A. Rainò

A high rejection transition radiation detector prototype to distinguish positrons from protons in a cosmic ray space laboratory

Abstract We have carefully implemented a transition radiation detector prototype in order to design a similar device having 75 × 150 cm 2 active surface that will discriminate positrons from protons. This detector will be part of the spectrometer of the experiment WIZARD, planned to fly at 180 miles altitude on the NASA Space Station “FREEDOM” to search for primordial antimatter. Since the positron to proton ratio is expected to be of the order of 10 −4 , we have pushed the proton rejection factor of the spectrometer beyond this value using a compact transition radiation detector equipped with properly designed “cluster counting” electronics.

STRAW CHAMBERS OPERATING IN VACUUM FOR PARTICLE TRACKING AND TRANSITION RADIATION DETECTION IN ACCELERATOR AND SPACE EXPERIMENTS

We have designed and tested some straw tubes prototype detectors to investigate the possibility to operate a full size chamber with extremely reduced gas leaks in a high vacuum environment in accelerator experiments or in sealed mode for astroparticle physics researches in outer space. After completing the tests we have finally built a tracking detector of 1300 channels which has run in a vacuum chamber in the experiment E864 at BNL with a leak of 7 × 10−3Torr l/s compatible with the permeability of the materials used.

A transition radiation detector for positron identification in a balloon-borne particle astrophysics experiment

Abstract We have built and tested a transition radiation detector of about 76 × 80 cm 2 active surface to discriminate positrons from protons in an experiment performed on a balloon flight to search for primordial antimatter. The TRD is made of ten modules each consisting of a carbon fiber radiator followed by a multiwire proportional chamber. In order to achieve a proton-electron rejection factor of the order of 10 −3 with a strict limitation on power consumption to about 40 mW per chamber channel, as required by experimental constraints, we have developed a low power consumption “cluster counting” electronics. Different analysis procedures of calibration data are shown. In addition, comparisons of the performances of this detector are also made with a previous similar prototype equipped with standard fast electronics and similar detectors from other authors.

WiZard SiW imaging calorimeter: a preliminary study on its particle identification capability during a balloon flight in 1993

Abstract The WiZard Collaboration is engaged in a program to study the antimatter components of the cosmic rays. A silicon-tungsten (Wiue5f8W) imaging calorimeter has been developed as part of this program. We present its performance and preliminary results, obtained during a balloon flight on September 8, 1993. The flight was dedicated to the measurement of the positron spectrum in the energy range 4–50 GeV and took place from Ft. Sumner, New Mexico.

Search for exotic strange quark matter in high energy nuclear reactions

Abstract We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/ c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A −8 per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter.We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A<100 droplets of strange quark matter). We thus set upper limits on the production of these exotic states at the level of 1-6 x 10^{-8} per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter.

Study of the combined particle identification capability of a transition radiation detector and a silicon imaging calorimeter during the TS93 balloon flight

Abstract The WiZard Collaboration is involved in a program studying the antimatter components of the cosmic rays. A transition radiation detector and a silicon-tungsten calorimeter with imaging capabilities have been built as part of this program. We present the combined performance of these two detectors for positron identification during a balloon flight on September 8, 1993. The flight was dedicated to the measurement of the positron spectrum in the energy range 4–50 GeV and was launched from Ft. Summer, New Mexico.

A large area transition radiation detector to measure the energy of muons in the Gran Sasso underground laboratory

Abstract We have designed and built a transition radiation detector of 36 m2 area in order to measure the residual energy of muons penetrating in the Gran Sasso cosmic ray underground laboratory up to the TeV region. It consists of three adjacent modules, each of 2 × 6 m2 area. Polystyrene square tubes, filled with a argon-carbon dioxide gas mixture, and polyethylene foam layers are used as proportional detectors and radiators respectively. We cover such a large surface with only 960 channels that provide adequate energy resolution and particle tracking for the astroparticle physics items to investigate. The detector has been calibrated using a reduced size prototype in a test beam. Results from one module exposed to cosmic rays at sea level are shown.

R & D results from the NOE scintillating fiber calorimeter,

Abstract The development of the NOE calorimeter, based on scintillating fiber technology, has undergone four years of intense R&D activity. Measurements of light attenuation and time resolution have been carried out on a variety of commercially available scintillating fibers. Both these parameters are important for the optimization of the design of the NOE calorimeter. Experimental results on the fiber attenuation length and light yield make us confident on the possibility to build a 8×8 m 2 cross-section calorimeter without noticeable loss of signal. The time resolution is resulted to be of the order of 1xa0ns, sufficient for up/down discrimination in the final calorimeter setup, by means of the time-of-flight method. Several tests performed to optimize the elementary cell of the calorimeter are also described.

Identification of cosmic ray electrons and positrons by neural networks

Abstract A data analysis based on artificial neural network classifiers has been done to identify cosmic ray electrons and positrons detected with the balloon-borne NMSU/Wizard-TS93 experiment. The information is provided by two ancillary and independent particle detectors: a transition radiation detector and a silicon-tungsten imaging calorimeter. Electrons and positrons measured during the flight have been identified with background rejection factors of 80 ± 3 and 500 ± 37 at signal efficiencies of 72 ± 3% and 86 ± 2% for the transition radiation detector and silicon-tungsten imaging calorimeter, respectively. The ability of the artificial neural network classifiers to perform a careful multidimensional analysis surpasses the results achieved by conventional methods.

The NOE detector for a long baseline neutrino oscillation experiment

Abstract The project of a large underground experiment, NOE (Neutrino Oscillation Experiment), composed by modules of scintillating fiber calorimeter interleaved with TRD modules, total weight 6.7 ktons, is presented. This apparatus has been optimized for long baseline neutrino oscillation studies, in particular to be sensitive in the region of sin2 2θ and Δm2 suggested by the atmospheric neutrino anomaly (fig. 3).