LHCb

Abstract:

Fragmentation properties of a sample of two-jet events measured by the UA2 detector at the CERN pp Collider are described. The energy flow is compared with different model predictions. The charged particle multiplicity in jets is found to exceed extrapolations from lower energy e+e- jet data. © 1984.

Abstract:

Jet production properties at s = 540 GeV have been measured in the UA2 detector at the CERN pp Collider. Results on the total transverse momentum of the jet system, on the parton density in the nucleon (structure function) and on the two-jet angular distributions are reported. The data are compared with QCD predictions and extrapolations from lower energy experiments. © 1984.

Abstract:

The production of electrons with very high transverse momentum has been studied in the UA2 experiment at the CERN {Mathematical expression} collider ( {Mathematical expression}=540 GeV). From a sample of events containing an electron candidate with pT>15 GeV/c, we extract a clear signal resulting from the production of the charged intermediate vector boson W±, which subsequently decays into an electron and a neutrino. We study the W production and decay properties. Further-more, we refine our results on the production and decay of the neutral vector boson Z0. Finally, we compare the experimental results to the predictions of the standard model of the unified electro-weak theory. © 1984 Springer-Verlag.

Abstract:

We have observed inclusive production of D0 and D+ mesons, and their charge conjugates, in e+e- annihilation at 29 GeV on the basis of a data sample of 106 pb-1. These signals correspond to R values of R (D0+D0)=1.8±0.5 and R (D++D-)=1.2±0.4. Taking the D+ and D0 data together, we measure a charge asymmetry of A=-0.08±0.12 for charmed quarks. A comparison of R (D+D) with R (D*+D*) obtained via the process D*+D0+ gives a DD* ratio of 1.0-0.2+0.3, indicating that direct D* production dominates over direct D production. © 1984 The American Physical Society.

Abstract:

During the initial data run with the High Resolution Spectrometer (HRS) at SLAC PEP, an integrated luminosity of 19.6 pb-1 at a center-of-mass energy of 29 GeV was accumulated. The data on Bhabha scattering and muon pair production are compared with the predictions of QED and the standard model of electroweak interactions. The measured forward-backward charge asymmetry in the angular distribution of muon pairs is -8.4% 4.3%. A comparison between the data and theoretical predictions places limits on alternative descriptions of leptons and their interactions. The existence of heavy electronlike or photonlike objects that alter the structure of the QED vertices or modify the propagator are studied in terms of the QED cutoff parameters. The Bhabha-scattering results give a lower limit on a massive photon and upper limits on the effective size of the electron of +>121 GeV and ->118 GeV at the 95% confidence level. Muon pair production yields +>172 GeV and ->172 GeV. If electrons have substructure, the magnitude and character of the couplings of the leptonic constituents affects the Bhabha-scattering angular distributions to such an extent that limits on the order of a TeV can be extracted on the effective interaction length of the components. For models in which the constituents interact with vector couplings of strength g241, the energy scale VV for the contact interaction is measured to be greater than 1419.0 GeV at the 95% confidence level. We set limits on the production of supersymmetric scalar electrons through s-channel single-photon annihilation and t-channel inelastic scattering. Using events with two noncollinear electrons and no other charged or observed neutral particles in the final state, we see one event which is consistent with a simple supersymmetric model but which is also consistent with QED. This allows us to exclude the scalar electron to 95% confidence level in the mass range 1.8 to 14.2 GeV/c2. © 1984 The American Physical Society.