arXiv subjects

M. Giorgini

Publications and source records attributed to M. Giorgini.

At least 37 records · Page 2Linked to original sources

arXiv2006

Bulk Etch Rate Measurements and Calibrations of Plastic Nuclear Track Detectors

New calibrations of CR39 and Makrofol nuclear track detectors have been obtained using 158 A GeV Pb (82+) and In (49+) ions; a new method for the bulk etch rate determination, using both cone height and base diameter measurements was developed. The CR39 charge resolution based on the etch-pit base area measurement is adequate to identify nuclear fragments in the interval 7 <= Z/beta <= 49. For CR39 the detection threshold is at REL~50 MeV cm^2/g, corresponding to a nuclear fragment with Z/beta~7. Base cone area distributions for Makrofol foils exposed to Pb (82+) ions have shown for the first time all peaks due to nuclear fragments with Z > 50; the distribution of the etched cone heights shows well separated individual peaks for Z/beta = 78 - 83 (charge pickup). The Makrofol detection threshold is at REL 2700 MeV cm^2/g, corresponding to a nuclear fragment with Z/beta~50.

physics.ins-det↗

arXiv2006

The Opera Experiment

The physics motivations and the detector design of the long baseline OPERA experiment are discussed; OPERA is a hybrid detector made of several types of electronic subdetectors, 2 magnets and lead/nuclear emulsions ``brick'' walls. It is located in the Gran Sasso underground lab, 732 km from CERN, on the CNGS neutrino beam. A summary of the performances and of the physics plans are presented.

physics.ins-det↗

arXiv2006

Hardware performance of a scanning system for high speed analysis of nuclear emulsions

The use of nuclear emulsions in very large physics experiments is now possible thanks to the recent improvements in the industrial production of emulsions and to the development of fast automated microscopes. In this paper the hardware performances of the European Scanning System (ESS) are described. The ESS is a very fast automatic system developed for the mass scanning of the emulsions of the OPERA experiment, which requires microscopes with scanning speeds of about 20 cm^2/h in an emulsion volume of 44 micron thickness.

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↗

arXiv2006

Search for nuclearites with the SLIM detector

The strange quark matter (SQM) may be the ground state of QCD; nuggets of SQM could be present in cosmic rays (CR). SLIM is a large area experiment, using CR39 and Makrofol track etch detectors, presently deployed at the high altitude CR Laboratory of Chacaltaya, Bolivia. We discuss the expected properties of SQM, from the point of view of its search with SLIM. We present also some preliminary results from SLIM.

hep-ex↗

arXiv2005

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

The energy spectrum of neutrino-induced upward-going muons in MACRO was analysed in terms of special relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of nu_mu <--> nu_tau transitions. The data disfavour these exotic possibilities even at a sub-dominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameters. These limits can also be re-interpreted as upper bounds on the parameters describing violation of the Equivalence Principle.

hep-ex↗

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

Search for nuclearites with the SLIM detector

We discuss the properties of cosmic ray nuclearites, from the point of view of their search with large nuclear track detector arrays exposed at different altitudes, in particular with the SLIM experiment at the Chacaltaya high altitude lab (5290 m a.s.l.). We present calculations concerning their propagation in the Earth atmosphere and discuss their possible detection with CR39 and Makrofol nuclear track detectors.

hep-ex↗

arXiv2005

Atmospheric neutrino oscillations

The latest results from the Soudan 2, MACRO and SuperKamiokande experiments on atmospheric neutrino oscillations are summarised and discussed. In particular a discussion is made on the Monte Carlo simulations used for the atmospheric neutrino flux.

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↗

arXiv2002

Atmospheric neutrino oscillations with the MACRO detector

After a short overview of the MACRO detector, located at the Gran Sasso Laboratory, I shall present and discuss the results on atmospheric muon neutrino oscillations, concerning low ( ~ 4 GeV) and high ( ~ 50 GeV) energy data. Using the Multiple Coulomb Scattering of muons inside the lower part of the detector, estimates of the neutrino energy were made event by event for the high energy sample. The data on angular distributions, absolute flux and L/E_nu distribution favor nu_mu <--> nu_tau oscillations with maximal mixing and Delta m^2=2.5 x 10^-3 eV^2.

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

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

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↗