PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) was a cosmic ray research module attached to an Earth orbiting satellite. PAMELA was launched on 15 June 2006 and was the first satellite-based experiment dedicated to the detection of cosmic rays, with a particular focus on their antimatter component, in the form of positrons and antiprotons. Other objectives included long-term monitoring of the solar modulation of cosmic rays, measurements of energetic particles from the Sun, high-energy particles in Earth's magnetosphere and Jovian electrons. It was also hoped that it may detect evidence of dark matter annihilation.[1] PAMELA operations were terminated in 2016,[2] as were the operations of the host-satellite Resurs-DK1. The experiment was a recognized CERN experiment (RE2B).[3][4]
PAMELA was the largest device up to the time built by the Wizard collaboration, which includes Russia, Italy, Germany and Sweden and has been involved in many satellite and balloon-based cosmic ray experiments such as Fermi-GLAST. The 470 kg, US$32 million (EU€24.8 million, UK£16.8 million) instrument was originally projected to have a three-year mission. However, this durable module remained operational and made significant scientific contributions until 2016.
PAMELA is mounted on the upward-facing side of the Resurs-DK1 Russian satellite.[1] It was launched by a Soyuz rocket from Baikonur Cosmodrome on 15 June 2006. PAMELA has been put in a polar elliptical orbit at an altitude between 350 and 610 km, with an inclination of 70°.
Design
The apparatus is 1.3 m high, has a total mass of 470 kg and a power consumption of 335 W. The instrument is built around a permanent magnet spectrometer with a silicon microstrip tracker that provides rigidity and dE/dx information. At its bottom is a silicon-tungsten imaging calorimeter, a neutron detector and a shower tail scintillator to perform lepton/hadron discrimination. A Time of Flight (ToF), made of three layers of plastic scintillators, is used to measure the velocity and charge of the particle. An anticounter system made of scintillators surrounding the apparatus is used to reject false triggers and albedo particles during off-line analysis.[5]
Preliminary data (released August 2008, ICHEP Philadelphia) indicate an excess of positrons in the range 10–60 GeV. This is thought to be a possible sign of dark matter annihilation:[6][7] hypothetical WIMPs colliding with and annihilating each other to form gamma rays, matter and antimatter particles. Another explanation considered for the indication mentioned above is the production of electron-positron pairs on pulsars with subsequent acceleration in the vicinity of the pulsar.
The first two years of data were released in October 2008 in three publications.[8][9] The positron excess was confirmed and found to persist up to 90 GeV. Surprisingly, no excess of antiprotons was found. This is inconsistent with predictions from most models of dark matter sources, in which the positron and antiproton excesses are correlated.
A paper, published on 15 July 2011, confirmed earlier speculation that the Van Allen belt could confine a significant flux of antiprotons produced by the interaction of the Earth's upper atmosphere with cosmic rays.[10] The energy of the antiprotons has been measured in the range of 60–750 MeV. Cosmic rays collide with atoms in the upper atmosphere creating antineutrons, which in turn decay to produce the antiprotons. They were discovered in a part of the Van Allen belt closest to Earth.[11] When an antiproton interacts with a normal particle, both are annihilated. Data from PAMELA indicated that these annihilation events occurred a thousand times more often than would be expected in the absence of antimatter. The data that contained evidence of antimatter were gathered between July 2006 and December 2008.[12][13]
Boron and carbon flux measurements were published in July 2014,[14] important to explaining trends in cosmic ray positron fraction.[15]
The summary document of the operations of PAMELA was published in 2017.[2]
Sources of error
Between 1 and 100 GeV, PAMELA is exposed to one hundred times as many electrons as antiprotons. At 1 GeV there are one thousand times as many protons as positrons and at 100 GeV ten thousand times as many. Therefore, to correctly determine the antimatter abundances, it is critical that PAMELA is able to reject the matter background. The PAMELA collaboration claimed in "The electron hadron separation performance of the PAMELA electromagnetic calorimeter" that less than one proton in 100,000 is able to pass the calorimeter selection and be misidentified as a positron when the energy is less than 200 GeV.
The ratio of matter to antimatter in cosmic rays of energy less than 10 GeV that reach PAMELA from outside the Solar System depends on solar activity and in particular on the point in the 11 year solar cycle. The PAMELA team has invoked this effect to explain the discrepancy between their low energy results and those obtained by CAPRICE, HEAT and AMS-01, which were collected during that half of the cycle when the solar magnetic field had the opposite polarity. It is important to note that these results are consistent with the series of positron / electron measurements obtain by AESOP, which has spanned coverage over both polarities. Also the PAMELA experiment has contradicted an earlier claim by the HEAT experiment of anomalous positrons in the 6 GeV to 10 GeV range.
