A. Castellina

Measurement of the depth of maximum of extensive air showers above 10(18) eV

We describe the measurement of the depth of maximum, Xmax, of the longitudinal development of air showers induced by cosmic rays. Almost four thousand events above 10^18 eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/- 0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.

Experimental Study of Atmospheric Neutrino Flux in the NUSEX Experiment

The fully contained events detected in the NUSEX nucleon stability experiment have been analysed to search for possible anomalies in the fluxes of atmospheric neutrinos. The measured flux of muon neutrinos is in very good agreement with predictions and no anomaly has been found in the ratio between the rate of electron and muon neutrino events.

Measurement of the cosmic ray hadron spectrum up to 30-TeV at mountain altitude: The Primary proton spectrum

The flux of cosmic ray hadrons at the atmospheric depth of 820 g/cm^2 has been measured by means of the EAS-TOP hadron calorimeter (Campo Imperatore, National Gran Sasso Laboratories, 2005 m a.s.l.). The hadron spectrum is well described by a single power law : S(E_h) = (2.25 +- 0.21 +- 0.34(sys)) 10^(-7)(E_h/1000)^(-2.79 +- 0.05) m^(-2) s^(-1) sr^(-1) GeV^(-1) over the energy range 30 GeV-30 TeV. The procedure and the accuracy of the measurement are discussed. The primary proton spectrum is derived from the data by using the CORSIKA/QGSJET code to compute the local hadron flux as a function of the primary proton spectrum and to calculate and subtract the heavy nuclei contribution (basing on direct measurements). Over a wide energy range E_0 = 0.5-50 TeV its best fit is given by a single power law : S(E_0) = (9.8 +- 1.1 +- 1.6(sys)) 10^(-5) (E_0/1000)^(-2.80 +- 0.06) m^(-2) s^(-1) sr^(-1) GeV^(-1). The validity of the CORSIKA/QGSJET code for such application has been checked using the EAS-TOP and KASCADE experimental data by reproducing the ratio of the measured hadron fluxes at the two experimental depths (820 and 1030 g/cm^2 respectively) at better than 10% in the considered energy range.

Limits on low-energy neutrino fluxes with the Mont Blanc liquid scintillator detector

Abstract The LSD liquid scintillation detector has been operating since 1985 as an underground neutrino observatory in the Mont Blanc Laboratory with the main objective of detecting antineutrino bursts from collapsing stars. In August 1988 the construction of an additional lead and borex paraffin shield considerably reduced the radioactive background and increased the sensitivity of the apparatus. In this way the search for steady fluxes of low-energy neutrinos of different flavours through their interactions with free protons and carbon nuclei of the scintillator was made possible. No evidence for a galactic collapse was observed during the whole period of measurement. The corresponding 90% c.l. upper limit on the galactic collapses rate is 0.45 y −1 for a burst duration of ΔT ⩽ 10 s. After analysing the last 3 years data, the following 90% c.l. upper limits on the steady neutrino and antineutrino fluxes were obtained: Φ( \ gn e ) 4 \ gn e s −1 cm −2 9 ⩽ E ν ⩽ 50MeV Φ( \ gn e ) 3 \ gn e s −1 cm −2 20 ⩽ E ν ⩽ 50MeV Φ(ν e ) 3 ν e s −1 cm −2 25 ⩽ E ν ⩽ 50 MeV Φ(ν μ + τ ) 7 ν μ + τ s −1 cm −2 20 ⩽ E ν ⩽ 100 MeV Φ( \ gn μ + τ ) 7 \ gn μ + τ s −1 cm −2 20 ⩽ E ν ⩽ 100 MeV In particular comparing the obtained upper limit on the \ gn e flux for 9 ⩽ E ν ⩽ 20 MeV to the solar ν e flux predicted by the standard solar model in the same range of energy, we can exclude the possibility that more than 6.3% of the solar ν e s flux can change to \ gn e . Finally the first limits on the flux of relic supernova neutrinos of all flavours as a function of the neutrino sea temperature are presented.

