arXiv subjects

A. Margiotta

Publications and source records attributed to A. Margiotta.

At least 127 records · Page 7Linked to original sources

arXiv2008

Magnetic Monopole Search at high altitude with the SLIM experiment

The SLIM experiment was a large array of nuclear track detectors located at the Chacaltaya high altitude Laboratory (5230 m a.s.l.). The detector was in particular sensitive to Intermediate Mass Magnetic Monopoles, with masses 10^5 < M <10^{12} GeV. From the analysis of the full detector exposed for more than 4 years a flux upper limit of 1.3 x 10^{-15} cm^{-2} s^{-1} sr^{-1} for downgoing fast Intermediate Mass Monopoles was established at the 90% C.L.

hep-ex↗

arXiv2008

Results of the Search for Strange Quark Matter and Q-balls with the SLIM Experiment

The SLIM experiment at the Chacaltaya high altitude laboratory was sensitive to nuclearites and Q-balls, which could be present in the cosmic radiation as possible Dark Matter components. It was sensitive also to strangelets, i.e. small lumps of Strange Quark Matter predicted at such altitudes by various phenomenological models. The analysis of 427 m^2 of Nuclear Track Detectors exposed for 4.22 years showed no candidate event. New upper limits on the flux of downgoing nuclearites and Q-balls at the 90% C.L. were established. The null result also restricts models for strangelets propagation through the Earth atmosphere.

hep-ex↗

arXiv2008

The treatment and rejection of two "strange" candidate events in the SLIM experiment

During the analysis of the CR39 Nuclear Track Detectors (NTDs) of the SLIM experiment exposed at the high altitude lab of Chacaltaya (Bolivia) we observed a sequence of puzzling etch-pits. We made a detailed investigation of all the CR39 and Makrofol detectors in the same stack and in all the stacks around the candidate event. We found a second puzzling sequence of etch-pits (plus some single etch-pits). The analysis of this configuration was important because we were searching for rare particles (Magnetic Monopoles, Nuclearites, Q-balls) in the cosmic radiation. Thus we analyzed in detail the evolution with increasing etching time of the etch-pits. We concluded that the two sequences of the etch-pits (and some other background etch-pits) may have originated from a rare manufacture malfunctioning which involved 1 m^2 of produced CR39.

hep-ex↗

arXiv2007

The MACRO Experiment at Gran Sasso

In this overview of the MACRO experiment we recall the structure of the detector and discuss several physics topics: atmospheric neutrinos and neutrino oscillations, high energy neutrino astronomy, searches for WIMPs and for low energy stellar gravitational collapse neutrinos, stringent upper limits on GUT magnetic monopoles, high energy downgoing muons, primary cosmic ray composition and shadowing of primary cosmic rays by the Moon and the Sun.

hep-ex↗

arXiv2006

Fragmentation studies of high energy ions using CR39 nuclear track detectors

We report on the measurements of the total charge changing fragmentation cross sections in high-energy nucleus-nucleus collisions using Fe, Si and Pb incident ions. Several stacks of CR39 nuclear track detectors with different target combinations were exposed at normal incidence to high energy accelerator beams to integrated densities of about 2000 ions/cm^2. The nuclear track detector foils were chemically etched, and ion tracks were measured using an automatic image analyzer system. The cross section determination is based on the charge identification of beam ions and their fragments and on the reconstruction of their path through the stacks.

physics.ins-det↗

arXiv2006

Nuclear Track Detectors for Environmental Studies and Radiation Monitoring

Several improvements were made for Nuclear Track Detectors (NTDs) used for environmental studies and for particle searches. A new method was used to determine the bulk etch rate of CR39 and Makrofol NTDs. It is based on the simultaneous measurement of the diameter and of the height of etch-pit cones caused by relativistic heavy ions (158 A GeV Pb(82+) and In(49+) ions) and their fragments. The use of alcohol in the etching solution improves the surface quality of NTDs and it raises their thresholds. The detectors were used for the determination of nuclear fragmentation cross sections of Iron and Silicon ions of 1.0 and 0.41 GeV/nucleon. These measurements are important for the determination of doses in hadron therapy and for doses received by astronauts. The detectors were also used in the search of massive particles in the cosmic radiation, for the determination of the mass spectrum of cosmic rays and for the evaluation of Po(210) alpha decay and of natural radon concentrations.

physics.ins-det↗

arXiv2006

Nuclear Track Detectors for Particle Searches

In this paper we report a search for intermediate mass magnetic monopoles and nuclearites using CR39 and Makrofol Nuclear Track Detectors (NTDs) of the SLIM large area experiment, 440 m^2 exposed at the high altitude laboratory of Chacaltaya (Bolivia) and about 100 m^2 at Koksil, Himalaya (Pakistan). We discuss the new chemical etching and improved analysis of the SLIM CR39 sheets. Preliminary limits are based on 316 $m^2$ of CR39 NTDs exposed for 3.9 y.

