Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope

M. Ackermann, M. Ajello, A. Allafort, W. B. Atwood, L. Baldini, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, A. Bouvier, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, S. Buson & 131 others G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, E. Charles, A. Chekhtman, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, S. Cutini, A. De Angelis, F. De Palma, C. D. Dermer, S. W. Digel, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, P. Fortin, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, J. E. Grove, S. Guiriec, M. Gustafsson, D. Hadasch, A. K. Harding, M. Hayashida, R. E. Hughes, G. Jóhannesson, A. S. Johnson, T. Kamae, H. Katagiri, Jun Kataoka, J. Knödlseder, M. Kuss, J. Lande, L. Latronico, M. Lemoine-Goumard, M. Llena Garde, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, G. M. Madejski, M. N. Mazziotta, J. E. McEnery, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, P. L. Nolan, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, D. Parent, M. Pesce-Rollins, M. Pierbattista, F. Piron, G. Pivato, T. A. Porter, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, R. W. Romani, M. Roth, H. F W Sadrozinski, C. Sbarra, T. L. Schalk, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, A. W. Strong, H. Takahashi, T. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, L. Tibaldo, M. Tinivella, D. F. Torres, G. Tosti, E. Troja, Y. Uchiyama, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, B. L. Winer, K. S. Wood, M. Wood, Z. Yang, S. Zimmer

    Research output: Contribution to journalArticle

    426 Citations (Scopus)

    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 Earth's shadow, which is offset in opposite directions for opposite charges due to 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 and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.

    Original languageEnglish
    Article number011103
    JournalPhysical Review Letters
    Volume108
    Issue number1
    DOIs
    Publication statusPublished - 2012 Jan 5

    Fingerprint

    cosmic rays
    positrons
    telescopes
    electrons
    magnets
    protons
    energy
    estimates
    magnetic fields

    ASJC Scopus subject areas

    • Physics and Astronomy(all)

    Cite this

    Ackermann, M., Ajello, M., Allafort, A., Atwood, W. B., Baldini, L., Barbiellini, G., ... Zimmer, S. (2012). Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope. Physical Review Letters, 108(1), [011103]. https://doi.org/10.1103/PhysRevLett.108.011103

    Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope. / Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; De Angelis, A.; De Palma, F.; Dermer, C. D.; Digel, S. W.; Do Couto E Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Harding, A. K.; Hayashida, M.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, Jun; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lemoine-Goumard, M.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Parent, D.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Romani, R. W.; Roth, M.; Sadrozinski, H. F W; Sbarra, C.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Strong, A. W.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Wood, M.; Yang, Z.; Zimmer, S.

    In: Physical Review Letters, Vol. 108, No. 1, 011103, 05.01.2012.

