Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum

A. Aab, P. Abreu, M. Aglietta, E. J. Ahn, I. Al Samarai, I. F M Albuquerque, I. Allekotte, P. Allison, A. Almela, J. Alvarez Castillo, J. Alvarez-Muñiz, M. Ambrosio, G. A. Anastasi, L. Anchordoqui, B. Andrada, S. Andringa, C. Aramo, F. Arqueros, N. Arsene, H. AsoreyP. Assis, J. Aublin, G. Avila, A. M. Badescu, A. Balaceanu, C. Baus, J. J. Beatty, K. H. Becker, J. A. Bellido, C. Berat, M. E. Bertaina, X. Bertou, P. L. Biermann, P. Billoir, J. Biteau, S. G. Blaess, A. Blanco, J. Blazek, C. Bleve, M. Boháčová, D. Boncioli, C. Bonifazi, N. Borodai, A. M. Botti, J. Brack, I. Brancus, T. Bretz, A. Bridgeman, F. L. Briechle, P. Buchholz, A. Bueno, S. Buitink, M. Buscemi, K. S. Caballero-Mora, B. Caccianiga, L. Caccianiga, A. Cancio, F. Canfora, L. Caramete, R. Caruso, A. Castellina, G. Cataldi, L. Cazon, R. Cester, A. G. Chavez, A. Chiavassa, J. A. Chinellato, J. Chudoba, R. W. Clay, R. Colalillo, A. Coleman, L. Collica, M. R. Coluccia, R. Conceição, F. Contreras, M. J. Cooper, S. Coutu, C. E. Covault, J. Cronin, R. Dallier, S. D'Amico, B. Daniel, S. Dasso, K. Daumiller, B. R. Dawson, R. M. de Almeida, S. J. de Jong, G. De Mauro, J. R T de Mello Neto, I. De Mitri, J. de Oliveira, V. de Souza, J. Debatin, L. del Peral, O. Deligny, C. Di Giulio, A. Di Matteo, M. L. Díaz Castro, F. Diogo, C. Dobrigkeit, J. C. D'Olivo, A. Dorofeev, R. C. dos Anjos, M. T. Dova, A. Dundovic, J. Ebr, R. Engel, M. Erdmann, M. Erfani, C. O. Escobar, J. Espadanal, A. Etchegoyen, H. Falcke, K. Fang, G. Farrar, A. C. Fauth, N. Fazzini, B. Fick, J. M. Figueira, A. Filevich, A. Filipčič, O. Fratu, M. M. Freire, T. Fujii, A. Fuster, B. García, D. Garcia-Pinto, F. Gaté, H. Gemmeke, A. Gherghel-Lascu, P. L. Ghia, U. Giaccari, M. Giammarchi, M. Giller, D. Głas, C. Glaser, H. Glass, G. Golup, M. Gómez Berisso, P. F. Gómez Vitale, N. González, B. Gookin, J. Gordon, A. Gorgi, P. Gorham, P. Gouffon, A. F. Grillo, T. D. Grubb, F. Guarino, G. P. Guedes, M. R. Hampel, P. Hansen, D. Harari, T. A. Harrison, J. L. Harton, Q. Hasankiadeh, A. Haungs, T. Hebbeker, D. Heck, P. Heimann, A. E. Herve, G. C. Hill, C. Hojvat, E. Holt, P. Homola, J. R. Hörandel, P. Horvath, M. Hrabovský, T. Huege, J. Hulsman, A. Insolia, P. G. Isar, I. Jandt, S. Jansen, J. A. Johnsen, M. Josebachuili, A. Kääpä, O. Kambeitz, K. H. Kampert, P. Kasper, I. Katkov, B. Keilhauer, E. Kemp, R. M. Kieckhafer, H. O. Klages, M. Kleifges, J. Kleinfeller, R. Krause, N. Krohm, D. Kuempel, G. Kukec Mezek, N. Kunka, A. Kuotb Awad, D. LaHurd, L. Latronico, M. Lauscher, P. Lautridou, P. Lebrun, R. Legumina, M. A. Leigui de Oliveira, A. Letessier-Selvon, I. Lhenry-Yvon, K. Link, L. Lopes, R. López, A. López Casado, Q. Luce, A. Lucero, M. Malacari, M. Mallamaci, D. Mandat, P. Mantsch, A. G. Mariazzi, I. C. Mariş, G. Marsella, D. Martello, H. Martinez, O. Martínez Bravo, J. J. Masías Meza, H. J. Mathes, S. Mathys, J. Matthews, J. A J Matthews, G. Matthiae, E. Mayotte, P. O. Mazur, C. Medina, G. Medina-Tanco, D. Melo, A. Menshikov, S. Messina, M. I. Micheletti, L. Middendorf, I. A. Minaya, L. Miramonti, B. Mitrica, D. Mockler, L. Molina-Bueno, S. Mollerach, F. Montanet, C. Morello, M. Mostafá, G. Müller, M. A. Muller, S. Müller, I. Naranjo, S. Navas, L. Nellen, J. Neuser, P. H. Nguyen, M. Niculescu-Oglinzanu, M. Niechciol, L. Niemietz, T. Niggemann, D. Nitz, D. Nosek, V. Novotny, H. Nožka, L. A. Núñez, L. Ochilo, F. Oikonomou, A. Olinto, D. Pakk Selmi-Dei, M. Palatka, J. Pallotta, P. Papenbreer, G. Parente, A. Parra, T. Paul, M. Pech, F. Pedreira, J. Pȩkala, R. Pelayo, J. Peña-Rodriguez, L. A S Pereira, L. Perrone, C. Peters, S. Petrera, J. Phuntsok, R. Piegaia, T. Pierog, P. Pieroni, M. Pimenta, V. Pirronello, M. Platino, M. Plum, C. Porowski, R. R. Prado, P. Privitera, M. Prouza, E. J. Quel, S. Querchfeld, S. Quinn, R. Ramos-Pollant, J. Rautenberg, O. Ravel, D. Ravignani, D. Reinert, B. Revenu, J. Ridky, M. Risse, P. Ristori, V. Rizi, W. Rodrigues de Carvalho, G. Rodriguez Fernandez, J. Rodriguez Rojo, M. D. Rodríguez-Frías, D. Rogozin, J. Rosado, M. Roth, E. Roulet, A. C. Rovero, S. J. Saffi, A. Saftoiu, H. Salazar, A. Saleh, F. Salesa Greus, G. Salina, J. D. Sanabria Gomez, F. Sánchez, P. Sanchez-Lucas, E. M. Santos, E. Santos, F. Sarazin, B. Sarkar, R. Sarmento, C. Sarmiento-Cano, R. Sato, C. Scarso, M. Schauer, V. Scherini, H. Schieler, D. Schmidt, O. Scholten, P. Schovánek, F. G. Schröder, A. Schulz, J. Schulz, J. Schumacher, S. J. Sciutto, A. Segreto, M. Settimo, A. Shadkam, R. C. Shellard, G. Sigl, G. Silli, O. Sima, A. Śmiałkowski, R. Šmída, G. R. Snow, P. Sommers, S. Sonntag, J. Sorokin, R. Squartini, D. Stanca, S. Stanič, J. Stasielak, F. Strafella, F. Suarez, M. Suarez Durán, T. Sudholz, T. Suomijärvi, A. D. Supanitsky, M. S. Sutherland, J. Swain, Z. Szadkowski, O. A. Taborda, A. Tapia, A. Tepe, V. M. Theodoro, C. Timmermans, C. J. Todero Peixoto, L. Tomankova, B. Tomé, A. Tonachini, G. Torralba Elipe, D. Torres Machado, M. Torri, P. Travnicek, M. Trini, R. Ulrich, M. Unger, M. Urban, A. Valbuena-Delgado, J. F. Valdés Galicia, I. Valiño, L. Valore, G. van Aar, P. van Bodegom, A. M. van den Berg, A. van Vliet, E. Varela, B. Vargas Cárdenas, G. Varner, J. R. Vázquez, R. A. Vázquez, D. Veberič, V. Verzi, J. Vicha, L. Villaseñor, S. Vorobiov, H. Wahlberg, O. Wainberg, D. Walz, A. A. Watson, M. Weber, A. Weindl, L. Wiencke, H. Wilczyński, T. Winchen, D. Wittkowski, B. Wundheiler, S. Wykes, L. Yang, D. Yelos, P. Younk, A. Yushkov, E. Zas, D. Zavrtanik, M. Zavrtanik, A. Zepeda, B. Zimmermann, M. Ziolkowski, Z. Zong, F. Zuccarello

