Testing hadronic interactions beyond 100 TeV with the Pierre Auger Observatory

by Dr Lorenzo Cazon (LIP)

Thursday 15 Dec 2016, 11:30 → 12:30 Portugal

Sala de seminários (LIP (Av. Elias Garcia, 14))

Tens of particle reactions at centre-of-mass energies well beyond 100 TeV are happening at the top of the atmosphere every second. The Pierre Auger Observatory is able to collect the air showers of particles produced after these collisions at a rate of 3000 per year. In order to infer the energy and mass composition of the primary arriving particles that create those gigantic cascades, Auger uses High Energy Hadronic models which must be extrapolated from the energy and kinematic regions available to the LHC to the unknown. The Pierre Auger has confirmed a significant deficit or muons within the air shower simulations performed with such post-LHC high energy models when compared to data of the order of 30% (for the EPOS-LHC model) or 50% (for the QGSJetII.04 model). Yet, the best model on predicting the number of muon, EPOS-LHC, dramatically fails to predict the production depth of muons in the atmosphere. These results might indicate the presence of new particle physics phenomena that has not been properly accounted yet in models. In this seminar, the history of this finding and its implications will be discussed, and what is the current status of our understanding of the UHECR origin.