Energy spectrum and angular distribution of prompt cosmic-ray muons

SummaryThe energy spectrum and angular distribution of atmospheric prompt muons are calculated by using an integral solution for production of charmed particles, their decay and muon transport in the atmosphere. Current experimental information from accelerator and theoretical ideas about charm cross-section and semi-leptonic decay are used to give a reference prompt muon spectrum to compare with that from conventional sources (π and K decay). The obtained differential spectrum has an energy dependence which approaches that of the primary cosmic rays. The integral intensity of prompt muons is equal to the conventional one at about 250 TeV. The angular distribution is found to be practically flat in the range (0÷80)0 irrespective of the muon energy. On the basis of this analysis we estimate that accurate measurements of muon energy spectrum and angular distribution at energies greater than 10 TeV should allow one to obtain useful information regarding charm hadroproduction cross-section in the 100 TeV region.RiassuntoSi calcola uno spettro di muoni pronti per confrontarlo con quello di sorgenti convenzionali (decadimenti da π, K) usando sezioni d’urto di produzione di particelle charmate e decadimenti semileptonici ottenuti da dati di acceleratori e da recenti calcoli teorici. Lo spettro differenziale dei muoni pronti ha una dipendenza dall’energia simile a quella dei raggi cosmici primari. L’intensità integrale dei muoni pronti raggiunge quella convenzionale a circa 250 TeV e la distribuzione angolare è praticamente isotropa nell’intervallo (0÷80)o non dipendendo dall’energia dei muoni. Sulla base di questa analisi noi riteniamo che un’accurata misura della distribuzione angolare e dello spettro in energia dei muoni ad energie maggiori di 10 TeV possano permettere di ottenere utili informazioni sulla sezione d’urto della produzione adronica di particelle charmate nella regione dei 100 TeV.

The limit to the UHE extraterrestrial neutrino flux from the observations of horizontal air showers at EAS-TOP

Abstract Extensive Air Showers at large zenith angles θ > 70° (Horizontal Air Showers, HAS) are observed at the EAS-TOP array at Campo Imperatore (Gran Sasso Laboratories). The rate of these events exceeds the one due to primary cosmic rays (at this angles) and therefore these showers have to be generated by penetrating particles. Assuming that they are produced by atmospheric muons we derived the muon flux as Fμ(> 30 TeV) = 1.1 × 10−11cm−2s−1sr−1, in good agreement with the underground measurements. The upper limits for diffuse neutrino radiation from these measurements is Iν(> 105GeV) dI ν e (E 0 )/dE ν e −18 cm −2 s −1 sr −1 GeV −1 , for the resonant ( E 0 = m W 2 2m e = 6.4 × 10 6 GeV ) neutrinos.

Upper limit on the prompt muon flux derived from the LVD underground experiment

We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured depth-angular distribution of muon intensities has been used to obtain the normalization factor, A, the power index, gamma, of the primary all-nucleon spectrum and the ratio, R_c, of prompt muon flux to that of pi-mesons - the main parameters which determine the spectrum of cosmic ray muons at the sea level. The value of gamma = 2.77 +/- 0.05 (68% C.L.) and R_c<2.0 x 10^-3 (95% C.L.) have been obtained. The upper limit to the prompt muon flux favours the models of charm production based on QGSM and the dual parton model.

Experimental Study of Upward Stopping Muons in NUSEX

A search for upward-going stopping muon events has been performed using the NUSEX detector. The experimental flux (1.31???0.46)???10-13??/cm2 s sr is in good agreement with the theoretical expectations of muon production from atmospheric neutrinos. The experimental limit on the flux of muons produced by high-energy neutrinos from the Sun is compared to the expectations based on cold-dark-matter hypothesis, and mass limits on different candidates are set.

Multiple interactions of muons in the NUSEX detector and muon energy spectrum deep underground

Abstract Multiple electromagnetic interactions of high energy cosmic ray muons in the NUSEX detector (5000 mwe underground) have been analysed. Different modes of the pair meter technique have been used to investigate the muon energy spectrum shape at the observation depth. The observed event distributions are in good agreemetn with the expectation based on the usual picture of underground muon spectra. The first experimental estimates of the muon spectrum parameters at great depths have been obtained. A comparison of the estimated average muon energy with the available theoretical calculations is given.

Search for fractionally charged particles in the Mont Blanc LSD scintillation detector

Abstract An analysis of the events recorded by the Mont Blanc Neutrino Scintillation Detector was performed in order to search for fractionally charged particles with |Q| = 1 3 and |Q| = 2 3 . In a live time of 2378 days, the obtained 90% C. L. upper limits on the fluxes of fractionally charged particles in the core of our detector are Φ(|Q| = 1 3 ) −13 cm −2 s −1 sr −1 and Φ(|Q| = 2 3 ) −13 cm −2 s −1 sr −1 , the best available limits obtained by scintillation counters technique.