G. Sirri

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 � 20 cm 2 =h in an emulsion volume of 44mm thickness.

Momentum measurement by the angular method in the Emulsion Cloud Chamber

We present the first automated momentum measurement in an Emulsion Cloud Chamber, consisting of multiple sandwiches of lead plates and nuclear emulsion sheets. The measurement is based on the detection of the multiple Coulombscattering analysed by the so-called angular method. A 3 X0 chamber was exposed to 2, 3 and 4 GeV=c p � : A pion momentum resolution of 36% at 4 GeV=c; 35% at 3 GeV=c and 28% for 2 GeV=c was achieved.

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

Abstract We report the measurement of the fragmentation cross sections in high-energy nucleus–nucleus collisions using the 158xa0Axa0GeV Pb82+ beam from the CERN-SPS. The fragments have charges changed from that of the incident projectile nucleus by ΔZ=ZPb−Zfrag, with 8⩽ΔZ

Track reconstruction in the emulsion-lead target of the OPERA experiment using the ESS microscope

The OPERA experiment, designed to conclusively prove the existence of ????? oscillations in the atmospheric sector, makes use of a massive lead-nuclear emulsion target to observe the appearance of ??s in the CNGS ?? beam. The location and analysis of the neutrino interactions in quasi real-time required the development of fast computer-controlled microscopes able to reconstruct particle tracks with sub-micron precision and high efficiency at a speed of ~20 cm2/h. This paper describes the performance in particle track reconstruction of the European Scanning System, a novel automatic microscope for the measurement of emulsion films developed for OPERA.

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

The energy spectrum of neutrino-induced upward-going muons in MACRO has been analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of v(u) -> v(tau) transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter vertical bar Delta v vertical bar < 6 x 10(-24) at sin2 theta(v) = 0 and vertical bar Delta(v)vertical bar < 2.5-5 x 10(-26) at sin 2 theta(v) = +/- 1. These limits can also be re-interpreted as upper bounds on the parameters describing violation of the equivalence principle. (c) 2005 Elsevier B.V. All rights reserved.

Electron/pion separation with an emulsion cloud chamber by using a neural network.

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.

High-speed analysis of nuclear emulsion films with the use of dry objective lenses

The extensive use of nuclear emulsions as precise tracking detectors in experimental physics has been made possible due to recent advances in the production of novel emulsion films and to the development of automatic scanning devices. The scanning speed of such systems has exceeded the level of 20 cm2 of emulsion surface per hour. High-speed automatic scanning systems, such as those developed by the OPERA Collaboration, are able to reconstruct particle tracks in nuclear emulsions with excellent accuracy. However, the high-magnification oil immersion objectives used in these systems assume deposition and removal of oil onto and from the emulsion films. This is a major technological obstacle in the automatization of the emulsion feeding to the microscope, as required for large scale use as in the case of the OPERA neutrino oscillation experiment. In order to overcome this problem, an innovative technique of nuclear emulsion films scanning with the use of dry objective lenses has been developed and successfully applied to the experiment.

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.

A new automatic microscope for high-speed nuclear emulsion analysis of the OPERA experiment

The large amount of emulsion plates to be analysed in the OPERA experiment requires the development of a new generation of automatic microscopes with an order of magnitude improvement in speed with respect to analogous past systems. We report on the large R&D effort in realizing automatic microscopes with a scanning speed of 20 cm2 per hour, describing the progress in the mechanics, optics and in the technology of image acquisition and analysis. We also report on the features and performances of the scanning system (precisions, angular and position resolutions and efficiencies) evaluated exposing stacks of emulsions to high momentum pion beam at CERN.