See also
AMS-02 is a high energy physics experiment mounted to the exterior of the International Space Station featuring advanced particle identification and large acceptance of 0.3m2sr. AMS-02 has been in operation since May 2011. More than 100 billion charged cosmic ray events were recorded by AMS so far.
References
^ abcVincenzo Buttaro (ed.). "The Space Mission PAMELA". Retrieved 4 September 2009.
^ abAdriani, O; et al. (PAMELA Collaboration) (2018). "Ten Years of PAMELA in Space". Rivista del Nuovo Cimento. 10 (2017): 473–522. arXiv:1801.10310. Bibcode:2018arXiv180110310A. doi:10.1393/ncr/i2017-10140-x. S2CID 119078426.
^"Recognized Experiments at CERN". The CERN Scientific Committees. CERN. Retrieved 20 January 2020.
^"RE2B/PAMELA : A Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics". CERN. Retrieved 20 January 2020.
^Casolino, M; et al. (2008). "Launch of the Space experiment PAMELA". Advances in Space Research. 42 (3): 455–466. arXiv:0708.1808. Bibcode:2008AdSpR..42..455C. doi:10.1016/j.asr.2007.07.023. S2CID 119608020.
^Cholis, Ilias; Finkbeiner, Douglas P; Goodenough, Lisa; Weiner, Neal (2009). "The PAMELA Positron Excess from Annihilations into a Light Boson". Journal of Cosmology and Astroparticle Physics. 2009 (12): 007. arXiv:0810.5344. Bibcode:2009JCAP...12..007C. doi:10.1088/1475-7516/2009/12/007. S2CID 73574983.
^Casolino, M; et al. (2008). "Two years of flight of the Pamela experiment: Results and perspectives". Journal of the Physical Society of Japan. 78: 35–40. arXiv:0810.4980. Bibcode:2009JPSJ...78S..35C. doi:10.1143/JPSJS.78SA.35. S2CID 119187767.
^Adriani, O; et al. (2009). "Observation of an anomalous positron abundance in the cosmic radiation". Nature. 458 (7238): 607–609. arXiv:0810.4995. Bibcode:2009Natur.458..607A. doi:10.1038/nature07942. PMID 19340076. S2CID 11675154.
^Adriani, O.; et al. (2011). "The Discovery of Geomagnetically Trapped Cosmic-Ray Antiprotons". The Astrophysical Journal Letters. 737 (2): L29. arXiv:1107.4882. Bibcode:2011ApJ...737L..29A. doi:10.1088/2041-8205/737/2/L29.
^Than, Ker (10 August 2011). "Antimatter Found Orbiting Earth—A First". National Geographic Society. Retrieved 12 August 2011.
^Cowen, Ron (9 August 2011). . Science. Archived from the original on 24 October 2011. Retrieved 12 August 2011.
^Chung, Emily (8 August 2011). "Antimatter belt surrounds Earth". CBC News. Retrieved 12 August 2011.
^Adriani, O; et al. (31 July 2014). "Measurement of Boron and Carbon Fluxes in Cosmic Rays with the Pamela Experiment". Astrophysical Journal. 791 (2): 93. arXiv:1407.1657. Bibcode:2014ApJ...791...93A. doi:10.1088/0004-637X/791/2/93. S2CID 53002540.
^Cholis, Ilias; Hooper, Dan (24 February 2014). "Constraining the origin of the rising cosmic ray positron fraction with the boron-to-carbon ratio". Physical Review D. 89 (4): 043013. arXiv:1312.2952. Bibcode:2014PhRvD..89d3013C. doi:10.1103/PhysRevD.89.043013. S2CID 96470471.