    Research output: Contribution to journalArticle

    Abstract

    We report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the ‘ankle’ at lg⁡(E/eV)=18.5–19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A>4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.

    Original languageEnglish (US)
    Pages (from-to)288-295
    Number of pages8
    JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
    Volume762
    DOIs
    StatePublished - Nov 10 2016

    Fingerprint

    cosmic rays
    cosmic ray showers
    showers
    observatories
    stations
    primary cosmic rays
    protons
    water
    energy
    generators
    helium
    electromagnetism
    fluorescence
    nuclei
    sensitivity
    detectors

    Keywords

    • Ankle
    • Cosmic rays
    • Mass composition
    • Pierre Auger Observatory

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics

    Cite this

    Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum. / Aab, A.; Abreu, P.; Aglietta, M.; Ahn, E. J.; Al Samarai, I.; Albuquerque, I. F M; Allekotte, I.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Ambrosio, M.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arqueros, F.; Arsene, N.; Asorey, H.; Assis, P.; Aublin, J.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; Dallier, R.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R T; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; del Peral, L.; Deligny, O.; Di Giulio, C.; Di Matteo, A.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; Dorofeev, A.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fratu, O.; Freire, M. M.; Fujii, T.; Fuster, A.; García, B.; Garcia-Pinto, D.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Glass, H.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gookin, B.; Gordon, J.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Hasankiadeh, Q.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Johnsen, J. A.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Keilhauer, B.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; LaHurd, D.; Latronico, L.; Lauscher, M.; Lautridou, P.; Lebrun, P.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lopes, L.; López, R.; López Casado, A.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A J; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Messina, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Mockler, D.; Molina-Bueno, L.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafá, M.; Müller, G.; Muller, M. A.; Müller, S.; Naranjo, I.; Navas, S.; Nellen, L.; Neuser, J.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, H.; Núñez, L. A.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A S; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollant, R.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Reinert, D.; Revenu, B.; Ridky, J.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Rogozin, D.; Rosado, J.; Roth, M.; Roulet, E.; Rovero, A. C.; Saffi, S. J.; Saftoiu, A.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sanabria Gomez, J. D.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Scarso, C.; Schauer, M.; Scherini, V.; Schieler, H.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Sorokin, J.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Strafella, F.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Taborda, O. A.; Tapia, A.; Tepe, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Torri, M.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valbuena-Delgado, A.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczyński, H.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yang, L.; Yelos, D.; Younk, P.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.

