We have measured the flux of cosmic muons in the Laboratori Nazionali del Gran Sasso at 3800 m.w.e. to be (3.432 +/- 0.003) center dot 10(-4) m(-2) s(-1) based on ten years of Borexino data acquired between May 2007 and May 2017. A seasonal modulation with a period of (366.3 +/- 0.6) d and a relative amplitude of (1.36 +/- 0.04)% is observed. The phase is measured to be (181.7 +/- 0.4) d, corresponding to a maximum at the 1 st of July. Using data inferred from global atmospheric models, we show the muon flux to be positively correlated with the atmospheric temperature and measure the e ff ective temperature coe ffi cient alpha(T) = 0.90 +/- 0.02. The origin of cosmic muons from pion and kaon decays in the atmosphere allows to interpret the e ff ective temperature coe ffi cient as an indirect measurement of the atmospheric kaon-topion production ratio r(K/pi) = 0.11(-0.07)(+0.11) for primary energies above 18TeV. We find evidence for a long-term modulation of the muon flux with a period of similar to 3000 d and a maximum in June 2012 that is not present in the atmospheric temperature data. A possible correlation between this modulation and the solar activity is investigated. The cosmogenic neutron production rate is found to show a seasonal modulation in phase with the cosmic muon flux but with an increased amplitude of (2.6 +/- 0.4)%.

Modulations of the cosmic muon signal in ten years of Borexino data

Galbiati C;
2019

Abstract

We have measured the flux of cosmic muons in the Laboratori Nazionali del Gran Sasso at 3800 m.w.e. to be (3.432 +/- 0.003) center dot 10(-4) m(-2) s(-1) based on ten years of Borexino data acquired between May 2007 and May 2017. A seasonal modulation with a period of (366.3 +/- 0.6) d and a relative amplitude of (1.36 +/- 0.04)% is observed. The phase is measured to be (181.7 +/- 0.4) d, corresponding to a maximum at the 1 st of July. Using data inferred from global atmospheric models, we show the muon flux to be positively correlated with the atmospheric temperature and measure the e ff ective temperature coe ffi cient alpha(T) = 0.90 +/- 0.02. The origin of cosmic muons from pion and kaon decays in the atmosphere allows to interpret the e ff ective temperature coe ffi cient as an indirect measurement of the atmospheric kaon-topion production ratio r(K/pi) = 0.11(-0.07)(+0.11) for primary energies above 18TeV. We find evidence for a long-term modulation of the muon flux with a period of similar to 3000 d and a maximum in June 2012 that is not present in the atmospheric temperature data. A possible correlation between this modulation and the solar activity is investigated. The cosmogenic neutron production rate is found to show a seasonal modulation in phase with the cosmic muon flux but with an increased amplitude of (2.6 +/- 0.4)%.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12571/937
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