H. Jeremie

Fast circle fit with the conformal mapping method

Abstract A slight modification of the conformal mapping method transforms circular tracks into parabolas with small curvature. A fast linear fit to these parabolas yields the original circle parameters.

Design and tests of the z-coordinate drift chamber system for the opal central detector at LEP

Abstract A system of drift chambers has been designed to make high resolution measurements of the z -coordinates of charged tracks at the outer radius of the OPAL central detector at LEP. The unit module of this detector is a 25 cm drift length bidirectional cell with six sense wires in a thin 50 cm wide by 29 mm high drift slot. Tests indicate that the chamber has a wide and stable electric field operating range and its performance is unaffected by small misalignments between the drift electric field and an external magnetic field. The drift cell was found to have uniform acceptance up to its geometrical boundaries, and the z -resolution for beam tracks normal to the chamber was measured to be in the range of 40–175 μm.

Time spectra of random coincidences for time-to-amplitude converters

Abstract The distortions of time spectra observed in time-to-amplitude converters, due to dead time effects, are calculated both for uncorrelated and correlated input pulses.

Efficiency of Billoir's track fitting method for the OPAL central detector

Abstract Track fitting in the OPAL central detector can be improved at low energies with a recursive method due to Billoir [1], which accounts for multiple scattering.

Microscopic Monte Carlo, an alternative method for calculating multiple Coulomb scattering

Abstract A Monte Carlo calculation of multiple Coulomb scattering is presented that traces a particle through a medium following directly the individual scatterings. The method is best suited to applications where a precisely calculated trajectory in a gas-filled device is needed.

New measurement of the beta decay rate of the16N(0−)-16O(0+) transition

The beta decay rate of the16N(0−; 120keV) →16O(0+, G.S.) transition has been remeasured. Our result (Λβ=0.48±0.024 s−1) is in excellent agreement with a previous measurement but strongly disagrees with another experimental value. The two agreeing results provide an experimental verification of the importance of meson exchange currents in 0+-0− weak transitions. A value ofgp/gA∼11–12 can be inferred from the correspondingΛμ rate.

The neutron-neutron scattering length from a complete experiment on the 3H(d, 2n)3He reaction at 8.45 MeV

Abstract The spectrum of the time-differences between the two neutrons from the 3H(d, 2n)3He reaction detected by two plastic scintillators situated at 0.2 and 2.0 m from the target was measured at 0°. The spectrum was compared with a Jost-function final-state interaction enhancement factor and yielded a value of 16.2 ± 1.2 fm for an−n, the neutron-neutron scattering length.

The detection of electrons in the 10 MeV range by plastic scintillators

Abstract Response functions for electrons from 1 to 12 MeV have been measured with a plastic scintillator telescope. A parametrization model for these response functions has been found to give good results at all energies. Furthermore it was established that the type of reflector used for the scintillator has a considerable influence on the response functions. A mechanism for this influence has been proposed and tested by Monte Carlo calculations.

A recirculating gas target for the measurement of very short-lived beta-decays

Abstract The properties of a recirculating gas target for the measurement of short-lived β-decays are investigated. It is found that flow velocity and recirculation time can be adjusted to obtain good background elimination. The decay curve and energy spectrum of the 0- (120 keV) state of 16 N (T 1 2 = 5.25 μ s ) are presented.

Cross-section for ejection of deuterons from 6Li by electrons

Abstract The cross-section for ejection of deuterons from 6 Li is estimated in Born-approximation neglecting electric-quadrupole and magnetic scattering. The s- and p-state of 6 Li are described by simple and perturbed harmonic-oscillator wave functions respectively. Absorption is accounted for through a modified eikonal approximation and the results are normalized to elastic electron-deuteron scattering.