Agafonova,N. Yu.AgafonovaAglietta, M.M.AgliettaAntonioli, P.P.AntonioliAshikhmin, V. V.V. V.AshikhminBari, G.G.BariBruno, G.G.BrunoDobrynina, E. A.E. A.DobryninaEnikeev, R. I.R. I.EnikeevFulgione, W.W.FulgioneGaleotti, P.P.GaleottiGarbini, M.M.GarbiniGhia, P. L.P. L.GhiaGiusti, P.P.GiustiKemp, E.E.KempMalgin, A. S.A. S.MalginMolinario, A.A.MolinarioPersiani, R.R.PersianiPless, I. A.I. A.PlessRubinetti, S.S.RubinettiRyazhskaya, O. G.O. G.RyazhskayaSartorelli, G.G.SartorelliShakiryanova, I. R.I. R.ShakiryanovaSelvi, M.M.SelviTaricco, C.C.TariccoTRINCHERO, GIAN CARLOGIAN CARLOTRINCHEROVigorito, C. F.C. F.VigoritoYakushev, V. F.V. F.YakushevZichichi, A.A.Zichichi2021-05-042021-05-0420192470-0010http://hdl.handle.net/20.500.12386/30954The Large Volume Detector (LVD), hosted in the INFN Laboratori Nazionali del Gran Sasso, is triggered by atmospheric muons at a rate of $\sim 0.1$~Hz. The data collected over almost a quarter of century are used to study the muon intensity underground. The 50-million muon series, the longest ever exploited by an underground instrument, allows for the accurate long-term monitoring of the muon intensity underground. This is relevant as a study of the background in the Gran Sasso Laboratory, which hosts a variety of long-duration, low-background detectors. We describe the procedure to select muon-like events as well as the method used to compute the exposure. We report the value of the average muon flux measured from 1994 to 2017: $\mathrm{I_{\mu}^0 = 3.35 \pm 0.0005^{stat}\pm 0.03^{sys} \cdot 10^{-4} ~m^{-2} s^{-1}}$. We show that the intensity is modulated around this average value due to temperature variations in the stratosphere. We quantify such a correlation by using temperature data from the European Center for Medium-range Weather Forecasts: we find an effective temperature coefficient $\mathrm{\alpha_{T}} = 0.94\pm0.01^{stat} \pm0.01^{sys}$, in agreement with other measurements at the same depth. We scrutinise the spectral content of the time series of the muon intensity by means of the Lomb-Scargle analysis. This yields the evidence of a 1-year periodicity, as well as the indication of others, both shorter and longer, suggesting that the series is not a pure sinusoidal wave. Consequently, and for the first time, we characterise the observed modulation in terms of amplitude and position of maximum and minimum on a year-by-year basis.STAMPAenArticle10.1103/PhysRevD.100.0620022-s2.0-85072995078http://arxiv.org/abs/1909.04579v2https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.062002FIS/01 - FISICA SPERIMENTALE