S. Petrera

Measurement of the pressure dependence of air fluorescence emission induced by electrons

The fluorescence detection of ultra high energy (>10^18 eV) cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules, which are excited by the cosmic ray shower particles along their path in the atmosphere. We have made a precise measurement of the fluorescence light spectrum excited by MeV electrons in dry air. We measured the relative intensities of 34 fluorescence bands in the wavelength range from 284 to 429 nm with a high resolution spectrograph. The pressure dependence of the fluorescence spectrum was also measured from a few hPa up to atmospheric pressure. Relative intensities and collisional quenching reference pressures for bands due to transitions from a common upper level were found in agreement with theoretical expectations. The presence of argon in air was found to have a negligible effect on the fluorescence yield. We estimated that the systematic uncertainty on the cosmic ray shower energy due to the pressure dependence of the fluorescence spectrum is reduced to a level of 1% by the AIRFLY results presented in this paper.

Observation of a likely example of the decay of a charmed particle produced in a high energy neutrino interaction

Abstract In a study of neutrino interactions occurring in nuclear emulsion, an event has been found that is most readily interpreted as the decay of a charmed particle with lifetime a few times 10 −13 s.

Temperature and Humidity Dependence of Air Fluorescence Yield measured by AIRFLY

Abstract The fluorescence detection of ultra high energy cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules over a wide range of atmospheric parameters, corresponding to altitudes typical of the cosmic ray shower development in the atmosphere. We have studied the temperature and humidity dependence of the fluorescence light spectrum excited by MeV electrons in air. Results for the 313.6, 337.1, 353.7 and 391.4xa0nm bands are reported in this paper. We found that the temperature and humidity dependence of the quenching process changes the fluorescence yield by a sizeable amount (up to 20% for the temperature dependence in the 391.4xa0nm band) and its effect must be included for a precise estimation of the energy of ultra high energy cosmic rays.

A method to evaluate the detection efficiency and the mean life-time of short lived particles

Abstract We describe a method to evaluate the detection efficiency of short lived particles when the decay path is of the same order of magnitude as the spatial resolving power. We then consider the possibility to determine the mean life-time from angular and path distributions without knowing momenta and when undetected neutral particles are present at the decay vertex. The statistical weight of a sample is computed in different conditions.

A Search for Charmed Particles Originating from the Interactions of 300-GeV/c Protons in Emulsion Nuclei.

Abstract The associated production of charmed particles by the interactions of 300 GeV/ c protons with complex nuclei has been sought using nuclear emulsions. The failure to observe any candidates for this process among some 60,000 interactions investigated implies, provided charmed particles lifetimes are in the range 10 −12 to 10 −14 s, a cross section for their associated production by the interactions of 300 GeV/ c protons with nucleons of less than 1.5 microbarns at a 90% confidence level.

Two-particle rapidity correlations in proton-nucleus interactions at 300 GeV

Abstract The single- and two-particle inclusive rapidity distributions for proton-nucleus interactions at 300 GeV in nuclear emulsions are presented. The analysis of the data with the two-particle rapidity correlation function R ( ν 1 , ν 2 ) shows clear evidence of short range correlations. A remarkable asymmetry between projectile and target hemisphere is found.

Track discrimination of low-energy nuclei in plastics

Abstract The efficiency of nitrocellulose-plastic sheets as external detectors is studied as a function of impinging-particles angle, energy-loss rate and other experimental conditions also in the presence of a high background of neutral and singly-charged particles. The discrimination among low-energy nuclei (2⩽ Z ⩽6) with a two-step method of analysis was achieved with the definition of a parameter ( w ), connected with the measured etched length of the tracks, that ensures their almost certain assignment to the various nuclear species.

An interactive system for emulsion data acquisition

We describe an interactive system, based on a micro-processor, for the acquisition and elaboration of nuclear emulsion measurements. The device consists of a Koritska R4 microscope coupled with a telecamera and with a motor driven stage for automatic displacement in the three directions. Both the pair of internal coordinates and the three external coordinates are digitized. The interactive management of the system is carried out with a PDP11/34.

Detection and measurement of very short flight paths in nuclear emulsions

Abstract The application of the nuclear emulsion technique to detect and measure flight paths of unstable particles shorter than a few microns is given. Besides the description of the method of measurement and of the analysis, particular care is paid to the possible sources of biases. It is concluded that the transverse distances of the decay prongs to the primary vertex can be determined with a mean accuracy ∼0.05 μ m.

Comparative study of inclusive correlation functions in proton interactions on emulsion nuclei

Abstract R ( η 1 , η 2 ) and C ( η 1 , η 2 ) inclusive correlation functions are studied in 300 GeV proton interactions on emulsion nuclei. Their dependence on nuclear excitation is investigated and some differences between their behaviours are pointed out. The interpretation of experimental data is attempted in the framework of a repeated independent collision picture of hadron-nucleus interactions. The introduction of clustering patterns in produced hadronic matter provides a qualitative description of the target dependence of correlations.