    In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol. 762, 10.11.2016, p. 288-295.

    Research output: Contribution to journalArticle

    Aab, A, Abreu, P, Aglietta, M, Ahn, EJ, Al Samarai, I, Albuquerque, IFM, Allekotte, I, Allison, P, Almela, A, Alvarez Castillo, J, Alvarez-Muñiz, J, Ambrosio, M, Anastasi, GA, Anchordoqui, L, Andrada, B, Andringa, S, Aramo, C, Arqueros, F, Arsene, N, Asorey, H, Assis, P, Aublin, J, Avila, G, Badescu, AM, Balaceanu, A, Baus, C, Beatty, JJ, Becker, KH, Bellido, JA, Berat, C, Bertaina, ME, Bertou, X, Biermann, PL, Billoir, P, Biteau, J, Blaess, SG, Blanco, A, Blazek, J, Bleve, C, Boháčová, M, Boncioli, D, Bonifazi, C, Borodai, N, Botti, AM, Brack, J, Brancus, I, Bretz, T, Bridgeman, A, Briechle, FL, Buchholz, P, Bueno, A, Buitink, S, Buscemi, M, Caballero-Mora, KS, Caccianiga, B, Caccianiga, L, Cancio, A, Canfora, F, Caramete, L, Caruso, R, Castellina, A, Cataldi, G, Cazon, L, Cester, R, Chavez, AG, Chiavassa, A, Chinellato, JA, Chudoba, J, Clay, RW, Colalillo, R, Coleman, A, Collica, L, Coluccia, MR, Conceição, R, Contreras, F, Cooper, MJ, Coutu, S, Covault, CE, Cronin, J, Dallier, R, D'Amico, S, Daniel, B, Dasso, S, Daumiller, K, Dawson, BR, de Almeida, RM, de Jong, SJ, De Mauro, G, de Mello Neto, JRT, De Mitri, I, de Oliveira, J, de Souza, V, Debatin, J, del Peral, L, Deligny, O, Di Giulio, C, Di Matteo, A, Díaz Castro, ML, Diogo, F, Dobrigkeit, C, D'Olivo, JC, Dorofeev, A, dos Anjos, RC, Dova, MT, Dundovic, A, Ebr, J, Engel, R, Erdmann, M, Erfani, M, Escobar, CO, Espadanal, J, Etchegoyen, A, Falcke, H, Fang, K, Farrar, G, Fauth, AC, Fazzini, N, Fick, B, Figueira, JM, Filevich, A, Filipčič, A, Fratu, O, Freire, MM, Fujii, T, Fuster, A, García, B, Garcia-Pinto, D, Gaté, F, Gemmeke, H, Gherghel-Lascu, A, Ghia, PL, Giaccari, U, Giammarchi, M, Giller, M, Głas, D, Glaser, C, Glass, H, Golup, G, Gómez Berisso, M, Gómez Vitale, PF, González, N, Gookin, B, Gordon, J, Gorgi, A, Gorham, P, Gouffon, P, Grillo, AF, Grubb, TD, Guarino, F, Guedes, GP, Hampel, MR, Hansen, P, Harari, D, Harrison, TA, Harton, JL, Hasankiadeh, Q, Haungs, A, Hebbeker, T, Heck, D, Heimann, P, Herve, AE, Hill, GC, Hojvat, C, Holt, E, Homola, P, Hörandel, JR, Horvath, P, Hrabovský, M, Huege, T, Hulsman, J, Insolia, A, Isar, PG, Jandt, I, Jansen, S, Johnsen, JA, Josebachuili, M, Kääpä, A, Kambeitz, O, Kampert, KH, Kasper, P, Katkov, I, Keilhauer, B, Kemp, E, Kieckhafer, RM, Klages, HO, Kleifges, M, Kleinfeller, J, Krause, R, Krohm, N, Kuempel, D, Kukec Mezek, G, Kunka, N, Kuotb Awad, A, LaHurd, D, Latronico, L, Lauscher, M, Lautridou, P, Lebrun, P, Legumina, R, Leigui de Oliveira, MA, Letessier-Selvon, A, Lhenry-Yvon, I, Link, K, Lopes, L, López, R, López Casado, A, Luce, Q, Lucero, A, Malacari, M, Mallamaci, M, Mandat, D, Mantsch, P, Mariazzi, AG, Mariş, IC, Marsella, G, Martello, D, Martinez, H, Martínez Bravo, O, Masías Meza, JJ, Mathes, HJ, Mathys, S, Matthews, J, Matthews, JAJ, Matthiae, G, Mayotte, E, Mazur, PO, Medina, C, Medina-Tanco, G, Melo, D, Menshikov, A, Messina, S, Micheletti, MI, Middendorf, L, Minaya, IA, Miramonti, L, Mitrica, B, Mockler, D, Molina-Bueno, L, Mollerach, S, Montanet, F, Morello, C, Mostafá, M, Müller, G, Muller, MA, Müller, S, Naranjo, I, Navas, S, Nellen, L, Neuser, J, Nguyen, PH, Niculescu-Oglinzanu, M, Niechciol, M, Niemietz, L, Niggemann, T, Nitz, D, Nosek, D, Novotny, V, Nožka, H, Núñez, LA, Ochilo, L, Oikonomou, F, Olinto, A, Pakk