A. J. Martin

The OPAL silicon strip microvertex detector with two coordinate readout

The OPAL experiment at the CERN LEP collider recently upgraded its silicon strip microvertex detector from one coordinate readout (φ only) to two coordinate readout (φ and z). This allows three dimensional vertex reconstruction and should improve lifetime measurements as well as b quark jet identification. This paper describes the new microvertex detector system with emphasis on the novel techniques and new components used to obtain the second coordinate information. These include the use of back-to-back single-sided detectors with orthogonally oriented readout strips, a gold printed circuit on a thin glass substrate to route the z strip signals to the electronics at the end of the detector, and the use of MX7 readout chips. Results on the performance of the new detector are presented.

Global jet properties at 14–44 GeV center of mass energy ine+e− annihilation

AbstractJet properties ine+e− annihilation at center of mass energies of 14, 22, 35 and 43.7 GeV were studied with the data collected in the TASSO detector at PETRA, using the same evaluation procedures for all the energies. The total hadronic cross section ratio for the center of mass energy interval 39–47 GeV was determined to be ℛ=4.11±0.05 (stat)±0.18(syst.) atn

Pion, kaon and proton cross sections ine+e− annihilation at 34 GeV and 44 GeV c.m. energy

langle sqrt s rangle = 43 - 7

A study of jets fromb quarks produced ine+e− annihilations at\(\sqrt s = 35 - 46\) GeV

n GeV. Corrected distributions of global shape variables are presented as well as the inclusive charged particle distributions for scaled momentum and transverse momentum. The center of mass energy evolution of the average sphericity, thrust, aplanarity and particle momentum is shown.

A study of Energy-Energy correlations between 12 and 46.8 GeV C.M. Energies

We report on an analysis of the multiplicity distributions of charged particles produced ine+e− annihilation into hadrons at c.m. energies between 14 and 46.8 GeV. The charged multiplicity distributions of the whole event and single hemisphere deviate significantly from the Poisson distribution but follow approximate KNO scaling. We have also studied the multiplicity distributions in various rapidity intervals and found that they can be well described by the negative binomial distribution only for small central intervals. We have also analysed forward-backward multiplicity correlations for different energies and selections of particle charge and shown that they can be understood in terms of the fragmentation properties of the different quark flavours and by the production and decay of resonances. These correlations are well reproduced by the Lund string model.

A Study of Bhabha Scattering at {PETRA} Energies

AbstractThe inclusive production of π± andK± mesons and of protons and antiprotons ine+e− annihilations has been measured at 34 GeV and 44 GeV center of mass energy; in addition π± mesons have been measured at 44 GeV c.m. energy. Differential cross sections and particle yields are given. At 34 GeV average multiplicities are:n

Experimental study of jet masses ine+e− annihilation at c.m. energies between 12 and 43.5 GeV

begin{gathered} leftlangle {nleft( {pi ^ pm } right)} rightrangle = 10.9 pm 0.5,leftlangle {nleft( {K^ pm } right)} rightrangle = 1.76 pm 0.20, hfill leftlangle {nleft( {p + bar p} right)} rightrangle = 0.67 pm 0.06 hfill end{gathered}