed)abstract
- On the 15(th) of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The instrument 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 primary scientific goal is the measurement of the antiproton and positron energy spectrum 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. Results of the antiproton and positron data will be presented.
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10. |
- Bazilevskaya, G. A., et al.
(author)
-
Solar energetic particle events in 2006-2012 in the PAMELA experiment data
- 2013
-
In: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 409:1
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Journal article (peer-reviewed)abstract
- The PAMELA magnetic spectrometer launched in June 2006 has observed the last strong energetic solar particle event of the 23rd solar cycle in December 2006. Subsequent long minimum of solar activity and weak development of the 24th solar cycle led to a deficit in the solar energetic particle events on the Earth orbit. As a result, only few events with protons accelerated above 100 MeV occurred in 2010-2012. The paper gives the preliminary results on energetic solar particles in the beginning of the 24th solar circle as measured with the PAMELA instrument.
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11. |
- Bazilevskaya, G. A., et al.
(author)
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Solar proton events at the end of the 23rd and start of the 24th solar cycle recorded in the PAMELA experiment
- 2013
-
In: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 77:5, s. 493-496
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Journal article (peer-reviewed)abstract
- The PAMELA magnetic spectrometer was launched into a near-Earth orbit on board the Resurs-DK1 satellite in June 2006; in December 2006, it recorded the last strong solar high-energy particle event of the 23rd solar cycle. A deficit was thereafter observed in solar energetic particle events because of the lengthy solar activity minimum and the weak evolution of the next (24th) solar cycle. As a result, only a few solar events involving protons with energies of more than 100 MeV were recorded between 2010 and 1012. This work presents the preliminary results from measurements of charged particle fluxes in these events, recorded by the Pamela spectrometer.
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12. |
- Boezio, M., et al.
(author)
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PAMELA and indirect dark matter searches
- 2009
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 105023-
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Journal article (peer-reviewed)abstract
- We present a review of the experimental results obtained by PAMELA in measuring the (p, (p) over bar ) and e(+/-) abundance in cosmic rays. In this context, we discuss the interpretation of the observed anomalous positron excess in terms of the annihilation of dark matter particles as well as in terms of standard astrophysical sources. Moreover we show the constraints on dark matter models from (p) over bar data.
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13. |
- Boezio, M., et al.
(author)
-
The PAMELA space mission for antimatter and dark matter searches in space
- 2012
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In: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 213:1-3, s. 147-158
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Journal article (peer-reviewed)abstract
- 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.
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14. |
- Bruno, A., et al.
(author)
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First detection of geomagnetically trapped antiprotons by the PAMELA experiment
- 2011
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In: Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011. - : Institute of High Energy Physics. ; , s. 86-89
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Conference paper (peer-reviewed)abstract
- We present the measurement of geomagnetically trapped antiprotons in the South Atlantic Anomaly performed by the PAMELA satellite-bourne experiment. The existence of an antiproton radiation belt, predicted by several models as the product of cosmic ray interactions with the residual terrestrial atmosphere, is evidenced for the first time. PAMELA measured the antiproton spectrum in the kinetic energy range between 60 and 750 MeV, reporting a trapped antiproton flux which exceeds by about 3 orders of magnitude the interplanetary cosmic ray antiproton flux. An estimation of the mean under-cutoff antiproton flux outside radiation belts has been also provided.
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15. |
- Bruno, A., et al.
(author)
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Precise cosmic rays measurements with PAMELA
- 2013
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In: Acta Polytechnica. - 1210-2709. ; 53:Suppl.1, s. 712-717
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Journal article (peer-reviewed)abstract
- The PAMELA experiment was launched on board the Resurs-DK1 satellite on June 15th 2006. The apparatus was designed to conduct precision studies of charged cosmic radiation over a wide energy range, from tens of MeV up to several hundred GeV, with unprecedented statistics. In five years of continuous data taking in space, PAMELA accurately measured the energy spectra of cosmic ray antiprotons and positrons, as well as protons, electrons and light nuclei, sometimes providing data in unexplored energetic regions. These important results have shed new light in several astrophysical fields like: an indirect search for Dark Matter, a search for cosmological antimatter (anti-Helium), and the validation of acceleration, transport and secondary production models of cosmic rays in the Galaxy. Some of the most important items of Solar and Magnetospheric physics were also investigated. Here we present the most recent results obtained by the PAMELA experiment.
