Quark–hadron duality: Pinched kernel approach

Hadronic spectral functions measured by the ALEPH collaboration in the vector and axial-vector channels are used to study potential quark–hadron duality violations (DV). This is done entirely in the framework of pinched kernel finite energy sum rules (FESR), i.e. in a model independent fashion. The kinematical range of the ALEPH data is effectively extended up to s = 10 GeV2 by using an appropriate kernel, and assuming that in this region the spectral functions are given by perturbative QCD. Support for this assumption is obtained by using e[Formula: see text] e[Formula: see text] annihilation data in the vector channel. Results in both channels show a good saturation of the pinched FESR, without further need of explicit models of DV.

FACTORIZATION OF THE CHARGE CORRELATION FUNCTION IN $B^0 {\bar B}^0$ OSCILLATIONS

Extraction of the mass difference Δm from [Formula: see text] oscillations involves tagging of bottom flavor at production and at decay. The charge correlation function is the asymmetry between the unmixed and mixed events. In their data using the lepton-jet-method, the ALEPH collaboration recently verified that this asymmetry factorizes into two parts, one depending on the production tag and the other on the decay tag. Except for this particular "verification", analyses of experiments on the time-dependence of beon oscillations have been assuming this factorization, without statement or explanation of their assumption. We theoretically explain this factorization as arising from the neglect of terms which involve CP-violation in the second order.

STUDY OF e+e− INTERACTIONS AT CENTER-OF-MASS ENERGIES OF 130 AND 136 GeV

At the end of 1995, the LEP collider at CERN was operated at center-of-mass energies of 130 and 136 GeV and data corresponding to about 6 pb−1 were collected by each of the four LEP experiments. The cross-sections for fermion-pair production processes and the forward-backward asymmetries for charged lepton pairs were measured and compared to the standard model predictions. Events containing only energetic photons in the final state were used to look for effects arising from new physics. Direct searches for new particles predicted by various models beyond the standard model were performed. Searches for pair or singly produced excited leptons, for unstable charged and neutral heavy leptons, and for supersymmetric particles (chargino, neutralino, scalar leptons and scalar top quark) resulted in new exclusion limits. The ALEPH collaboration reported an excess of four-jet events in its data, which was not confirmed by the other LEP experiments.