Measurement of the Fluctuations in the Number of Muons in Extensive Air Showers with the Pierre Auger Observatory Aab, A. Bueno Villar, Antonio Carceller López, Juan Miguel Pierre Auger Collaboration The successful installation, commissioning, and operation of the Pierre Auger Observatory would not have been possible without the strong commitment and effort from the technical and administrative staff in Malargue. We are very grateful to the following agencies and organizations for financial support: Argentina-Comision Nacional de Energia Atomica, Agencia Nacional de Promocion Cientifica y Tecnologica (ANPCyT), Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Gobierno de la Provincia de Mendoza, Municipalidad de Malargue, NDM Holdings and Valle Las Lenas; in gratitude for their continuing cooperation over land access; Australia-the Australian Research Council; BrazilConselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundacao de Amparo a Pesquisa do Estado de Rio de Janeiro (FAPERJ), Sao Paulo Research Foundation (FAPESP) Grants No. 2019/10151-2, No. 2010/07359-6, and No. 1999/05404-3, Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes (MCTIC); Ministry of Education, Youth and Sports of the Czech RepublicGrants No. MSMT CR LTT18004, No. LM2015038, No. LM2018102, No. CZ.02.1.01/0.0/0.0/16_013/0001402, No. CZ.02.1.01/0.0/0.0/18_046/0016010, and No. CZ.02.1.01/0.0/0.0/17_049/0008422; France-Centre de Calcul IN2P3/CNRS, Centre National de la Recherche Scientifique (CNRS), Conseil Regional Ile-de-France, Departement Physique Nucl ' eaire et Corpusculaire (PNC-IN2P3/CNRS), Departement Sciences de l'Univers (SDU-INSU/CNRS), Institut Lagrange de Paris (ILP) Grant No. LABEX ANR-10-LABX-63 within the Investissements d'Avenir Programme Grant No. ANR11-IDEX-0004-02; Germany-Bundesministerium fur Bildung und Forschung (BMBF), Deutsche Forschungsgemeinschaft (DFG), Finanzministerium Baden-Wurttemberg, Helmholtz Alliance for Astroparticle Physics (HAP), Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF), Ministerium fur Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen, Ministerium fur Wissenschaft, Forschung und Kunst des Landes Baden-Wurttemberg; Italy-Istituto Nazionale di Fisica Nucleare (INFN), Istituto Nazionale di Astrofisica (INAF), Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR), CETEMPS Center of Excellence, Ministero degli Affari Esteri (MAE); Mexico-Consejo Nacional de Ciencia y Tecnologia (CONACYT) Grant No. 167733, Universidad Nacional Autonoma de Mexico (UNAM), PAPIIT DGAPA-UNAM; The Netherlands-Ministry of Education, Culture and Science, Netherlands Organisation for Scientific Research (NWO), Dutch national e-infrastructure with the support of SURF Cooperative; Poland-Ministry of Science and Higher Education, Grant No. DIR/WK/2018/11, National Science Centre, Grants No. 2013/08/M/ST9/00322, No. 2016/23/B/ST9/01635, and No. HARMONIA 5-2013/10/M/ST9/00062, UMO-2016/22/M/ST9/00198; Portugal -Portuguese national funds and FEDER funds within Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia (COMPETE); Romania-Romanian Ministry of Education and Research, the Program Nucleu within MCI (PN19150201/16N/2019 and PN19060102), and project PN-III-P1-1.2-PCCDI-2017-0839/19PCCDI/2018 within PNCDI III; Slovenia-Slovenian Research Agency, Grants No. P1-0031, No. P1-0385, No. I00033, No. N1-0111; Spain-Ministerio de Economia, Industria y Competitividad (FPA2017-85114-P and FPA2017-85197-P), Xunta de Galicia (ED431C 2017/07), Junta de Andalucia (SOMM17/6104/UGR), Feder Funds, RENATA Red Nacional Tematica de Astroparticulas (FPA2015-68783-REDT), and Maria de Maeztu Unit of Excellence (MDM-2016-0692); U.S.Department of Energy, Awards No. DE-AC0207CH11359, No. DE-FR02-04ER41300, No. DE-FG0299ER41107, and No. DE-SC0011689, National Science Foundation, Grant No. 0450696, The Grainger Foundation, Marie Curie-IRSES/EPLANET, European Particle Physics Latin American Network, and UNESCO. We present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultrahigh energy cosmic rays. We find that the measured fluctuations are in good agreement with predictions from air shower simulations. This observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultrahigh energies. Our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop. 2021-06-18T07:42:18Z 2021-06-18T07:42:18Z 2021-04-16 info:eu-repo/semantics/article Aab, A... [et al.] (2021). Measurement of the fluctuations in the number of muons in extensive air showers with the Pierre Auger Observatory. Physical review letters, 126(15), 152002. DOI: [10.1103/PhysRevLett.126.152002] http://hdl.handle.net/10481/69265 10.1103/PhysRevLett.126.152002 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España American Physical Society