physics.ins-det↗

arXiv2006

Rare Particle Searches with the high altitude SLIM experiment

The search for rare particles in the cosmic radiation remains one of the main aims of non-accelerator particle astrophysics. Experiments at high altitude allow lower mass thresholds with respect to detectors at sea level or underground. The SLIM experiment is a large array of nuclear track detectors located at the Chacaltaya High Altitude Laboratory (5290 m a.s.l.). The preliminary results from the analysis of a part of the first 236 sq.m exposed for more than 3.6 y are here reported. The detector is sensitive to Intermediate Mass Magnetic Monopoles and to SQM nuggets and Q-balls, which are possible Dark Matter candidates.

hep-ex↗

arXiv2005

Atmospheric muon background in the ANTARES detector

An evaluation of the background due to atmospheric muons in the ANTARES high energy neutrino telescope is presented. Two different codes for atmospheric shower simulation have been used. Results from comparisons between these codes at sea level and detector level are presented. The first results on the capability of ANTARES to reject this class of background are given.

astro-ph↗

arXiv2005

Time variations in the deep underground muon flux measured by MACRO

More than 30 million of high-energy muons collected with the MACRO detector at the underground Gran Sasso Laboratory have been used to search for flux variations of different natures. Two kinds of studies were carried out: search for periodic variations and for the occurrence of clusters of events. Different analysis methods, including Lomb-Scargle spectral analysis and Scan Test statistics have been applied to the data.

astro-ph↗

arXiv2005

Search for exotic contributions to atmospheric neutrino oscillations

The energy spectrum of neutrino-induced upward-going muons in MACRO was analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant effect. The data disfavor these possibilities even at a sub-dominant level; stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter $|Δv| < 6 \times 10^{-24}$ at $\sin 2θ_v$ = 0 and $|Δv| < 2.5 ÷5 \times 10^{-26}$ at $\sin 2θ_v$ = $\pm$1. The limits can be re-interpreted as bounds on the Equivalence Principle violation parameters.

hep-ex↗

arXiv2005

Search for spontaneous muon emission from lead nuclei

We describe a possible search for muonic radioactivity from lead nuclei using the base elements ("bricks" composed by lead and nuclear emulsion sheets) of the long-baseline OPERA neutrino experiment. We present the results of a Monte Carlo simulation concerning the expected event topologies and estimates of the background events. Using few bricks, we could reach a good sensitivity level.

hep-ex↗

arXiv2005

A parameterisation of single and multiple muons in the deep water or ice

Atmospheric muons play an important role in underwater/ice neutrino detectors. In this paper, a parameterisation of the flux of single and multiple muon events, their lateral distribution and of their energy spectrum is presented. The kinematics parameters were modelled starting from a full Monte Carlo simulation of the interaction of primary cosmic rays with atmospheric nuclei; secondary muons reaching the sea level were propagated in the deep water. The parametric formulas are valid for a vertical depth of 1.5-5 km w.e. and up to 85 deg for the zenith angle, and can be used as input for a fast simulation of atmospheric muons in underwater/ice detectors.

hep-ph↗

arXiv2005

MACRO results on atmospheric neutrinos

We discuss the final results of the MACRO experiment on atmospheric neutrino oscillations. The data concern 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 favor 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. A preliminary search for possible Lorentz invariance violation contributions to atmospheric neutrino oscillations is presented and discussed.

hep-ex↗

arXiv2005

Search for a Lorentz invariance violation contribution in atmospheric neutrino oscillations using MACRO data

Neutrino-induced upward-going muons in MACRO have been analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of nu_mu -> nu_tau transitions. The data disfavor these exotic possibilities even at a sub-dominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter |Delta v| < 6 * 10^(-24) at sin2theta_v = 0 and |Delta v| < 2.5--5 * 10^(-26) at sin2theta_v = +/-1. These limits can also be re-interpreted as upper bounds on the parameters describing violation of the Equivalence Principle.

hep-ex↗

arXiv2005

Time correlations of high energy muons in an underground detector

We present the result of a search for correlations in the arrival times of high energy muons collected from 1995 till 2000 with the streamer tube system of the complete MACRO detector at the underground Gran Sasso Lab. Large samples of single muons (8.6 million), double muons (0.46 million) and multiple muons with multiplicities from 3 to 6 (0.08 million) were selected. These samples were used to search for time correlations of cosmic ray particles coming from the whole upper hemisphere or from selected space cones. The results of our analyses confirm with high statistics a random arrival time distribution of high energy cosmic rays.

astro-ph↗

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↗