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Abstract ALICE is a large experiment at the CERN Large Hadron Collider. Located 52 meters underground, its detectors are suitable to measure muons produced by cosmic-ray interactions in the atmosphere. In this paper, the studies of the cosmic muons registered by ALICE during Run 2 (2015–2018) are described.The analysis is limited to multimuon events defined as events with more than four detected muons (N_μ> 4) and in the zenith angle range 0° < θ < 50°. The results are compared with Monte Carlo simulations using three of the main hadronic interaction models describing the air shower development in the atmosphere: QGSJET-II-04, EPOS-LHC, and SIBYLL 2.3d.The interval of the primary cosmic-ray energy involved in the measuredmuon multiplicity distribution is about4 × 10¹⁵<E_prim< 6 × 10¹⁶eV.In this interval none of the three models is able to describe precisely the trend of the composition of cosmic rays as the energy increases. However,QGSJET-II-04 is found to be the only model capable of reproducing reasonably well the muon multiplicity distribution, assuming a heavy composition of the primary cosmic raysover the whole energy range, while SIBYLL 2.3d and EPOS-LHC underpredict thenumber of muons in a large interval of multiplicity by more than 20% and 30%, respectively.The rate of high muon multiplicity events (N_μ> 100) obtainedwith QGSJET-II-04 and SIBYLL 2.3d is compatible with the data, while EPOS-LHC produces a significantly lower rate (55% of the measured rate). For both QGSJET-II-04 and SIBYLL 2.3d, the rate is close to the data when the composition is assumed to be dominated by heavy elements, an outcome compatible with the average energy E_prim∼ 10¹⁷eV of these events.This result places significant constraints on more exotic production mechanisms. 

This work aims to differentiate strangeness produced from hard processes (jetlike) and softer processes (underlying event) by measuring the angular correlation between a high-momentum trigger hadron ( $h$) acting as a jet proxy and a produced strange hadron [ $\varphi \left(1020\right)$meson]. Measuring $h\text{−}\varphi$correlations at midrapidity in $p$-Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$as a function of event multiplicity provides insight into the microscopic origin of strangeness enhancement in small collision systems. The jetlike and the underlying-event-like strangeness production are investigated as a function of event multiplicity. They are also compared between a lower and higher momentum region. The evolutions of the per-trigger yields within the near-side (aligned with the trigger hadron) and away-side (in the opposite direction of the trigger hadron) jets are studied separately, allowing for the characterization of two distinct jetlike production regimes. Furthermore, the $h\text{−}\varphi$correlations within the underlying event give access to a production regime dominated by soft production processes, which can be compared directly to the in-jet production. Comparisons between $h\text{−}\varphi$and dihadron correlations show that the observed strangeness enhancement is largely driven by the underlying event, where the $\varphi /h$ratio is significantly larger than within the jet regions. As multiplicity increases, the fraction of the total $\varphi \left(1020\right)$yield coming from jets decreases compared to the underlying event production, leading to high-multiplicity events being dominated by the increased strangeness production from the underlying event. ©2024 CERN, for the ALICE Collaboration2024CERN