Projected sensitivity of DMRadio-m3 : A search for the QCD axion below 1 μeV
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Nuclear medium effects on meson production are studied using the binary-collision scaled cross section ratio between events of different charged-particle multiplicities from proton-lead collisions. Data, collected by the CMS experiment in 2016 at a nucleon-nucleon center-of-mass energy of , corresponding to an integrated luminosity of , were used. The scaling factors in the ratio are determined using a novel approach based on the cross sections measured in the same events. The scaled ratio for is consistent with unity for all event multiplicities, putting stringent constraints on nuclear modification for heavy flavor. © 2025 CERN, for the CMS Collaboration2025CERNmore » « less
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We present measurements of the atmospheric depth of the shower maximum , inferred for the first time on an event-by-event level using the surface detector of the Pierre Auger Observatory. Using deep learning, we were able to extend measurements of the distributions up to energies of 100 EeV ( ), not yet revealed by current measurements, providing new insights into the mass composition of cosmic rays at extreme energies. Gaining a 10-fold increase in statistics compared to the fluorescence detector data, we find evidence that the rate of change of the average with the logarithm of energy features three breaks at , , and , in the vicinity to the three prominent features (ankle, instep, suppression) of the cosmic-ray flux. The energy evolution of the mean and standard deviation of the measured distributions indicates that the mass composition becomes increasingly heavier and purer, thus being incompatible with a large fraction of light nuclei between 50 and 100 EeV. Published by the American Physical Society2025more » « less
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