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M. Aglietta

Publications and source records attributed to M. Aglietta.

At least 127 records · Page 7Linked to original sources
arXiv2010

Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{$6\times 10^{19}$eV}. The anisotropy was measured by the fraction of arrival directions that are less than $3.1^\circ$ from the position of an active galactic nucleus within 75 Mpc (using the Véron-Cetty and Véron $12^{\rm th}$ catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is $(38^{+7}_{-6})%$, compared with $21%$ expected for isotropic cosmic rays. This is down from the early estimate of $(69^{+11}_{-13})%$. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.

astro-ph.HE↗
arXiv2009

The Fluorescence Detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions.

astro-ph.IM↗
arXiv2009

Operations of and Future Plans for the Pierre Auger Observatory

Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.

astro-ph.IM↗
arXiv2009

Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory

From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV (1 EeV = 10^18 eV) respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top-down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section.

astro-ph.HE↗
arXiv2009

Evolution of the cosmic ray anisotropy above 10^{14} eV

The amplitude and phase of the cosmic ray anisotropy are well established experimentally between 10^{11} eV and 10^{14} eV. The study of their evolution into the energy region 10^{14}-10^{16} eV can provide a significant tool for the understanding of the steepening ("knee") of the primary spectrum. In this letter we extend the EAS-TOP measurement performed at E_0 around 10^{14} eV, to higher energies by using the full data set (8 years of data taking). Results derived at about 10^{14} and 4x10^{14} eV are compared and discussed. Hints of increasing amplitude and change of phase above 10^{14} eV are reported. The significance of the observation for the understanding of cosmic ray propagation is discussed.

astro-ph.HE↗
arXiv2008

Performances and stability of a 2.4 ton Gd organic liquid scintillator target for antineutrino detection

In this work we report the performances and the chemical and physical properties of a (2 x 1.2) ton organic liquid scintillator target doped with Gd up to ~0.1%, and the results of a 2 year long stability survey. In particular we have monitored the amount of both Gd and primary fluor actually in solution, the optical and fluorescent properties of the Gd-doped liquid scintillator (GdLS) and its performances as a neutron detector, namely neutron capture efficiency and average capture time. The experimental survey is ongoing, the target being continuously monitored. After two years from the doping time the performances of the Gd-doped liquid scintillator do not show any hint of degradation and instability; this conclusion comes both from the laboratory measurements and from the "in-tank" measurements. This is the largest stable Gd-doped organic liquid scintillator target ever produced and continuously operated for a long period.

physics.ins-det↗
arXiv2007

First CNGS events detected by LVD

The CERN Neutrino to Gran Sasso (CNGS) project aims to produce a high energy, wide band $ν_μ$ 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 $ν_τ$ 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.

hep-ex↗
arXiv2007

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.

astro-ph↗
arXiv2006

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 $θ_{13}$, presently unknown. Finally we discuss the astrophysical uncertainties, showing their importance and comparing it with the effect of neutrino oscillations on the expected signal.

hep-ph↗
arXiv2004

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.

astro-ph↗
arXiv2003

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 $ν$ 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 $ν$-{\rm Fe} interactions, we include the Earth matter effects and, finally, we study also the inverted mass hierarchy case.

hep-ph↗
arXiv2003

CNGS beam monitor with the LVD detector

The importance of an adequate CNGS beam monitor at the Gran Sasso Laboratory has been stressed in many papers. Since the number of internal $ν_μ$ CC and NC interactions in the various detectors will not allow to collect statistics rapidly, one should also be able to detect the $ν_μ$ CC interactions in the upstream rock. In this study we have investigated the performances of the LVD detector as a monitor for the CNGS neutrino beam. Thanks to its wide area ($13 \times 11 m^2$ orthogonal to the beam direction) LVD can detect about 120 muons per day originated by $ν_μ$ CC interactions in the rock. The LVD total mass is $\sim2 kt$. This allows to get 30 more CNGS events per day as internal $(NC + CC)$ $ν_μ$ interactions, for a total of $\sim 150$ events per day. A 3% statistical error can be reached in 7 days. Taking into account the time characteristics of the CNGS beam, the cosmic muon background can be reduced to a negligible level, of the order of 1.5 events per day.

hep-ex↗
arXiv2001

Effects of neutrino oscillations on the supernova signal in LVD

We study the impact of neutrino oscillations on the supernova neutrino signal in the Large Volume Detector (LVD). The number of expected events for a galactic supernova (D=10 kpc) is calculated, assuming neutrino masses and mixing that explain solar and atmospheric neutrino results. The possibility to detect neutrinos in different channels makes LVD sensitive to different scenarios for neutrino properties, such as normal or inverted neutrino mass hierarchy, and/or adiabatic or non adiabatic MSW resonances associated to U(e3). Of particular importance are the charged current reactions on carbon: oscillations increase by almost one order of magnitude the number of events expected from this channel.

astro-ph↗
arXiv1999

Measurement of neutrino oscillations by means of a high density detector on the atmospheric neutrino beam

A high-density calorimeter, consisting of magnetized iron planes interleaved by RPCs, as tracking and timing devices, is a good candidate for a next generation experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to $ν_μ\to ν_x$ oscillation with $Δm^2 > 6 \times 10^{-5}$ and mixing near to maximal and fully cover the region of oscillation parameters suggested by Super-Kamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the L/E spectrum ($ν_μ$ disappearance). For $Δm^2 > 3 \times 10^{-3}$ eV$^2$, this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos ($ν_τ$ appearance).

hep-ex↗