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G. Giacomelli

Publications and source records attributed to G. Giacomelli.

At least 109 records · Page 6Linked to original sources
arXiv2004

New MACRO results on atmospheric neutrino oscillations

The final results of the MACRO experiment on atmospheric neutrino oscillations are presented and discussed. The data concern different event topologies with average neutrino energies of ~3 and ~50 GeV. Multiple Coulomb Scattering of the high energy muons in absorbers was used to estimate the neutrino energy of each event. The angular distributions, the L/E_nu distribution, the particle ratios and the absolute fluxes all favour nu_mu --> nu_tau oscillations with maximal mixing and Delta m^2 =0.0023 eV^2. A discussion is made on the Monte Carlos used for the atmospheric neutrino flux. Some results on neutrino astrophysics are also briefly discussed.

hep-ex↗
arXiv2004

MACRO results on atmospheric neutrino oscillations

The final results of the MACRO experiment on atmospheric neutrino oscillations are presented. The data concern different event topologies with average neutrino energies of ~ 3 and ~ 50 GeV. Multiple Coulomb Scattering of the high energy muons was used to estimate the neutrino energy event by event. The angular distributions, the L/E_nu distribution, the particle ratios and the absolute fluxes all favour nu_mu --> nu_tau oscillations with maximal mixing and Delta m^2 ~ 0.0023 eV^2. Emphasis is given to measured ratios which are not affected by Monte Carlo (MC) absolute normalization; a discussion is made on MC uncertainties.

hep-ex↗
arXiv2004

Search for possible neutrino radiative decays during the 2001 total solar eclipse

We present the results of the observations performed in the occasion of the June 21, 2001 total solar eclipse, looking for visible photons emitted trough a possible radiative decay of solar neutrinos. We establish lower limits for the neutrino proper lifetimes larger than 1000 s/eV, for neutrino masses larger than 0.01 eV.

hep-ex↗
arXiv2003

Experimental Study of Noise-induced Phase Synchronization in Vertical-cavity Lasers

We report the experimental evidence of noise-induced phase synchronization in a vertical cavity laser. The polarized laser emission is entrained with the input periodic pump modulation when an optimal amount of white, gaussian noise is applied. We characterize the phenomenon, evaluating the average frequency of the output signal and the diffusion coefficient of the phase difference variable. Their values are roughly independent on different waveforms of periodic input, provided that a simple condition for the amplitudes is satisfied. The experimental results are compared with numerical simulations of a Langevin model.

cond-mat.stat-mech↗
arXiv2003

Monte Carlo simulation of an experiment looking for radiative solar neutrino decays

We analyse the possibility of detecting visible photons from a hypothetical radiative decay of solar neutrinos. Our study is focused on the simulation of such measurements during total solar eclipses and it is based on the BP2000 Standard Solar Model and on the most recent experimental information concerning the neutrino properties.

hep-ph↗
arXiv2003

Neutrino Physics and Astrophysics with the MACRO Experiment at the Gran Sasso Lab

The results of the MACRO experiment on atmospheric neutrino oscillations are presented and discussed. The data concern different event topologies with average neutrino energies of ~ 4 and ~ 50 GeV. The Multiple Coulomb Scattering of muons in the MACRO absorbers was used to estimate the neutrino energy of each event of the higher energy sample. The angular distributions, the absolute fluxes and the L/E distribution favour nu_mu <--> nu_tau oscillations with maximal mixing and Delta m^2=0.0025 eV^2. Results are presented on the searches for astrophysical sources of high energy muon neutrinos, for bursts of electron antineutrinos from stellar gravitational collapses and on indirect searches for WIMPs from the Earth and from the Sun.

hep-ex↗
arXiv2003

Search for GUT Magnetic Monopoles with the MACRO Experiment at the Gran Sasso Lab

The final results of the MACRO experiment on the search for GUT supermassive magnetic monopoles in the penetrating cosmic radiation are presented and discussed. The 90% CL upper limits are at the level of 1.5 - 2 x 10^-16 cm^-2 s^-1 sr^-1 for 0.0004 < beta < 1. Similar limits were obtained for nuclearites. Limits for the MM catalysis of proton decay are at 3 - 4 x 10^-16 cm^-2 s^-1 sr^-2 for 10^-4 < beta < 6 x 10^-3.