External links
PAMELA experiment's old homepage
PAMELA experiment's homepage
January 29, 2023
pamela, detector, other, uses, pamela, disambiguation, pamela, payload, antimatter, matter, exploration, light, nuclei, astrophysics, cosmic, research, module, attached, earth, orbiting, satellite, pamela, launched, june, 2006, first, satellite, based, experim. For other uses see PAMELA disambiguation PAMELA Payload for Antimatter Matter Exploration and Light nuclei Astrophysics was a cosmic ray research module attached to an Earth orbiting satellite PAMELA was launched on 15 June 2006 and was the first satellite based experiment dedicated to the detection of cosmic rays with a particular focus on their antimatter component in the form of positrons and antiprotons Other objectives included long term monitoring of the solar modulation of cosmic rays measurements of energetic particles from the Sun high energy particles in Earth s magnetosphere and Jovian electrons It was also hoped that it may detect evidence of dark matter annihilation 1 PAMELA operations were terminated in 2016 2 as were the operations of the host satellite Resurs DK1 The experiment was a recognized CERN experiment RE2B 3 4 PAMELA Organization PAMELA groupMission Type Cosmic RayHost Satellite Resurs DK1Launch 15 June 2006Launch vehicle Soyuz FGLaunch site Baikonur CosmodromeMission duration 3 years planned over 9 years achievedMission end 7 February 2016Mass 470 kgMax length 1300 mmPower consumption 335 WattsWebpage PAMELA homepageOrbital elements Resurs DK1 Inclination 70 degreesOrbit quasi polar ellipticalMin altitude 360 kmMax altitude 604 kmPeriod 94 02 min Contents 1 Development and launch 2 Design 3 Results 4 Sources of error 5 See also 6 References 7 External linksDevelopment and launch EditPAMELA was the largest device up to the time built by the Wizard collaboration which includes Russia Italy Germany and Sweden and has been involved in many satellite and balloon based cosmic ray experiments such as Fermi GLAST The 470 kg US 32 million EU 24 8 million UK 16 8 million instrument was originally projected to have a three year mission However this durable module remained operational and made significant scientific contributions until 2016 PAMELA is mounted on the upward facing side of the Resurs DK1 Russian satellite 1 It was launched by a Soyuz rocket from Baikonur Cosmodrome on 15 June 2006 PAMELA has been put in a polar elliptical orbit at an altitude between 350 and 610 km with an inclination of 70 Design EditThe apparatus is 1 3 m high has a total mass of 470 kg and a power consumption of 335 W The instrument is built around a permanent magnet spectrometer with a silicon microstrip tracker that provides rigidity and dE dx information At its bottom is a silicon tungsten imaging calorimeter a neutron detector and a shower tail scintillator to perform lepton hadron discrimination A Time of Flight ToF made of three layers of plastic scintillators is used to measure the velocity and charge of the particle An anticounter system made of scintillators surrounding the apparatus is used to reject false triggers and albedo particles during off line analysis 5 Sensitivity 1 Particle Energy RangeAntiproton flux 80 MeV 190 GeVPositron flux 50 MeV 270 GeVElectron flux up to 400 GeVProton flux up to 700 GeVElectron positron flux up to 2 TeVLight nuclei up to Z 6 up to 200 GeV nLight isotopes D 3He up to 1 GeV nAntinuclei search sensitivity better than 10 7 antiHe HeResults EditPreliminary data released August 2008 ICHEP Philadelphia indicate an excess of positrons in the range 10 60 GeV This is thought to be a possible sign of dark matter annihilation 6 7 hypothetical WIMPs colliding with and annihilating each other to form gamma rays matter and antimatter particles Another explanation considered for the indication mentioned above is the production of electron positron pairs on pulsars with subsequent acceleration in the vicinity of the pulsar The first two years of data were released in October 2008 in three publications 8 9 The positron excess was confirmed and found to persist up to 90 GeV Surprisingly no excess of antiprotons was found This is inconsistent with predictions from most models of dark matter sources in which the positron and antiproton excesses are correlated A paper published on 15 July 2011 confirmed earlier speculation that the Van Allen belt could confine a significant flux of antiprotons produced by the interaction of the Earth s upper atmosphere with cosmic rays 10 The energy of the antiprotons has been measured in the range of 60 750 MeV Cosmic rays collide with atoms in the upper atmosphere creating antineutrons which in turn decay to produce the antiprotons They were discovered in a part of the Van Allen belt closest to Earth 11 When an antiproton interacts with a normal particle both are annihilated Data from PAMELA indicated that these