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https://hdl.handle.net/2440/103668
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Type: | Journal article |
Title: | Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum |
Author: | Aab, A. Abreu, P. Aglietta, M. Ahn, E. Al Samarai, I. Albuquerque, I. Allekotte, I. Allison, P. Almela, A. Alvarez Castillo, J. Alvarez-Muñiz, J. Ambrosio, M. Anastasi, G. Anchordoqui, L. Andrada, B. Andringa, S. Aramo, C. Arqueros, F. Arsene, N. Asorey, H. et al. |
Citation: | Physics Letters B: Nuclear Physics and Particle Physics, 2016; 762:288-295 |
Publisher: | Elsevier |
Issue Date: | 2016 |
ISSN: | 0370-2693 1873-2445 |
Statement of Responsibility: | Pierre Auger Collaboration ... P.L.Biermann ... S.G. Blaess ... R.W.Clay ... M.J. Cooper ... B.R. Dawson ... et.al. |
Abstract: | We report a first measurement for ultrahighenergy 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 electro- magnetic 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 uncer- tainties 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 disfavoredas the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth |
Keywords: | Pierre Auger Observatory; Cosmic rays; Mass composition; Ankle |
Rights: | © 2016 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP |
DOI: | 10.1016/j.physletb.2016.09.039 |
Grant ID: | MSMT CR LG15014 LO1305 LM2015038 |
Published version: | http://dx.doi.org/10.1016/j.physletb.2016.09.039 |
Appears in Collections: | Aurora harvest 3 IPAS publications |
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hdl_103668.pdf | Published version | 1.74 MB | Adobe PDF | View/Open |
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