Selmi-Dei, D, Palatka, M, Pallotta, J, Papenbreer, P, Parente, G, Parra, A, Paul, T, Pech, M, Pedreira, F, Pȩkala, J, Pelayo, R, Peña-Rodriguez, J, Pereira, LAS, Perrone, L, Peters, C, Petrera, S, Phuntsok, J, Piegaia, R, Pierog, T, Pieroni, P, Pimenta, M, Pirronello, V, Platino, M, Plum, M, Porowski, C, Prado, RR, Privitera, P, Prouza, M, Quel, EJ, Querchfeld, S, Quinn, S, Ramos-Pollant, R, Rautenberg, J, Ravel, O, Ravignani, D, Reinert, D, Revenu, B, Ridky, J, Risse, M, Ristori, P, Rizi, V, Rodrigues de Carvalho, W, Rodriguez Fernandez, G, Rodriguez Rojo, J, Rodríguez-Frías, MD, Rogozin, D, Rosado, J, Roth, M, Roulet, E, Rovero, AC, Saffi, SJ, Saftoiu, A, Salazar, H, Saleh, A, Salesa Greus, F, Salina, G, Sanabria Gomez, JD, Sánchez, F, Sanchez-Lucas, P, Santos, EM, Santos, E, Sarazin, F, Sarkar, B, Sarmento, R, Sarmiento-Cano, C, Sato, R, Scarso, C, Schauer, M, Scherini, V, Schieler, H, Schmidt, D, Scholten, O, Schovánek, P, Schröder, FG, Schulz, A, Schulz, J, Schumacher, J, Sciutto, SJ, Segreto, A, Settimo, M, Shadkam, A, Shellard, RC, Sigl, G, Silli, G, Sima, O, Śmiałkowski, A, Šmída, R, Snow, GR, Sommers, P, Sonntag, S, Sorokin, J, Squartini, R, Stanca, D, Stanič, S, Stasielak, J, Strafella, F, Suarez, F, Suarez Durán, M, Sudholz, T, Suomijärvi, T, Supanitsky, AD, Sutherland, MS, Swain, J, Szadkowski, Z, Taborda, OA, Tapia, A, Tepe, A, Theodoro, VM, Timmermans, C, Todero Peixoto, CJ, Tomankova, L, Tomé, B, Tonachini, A, Torralba Elipe, G, Torres Machado, D, Torri, M, Travnicek, P, Trini, M, Ulrich, R, Unger, M, Urban, M, Valbuena-Delgado, A, Valdés Galicia, JF, Valiño, I, Valore, L, van Aar, G, van Bodegom, P, van den Berg, AM, van Vliet, A, Varela, E, Vargas Cárdenas, B, Varner, G, Vázquez, JR, Vázquez, RA, Veberič, D, Verzi, V, Vicha, J, Villaseñor, L, Vorobiov, S, Wahlberg, H, Wainberg, O, Walz, D, Watson, AA, Weber, M, Weindl, A, Wiencke, L, Wilczyński, H, Winchen, T, Wittkowski, D, Wundheiler, B, Wykes, S, Yang, L, Yelos, D, Younk, P, Yushkov, A, Zas, E, Zavrtanik, D, Zavrtanik, M, Zepeda, A, Zimmermann, B, Ziolkowski, M, Zong, Z & Zuccarello, F 2016, 'Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum', Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, vol. 762, pp. 288-295. https://doi.org/10.1016/j.physletb.2016.09.039
    Aab, A. ; Abreu, P. ; Aglietta, M. ; Ahn, E. J. ; Al Samarai, I. ; Albuquerque, I. F M ; Allekotte, I. ; Allison, P. ; Almela, A. ; Alvarez Castillo, J. ; Alvarez-Muñiz, J. ; Ambrosio, M. ; Anastasi, G. A. ; Anchordoqui, L. ; Andrada, B. ; Andringa, S. ; Aramo, C. ; Arqueros, F. ; Arsene, N. ; Asorey, H. ; Assis, P. ; Aublin, J. ; Avila, G. ; Badescu, A. M. ; Balaceanu, A. ; Baus, C. ; Beatty, J. J. ; Becker, K. H. ; Bellido, J. A. ; Berat, C. ; Bertaina, M. E. ; Bertou, X. ; Biermann, P. L. ; Billoir, P. ; Biteau, J. ; Blaess, S. G. ; Blanco, A. ; Blazek, J. ; Bleve, C. ; Boháčová, M. ; Boncioli, D. ; Bonifazi, C. ; Borodai, N. ; Botti, A. M. ; Brack, J. ; Brancus, I. ; Bretz, T. ; Bridgeman, A. ; Briechle, F. L. ; Buchholz, P. ; Bueno, A. ; Buitink, S. ; Buscemi, M. ; Caballero-Mora, K. S. ; Caccianiga, B. ; Caccianiga, L. ; Cancio, A. ; Canfora, F. ; Caramete, L. ; Caruso, R. ; Castellina, A. ; Cataldi, G. ; Cazon, L. ; Cester, R. ; Chavez, A. G. ; Chiavassa, A. ; Chinellato, J. A. ; Chudoba, J. ; Clay, R. W. ; Colalillo, R. ; Coleman, A. ; Collica, L. ; Coluccia, M. R. ; Conceição, R. ; Contreras, F. ; Cooper, M. J. ; Coutu, S. ; Covault, C. E. ; Cronin, J. ; Dallier, R. ; D'Amico, S. ; Daniel, B. ; Dasso, S. ; Daumiller, K. ; Dawson, B. R. ; de Almeida, R. M. ; de Jong, S. J. ; De Mauro, G. ; de Mello Neto, J. R T ; De Mitri, I. ; de Oliveira, J. ; de Souza, V. ; Debatin, J. ; del Peral, L. ; Deligny, O. ; Di Giulio, C. ; Di Matteo, A. ; Díaz