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 ($N_\mu>4$) and in the zenith angle range $0^{\circ}<\theta<50^{\circ}$. 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 2.3. The interval of the primary cosmic-ray energy involved in the measured muon multiplicity distribution is about $ 4 \times 10^{15}<E_\mathrm{prim}< 6 \times 10^{16}$~eV. 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 is found to be the only model capable of reproducing reasonably well the muon multiplicity distribution, assuming a heavy composition of the primary cosmic rays over the whole energy range, while SIBYLL and EPOS-LHC underpredict the number of muons in a large interval of multiplicity by more than $20\%$ and $30\%$, respectively. The rate of high muon multiplicity events ($N_\mu>100$) obtained with QGSJET and SIBYLL is compatible with the data, while EPOS-LHC produces a significantly lower rate ($55\%$ of the measured rate). For both QGSJET and SIBYLL, 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 $E_\mathrm{prim} \sim 10^{17}$~eV of these events. This result places significant constraints on more exotic production mechanisms.
Muon multiplicity distribution measured with the ALICE apparatus and obtained for the whole data sample of Run 2 corresponding to a live time of 62.5 days. The data points are grouped in multiplicity intervals with a width of five units ($N_\mu=5-9,~N_\mu=10-14,~...$), and are located at the center of each interval ($N_\mu=7,~N_\mu=12,~...$). The vertical error bars represent the statistical uncertainties.
Muon multiplicity distribution measured with the ALICE apparatus and obtained for the whole data sample of Run 2 corresponding to a live time of 62.5 days. The data are the same as Fig. 3 but each bin corresponds to a single muon multiplicity ($N_\mu=1,2,3,~...$); the distribution starts at $N_\mu=5$. The vertical error bars represent the statistical uncertainties.
Measured muon multiplicity distribution compared with simulations from CORSIKA Monte Carlo generator using QGSJET-II-04 (top), SIBYLL 2.3 (middle), and EPOS-LHC (bottom) as hadronic interaction models for proton and iron primary cosmic rays. Iron points are slightly shifted to the right to avoid overlapping with the data points. The total uncertainties in the MC simulations are given by the vertical bars, while the boxes give the systematic uncertainties of the data and the vertical bars the statistical ones.
We have analyzed a data set taken over 2.76 years live time with the Baikal neutrino telescope NT200. The goal of the analysis is to search for neutrinos from dark matter annihilation in the center of the Sun. Apart from the conventional annihilation channels $b\bar{b}$, $W^+W^-$ and $\tau^+\tau^-$ we consider also the annihilation of dark matter particles into monochromatic neutrinos. From the absence of any excess of events from the direction of the Sun over the expected background, we derive 90% upper limits on the fluxes of muons and muon neutrinos from the Sun, as well as on the elastic cross sections of dark matter scattering on protons.
Process: DM DM --> BOTTOM BOTTOMBAR. Half-cone angle GAMMA, 90% upper limit N(SIGNAL) on the number of signal events, the muon flux PHI(MU), the dark matter annihilation rate in the Sun GAMMA(ANN), the dark matter-proton spin-dependent SIG(SD) and spin-independent SIG(SI) scattering cross sections and neutrino flux PHI(NU).
Process: DM DM --> TAU+ TAU-. Half-cone angle GAMMA, 90% upper limit N(SIGNAL) on the number of signal events, the muon flux PHI(MU), the dark matter annihilation rate in the Sun GAMMA(ANN), the dark matter-proton spin-dependent SIG(SD) and spin-independent SIG(SI) scattering cross sections and neutrino flux PHI(NU).
Process: DM DM --> W+ W-. Half-cone angle GAMMA, 90% upper limit N(SIGNAL) on the number of signal events, the muon flux PHI(MU), the dark matter annihilation rate in the Sun GAMMA(ANN), the dark matter-proton spin-dependent SIG(SD) and spin-independent SIG(SI) scattering cross sections and neutrino flux PHI(NU).
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