hep-ex↗
arXiv2003

Magnetic Monopole Searches

In this lecture notes will be discussed the status of the searches (i) for classical Dirac Magnetic Monopoles (MMs) at accelerators, (ii) for GUT superheavy MMs in the penetrating cosmic radiation and (iii) for Intermediate Mass MMs in the cosmic radiation underground, underwater and at high altitude. An outlook and a discussion on future searches follows.

hep-ex↗
arXiv2002

Astroparticle Physics

The main issues in non-accelerator astroparticle physics are reviewed and discussed. A short description is given of the experimental methods, of many experiments and of their experimental results.

hep-ex↗
arXiv2002

Status Report of the MACRO Experiment for the year 2001

In this 2001 status report of the MACRO experiment, results are presented on atmospheric neutrinos and neutrino oscillations, high energy neutrino astronomy, searches for WIMPs, search for low energy stellar gravitational collapse neutrinos, stringent upper limits on GUT magnetic monopoles, nuclearites and lightly ionizing particles, high energy downgoing muons, primary cosmic ray composition and shadowing of primary cosmic rays by the Moon and the Sun.

hep-ex↗
arXiv2002

Fragmentation cross sections of 158 A GeV Pb ions in various targets measured with CR39 nuclear track detectors

We report the measurement of the fragmentation cross sections in high-energy nucleus-nucleus collisions using the 158 A GeV Pb beam from the CERN-SPS. The fragments have charges changed from that of the incident projectile nucleus by $ΔZ=Z_{Pb}-Z_{frag}$, with 8 <ΔZ <75. The targets range from polyethylene to lead. Charge identification is made with CR39 nuclear track detectors, measured with an automatic image analyzer system. The measured fragmentation cross sections are parameterized with an empirical relation in terms of the atomic mass of the target, and of the charge of the final fragment.

hep-ex↗
arXiv2002

Atmospheric neutrino oscillations

The recent results from the Soudan 2, MACRO and SuperKamiokande experiments on atmospheric neutrino oscillations are summarized and discussed. Some features of possible future atmospheric neutrino experiments are presented.

hep-ex↗
arXiv2001

Magnetic Monopoles

We discuss the experimental situation of direct searches at accelerators for Dirac magnetic monopoles, and in the penetrating cosmic radiation for the superheavy magnetic monopoles predicted by GUT theories. We also discuss the searches for intermediate mass monopoles (wich are predicted by theories in extra dimensions), and for nuclearites and Q-balls.

hep-ex↗
arXiv2001

Atmospheric neutrino oscillations in MACRO

In this paper we first give a short overview of the MACRO detector, which was operational at the Gran Sasso Laboratory from 1989 till 2000. Then we present and discuss the results on atmospheric neutrino oscillations, concerning medium (~4 GeV) and high (~50 GeV) energy data. Using the Multiple Coulomb Scattering of muons inside the lower part of the detector, estimates of neutrino energies were made for the high energy sample. The MACRO data, angular distributions, absolute flux and L/E_nu distributions favour nu_mu <--> nu_tau oscillations with maximal mixing and Dm^2=2.5 x 10^-3 eV^2.

hep-ex↗
arXiv2001

Search for radiative decays of solar neutrinos during a solar eclipse

A search for possible radiative decays of solar neutrinos with emission of photons in the visible range may be performed during total solar eclipses. We discuss some results obtained from the digitized images recorded during the August 11, 1999 total solar eclipse in Romania, and report on the observations made in June 21, 2001, in Zambia. Added reference for Section 1.

hep-ex↗
arXiv2001

New calibrations and time stability of the response of the INTERCAST CR-39

We present new calibrations of different production batches (from 1989 to 1999) of the INTERCAST CR-39, using the BNL-AGS 1 A GeV iron beam. The comparison with previous results, obtained with the 158 A GeV lead beam from the CERN-SPS shows that, while each production batch has a different calibration curve (mainly due to minor differences in the production conditions), the aging effect is negligible. We also tested the dependence of the CR-39 response from the time elapsed between exposure and analysis (fading effect). The fading effect, if present, is less than 10%. It may be compatible with the experimental uncertainties on the bulk etching rate vB.

hep-ex↗