Castro, M. L. ; Diogo, F. ; Dobrigkeit, C. ; D'Olivo, J. C. ; Dorofeev, A. ; dos Anjos, R. C. ; Dova, M. T. ; Dundovic, A. ; Ebr, J. ; Engel, R. ; Erdmann, M. ; Erfani, M. ; Escobar, C. O. ; Espadanal, J. ; Etchegoyen, A. ; Falcke, H. ; Fang, K. ; Farrar, G. ; Fauth, A. C. ; Fazzini, N. ; Fick, B. ; Figueira, J. M. ; Filevich, A. ; Filipčič, A. ; Fratu, O. ; Freire, M. M. ; Fujii, T. ; Fuster, A. ; García, B. ; Garcia-Pinto, D. ; Gaté, F. ; Gemmeke, H. ; Gherghel-Lascu, A. ; Ghia, P. L. ; Giaccari, U. ; Giammarchi, M. ; Giller, M. ; Głas, D. ; Glaser, C. ; Glass, H. ; Golup, G. ; Gómez Berisso, M. ; Gómez Vitale, P. F. ; González, N. ; Gookin, B. ; Gordon, J. ; Gorgi, A. ; Gorham, P. ; Gouffon, P. ; Grillo, A. F. ; Grubb, T. D. ; Guarino, F. ; Guedes, G. P. ; Hampel, M. R. ; Hansen, P. ; Harari, D. ; Harrison, T. A. ; Harton, J. L. ; Hasankiadeh, Q. ; Haungs, A. ; Hebbeker, T. ; Heck, D. ; Heimann, P. ; Herve, A. E. ; Hill, G. C. ; Hojvat, C. ; Holt, E. ; Homola, P. ; Hörandel, J. R. ; Horvath, P. ; Hrabovský, M. ; Huege, T. ; Hulsman, J. ; Insolia, A. ; Isar, P. G. ; Jandt, I. ; Jansen, S. ; Johnsen, J. A. ; Josebachuili, M. ; Kääpä, A. ; Kambeitz, O. ; Kampert, K. H. ; Kasper, P. ; Katkov, I. ; Keilhauer, B. ; Kemp, E. ; Kieckhafer, R. M. ; Klages, H. O. ; Kleifges, M. ; Kleinfeller, J. ; Krause, R. ; Krohm, N. ; Kuempel, D. ; Kukec Mezek, G. ; Kunka, N. ; Kuotb Awad, A. ; LaHurd, D. ; Latronico, L. ; Lauscher, M. ; Lautridou, P. ; Lebrun, P. ; Legumina, R. ; Leigui de Oliveira, M. A. ; Letessier-Selvon, A. ; Lhenry-Yvon, I. ; Link, K. ; Lopes, L. ; López, R. ; López Casado, A. ; Luce, Q. ; Lucero, A. ; Malacari, M. ; Mallamaci, M. ; Mandat, D. ; Mantsch, P. ; Mariazzi, A. G. ; Mariş, I. C. ; Marsella, G. ; Martello, D. ; Martinez, H. ; Martínez Bravo, O. ; Masías Meza, J. J. ; Mathes, H. J. ; Mathys, S. ; Matthews, J. ; Matthews, J. A J ; Matthiae, G. ; Mayotte, E. ; Mazur, P. O. ; Medina, C. ; Medina-Tanco, G. ; Melo, D. ; Menshikov, A. ; Messina, S. ; Micheletti, M. I. ; Middendorf, L. ; Minaya, I. A. ; Miramonti, L. ; Mitrica, B. ; Mockler, D. ; Molina-Bueno, L. ; Mollerach, S. ; Montanet, F. ; Morello, C. ; Mostafá, M. ; Müller, G. ; Muller, M. A. ; Müller, S. ; Naranjo, I. ; Navas, S. ; Nellen, L. ; Neuser, J. ; Nguyen, P. H. ; Niculescu-Oglinzanu, M. ; Niechciol, M. ; Niemietz, L. ; Niggemann, T. ; Nitz, D. ; Nosek, D. ; Novotny, V. ; Nožka, H. ; Núñez, L. A. ; Ochilo, L. ; Oikonomou, F. ; Olinto, A. ; Pakk Selmi-Dei, D. ; Palatka, M. ; Pallotta, J. ; Papenbreer, P. ; Parente, G. ; Parra, A. ; Paul, T. ; Pech, M. ; Pedreira, F. ; Pȩkala, J. ; Pelayo, R. ; Peña-Rodriguez, J. ; Pereira, L. A S ; Perrone, L. ; Peters, C. ; Petrera, S. ; Phuntsok, J. ; Piegaia, R. ; Pierog, T. ; Pieroni, P. ; Pimenta, M. ; Pirronello, V. ; Platino, M. ; Plum, M. ; Porowski, C. ; Prado, R. R. ; Privitera, P. ; Prouza, M. ; Quel, E. J. ; Querchfeld, S. ; Quinn, S. ; Ramos-Pollant, R. ; Rautenberg, J. ; Ravel, O. ; Ravignani, D. ; Reinert, D. ; Revenu, B. ; Ridky, J. ; Risse, M. ; Ristori, P. ; Rizi, V. ; Rodrigues de Carvalho, W. ; Rodriguez Fernandez, G. ; Rodriguez Rojo, J. ; Rodríguez-Frías, M. D. ; Rogozin, D. ; Rosado, J. ; Roth, M. ; Roulet, E. ; Rovero, A. C. ; Saffi, S. J. ; Saftoiu, A. ; Salazar, H. ; Saleh, A. ; Salesa Greus, F. ; Salina, G. ; Sanabria