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16. |
- Bruno, A., et al.
(author)
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Trapped protons in SAA measured by the PAMELA experiment
- 2011
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In: Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011. - : Institute of High Energy Physics. ; , s. 82-85
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Conference paper (peer-reviewed)abstract
- An accurate measurement of under cutoff proton fluxes in the energy range 60 MeV ÷ 3 GeV has been performed by the PAMELA satellite-borne experiment. Thanks to the high identification performances and to the semipolar and elliptic satellite orbit, PAMELA is able to provide information about spectra and composition of particles in different regions of the magnetosphere. Here we present the measurement of the geomagnetically trapped protons from the inner radiation belt (SAA). The fluxes as a function of equatorial pitch angle and McIlwain L-shell are reported.
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17. |
- De Simone, N., et al.
(author)
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Latitudinal and radial gradients of galactic cosmic ray protons in the inner heliosphere - PAMELA and Ulysses observations
- 2011
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In: Astrophysics and Space Sciences Transactions (ASTRA). - : Copernicus GmbH. - 1810-6528 .- 1810-6536. ; 7:3, s. 425-434
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Journal article (peer-reviewed)abstract
- Ulysses, launched on 6 October 1990, was placed in an elliptical, high inclined (80.2°) orbit around the Sun, and was switched off in June 2009. It has been the only spacecraft exploring high-latitude regions of the inner heliosphere. The Kiel Electron Telescope (KET) aboard Ulysses measures electrons from 3 MeV to a few GeV and protons and helium in the energy range from 6 MeV/nucleon to above 2 GeV/nucleon. The PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) space borne experiment was launched on 15 June 2006 and is continuously collecting data since then. The apparatus measures electrons, positrons, protons, anti-protons and heavier nuclei from about 100 MeV to several hundreds of GeV. Thus the combination of Ulysses and PAMELA measurements is ideally suited to determine the spatial gradients during the extended minimum of solar cycle 23. For protons in the rigidity interval 1.6-1.8 GV we find a radial gradient of 2.7%/AU and a latitudinal gradient of -0.024%/degree. Although the latitudinal gradient is as expected negative, its value is much smaller than predicted by current particle propagation models. This result is of relevance for the study of propagation parameters in the inner heliosphere.
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18. |
- De Simone, N., et al.
(author)
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PAMELA : Measurements of matter and antimatter in space
- 2011
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In: Nuovo cimento della societa italiana de fisica. C, Geophysics and space physics. - 1124-1896 .- 1826-9885. ; 34:3, s. 79-87
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Journal article (peer-reviewed)abstract
- 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 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 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 (antihelium), 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 investigates phenomena connected with solar and earth physics. The main results and updated data will be presented.
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19. |
- Guessoum, N., et al.
(author)
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Positron annihilation on polycyclic aromatic hydrocarbon molecules in the interstellar medium
- 2010
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 402:2, s. 1171-1178
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Journal article (peer-reviewed)abstract
- We examine the annihilation of positrons on polycyclic aromatic hydrocarbon (PAH) molecules in interstellar medium (ISM) conditions. We estimate the annihilation rates of positrons on PAHs by a semi-empirical approach. We show that PAHs can play a significant role in the overall Galactic positron annihilation picture and use the annihilation rates and International Gamma-Ray Astrophysics Laboratory Galactic emission measurements to constrain the number of PAHs present in the ISM. We find an upper limit of 4.6 x 10(-7) for the PAH abundance (by number, relative to hydrogen).
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20. |
- Jean, P., et al.
(author)
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Positron transport in the interstellar medium
- 2009
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 508:3, s. 1099-1116
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Journal article (peer-reviewed)abstract
- Aims. We seek to understand the propagation mechanisms of positrons in the interstellar medium (ISM). This understanding is a key to determine whether the spatial distribution of the annihilation emission observed in our Galaxy reflects the spatial distribution of positron sources and, therefore, makes it possible to place constraints on the origin of positrons. Methods. We review the different processes that are likely to affect the transport of positrons in the ISM. These processes fall into three broad categories: scattering off magnetohydrodynamic waves, collisions with particles of the interstellar gas, and advection with large-scale fluid motions. We assess the efficiency of each process and describe its impact on the propagation of positrons. We also develop a model of positron propagation, based on Monte-Carlo simulations, which enable us to estimate the distances traveled by positrons in the different phases of the ISM. Results. We find that low-energy (less than or similar to 10 MeV) positrons generally have negligible interactions with magnetohydrodynamic waves, insofar as these waves are heavily damped. Positron propagation is mainly controlled by collisions with gas particles. Under these circumstances, positrons can travel very large distances (up to similar to 30 kpc/n(H,cm-3) for 1 MeV positrons) along magnetic field lines before annihilating.