    Research output: Contribution to journalArticle

    Ackermann, M, Ajello, M, Allafort, A, Atwood, WB, Baldini, L, Barbiellini, G, Bastieri, D, Bechtol, K, Bellazzini, R, Berenji, B, Blandford, RD, Bloom, ED, Bonamente, E, Borgland, AW, Bouvier, A, Bregeon, J, Brigida, M, Bruel, P, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Casandjian, JM, Cecchi, C, Charles, E, Chekhtman, A, Cheung, CC, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Conrad, J, Cutini, S, De Angelis, A, De Palma, F, Dermer, CD, Digel, SW, Do Couto E Silva, E, Drell, PS, Drlica-Wagner, A, Favuzzi, C, Fegan, SJ, Ferrara, EC, Focke, WB, Fortin, P, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Germani, S, Giglietto, N, Giommi, P, Giordano, F, Giroletti, M, Glanzman, T, Godfrey, G, Grenier, IA, Grove, JE, Guiriec, S, Gustafsson, M, Hadasch, D, Harding, AK, Hayashida, M, Hughes, RE, Jóhannesson, G, Johnson, AS, Kamae, T, Katagiri, H, Kataoka, J, Knödlseder, J, Kuss, M, Lande, J, Latronico, L, Lemoine-Goumard, M, Llena Garde, M, Longo, F, Loparco, F, Lovellette, MN, Lubrano, P, Madejski, GM, Mazziotta, MN, McEnery, JE, Michelson, PF, Mitthumsiri, W, Mizuno, T, Moiseev, AA, Monte, C, Monzani, ME, Morselli, A, Moskalenko, IV, Murgia, S, Nakamori, T, Nolan, PL, Norris, JP, Nuss, E, Ohno, M, Ohsugi, T, Okumura, A, Omodei, N, Orlando, E, Ormes, JF, Ozaki, M, Paneque, D, Parent, D, Pesce-Rollins, M, Pierbattista, M, Piron, F, Pivato, G, Porter, TA, Rainò, S, Rando, R, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Reposeur, T, Ritz, S, Romani, RW, Roth, M, Sadrozinski, HFW, Sbarra, C, Schalk, TL, Sgrò, C, Siskind, EJ, Spandre, G, Spinelli, P, Strong, AW, Takahashi, H, Takahashi, T, Tanaka, T, Thayer, JG, Thayer, JB, Tibaldo, L, Tinivella, M, Torres, DF, Tosti, G, Troja, E, Uchiyama, Y, Usher, TL, Vandenbroucke, J, Vasileiou, V, Vianello, G, Vitale, V, Waite, AP, Winer, BL, Wood, KS, Wood, M, Yang, Z & Zimmer, S 2012, 'Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope', Physical Review Letters, vol. 108, no. 1, 011103. https://doi.org/10.1103/PhysRevLett.108.011103
    Ackermann, M. ; Ajello, M. ; Allafort, A. ; Atwood, W. B. ; Baldini, L. ; Barbiellini, G. ; Bastieri, D. ; Bechtol, K. ; Bellazzini, R. ; Berenji, B. ; Blandford, R. D. ; Bloom, E. D. ; Bonamente, E. ; Borgland, A. W. ; Bouvier, A. ; Bregeon, J. ; Brigida, M. ; Bruel, P. ; Buehler, R. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Caraveo, P. A. ; Casandjian, J. M. ; Cecchi, C. ; Charles, E. ; Chekhtman, A. ; Cheung, C. C. ; Chiang, J. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; Conrad, J. ; Cutini, S. ; De Angelis, A. ; De Palma, F. ; Dermer, C. D. ; Digel, S. W. ; Do Couto E Silva, E. ; Drell, P. S. ; Drlica-Wagner, A. ; Favuzzi, C. ; Fegan, S. J. ; Ferrara, E. C. ; Focke, W. B. ; Fortin, P. ; Fukazawa, Y. ; Funk, S. ; Fusco, P. ; Gargano, F. ; Gasparrini, D. ; Germani, S. ; Giglietto, N. ; Giommi, P. ; Giordano, F. ; Giroletti, M. ; Glanzman, T. ; Godfrey, G. ; Grenier, I. A. ; Grove, J. E. ; Guiriec, S. ; Gustafsson, M. ; Hadasch, D. ; Harding, A. K. ; Hayashida, M. ; Hughes, R. E. ; Jóhannesson, G. ; Johnson, A. S. ; Kamae, T. ; Katagiri, H. ; Kataoka, Jun ; Knödlseder, J. ; Kuss, M. ; Lande, J. ; Latronico, L. ; Lemoine-Goumard, M. ; Llena Garde, M. ; Longo, F. ; Loparco, F. ; Lovellette, M. N. ; Lubrano, P. ; Madejski, G. M. ; Mazziotta, M. N. ; McEnery, J. E. ; Michelson, P. F. ; Mitthumsiri, W. ; Mizuno, T. ; Moiseev, A. A. ; Monte, C. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Nakamori, T. ; Nolan, P. L. ; Norris, J. P. ; Nuss, E. ; Ohno, M. ; Ohsugi, T. ; Okumura, A. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Ozaki, M. ; Paneque, D. ; Parent, D. ; Pesce-Rollins, M. ; Pierbattista, M. ; Piron, F. ; Pivato, G. ; Porter, T. A. ; Rainò, S. ; Rando, R. ; Razzano, M. ; Razzaque, S. ; Reimer, A. ; Reimer, O. ; Reposeur, T. ; Ritz, S. ; Romani, R. W. ; Roth, M. ; Sadrozinski, H. F W ; Sbarra, C. ; Schalk, T. L. ; Sgrò, C. ; Siskind, E. J. ; Spandre, G. ; Spinelli, P. ; Strong, A. W. ; Takahashi, H. ; Takahashi, T. ; Tanaka, T. ; Thayer, J. G. ; Thayer, J. B. ; Tibaldo, L. ; Tinivella, M. ; Torres, D. F. ; Tosti, G. ; Troja, E. ; Uchiyama, Y. ; Usher, T. L. ; Vandenbroucke, J. ; Vasileiou, V. ; Vianello, G. ; Vitale, V. ; Waite, A. P. ; Winer, B. L. ; Wood, K. S. ; Wood, M. ; Yang, Z. ; Zimmer, S. / Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope. In: Physical Review Letters. 2012 ; Vol. 108, No. 1.
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    title = "Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope",
    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 Earth's shadow, which is offset in opposite directions for opposite charges due to 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 and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.",
    author = "M. Ackermann and M. Ajello and A. Allafort and Atwood, {W. B.} and L. Baldini and G. Barbiellini and D. Bastieri and K. Bechtol and R. Bellazzini and B. Berenji and Blandford, {R. D.} and Bloom, {E. D.} and E. Bonamente and Borgland, {A. W.} and A. Bouvier and J. Bregeon and M. Brigida and P. Bruel and R. Buehler and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and Casandjian, {J. M.} and C. Cecchi and E. Charles and A. Chekhtman and Cheung, {C. C.} and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and J. Conrad and S. Cutini and {De Angelis}, A. and {De Palma}, F. and Dermer, {C. D.} and Digel, {S. W.} and {Do Couto E Silva}, E. and Drell, {P. S.} and A. Drlica-Wagner and C. Favuzzi and Fegan, {S. J.} and Ferrara, {E. C.} and Focke, {W. B.} and P. Fortin and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and S. Germani and N. Giglietto and P. Giommi and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and Grenier, {I. A.} and Grove, {J. E.} and S. Guiriec and M. Gustafsson and D. Hadasch and Harding, {A. K.} and M. Hayashida and Hughes, {R. E.} and G. J{\'o}hannesson and Johnson, {A. S.} and T. Kamae and H. Katagiri and Jun Kataoka and J. Kn{\"o}dlseder and M. Kuss and J. Lande and L. Latronico and M. Lemoine-Goumard and {Llena Garde}, M. and F. Longo and F. Loparco and Lovellette, {M. N.} and P. Lubrano and Madejski, {G. M.} and Mazziotta, {M. N.} and McEnery, {J. E.} and Michelson, {P. F.} and W. Mitthumsiri and T. Mizuno and Moiseev, {A. A.} and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and T. Nakamori and Nolan, {P. L.} and Norris, {J. P.} and E. Nuss and M. Ohno and T. Ohsugi and A. Okumura and N. Omodei and E. Orlando and Ormes, {J. F.} and M. Ozaki and D. Paneque and D. Parent and M. Pesce-Rollins and M. Pierbattista and F. Piron and G. Pivato and Porter, {T. A.} and S. Rain{\`o} and R. Rando and M. Razzano and S. Razzaque and A. Reimer and O. Reimer and T. Reposeur and S. Ritz and Romani, {R. W.} and M. Roth and Sadrozinski, {H. F W} and C. Sbarra and Schalk, {T. L.} and C. Sgr{\`o} and Siskind, {E. J.} and G. Spandre and P. Spinelli and Strong, {A. W.} and H. Takahashi and T. Takahashi and T. Tanaka and Thayer, {J. G.} and Thayer, {J. B.} and L. Tibaldo and M. Tinivella and Torres, {D. F.} and G. Tosti and E. Troja and Y. Uchiyama and Usher, {T. L.} and J. Vandenbroucke and V. Vasileiou and G. Vianello and V. Vitale and Waite, {A. P.} and Winer, {B. L.} and Wood, {K. S.} and M. Wood and Z. Yang and S. Zimmer",
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    TY - JOUR