annihilation events occurred a thousand times more often than would be expected in the absence of antimatter The data that contained evidence of antimatter were gathered between July 2006 and December 2008 12 13 Boron and carbon flux measurements were published in July 2014 14 important to explaining trends in cosmic ray positron fraction 15 The summary document of the operations of PAMELA was published in 2017 2 Sources of error EditBetween 1 and 100 GeV PAMELA is exposed to one hundred times as many electrons as antiprotons At 1 GeV there are one thousand times as many protons as positrons and at 100 GeV ten thousand times as many Therefore to correctly determine the antimatter abundances it is critical that PAMELA is able to reject the matter background The PAMELA collaboration claimed in The electron hadron separation performance of the PAMELA electromagnetic calorimeter that less than one proton in 100 000 is able to pass the calorimeter selection and be misidentified as a positron when the energy is less than 200 GeV The ratio of matter to antimatter in cosmic rays of energy less than 10 GeV that reach PAMELA from outside the Solar System depends on solar activity and in particular on the point in the 11 year solar cycle The PAMELA team has invoked this effect to explain the discrepancy between their low energy results and those obtained by CAPRICE HEAT and AMS 01 which were collected during that half of the cycle when the solar magnetic field had the opposite polarity It is important to note that these results are consistent with the series of positron electron measurements obtain by AESOP which has spanned coverage over both polarities Also the PAMELA experiment has contradicted an earlier claim by the HEAT experiment of anomalous positrons in the 6 GeV to 10 GeV range See also EditAMS 02 is a high energy physics experiment mounted to the exterior of the International Space Station featuring advanced particle identification and large acceptance of 0 3m2sr AMS 02 has been in operation since May 2011 More than 100 billion charged cosmic ray events were recorded by AMS so far References Edit a b c Vincenzo Buttaro ed The Space Mission PAMELA Retrieved 4 September 2009 a b Adriani O et al PAMELA Collaboration 2018 Ten Years of PAMELA in Space Rivista del Nuovo Cimento 10 2017 473 522 arXiv 1801 10310 Bibcode 2018arXiv180110310A doi 10 1393 ncr i2017 10140 x S2CID 119078426 Recognized Experiments at CERN The CERN Scientific Committees CERN Retrieved 20 January 2020 RE2B PAMELA A Payload for Antimatter Matter Exploration and Light nuclei Astrophysics CERN Retrieved 20 January 2020 Casolino M et al 2008 Launch of the Space experiment PAMELA Advances in Space Research 42 3 455 466 arXiv 0708 1808 Bibcode 2008AdSpR 42 455C doi 10 1016 j asr 2007 07 023 S2CID 119608020 Brumfiel Geoff 14 August 2008 Physicists await dark matter confirmation Nature 454 7206 808 809 doi 10 1038 454808b PMID 18704050 Cholis Ilias Finkbeiner Douglas P Goodenough Lisa Weiner Neal 2009 The PAMELA Positron Excess from Annihilations into a Light Boson Journal of Cosmology and Astroparticle Physics 2009 12 007 arXiv 0810 5344 Bibcode 2009JCAP 12 007C doi 10 1088 1475 7516 2009 12 007 S2CID 73574983 Casolino M et al 2008 Two years of flight of the Pamela experiment Results and perspectives Journal of the Physical Society of Japan 78 35 40 arXiv 0810 4980 Bibcode 2009JPSJ 78S 35C doi 10 1143 JPSJS 78SA 35 S2CID 119187767 Adriani O et al 2009 Observation of an anomalous positron abundance in the cosmic radiation Nature 458 7238 607 609 arXiv 0810 4995 Bibcode 2009Natur 458 607A doi 10 1038 nature07942 PMID 19340076 S2CID 11675154 Adriani O et al 2011 The Discovery of Geomagnetically Trapped Cosmic Ray Antiprotons The Astrophysical Journal Letters 737 2 L29 arXiv 1107 4882 Bibcode 2011ApJ 737L 29A doi 10 1088 2041 8205 737 2 L29 Than Ker 10 August 2011 Antimatter Found Orbiting Earth A First National Geographic Society Retrieved 12 August 2011 Cowen Ron 9 August 2011 Antimatter Belt Found Circling Earth Science Archived from the original on 24 October 2011 Retrieved 12 August 2011 Chung Emily 8 August 2011 Antimatter belt surrounds Earth CBC News Retrieved 12 August 2011 Adriani O et al 31 July 2014 Measurement of Boron and Carbon Fluxes in Cosmic Rays with the Pamela Experiment Astrophysical Journal 791 2 93 arXiv 1407 1657 Bibcode 2014ApJ 791 93A doi 10 1088 0004 637X 791 2 93 S2CID 53002540 Cholis Ilias Hooper Dan 24 February 2014 Constraining the origin of the rising cosmic ray positron fraction with the boron to carbon ratio Physical Review D 89 4 043013 arXiv 1312 2952 Bibcode 2014PhRvD 89d3013C doi 10 1103 PhysRevD 89 043013 S2CID 96470471 External links EditPAMELA experiment s old homepage PAMELA experiment s homepage Retrieved from https en wikipedia org w index php title PAMELA detector amp oldid 1061571268, wikipedia, wiki, book, books, library,
