Atmospheric Calorimetry above 1019^{19} eV: Shooting Lasers at the Pierre Auger Cosmic-Ray Observatory

The Pierre Auger Cosmic-Ray Observatory uses the earth's atmosphere as a calorimeter to measure extensive air-showers created by particles of astrophysical origin. Some of these particles carry joules of energy. At these extreme energies, test beams are not available in the conventional sense. Yet understanding the energy response of the observatory is important. For example, the propagation distance of the highest energy cosmic-rays through the cosmic microwave background radiation (CMBR) is predicted to be strong function of energy. This paper will discuss recently reported results from the observatory and the use of calibrated pulsed UV laser "test-beams" that simulate the optical signatures of ultra-high energy cosmic rays. The status of the much larger 200,000 km$^3$ companion detector planned for the northern hemisphere will also be outlined.Comment: 6 pages, 11 figures XIII International Conference on Calorimetry in High Energy Physic

Search for photons above 1019 eV with the surface detector of the Pierre Auger Observatory

We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above 1019 eV. Photons in the zenith angle range from 30 to 60 can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water- Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an E−2 diffuse flux of ultra-high energy photons above 1019 eV, 2×1019 eV and 4×1019 eV amounting to 2.11×10−3, 3.12×10−4 and 1.72×10−4 km−2 sr−1 yr−1, respectively. While the sensitivity of the present search around 2×1019 eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated.ANPCyT Spanish GovernmentConsejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET)Australian Research CouncilFonds de la Recherche Scientifique - FNRSFWOFinanciadora de Inovacao e Pesquisa (Finep)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) 2019/10151-2 2010/07359-6 1999/05404-3Czech Republic GovernmentMinistry of Education, Youth & Sports - Czech Republic LTT18004Marie Curie-IRSES/EPLANETCentre National de la Recherche Scientifique (CNRS)Conseil Rgional Ile-de-France PNC-IN2P3/CNRSInstitut Lagrange de Paris (ILP)LABEX ANR-10-LABX-63 ANR-11-IDEX-0004-02Federal Ministry of Education & Research (BMBF)German Research Foundation (DFG)Helmholtz Alliance for As-troparticle Physics (HAP)Helmholtz AssociationMinisterium fuuml;r Kultur und Wissenschaft des Landes Nordrhein-WestfalenMinisterium fuuml;r Wissenschaft, Forschung und Kunst des Landes Baden-Wuuml;rttemberg; Italy - Istituto Nazionale di Fisica Nucleare (INFN)Ministry of Education, Universities and Research (MIUR)Ministry of Foreign Affairs and International Cooperation (Italy)Consejo Nacional de Ciencia y Tecnologia (CONACyT) 167733Programa de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT) Universidad Nacional Autonoma de MexicoNetherlands Organization for Scientific Research (NWO) DIR/WK/2018/11National Science Centre, Poland 2016/22/M/ST9/00198 2016/23/B/ST9/01635 2020/39/B/ST9/01398FEDER funds within Programa Operacional Factores de CompetitividadeRomania - Ministry of Research, Inno-vation and Digitization, CNCS/CCCDI UEFISCDINational Nucleus Program TE128 PN-III-P1-1.1-TE-2021-0924/TE57/2022 PED289Slovenian Research Agency - Slovenia P1-0031Spanish Government FPA2017-85114-P PID2019-104676GB-C32Xunta de Galicia ED431C 2017/07Junta de Andalucia SOMM17/6104/UGR P18-FR-4314 FPA2015-68783-REDTMaria de Maeztu Unit of Excellence MDM-2016-0692United States Department of Energy (DOE) DE-AC02-07CH11359National Science Foundation (NSF) 0450696Grainger FoundationEuropean Particle Physics Latin American NetworkSpanish Governmen