arXiv subjects
Publications and source records attributed to L. Patrizii.
The Searches for classical Dirac Magnetic Monopoles (MMs) at accelerators, for GUT superheavy MMs in the penetrating cosmic radiation and for Intermediate Mass IMMs at high altitudes are discussed. Also the searches for nuclearites and Q-balls are considered.
We have studied the performance of a new algorithm for electron/pion separation in an Emulsion Cloud Chamber (ECC) made of lead and nuclear emulsion films. The software for separation consists of two parts: a shower reconstruction algorithm and a Neural Network that assigns to each reconstructed shower the probability to be an electron or a pion. The performance has been studied for the ECC of the OPERA experiment [1]. The $e/π$ separation algorithm has been optimized by using a detailed Monte Carlo simulation of the ECC and tested on real data taken at CERN (pion beams) and at DESY (electron beams). The algorithm allows to achieve a 90% electron identification efficiency with a pion misidentification smaller than 1% for energies higher than 2 GeV.
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.
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.
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.
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.
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.
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.
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.
We present the results from the CAKE (Cosmic Abundance below Knee Energy) balloon experiment which uses nuclear track detectors. The final experiment goal is the determination of the charge spectrum of CR nuclei with Z > 30 in the primary cosmic radiation. The detector, which has a geometric acceptance of \~ 1.7 m2 sr, was exposed in a trans-mediterranean stratospheric balloon flight. Calibrations of the detectors used (CR39 and Lexan), scanning strategies and algorithms for tracking particles in an automatic mode are presented. The present status of the results is discussed
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.
The search for magnetic monopoles 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 at the Chacaltaya High Altitude Laboratory (5290 m a.s.l.). The results from the analysis of 171 m$^2$ exposed for more than 3.5 y are here reported. The completion of the analysis of the whole detector will allow to set the lowest flux upper limit for Magnetic Monopoles in the mass range 10$^5$ - 10$^{12}$ GeV. The experiment is also sensitive to SQM nuggets and Q-balls, which are possible Dark Matter candidates.
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.
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.
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.
In these lecture notes we discuss the status of the searches for classical Dirac Magnetic Monopoles (MMs) at accelerators, for GUT superheavy MMs in the penetrating cosmic radiation and for Intermediate Mass MMs. Also the searches for nuclearites and Q-balls are considered.
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.
SLIM is a large area experiment (440 m2) installed at the Chacaltaya cosmic ray laboratory since 2001, and about 100 m2 at Koksil, Himalaya, since 2003. It is devoted to the search for intermediate mass magnetic monopoles (107-1013 GeV/c2) and nuclearites in the cosmic radiation using stacks of CR39 and Makrofol nuclear track detectors. In four years of operation it will reach a sensitivity to a flux of about 10-15 cm-2 s-1 sr-1. We present the results of the calibration of CR39 and Makrofol and the analysis of a first sample of the exposed detector.