Higher-order QED corrections to single-W production in electron-positron collisions

Four-fermion processes with a particle lost in the beam pipe are studied at LEP to perform precision tests of the electroweak theory. Leading higher-order QED corrections to such processes are analyzed within the framework of the Structure Functions (SF) approach. The energy scale entering the QED SF is determined by inspection of the soft and collinear limit of the O(alpha) radiative corrections to the four-fermion final states, paying particular attention to the process of single-W production. Numerical predictions are shown in realistic situations for LEP experiments and compared with existing results. A Monte Carlo event generator, including exact tree-level matrix elements, vacuum polarization, higher-order leading QED corrections and anomalous trilinear gauge couplings, is presented.Comment: LaTeX (using elsart), 21 pages, 8 .ps figure

Light Pair Correction to Bhabha Scattering at Small Angle

This work deals with the computation of electron pair correction to small angle Bhabha scattering, in order to contribute to the improvement of luminometry precision at LEP/SLC below 0.1% theoretical accuracy. The exact QED four-fermion matrix element for $e^+e^-\to e^+e^-e^+e^-$, including all diagrams and mass terms, is computed and different Feynman graph topologies are studied to quantify the error of approximate calculations present in the literature. Several numerical results, obtained by a Monte Carlo program with full matrix element, initial-state radiation via collinear structure functions, and realistic event selections, are shown and critically compared with the existing ones. The present calculation, together with recent progress in the sector of $O(\alpha^2)$ purely photonic corrections, contributes to achieve a total theoretical error in luminometry at the 0.05% level, close to the current experimental precision and important in view of the final analysis of the electroweak precision data.Comment: LaTeX2e, 28 pages, 8 figures include

Light-Pair Corrections to Small-Angle Bhabha Scattering in a Realistic Set-up at LEP

Light-pair corrections to small-angle Bhabha scattering have been computed in a realistic set-up for luminosity measurements at LEP. The effect of acollinearity and acoplanarity rejection criteria has been carefully analysed for typical calorimetric event selections. The magnitude of the correction, depending on the details of the considered set-up, is comparable with the present experimental error.Comment: 6 pages, LaTeX (elsart.sty), 4 tables, 1 figur

The CNGS Neutrino Beam

The CERN to Gran Sasso Neutrino beam (CNGS) was commissioned at CERN in early August 2006 and was first sent at low intensity to Gran Sasso on August 17, 2006. The Borexino, LVD and OPERA experiments continued the commissioning of their detectors and started taking data with practically no dead time. The CNGS collected several hundred events with clean time distributions.Comment: 11 pages, 14 EPS figures. Lecture given at the 2nd Latin American School on Cosmic Rays and Astrophysics, Puebla, Mexico, 30th August - 8th September 200

GPS-based CERN-LNGS time link for Borexino

We describe the design, the equipment, and the calibration of a new GPS based time link between CERN and the Borexino experiment at the Gran Sasso Laboratory in Italy. This system has been installed and operated in Borexino since March 2012, and used for a precise measurement of CNGS muon neutrinos speed in May 2012. The result of the measurement will be reported in a different letter.Comment: 13 pages, 11 figure