N. Yu. Agafonova

Study of the effect of neutrino oscillations on the supernova neutrino signal in the LVD detector

The LVD detector, located in the INFN Gran Sasso National Laboratory (Italy), studies supernova neutrinos through the interactions with protons and carbon nuclei in the liquid scintillator and interactions with the iron nuclei of the support structure. We investigate the effect of neutrino oscillations in the signal expected in the LVD detector. The MSW effect has been studied in detail for neutrinos travelling through the collapsing star and the Earth. We show that the expected number of events and their energy spectrum are sensitive to the oscillation parameters, in particular to the mass hierarchy and the value of

Single and multiple muons and the generation of neutrons in the LVD experiment

\theta_{13}

Temporal characteristics of light collection in the liquid scintillation counter with a volume of 1.5 m3 and quasi-mirror reflection

, presently unknown. Finally we discuss the astrophysical uncertainties, showing their importance and comparing it with the effect of neutrino oscillations on the expected signal.

Light collection in the scintillation counter with a volume of 1.5 m3 and quasi-mirror reflection

The large geometric factor and good spatial resolution of the Large Volume Detector (LVD) ensures statistically significant and highly accurate measurements of muon trajectories and determination of the multiplicity of muon groups. The developed algorithm allows us to reconstruct 2 × 106 muon events (single muons and muon groups). Characteristics of muon groups are obtained and the specific yield of neutrons produced by single muons, muon groups, and showers is determined.

The energy spectrum of neutrons produced by cosmic ray muons in LVD

The temporal behavior of light collection in the 1.5-m3-volume mirror-reflecting counter filled with a highly transmitting liquid scintillator has been investigated. Using the Monte Carlo method and assuming that the luminescence decay time of the liquid scintillator is zero (τLS = 0), it has been ascertained that, in the case of a short flash in a counter, the exponential phase of light collection is characterized by time τcol = 15.0 ± 1.7 ns, which is does not depend on scattering of light in the medium. The measured exponent index τact = 37 ± 3 ns of an actual pulse due to a muon is determined both by light collection time τcol ≈ 15 ns and luminescence decay time τLS ≈ 20 ns of the scintillator in the large-volume counter.

Search for the νμ→ντ Oscillation with the OPERA Hybrid Detector

Collection of light in a counter with mirror reflection from relief (nonflat) surfaces and with a high transparency of the liquid scintillator was investigated. Based on results of measurements and simulation of light collection, the dependence of light collection coefficient K on the relief of reflecting surfaces and the scintillator transparency was obtained using the Monte Carlo method. The light collection coefficient was K=(30.9+1.1)×10s-3, and the resolution of the distribution function for the K value over the counter volume was η ≈12%.

Analysis of Experimental Data on the Neutron Yield from Muons

The energy spectrum of neutrons produced by cosmic ray muons in the underground detector LVD (3650 m.w.e.) is obtained for the energy range of 30–450 MeV. The spectrum is derived using the energy release spectrum of neutron interaction products in 1.5 m3 scintillation counters.

Measurement of neutron number generated by cosmic-ray muons in iron using the LVD

This work reviews the status of the international OPERA experiment aimed at searching for the νμ → ντ oscillation. Development of the emulsion techniques in the preceding DONUT and CHORUS experiments is described. A brief overview of the NOMAD experiment is given, in which properties of ντ interactions were thoroughly investigated. Characteristics of the CERN-Gran Sasso (CNGS) neutrino beam are given, the structure of the OPERA hybrid detector and the functions of its subsystems are considered, and the automatic emulsion scanning technique is briefly reviewed. Uncertainties in reconstruction of event parameters using the electronic and emulsion detectors are discussed and the procedure adopted in the experiment for identification of ντ interactions is described. The main sources of background in the search for νμ → ντ oscillation are considered. Topologies of the first two ντ candidates observed in the OPERA emulsion detector are presented. Possibilities of increasing the ντ interaction selection efficiency using multidimensional criteria are briefly discussed.

Analysis of Seasonal Variations of the Cosmic Ray Muon Flux and Neutrons Produced by Muons in the LVD Detector

Experimental data accumulated over 60 years of studying the yield of cosmogenic neutrons in a liquid scintillator (YLS), iron (YFe), and lead (YPb) were analyzed. This analysis revealed that the main part of the results on the yield YLS were overestimated by about 30%. With allowance for this circumstance, all experimental data can be described by the dependence Y(Ēµ, A) = bnAβĒµα, where the product bnĒµα stands for the energy spent by a muon on neutron production. The exponents of α = 0.78 and β = 0.95 are determined by the properties of the medium and by neutron production in showers.

Present status of the opera experiment for the direct observation of neutrino oscillations in the νμ → ντ channel

The experiment to measure the neutrons numbers generated by muons in iron (Fe) and lead (Pb) carried out using LVD. A full Monte Carlo simulation of the actual geometric configuration of the experiment is performed. The first measurement results are obtained. The measured yield of neutrons produced by muons with an energy of 280 GeV in iron is 16 × 10−4 n/μ/(g cm−2).