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Measurement of separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope

Markus Ackermann 1 Marco Ajello 2 A. Allafort 2 W. B. Atwood 3 Luca Baldini 4 Guido Barbiellini 5 D. Bastieri 6 K. Bechtol 2 R. Bellazzini 4 B. Berenji 2 R. D. Blandford 2 E. D. Bloom 2 E. Bonamente 7 A.W. Borgland 2 A. Bouvier 3 J. Bregeon 4 M. Brigida 8, 9 Pascal Bruel 10 R. Buehler 10 S. Buson 6 G. A. Caliandro 11 R. A. Cameron 2 P. A. Caraveo 12 J. M. Casandjian 13 C. Cecchi 7 E. Charles 2 A. Chekhtman 14 C. C. Cheung 15 J. Chiang 2 S. Ciprini 16 R. Claus 2 J. Cohen-Tanugi 17 J. Conrad 18 S. Cutini 19 A. de Angelis 5 F. de Palma 9 C. D. Dermer 20 S.W. Digel 2 E. Do Couto E Silva 2 P. S. Drell 2 A. Drlica-Wagner 2 C. Favuzzi 9 S. J. Fegan 10 E. C. Ferrara 21 W. B. Focke 2 P. Fortin 10 Y. Fukazawa 22 S. Funk 2 P. Fusco 9 F. Gargano 9 D. Gasparrini 19 S. Germani 7 N. Giglietto 9 P. Giommi 19 F. Giordano 9 M. Giroletti 23 T. Glanzman 2 G. Godfrey 2 I. A. Grenier 13 J. E. Grove 20 S. Guiriec 24 M. Gustafsson 6 D. Hadasch 11 A. K. Harding 20 M. Hayashida 2, 25 R. E. Hughes 26 G. Jo'Hannesson 27 A. S. Johnson 2 T. Kamae 2 H. Katagiri 28 J. Kataoka 29 J. Kno¨dlseder 30, 31 M. Kuss 4 J. Lande 2 L. Latronico 32 M. Lemoine-Goumard 33 M. Llena Garde 34 F. Longo 5 F. Loparco 9 M. N. Lovellette 35 P. Lubrano 36 G. M. Madejski 2 M. N. Mazziotta 9 J. E. Mcenery 21 P. F. Michelson 2 W. Mitthumsiri 2 T. Mizuno 22 A. A. Moiseev 37, 38 C. Monte 9 M. E. Monzani 2 A. Morselli I.V. Moskalenko 2 S. Murgia 2 T. Nakamori P. L. Nolan 2 J. P. Norris E. Nuss 17 M. Ohno T. Ohsugi A. Okumura 2 N. Omodei 2 E. Orlando 2 J. F. Ormes M. Ozaki D. Paneque 2 D. Parent 39 M. Pesce-Rollins M. Pierbattista 13 F. Piron 17 G. Pivato T.A. Porter S. Raino' R. Rando M. Razzano S. Razzaque A. Reimer 2 O. Reimer 2 T. Reposeur 33 S. Ritz R.W. Romani 2 M. Roth H. F.-W. Sadrozinski C. Sbarra T. L. Schalk C. Sgro' E. J. Siskind G. Spandre P. Spinelli A.W. Strong H. Takahashi T. Takahashi T. Tanaka 2 J. G. Thayer 2 J. B. Thayer 2 L. Tibaldo M. Tinivella D. F. Torres G. Tosti E. Troja Y. Uchiyama 2 T. L. Usher 2 J. Vandenbroucke 2 V. Vasileiou 17 G. Vianello 2 V. Vitale A. P. Waite 2 B. L. Winer 26 K. S. Wood 35 M. Wood 2 Z. Yang 18 S. Zimmer 18
31 GAHEC - Galaxies, Astrophysique des Hautes Energies et Cosmologie
IRAP - Institut de recherche en astrophysique et planétologie
Abstract : We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting the Earth's shadow, which is offset in opposite directions for opposite charges due to the Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 GeV and 200 GeV. We confirm that the fraction rises with energy in the 20--100 GeV range and determine for the first time that it continues to rise between 100 and 200 GeV.
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Markus Ackermann, Marco Ajello, A. Allafort, W. B. Atwood, Luca Baldini, et al.. Measurement of separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Physical Review Letters, American Physical Society, 2012, 108, pp.0111103. ⟨10.1103/PhysRevLett.108.011103⟩. ⟨in2p3-00665926⟩

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