J.H. Field

First-level charged particle trigger for the L3 detector

Abstract A first-level charged particle trigger based on parallel processing and look-up tables has been developed for the L3 detector. It processes analog signals generated by the central tracking detector, a drift chamber with axial wires. The trigger decision is made on the total number of tracks, the number of coplanar pairs of tracks, or on more complicated topologies found in the projection normal to the beam axis. The system is very flexible and can be adjusted to a wide range of background conditions and tracking chamber efficiencies.

New calculations of cross-sections and charge asymmetries for lepton pair production and wide angle Bhabha scattering in e+ e- collisions near the Z peak

Abstract A new event generator for lepton pair production and wide angle Bhabha scattering, BHAGENE3, is presented. Both electroweak and higher order (beyond O(α) QED corrections are included. Comparisons are made with results from the programs, based on the structure function formalism, ALIBABA, TOPAZ0 and ZFITTER. For the case of the final states l + l − γγ ( l = e , μ , τ ) BHAGENE3 results are compared with those of Monte Carlo generators that use the exact O ( α 2 ) amplitudes.

The present theoretical error on the Bhabha scattering cross section in the luminometry region at LEP

Abstract The results concerning the theoretical evaluation of the small-angle Bhabha Scattering cross section obtained during the Workshop on Physics at LEP2 (CERN, Geneva, Switzerland, 1995) by the Working Group “Event Generators for Bhabha Scattering” are summarized. The estimate of the theoretical error on the cross section in the luminometry region is updated.

A covariant path amplitude description of flavour oscillations: the Gribov-Pontecorvo phasefor neutrino vacuum propagation is right

An extended study is performed of geometrical and kinematical assumptions used in calculations of the neutrino oscillation phase. The almost universally employed ‘equal velocity’ assumption, in which all neutrino mass eigenstates are produced at the same time, is shown to underestimate, by a factor of two, the neutrino propagation contribution to the phase. Taking properly into account, in a covariant path amplitude calculation, the incoherent nature of neutrino production as predicted by the Standard Model, results in an important source propagator contribution to the phase. It is argued that the commonly discussed Gaussian ‘wave packets’ have no basis within quantum mechanics and are the result of a confused amalgam of quantum and classical wave concepts. PACS 03.65.Bz, 14.60.Pq, 14.60.Lm, 13.20.Cz

THE NEW LEVEL-1 TRIGGER FOR THE FORWARD TAGGER OF THE L3 EXPERIMENT

Abstract A fast level-1 trigger processor for the Active Lead Ring calorimeter (ALR) and for the Very Small Angle Tagger (VSAT) of the L3 detector has been constructed and implemented. The main application is the study of single tagged two-photon collision processes at LEP II. Particular care has been taken to preserve the timing characteristics of the signal in order to allow bunch tagging in the multi-bunch mode of LEP.

A multi-hit ADC and TDC for the charged particle trigger of the L3 experiment☆

Abstract A Fastbus ADC and TDC module has been developed for the trigger of the L3 experiment. It provides fast and precise integration of successive pairs of charges derived from the charge division wires of the central tracking chamber, as well as a measurement of their drift times. The minimum separation time between digitizations is 170 ns. The charges are measured with a precision of 1 pC up to charges of 600 pC. The drift times are measured in 50 ns time bins. A system including 60 modules provides data allowing the reconstruction of charged particle tracks in three dimensions. This information is used in background rejection algorithms of the second and third level triggers.

Clock-transport synchronisation for neutrino time-of-flight measurements

A method to synchronise, at the sub-nanosecond level, clocks used for neutrino time-of-flight measurements is proposed. Clocks situated near the neutrino source and target are compared with a moveable clock that is transported between them. The general-relativistic theory of the procedure was tested and verified in an experiment performed by Hafele and Keating in 1972. It is suggested that use of such a synchronisation method may contribute to a precise test of the Sagnac effect—a measured velocity greater than c—for neutrinos of the proposed LBNE beam between Fermilab and the Homestake mine.

The experimental status of Higgs Sector of the Standard Electroweak Model at the end of the LEP-SLC era

A method is proposed to calculate the confidence level for agreement of data with the Standard Model (SM) by combining information from direct and indirect Higgs Boson searches. Good agreement with the SM is found for

Beam energy measurement at LEP2 using Møller scattering

m_H \simeq 120

Event generators for Bhabha scattering

GeV using the observables most sensitive to