Study of muon-induced neutron production, propagation and energy spectrum with the LVD detector at LNGS

High-energy neutrons, generated as a product of cosmic muon interactions in the rock or in the detector materials, represent the most Dangerous background for a large list of research topics such as reactor neutrino studies, the search for SN relic neutrinos, solar antineutrinos, dark matter, etc. (see Khalchukov F. F. et al., Nuovo Cimento C, 6 (1983) 320.) A high-energy neutron can be detected through a double signature: the first pulse is due to the recoil protons from n-p elastic scattering, while the second pulse is due to the thermalized neutron capture by a proton. Up to now there are few measurements of the muon-produced neutron flux at large depth underground. Moreover it is difficult to reproduce the measured data with Monte Carlo simulation because of the large uncertainties in the neutron production and propagation models. The LVD detector, situated at LNGS, has an ideal configuration for studying this kind of events because it is possible to detect both the muon track, using the high-acceptance tracking system, and the neutron interactions in the liquid scintillation detectors. We present here the results of the measurement, reporting the neutron flux at various distances from the muon track and for different neutron energies. Moreover, the analysis of the neutron yield as a function of the muon track length in the detector is described

Study of the Muon-Induced Neutron Background with the LVD Detector

LVD [1] is a neutrino telescope located in the Hall A of the Gran Sasso INFN laboratory; it consists of an array of 840 scintillator counters for a total mass of about 1000 tons. The detector is also equipped with a tracking system to reconstruct muons. Neutrons can be recognized through their interactions on protons which originate two subsequent pulses in a scintillator counter: a prompt signal due to the proton and a delayed signal due to the 2.2 MeV gamma ray from the neutron capture; the time delay distribution between the two pulses has an exponential shape with mean value 180 μs. The double signature can be seen in LVD by means of two different discrimination threshold; a high energy threshold, at about 7 MeV for the external counters (43%) and at about 4 MeV for the internal ones (57%), better shielded, for the proton recoil; a low energy threshold, at about 1 MeV and active for 1 ms after the high one, to allow the detection of the γ from the neutron capture. Taking into account the energy transfer in the interaction between neutron and proton, the proton quenching and the value of the high energy threshold of the detector, the neutrons with the double signature have energies greater than about 20 MeV. 3. Analysis and Result

The CNGS Neutrino Beam

The CERN to Gran Sasso Neutrino beam (CNGS) was commissioned at CERN in early August 2006 and was first sent at low intensity to Gran Sasso on August 17, 2006. The Borexino, LVD and OPERA experiments continued the commissioning of their detectors and started taking data with practically no dead time. The CNGS collected several hundred events with clean time distributions.Comment: 11 pages, 14 EPS figures. Lecture given at the 2nd Latin American School on Cosmic Rays and Astrophysics, Puebla, Mexico, 30th August - 8th September 200

A low background facility inside the LVD detector at Gran Sasso

The Large Volume Detector (LVD) in the Gran Sasso Laboratory of INFN is an observatory mainly devoted to search for neutrinos from core collapse supernovae. It consists of 1000 tons of liquid scintillator divided in 840 stainless steel tanks 1.5m$^3$ each. In this letter we present the possibility for LVD to work both as a passive shield and moderator for the low energy gamma and neutron background and as an active veto for muons and higher energy neutrons. An inner region inside the LVD structure ("LVD Core Facility") can be identified, with a volume of about 30m$^3$, with the neutron background typical of an underground laboratory placed at a much deeper site. This region can be realized with a negligible impact on the LVD operation and sensitive mass. The LVD Core Facility could be effectively exploited by a compact experiment for the search of rare events, such as double beta decay or dark matter.Comment: 5 pages, 2 figure

The EEE Project

The new experiment ``Extreme Energy Events'' (EEE) to detect extensive air showers through muon detection is starting in Italy. The use of particle detectors based on Multigap Resistive Plate Chambers (MRPC) will allow to determine with a very high accuracy the direction of the axis of cosmic ray showers initiated by primaries of ultra-high energy, together with a high temporal resolution. The installation of many of such 'telescopes' in numerous High Schools scattered all over the Italian territory will also allow to investigate coincidences between multiple primaries producing distant showers. Here we present the experimental apparatus and its tasks.Comment: 4 pages, 29th ICRC 2005, Pune, Indi

Study of the effect of neutrino oscillation on the supernova neutrino signal with the LVD detector

We present an update of our previous study (astro-ph/0112312) on how $\nu$ oscillations affect the signal from a supernova core collapse observed in the LVD detector at LNGS. In this paper we use a recent, more precise determination of the cross section (astro-ph/0302055) to calculate the expected number of inverse beta decay events, we introduce in the simulation also the $\nu$-{\rm Fe} interactions, we include the Earth matter effects and, finally, we study also the inverted mass hierarchy case.Comment: 4 pages, 4 figures, to appear in the Proceedings of ICRC 200

On-line recognition of supernova neutrino bursts in the LVD detector

In this paper we show the capabilities of the Large Volume Detector (INFN Gran Sasso National Laboratory) to identify a neutrino burst associated to a supernova explosion, in the absence of an "external trigger", e.g., an optical observation. We describe how the detector trigger and event selection have been optimized for this purpose, and we detail the algorithm used for the on-line burst recognition. The on-line sensitivity of the detector is defined and discussed in terms of supernova distance and electron anti-neutrino intensity at the source.Comment: Accepted for pubblication on Astroparticle Physics. 13 pages, 10 figure

First CNGS events detected by LVD

The CERN Neutrino to Gran Sasso (CNGS) project aims to produce a high energy, wide band $\nu_{\mu}$ beam at CERN and send it toward the INFN Gran Sasso National Laboratory (LNGS), 732 km away. Its main goal is the observation of the $\nu_{\tau}$ appearance, through neutrino flavour oscillation. The beam started its operation in August 2006 for about 12 days: a total amount of $7.6~10^{17}$ protons were delivered to the target. The LVD detector, installed in hall A of the LNGS and mainly dedicated to the study of supernova neutrinos, was fully operating during the whole CNGS running time. A total number of 569 events were detected in coincidence with the beam spill time. This is in good agreement with the expected number of events from Montecarlo simulations.Comment: Accepted for publication by the European Physical Journal C ; 7 pages, 11 figure

Search for low energy neutrinos in correlation with the 8 events observed by the EXPLORER and NAUTILUS detectors in 2001

We report on a search for low-energy neutrino (antineutrino) bursts in correlation with the 8 time coincident events observed by the gravitational waves detectors EXPLORER and NAUTILUS (GWD) during the year 2001. The search, conducted with the LVD detector (INFN Gran Sasso National Laboratory, Italy), has considered several neutrino reactions, corresponding to different neutrino species, and a wide range of time intervals around the (GWD) observed events. No evidence for statistically significant correlated signals in LVD has been found. Assuming two different origins for neutrino emission, the cooling of a neutron star from a core-collapse supernova or from coalescing neutron stars and the accretion of shocked matter, and taking into account neutrino oscillations, we derive limits to the total energy emitted in neutrinos and to the amount of accreting mass, respectively.Comment: Accepted for publication in Astronomy and Astrophysic

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 $\theta_{13}$, presently unknown. Finally we discuss the astrophysical uncertainties, showing their importance and comparing it with the effect of neutrino oscillations on the expected signal.Comment: Accepted for pubblication on Astroparticle Physics. 36 pages, 18 figure