Gomez, J. D. ; Sánchez, F. ; Sanchez-Lucas, P. ; Santos, E. M. ; Santos, E. ; Sarazin, F. ; Sarkar, B. ; Sarmento, R. ; Sarmiento-Cano, C. ; Sato, R. ; Scarso, C. ; Schauer, M. ; Scherini, V. ; Schieler, H. ; Schmidt, D. ; Scholten, O. ; Schovánek, P. ; Schröder, F. G. ; Schulz, A. ; Schulz, J. ; Schumacher, J. ; Sciutto, S. J. ; Segreto, A. ; Settimo, M. ; Shadkam, A. ; Shellard, R. C. ; Sigl, G. ; Silli, G. ; Sima, O. ; Śmiałkowski, A. ; Šmída, R. ; Snow, G. R. ; Sommers, P. ; Sonntag, S. ; Sorokin, J. ; Squartini, R. ; Stanca, D. ; Stanič, S. ; Stasielak, J. ; Strafella, F. ; Suarez, F. ; Suarez Durán, M. ; Sudholz, T. ; Suomijärvi, T. ; Supanitsky, A. D. ; Sutherland, M. S. ; Swain, J. ; Szadkowski, Z. ; Taborda, O. A. ; Tapia, A. ; Tepe, A. ; Theodoro, V. M. ; Timmermans, C. ; Todero Peixoto, C. J. ; Tomankova, L. ; Tomé, B. ; Tonachini, A. ; Torralba Elipe, G. ; Torres Machado, D. ; Torri, M. ; Travnicek, P. ; Trini, M. ; Ulrich, R. ; Unger, M. ; Urban, M. ; Valbuena-Delgado, A. ; Valdés Galicia, J. F. ; Valiño, I. ; Valore, L. ; van Aar, G. ; van Bodegom, P. ; van den Berg, A. M. ; van Vliet, A. ; Varela, E. ; Vargas Cárdenas, B. ; Varner, G. ; Vázquez, J. R. ; Vázquez, R. A. ; Veberič, D. ; Verzi, V. ; Vicha, J. ; Villaseñor, L. ; Vorobiov, S. ; Wahlberg, H. ; Wainberg, O. ; Walz, D. ; Watson, A. A. ; Weber, M. ; Weindl, A. ; Wiencke, L. ; Wilczyński, H. ; Winchen, T. ; Wittkowski, D. ; Wundheiler, B. ; Wykes, S. ; Yang, L. ; Yelos, D. ; Younk, P. ; Yushkov, A. ; Zas, E. ; Zavrtanik, D. ; Zavrtanik, M. ; Zepeda, A. ; Zimmermann, B. ; Ziolkowski, M. ; Zong, Z. ; Zuccarello, F. / Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum. In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. 2016 ; Vol. 762. pp. 288-295.
    @article{21738082a9b94eaa9ab871110774849c,
    title = "Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum",
    abstract = "We report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the ‘ankle’ at lg⁡(E/eV)=18.5–19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A>4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.",
    keywords = "Ankle, Cosmic rays, Mass composition, Pierre Auger Observatory",
    author = "A. Aab and P. Abreu and M. Aglietta and Ahn, {E. J.} and {Al Samarai}, I. and Albuquerque, {I. F M} and I. Allekotte and P. Allison and A. Almela and {Alvarez Castillo}, J. and J. Alvarez-Mu{\~n}iz and M. Ambrosio and Anastasi, {G. A.} and L. Anchordoqui and B. Andrada and S. Andringa and C. Aramo and F. Arqueros and N. Arsene and H. Asorey and P. Assis and J. Aublin and G. Avila and Badescu, {A. M.} and A. Balaceanu and C. Baus and Beatty, {J. J.} and Becker, {K. H.} and Bellido, {J. A.} and C. Berat and Bertaina, {M. E.} and X. Bertou and Biermann, {P. L.} and P. Billoir and J. Biteau and Blaess, {S. G.} and A. Blanco and J. Blazek and C. Bleve and M. Boh{\'a}čov{\'a} and D. Boncioli and C. Bonifazi and N. Borodai and Botti, {A. M.} and J. Brack and I. Brancus and T. Bretz and A. Bridgeman and Briechle, {F. L.} and P. Buchholz and A. Bueno and S. Buitink and M. Buscemi and Caballero-Mora, {K. S.} and B. Caccianiga and L. Caccianiga and A. Cancio and F. Canfora and L. Caramete and R. Caruso and A. Castellina and G. Cataldi and L. Cazon and R. Cester and Chavez, {A. G.} and A. Chiavassa and Chinellato, {J. A.} and J. Chudoba and Clay, {R. W.} and R. Colalillo and A. Coleman and L. Collica and Coluccia, {M. R.} and R. Concei{\cc}{\~a}o and F. Contreras and Cooper, {M. J.} and S. Coutu and Covault, {C. E.} and J. Cronin and R. Dallier and S. D'Amico and B. Daniel and S. Dasso and K. Daumiller and Dawson, {B. R.} and {de Almeida}, {R. M.} and {de Jong}, {S. J.} and {De Mauro}, G. and {de Mello Neto}, {J. R T} and {De Mitri}, I. and {de Oliveira}, J. and {de Souza}, V. and J. Debatin and {del Peral}, L. and O. Deligny and {Di Giulio}, C. and {Di Matteo}, A. and {D{\'i}az Castro}, {M. L.