High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large
number of particles along the beam collision axis, outside of the acceptance of existing LHC …

The present white paper is submitted as part of the “Snowmass” process to help inform the
long-term plans of the United States Department of Energy and the National Science …

We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the
surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of …

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 …

Cosmic rays are relativistic particles that come to the Earth from outer space. Despite a great
effort made in both experimental and theoretical research, their origin is still unknown. One …

It is well known that the fraction of energy in a hadron collision going into electromagnetic
particles (electrons and photons, including those from decays) has a large impact on the …

Nature is providing particles with energies exceeding 100 EeV. Their existence imposes
immediate questions: Are they ordinary particles, accelerated in extreme astrophysical …

We present a measurement of the momentum spectra of π±, K±, p±, Λ, Λ¯, and KS 0
produced in interactions of negatively charged pions with carbon nuclei at beam momenta of …

We test the predictions of hadronic interaction models regarding the depth of maximum of air-
shower profiles, X max, and ground-particle signals in water-Cherenkov detectors at 1000 m …

Experimental observations of extensive air showers have revealed an excess of the muon
content with respect to their theoretical simulations, which we refer to as the muon puzzle …