R. Lorenzi

A large acceptance spectrometer to study high-mass muon pairs

Abstract This paper gives the outlines of the NA3 large acceptance magnetic spectrometer equipped with multiwire proportional chambers running at the CERN-SPS in an extensive study of the production of high mass muon pairs by hadronic beams. A special feature of this experiment is the powerful and efficient trigger and data acquisition system which allows operation of the spectrometer with intense beams, yielding at the same time low trigger rate and high proportion of good events. Some aspects of the off-line analysis program are also described.

Mass and lifetime limits on new long-lived particles in 300 GeV/c π− interactions

A sensitive search has been done for the production of new long-lived and penetrating particles by 300 GeV/c negative pions. No new state —decaying into at least two charged known particles —has been detected with mass above 1 GeV/c2 and lifetime in the range 5·10−11 s to 5·10−7s. We give upper limits on production cross sections, and consequences on the existence of heavy “axion-like” particles, heavy neutrinos and supersymmetric particles. In particular, this experiment excludes the existence of light gluinos with lifetime in the range 5·10−11 to 10−8s: this closes the last “window of opportunity” for gluinos withM<2 GeV/c2 and lifetime measurable in particle physics experiments.

Limited streamer tubes for the OPAL hadron calorimeter

Abstract This paper describes the manufacture of multicell plastic limited streamer chambers for use in the hadron calorimeter of the OPAL detector at LEP. The chambers are of the PVC coverless type with highly resistive cathodes. We discuss the assembly procedure with particular emphasis on the crucial cathode preparation process. A summary of test results is also presented.

Operation of cylindrical wire spark-chambers in low-pressure helium

Abstract A pair of cylindrical wire spark-chambers is used for detecting alpha particles emitted in high-energy π 4 He interactions. A particular feature of the system is the low gas pressure employed, corresponding to a thickness of 0.7 mg/cm2. The angular error for 5.48-MeV alpha particles is 1.2° fwhm. The chambers are insensitive to minimum-ionizing particles.

A helium-recoil spectrometer

Abstract The instrument described is intended for the detection and measurement of α particles from coherent interactions of high-energy particles with 4 He nuclei. It allows the determination of the magnitude and the direction of the momenta of the helium recoils from interactions in a pressurized gas target. The measurements are carried out with spark chambers and scintillation counters. Recoils emitted at angles greater than 65° with respect to the beam direction are accepted and the range of azimuth angles covered is 294°.

Décodage de chambers à étincelles à fils par induction sur des lignes à retard

Abstract A read-out system constructed of lumped delay lines is used for a wire spark-chamber of dimensions 60×100 cm 2 . The lengths of the delay-line modules are between 30 and 35 cm and the delay is typically 70 ns/mm. The sparks are localised with a precision of 0.9 mm (fwhm) and resolved beyond a separation of 2 cm.

Measurement of punch-through particle fluxes from a 200 cm long beam dump hit by a 300 gev/c pion beam

Abstract We present a measurement of the particle flux punching through tungsten and iron beam dumps; the NA3 spectrometer was used. Momentum spectra and spatial distributions were determined for pions above GeV/ c and for strange particles (K ± , K s 0 , Λ , Ξ ; 15 p c ). Information on the effective attenuation length for strange particles was obtained by comparing the results from dumps of different lengths (200 and 220 cm).

A new read-out method for wire spark chambers operating in magnetic fields

Abstract A lumped delay line is used for read-out of a wire spark chamber. Preliminary measurements give a precision better than 0.5 mm and show that multiple sparks can be detected.