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

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 correlat...

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Autor principal:	Multitudinario:425
Formato:	JOUR
Materias:	Ankle Cosmic rays Mass composition Pierre Auger Observatory
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_03702693_v762_n_p288_Multitudinario
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	todo:paper_03702693_v762_n_p288_Multitudinario
record_format	dspace
spelling	todo:paper_03702693_v762_n_p288_Multitudinario2023-10-03T15:29:51Z Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum Multitudinario:425 Ankle Cosmic rays Mass composition Pierre Auger Observatory 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. © 2016 The Author(s) JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_03702693_v762_n_p288_Multitudinario
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Ankle Cosmic rays Mass composition Pierre Auger Observatory
spellingShingle	Ankle Cosmic rays Mass composition Pierre Auger Observatory Multitudinario:425 Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
topic_facet	Ankle Cosmic rays Mass composition Pierre Auger Observatory
description	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. © 2016 The Author(s)
format	JOUR
author	Multitudinario:425
author_facet	Multitudinario:425
author_sort	Multitudinario:425
title	Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
title_short	Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
title_full	Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
title_fullStr	Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
title_full_unstemmed	Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
title_sort	evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
url	http://hdl.handle.net/20.500.12110/paper_03702693_v762_n_p288_Multitudinario
work_keys_str_mv	AT multitudinario425 evidenceforamixedmasscompositionattheankleinthecosmicrayspectrum
_version_	1807315810118533120

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

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