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21. |
- Koldobskiy, S. A., et al.
(author)
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Galactic deuteron spectrum measured in PAMELA experiment
- 2013
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In: 23Rd European Cosmic Ray Symposium (And 32Nd Russian Cosmic Ray Conference). - : IOP Publishing.
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Conference paper (peer-reviewed)abstract
- Results of galactic deuteron spectrum measurement by means of PAMELA apparatus are described. PAMELA is an international experiment developed for antimatter search and measurement of p, He, electron and positron spectra in wide energy range. In addition, PAMELA allows to identify and measure deuteron spectrum at low energies. In this paper deuteron-to-proton ratio and deuteron spectrum are presented.
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22. |
- Maiorov, A. G., et al.
(author)
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Solar modulation of the spectra of protons and helium nuclei in the PAMELA experiment
- 2011
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In: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 75:6, s. 779-781
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Journal article (peer-reviewed)abstract
- We present the energy spectra of protons and helium nuclei of cosmic rays obtained in the PAMELA experiment on board the satellite RESURS-DK1 for the period from August 2006 to December 2009. The spectra were measured in the energy range of 100 MeV/nucleon to 100 GeV/nucleon using a magnetic spectrometer within the apparatus. Variations in the solar modulation potential for protons and helium nuclei were calculated on the basis of the monthly mean particle fluxes. A force field model was used to compare the modulation with measurements from balloon experiments, and with measurements from a network of neutron monitors.
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23. |
- Mayorov, A. G., et al.
(author)
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Antiprotons of galactic cosmic radiation in the PAMELA experiment
- 2013
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In: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 77:5, s. 602-605
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Journal article (peer-reviewed)abstract
- A method for antiproton selection against a background of electrons, based on a mathematical model of data classification using variations in interparticle interaction in a calorimeter, and a method for excluding events accompanied by scattering in the inner detectors of a tracking system (which result in errors in the measured trajectory's curvature and charge sign) from analysis are discussed in this paper. Antiproton spectra and antiproton/proton flux ratio at energies of 0.06 to 350 GeV with statistics of events surpassing those in [1] are obtained. The results can be used to create models for the generation and distribution of particles in the Galaxy, and for searching and studying the nature of hypothetical dark matter particles.
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24. |
- Mayorov, A. G., et al.
(author)
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The search for antihelium in cosmic rays using data from the PAMELA experiment
- 2011
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In: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 75:3, s. 331-333
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Journal article (peer-reviewed)abstract
- The generally accepted theory explaining the observed cosmological baryon asymmetry involves mechanisms of baryosynthesis that generate asymmetry in an initially baryon symmetric Universe. Due to the possible inhomogeneous spatial nature of such mechanisms, antimatter domains could arise in the Universe. This hypothesis can be tested by the direct measurement of fluxes of antinuclei in cosmic rays. Searching for antihelium nuclei is therefore among the objectives of the PAMELA experiment. We analyzed data from August 2006 to December 2009 and obtained a preliminary value for the upper limit of the antihelium/helium flux ratio that could lead to some restrictions on the existing theoretical models of the production and propagation of antimatter in the Galaxy.
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25. |
- Mayorov, A. G., et al.
(author)
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Upper limit on the antihelium flux in primary cosmic rays
- 2011
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In: JETP Letters. - 0021-3640 .- 1090-6487. ; 93:11, s. 628-631
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Journal article (peer-reviewed)abstract
- The explanation of the observed baryon asymmetry, i.e., the almost complete absence of antimatter in the visible part of the universe, is one of the most important problems in cosmology. The real asymmetry value can be determined by direct measurements of the fluxes of antinuclei with charges |Z| a (c) 3/4 2 in primary cosmic rays near the Earth. The results of the search for antihelium using data from the PAMELA experiment obtained from June 2006 to December 2009 are presented. No events with a charge of -2 have been detected in the rigidity range of 0.6-600 GV. An upper limit on the antihelium/helium flux ratio has been presented as a function of the energy. An integral upper level of 4.7 x 10(-7) is the lowest limit at rigidities above 14 GV.
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