Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
High Energy Astrophysical Phenomena
2016-11-24 v2
Abstract
We report a first measurement for ultra-high 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 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 . Scenarios such as the proton dip model, with almost pure compositions, are thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.
Cite
@article{arxiv.1609.08567,
title = {Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum},
author = {The Pierre Auger Collaboration and A. Aab and P. Abreu and M. Aglietta and E. J. Ahn and I. Al Samarai and I. F. M. Albuquerque and I. Allekotte and P. Allison and A. Almela and J. Alvarez Castillo and J. Alvarez-Muñiz and M. Ambrosio and G. A. Anastasi 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 A. M. Badescu and A. Balaceanu and C. Baus and J. J. Beatty and K. H. Becker and J. A. Bellido and C. Berat and M. E. Bertaina and X. Bertou and P. L. Biermann and P. Billoir and J. Biteau and S. G. Blaess and A. Blanco and J. Blazek and C. Bleve and M. Boháčová and D. Boncioli and C. Bonifazi and N. Borodai and A. M. Botti and J. Brack and I. Brancus and T. Bretz and A. Bridgeman and F. L. Briechle and P. Buchholz and A. Bueno and S. Buitink and M. Buscemi and K. S. Caballero-Mora 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 A. G. Chavez and A. Chiavassa and J. A. Chinellato and J. Chudoba and R. W. Clay and R. Colalillo and A. Coleman and L. Collica and M. R. Coluccia and R. Conceição and F. Contreras and M. J. Cooper and S. Coutu and C. E. Covault and J. Cronin and R. Dallier and S. D'Amico and B. Daniel and S. Dasso and K. Daumiller and B. R. Dawson and R. M. de Almeida and S. J. de Jong and G. De Mauro and J. R. T. de Mello Neto and I. De Mitri and J. de Oliveira and V. de Souza and J. Debatin and L. del Peral and O. Deligny and C. Di Giulio and A. Di Matteo and M. L. Díaz Castro and F. Diogo and C. Dobrigkeit and J. C. D'Olivo and A. Dorofeev and R. C. dos Anjos and M. T. Dova and A. Dundovic and J. Ebr and R. Engel and M. Erdmann and M. Erfani and C. O. Escobar and J. Espadanal and A. Etchegoyen and H. Falcke and K. Fang and G. Farrar and A. C. Fauth and N. Fazzini and B. Fick and J. M. Figueira and A. Filevich and A. Filipčič and O. Fratu and M. M. Freire and T. Fujii and A. Fuster and B. García and D. Garcia-Pinto and F. Gaté and H. Gemmeke and A. Gherghel-Lascu and P. L. Ghia and U. Giaccari and M. Giammarchi and M. Giller and D. Głas and C. Glaser and H. Glass and G. Golup and M. Gómez Berisso and P. F. Gómez Vitale and N. González and B. Gookin and J. Gordon and A. Gorgi and P. Gorham and P. Gouffon and A. F. Grillo and T. D. Grubb and F. Guarino and G. P. Guedes and M. R. Hampel and P. Hansen and D. Harari and T. A. Harrison and J. L. Harton and Q. Hasankiadeh and A. Haungs and T. Hebbeker and D. Heck and P. Heimann and A. E. Herve and G. C. Hill and C. Hojvat and E. Holt and P. Homola and J. R. Hörandel and P. Horvath and M. Hrabovský and T. Huege and J. Hulsman and A. Insolia and P. G. Isar and I. Jandt and S. Jansen and J. A. Johnsen and M. Josebachuili and A. Kääpä and O. Kambeitz and K. H. Kampert and P. Kasper and I. Katkov and B. Keilhauer and E. Kemp and R. M. Kieckhafer and H. O. Klages and M. Kleifges and J. Kleinfeller and R. Krause and N. Krohm and D. Kuempel and G. Kukec Mezek and N. Kunka and A. Kuotb Awad and D. LaHurd and L. Latronico and M. Lauscher and P. Lautridou and P. Lebrun and R. Legumina and M. A. Leigui de Oliveira and A. Letessier-Selvon and I. Lhenry-Yvon and K. Link and L. Lopes and R. López and A. López Casado and Q. Luce and A. Lucero and M. Malacari and M. Mallamaci and D. Mandat and P. Mantsch and A. G. Mariazzi and I. C. Mariş and G. Marsella and D. Martello and H. Martinez and O. Martínez Bravo and J. J. Masías Meza and H. J. Mathes and S. Mathys and J. Matthews and J. A. J. Matthews and G. Matthiae and E. Mayotte and P. O. Mazur and C. Medina and G. Medina-Tanco and D. Melo and A. Menshikov and S. Messina and M. I. Micheletti and L. Middendorf and I. A. Minaya and L. Miramonti and B. Mitrica and D. Mockler and L. Molina-Bueno and S. Mollerach and F. Montanet and C. Morello and M. Mostafá and G. Müller and M. A. Muller and S. Müller and I. Naranjo and S. Navas and L. Nellen and J. Neuser and P. H. Nguyen 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 L. A. Núñez and L. Ochilo and F. Oikonomou and A. Olinto and D. Pakk Selmi-Dei 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. Pękala and R. Pelayo and J. Peña-Rodriguez and L. A. S. Pereira 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 R. R. Prado and P. Privitera and M. Prouza and E. J. Quel 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 W. Rodrigues de Carvalho and G. Rodriguez Fernandez and J. Rodriguez Rojo and M. D. Rodríguez-Frías and D. Rogozin and J. Rosado and M. Roth and E. Roulet and A. C. Rovero and S. J. Saffi and A. Saftoiu and H. Salazar and A. Saleh and F. Salesa Greus and G. Salina and J. D. Sanabria Gomez and F. Sánchez and P. Sanchez-Lucas and E. M. Santos 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. Schovánek and F. G. Schröder and A. Schulz and J. Schulz and J. Schumacher and S. J. Sciutto and A. Segreto and M. Settimo and A. Shadkam and R. C. Shellard and G. Sigl and G. Silli and O. Sima and A. Śmiałkowski and R. Šmída and G. R. Snow 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 M. Suarez Durán and T. Sudholz and T. Suomijärvi and A. D. Supanitsky and M. S. Sutherland and J. Swain and Z. Szadkowski and O. A. Taborda and A. Tapia and A. Tepe and V. M. Theodoro and C. Timmermans and C. J. Todero Peixoto and L. Tomankova and B. Tomé and A. Tonachini and G. Torralba Elipe and D. Torres Machado and M. Torri and P. Travnicek and M. Trini and R. Ulrich and M. Unger and M. Urban and A. Valbuena-Delgado and J. F. Valdés Galicia and I. Valiño and L. Valore and G. van Aar and P. van Bodegom and A. M. van den Berg and A. van Vliet and E. Varela and B. Vargas Cárdenas and G. Varner and J. R. Vázquez and R. A. Vázquez and D. Veberič and V. Verzi and J. Vicha and L. Villaseñor and S. Vorobiov and H. Wahlberg and O. Wainberg and D. Walz and A. A. Watson 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},
journal= {arXiv preprint arXiv:1609.08567},
year = {2016}
}
Comments
Published version. Added journal reference and DOI. Added Report Number