CERN Accelerating science

CERN Internal Notes
Report number	CERN-ALEPH-2006-001 ; CERN-ALEPH-PHYSICS-2006-001
Title	A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model
Corporate author(s)	CERN. Geneva
Collaboration	ALEPH Collaboration ; DELPHI Collaboration ; L3 Collaboration ; OPAL Collaboration ; LEP Electroweak Working group
Submitted by	Nathalie.Grub@cern.ch on 14 Dec 2006
Free keywords	LEP2 ; EW line-shape and leptonic asymmetries
Abstract	This note presents a combination of published and preliminary electroweak results from the four LEP collaborations ALEPH, DELPHI, L3 and OPAL based on electron-positron collision data taken at centre-of-mass energies above the Z-pole, 130 GeV to 209 GeV (LEP-II), as prepared for the 2006 summer conferences. Averages are derived for di-fermion cross sections and forward-backward asymmetries, photon-pair, W-pair, Z-pair, single-W and single-Z cross sections, electroweak gauge boson couplings, W mass and width and W decay branching ratios. An investigation of the interference of photon and Z-boson exchange is presented, and colour reconnection and Bose-Einstein correlation analyses in W-pair production are combined. The main changes with respect to the experimental results presented in 2005 are new preliminary combinations of final LEP-II results on the mass and width of the W boson. Including the precision electroweak measurements performed at the Z pole published recently, the results are compared with precise electroweak measurements from other experiments, notably CDF and DØ at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the results obtained in high-Q^2 interactions, and used to predict results in low-Q^2 experiments, such as atomic parity violation, Möller scattering, and neutrino-nucleon scattering.