} and F. Diogo and C. Dobrigkeit and D'Olivo, {J. C.} and A. Dorofeev and {dos Anjos}, {R. C.} and Dova, {M. T.} and A. Dundovic and J. Ebr and R. Engel and M. Erdmann and M. Erfani and Escobar, {C. O.} and J. Espadanal and A. Etchegoyen and H. Falcke and K. Fang and G. Farrar and Fauth, {A. C.} and N. Fazzini and B. Fick and Figueira, {J. M.} and A. Filevich and A. Filipčič and O. Fratu and Freire, {M. M.} and T. Fujii and A. Fuster and B. Garc{\'i}a and D. Garcia-Pinto and F. Gat{\'e} and H. Gemmeke and A. Gherghel-Lascu and Ghia, {P. L.} and U. Giaccari and M. Giammarchi and M. Giller and D. Głas and C. Glaser and H. Glass and G. Golup and {G{\'o}mez Berisso}, M. and {G{\'o}mez Vitale}, {P. F.} and N. Gonz{\'a}lez and B. Gookin and J. Gordon and A. Gorgi and P. Gorham and P. Gouffon and Grillo, {A. F.} and Grubb, {T. D.} and F. Guarino and Guedes, {G. P.} and Hampel, {M. R.} and P. Hansen and D. Harari and Harrison, {T. A.} and Harton, {J. L.} and Q. Hasankiadeh and A. Haungs and T. Hebbeker and D. Heck and P. Heimann and Herve, {A. E.} and Hill, {G. C.} and C. Hojvat and E. Holt and P. Homola and H{\"o}randel, {J. R.} and P. Horvath and M. Hrabovsk{\'y} and T. Huege and J. Hulsman and A. Insolia and Isar, {P. G.} and I. Jandt and S. Jansen and Johnsen, {J. A.} and M. Josebachuili and A. K{\"a}{\"a}p{\"a} and O. Kambeitz and Kampert, {K. H.} and P. Kasper and I. Katkov and B. Keilhauer and E. Kemp and Kieckhafer, {R. M.} and Klages, {H. O.} and M. Kleifges and J. Kleinfeller and R. Krause and N. Krohm and D. Kuempel and {Kukec Mezek}, G. and N. Kunka and {Kuotb Awad}, A. and D. LaHurd and L. Latronico and M. Lauscher and P. Lautridou and P. Lebrun and R. Legumina and {Leigui de Oliveira}, {M. A.} and A. Letessier-Selvon and I. Lhenry-Yvon and K. Link and L. Lopes and R. L{\'o}pez and {L{\'o}pez Casado}, A. and Q. Luce and A. Lucero and M. Malacari and M. Mallamaci and D. Mandat and P. Mantsch and Mariazzi, {A. G.} and Mariş, {I. C.} and G. Marsella and D. Martello and H. Martinez and {Mart{\'i}nez Bravo}, O. and {Mas{\'i}as Meza}, {J. J.} and Mathes, {H. J.} and S. Mathys and J. Matthews and Matthews, {J. A J} and G. Matthiae and E. Mayotte and Mazur, {P. O.} and C. Medina and G. Medina-Tanco and D. Melo and A. Menshikov and S. Messina and Micheletti, {M. I.} and L. Middendorf and Minaya, {I. A.} and L. Miramonti and B. Mitrica and D. Mockler and L. Molina-Bueno and S. Mollerach and F. Montanet and C. Morello and M. Mostaf{\'a} and G. M{\"u}ller and Muller, {M. A.} and S. M{\"u}ller and I. Naranjo and S. Navas and L. Nellen and J. Neuser and Nguyen, {P. H.} and M. Niculescu-Oglinzanu and M. Niechciol and L. Niemietz and T. Niggemann and D. Nitz and D. Nosek and V. Novotny and H. Nožka and N{\'u}{\~n}ez, {L. A.} and L. Ochilo and F. Oikonomou and A. Olinto and {Pakk Selmi-Dei}, D. and M. Palatka and J. Pallotta and P. Papenbreer and G. Parente and A. Parra and T. Paul and M. Pech and F. Pedreira and J. Pȩkala and R. Pelayo and J. Pe{\~n}a-Rodriguez and Pereira, {L. A S} and L. Perrone and C. Peters and S. Petrera and J. Phuntsok and R. Piegaia and T. Pierog and P. Pieroni and M. Pimenta and V. Pirronello and M. Platino and M. Plum and C. Porowski and Prado, {R. R.} and P. Privitera and M. Prouza and Quel, {E. J.} and S. Querchfeld and S. Quinn and R. Ramos-Pollant and J. Rautenberg and O. Ravel and D. Ravignani and D. Reinert and B. Revenu and J. Ridky and M. Risse and P. Ristori and V. Rizi and {Rodrigues de Carvalho}, W. and {Rodriguez Fernandez}, G. and {Rodriguez Rojo}, J. and Rodr{\'i}guez-Fr{\'i}as, {M. D.