A new drift chamber concept with a special charge-sampling geometry, pulse shaping electronics and a 100 MHz flash ADC readout was for the first time operated in a colliding e+ e− beam environment. The detector formed part of the MARK J experiment at PETRA (DESY) during the last year before its final shutdown in November 1986. Operated with a CO2/i-C4H10 gas mixture at 1.9 bar, an intrinsic resolution of 40 μm for Bhabha events has been achieved.
A high-resolution drift chamber based on the time expansion principle has been built as a vertex detector for the Mark J experiment at DESY. The chamber design and the associated control and readout system are described. Results on chamber performance obtained from test beam measurements and first results from running at PETRA are reported.
A study of τ-lepton production in the CMS energy region from 14 to 46.8 GeV at PETRA is reported. The cross section, the decay branching ratio into μνν, and the electroweak parameters are determined with a total integrated luminosity of 115 pb−1.
The strong interaction coupling constant αs has been measured with a new method, the planar triple energy correlation in the reaction e+e- → hadrons at center-of-mass energies ranging from 14 GeV to 46.78 GeV. A complete second-order perturbative QCD calculation was used. ΛMS = 110 ± 30 −55+70 MeV is found.
We use the reaction e+e−→μ+μ−, in the Mark J detector at the DESY high-energy e+e− collider PETRA, to test the standard electroweak theory and find good agreement. We also set limits on the parameters of several extended gauge theories.Received 30 May 1985DOI:https://doi.org/10.1103/PhysRevLett.55.665©1985 American Physical Society