    T1 - Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope

    AU - Ackermann, M.

    AU - Ajello, M.

    AU - Allafort, A.

    AU - Atwood, W. B.

    AU - Baldini, L.

    AU - Barbiellini, G.

    AU - Bastieri, D.

    AU - Bechtol, K.

    AU - Bellazzini, R.

    AU - Berenji, B.

    AU - Blandford, R. D.

    AU - Bloom, E. D.

    AU - Bonamente, E.

    AU - Borgland, A. W.

    AU - Bouvier, A.

    AU - Bregeon, J.

    AU - Brigida, M.

    AU - Bruel, P.

    AU - Buehler, R.

    AU - Buson, S.

    AU - Caliandro, G. A.

    AU - Cameron, R. A.

    AU - Caraveo, P. A.

    AU - Casandjian, J. M.

    AU - Cecchi, C.

    AU - Charles, E.

    AU - Chekhtman, A.

    AU - Cheung, C. C.

    AU - Chiang, J.

    AU - Ciprini, S.

    AU - Claus, R.

    AU - Cohen-Tanugi, J.

    AU - Conrad, J.

    AU - Cutini, S.

    AU - De Angelis, A.

    AU - De Palma, F.

    AU - Dermer, C. D.

    AU - Digel, S. W.

    AU - Do Couto E Silva, E.

    AU - Drell, P. S.

    AU - Drlica-Wagner, A.

    AU - Favuzzi, C.

    AU - Fegan, S. J.

    AU - Ferrara, E. C.

    AU - Focke, W. B.

    AU - Fortin, P.

    AU - Fukazawa, Y.

    AU - Funk, S.

    AU - Fusco, P.

    AU - Gargano, F.

    AU - Gasparrini, D.

    AU - Germani, S.

    AU - Giglietto, N.

    AU - Giommi, P.

    AU - Giordano, F.

    AU - Giroletti, M.

    AU - Glanzman, T.

    AU - Godfrey, G.

    AU - Grenier, I. A.

    AU - Grove, J. E.

    AU - Guiriec, S.

    AU - Gustafsson, M.

    AU - Hadasch, D.

    AU - Harding, A. K.

    AU - Hayashida, M.

    AU - Hughes, R. E.

    AU - Jóhannesson, G.

    AU - Johnson, A. S.

    AU - Kamae, T.

    AU - Katagiri, H.

    AU - Kataoka, Jun

    AU - Knödlseder, J.

    AU - Kuss, M.

    AU - Lande, J.

    AU - Latronico, L.

    AU - Lemoine-Goumard, M.

    AU - Llena Garde, M.

    AU - Longo, F.

    AU - Loparco, F.

    AU - Lovellette, M. N.

    AU - Lubrano, P.

    AU - Madejski, G. M.

    AU - Mazziotta, M. N.

    AU - McEnery, J. E.

    AU - Michelson, P. F.

    AU - Mitthumsiri, W.

    AU - Mizuno, T.

    AU - Moiseev, A. A.

    AU - Monte, C.

    AU - Monzani, M. E.

    AU - Morselli, A.

    AU - Moskalenko, I. V.

    AU - Murgia, S.

    AU - Nakamori, T.

    AU - Nolan, P. L.

    AU - Norris, J. P.

    AU - Nuss, E.

    AU - Ohno, M.

    AU - Ohsugi, T.

    AU - Okumura, A.

    AU - Omodei, N.

    AU - Orlando, E.

    AU - Ormes, J. F.

    AU - Ozaki, M.

    AU - Paneque, D.

    AU - Parent, D.

    AU - Pesce-Rollins, M.

    AU - Pierbattista, M.

    AU - Piron, F.

    AU - Pivato, G.

    AU - Porter, T. A.

    AU - Rainò, S.

    AU - Rando, R.

    AU - Razzano, M.

    AU - Razzaque, S.

    AU - Reimer, A.

    AU - Reimer, O.

    AU - Reposeur, T.

    AU - Ritz, S.

    AU - Romani, R. W.

    AU - Roth, M.

    AU - Sadrozinski, H. F W

    AU - Sbarra, C.

    AU - Schalk, T. L.

    AU - Sgrò, C.

    AU - Siskind, E. J.

    AU - Spandre, G.

    AU - Spinelli, P.

    AU - Strong, A. W.

    AU - Takahashi, H.

    AU - Takahashi, T.

    AU - Tanaka, T.

    AU - Thayer, J. G.

    AU - Thayer, J. B.

    AU - Tibaldo, L.

    AU - Tinivella, M.

    AU - Torres, D. F.

    AU - Tosti, G.

    AU - Troja, E.

    AU - Uchiyama, Y.

    AU - Usher, T. L.

    AU - Vandenbroucke, J.

    AU - Vasileiou, V.

    AU - Vianello, G.

    AU - Vitale, V.

    AU - Waite, A. P.

    AU - Winer, B. L.

    AU - Wood, K. S.

    AU - Wood, M.

    AU - Yang, Z.

    AU - Zimmer, S.

    PY - 2012/1/5

    Y1 - 2012/1/5

    N2 - 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 Earth's shadow, which is offset in opposite directions for opposite charges due to 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 and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.

    AB - 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 Earth's shadow, which is offset in opposite directions for opposite charges due to 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 and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.

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    UR - http://www.scopus.com/inward/citedby.url?scp=84860117875&partnerID=8YFLogxK

    U2 - 10.1103/PhysRevLett.108.011103

    DO - 10.1103/PhysRevLett.108.011103

    M3 - Article

    VL - 108

    JO - Physical Review Letters

    JF - Physical Review Letters

    SN - 0031-9007

    IS - 1

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    ER -