} and D. Rogozin and J. Rosado and M. Roth and E. Roulet and Rovero, {A. C.} and Saffi, {S. J.} and A. Saftoiu and H. Salazar and A. Saleh and {Salesa Greus}, F. and G. Salina and {Sanabria Gomez}, {J. D.} and F. S{\'a}nchez and P. Sanchez-Lucas and Santos, {E. M.} and E. Santos and F. Sarazin and B. Sarkar and R. Sarmento and C. Sarmiento-Cano and R. Sato and C. Scarso and M. Schauer and V. Scherini and H. Schieler and D. Schmidt and O. Scholten and P. Schov{\'a}nek and Schr{\"o}der, {F. G.} and A. Schulz and J. Schulz and J. Schumacher and Sciutto, {S. J.} and A. Segreto and M. Settimo and A. Shadkam and Shellard, {R. C.} and G. Sigl and G. Silli and O. Sima and A. Śmiałkowski and R. Šm{\'i}da and Snow, {G. R.} and P. Sommers and S. Sonntag and J. Sorokin and R. Squartini and D. Stanca and S. Stanič and J. Stasielak and F. Strafella and F. Suarez and {Suarez Dur{\'a}n}, M. and T. Sudholz and T. Suomij{\"a}rvi and Supanitsky, {A. D.} and Sutherland, {M. S.} and J. Swain and Z. Szadkowski and Taborda, {O. A.} and A. Tapia and A. Tepe and Theodoro, {V. M.} and C. Timmermans and {Todero Peixoto}, {C. J.} and L. Tomankova and B. Tom{\'e} and A. Tonachini and {Torralba Elipe}, G. and {Torres Machado}, D. and M. Torri and P. Travnicek and M. Trini and R. Ulrich and M. Unger and M. Urban and A. Valbuena-Delgado and {Vald{\'e}s Galicia}, {J. F.} and I. Vali{\~n}o and L. Valore and {van Aar}, G. and {van Bodegom}, P. and {van den Berg}, {A. M.} and {van Vliet}, A. and E. Varela and {Vargas C{\'a}rdenas}, B. and G. Varner and V{\'a}zquez, {J. R.} and V{\'a}zquez, {R. A.} and D. Veberič and V. Verzi and J. Vicha and L. Villase{\~n}or and S. Vorobiov and H. Wahlberg and O. Wainberg and D. Walz and Watson, {A. A.} and M. Weber and A. Weindl and L. Wiencke and H. Wilczyński and T. Winchen and D. Wittkowski and B. Wundheiler and S. Wykes and L. Yang and D. Yelos and P. Younk and A. Yushkov and E. Zas and D. Zavrtanik and M. Zavrtanik and A. Zepeda and B. Zimmermann and M. Ziolkowski and Z. Zong and F. Zuccarello",
    year = "2016",
    month = "11",
    day = "10",
    doi = "10.1016/j.physletb.2016.09.039",
    language = "English (US)",
    volume = "762",
    pages = "288--295",
    journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",
    issn = "0370-2693",
    publisher = "Elsevier",

    }

    TY - JOUR

    T1 - Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum

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    AU - Zimmermann, B.

    AU - Ziolkowski, M.

    AU - Zong, Z.

    AU - Zuccarello, F.

    PY - 2016/11/10

    Y1 - 2016/11/10

    N2 - We report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the ‘ankle’ at lg⁡(E/eV)=18.5–19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A>4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.

    AB - We report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the ‘ankle’ at lg⁡(E/eV)=18.5–19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A>4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.

    KW - Ankle

    KW - Cosmic rays

    KW - Mass composition

    KW - Pierre Auger Observatory

    UR - http://www.scopus.com/inward/record.url?scp=84990853667&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84990853667&partnerID=8YFLogxK

    U2 - 10.1016/j.physletb.2016.09.039

    DO - 10.1016/j.physletb.2016.09.039

    M3 - Article

    AN - SCOPUS:84990853667

    VL - 762

    SP - 288

    EP - 295

    JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

    JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

    SN - 0370-2693

    ER -