B. Lorazo

A Search for highly ionizing particles produced at the OPAL intersection point at LEP

Abstract We report the results from a search for highly ionizing and magnetically charged particles at the OPAL intersection point at the LEP e + e − storage ring. The search was sensitive to Dirac monopoles with magnetic charge in the range 0.9 g D g g D , where 68.5 e ≡ g D . New upper limits are established on the production of monopoles with charge g D and mass up to 45.0 GeV/ c 2 .

Detector for magnetic monopoles at OPAL

Abstract We describe two independent methods, employed in the OPAL experiment at LEP, for detection of magnetic monopoles and other highly ionizing particles. The first employs passive track-recording plastic detectors incorporated into the apparatus. The second utilizes the d E d X measurement capability of the OPAL JET chamber in association with a dedicated trigger. In addition, energetic particles carrying magnetic charge can be identified by their trajectory in the OPAL magnetic field.

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.

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.

The broken-pair model versus the quasi-particle scheme: Two different formalisms?

Abstract The particle-number conserving Broken-Pair Model (BPM) and the Quasi-Particle Scheme (QPS) are shown to be nothing but two aspects of the same formalism. As a consequence, the old problem of the number-projection becomes elementary and BPM is algebraically as simple as QPS. Furthermore, owing to the existence of simple recursion formulas, BPM is also numerically as tractable as QPS.

Nuclear spectroscopy data sorting with parallel processors

Abstract Software for off-line sorting of data from high-spin nuclear-spectroscopy experiments has been developed for the Fermilab ACP parallel processors. The performance of the codes has been measured for various data analyses. The sorting of multicoincidence data from germanium detectors into high-resolution matrices, as well as more complex data analyses, can be done at rates of about 10 million events per hour.