Status of electroweak tests with heavy quarks

The measurements of the partial decay-widths and forward-backward asymmetries for \rm{Z} \rightarrow \bb and \rm{Z} \rightarrow \cc test the Z couplings to the initial state \ee pair and th e heavy quarks in the final state. The four LEP detectors have registered about four million hadronic Z decays each and SLD at SLC has recorded 300000 Z decays with highly polarised electron be ams. The high statistics as well as the good tracking, vertexing and particle identification capabilities of the detectors allow high precision measurements of these quantities. The measurements of the electroweak observables with heavy quarks are reviewed. The results of the different analyses are combined and interpreted within the framework of the Standard Model of electroweak interactio ns. In all cases good agreement with the Standard Model predictions is found, severely limiting the room for modifications of these quantities from new physics

Model Independent Limit of the Z-Decay-Width into Unknown Particles

Using the LEP lineshape data combined by the LEP electroweak working group and the left-right asymmetry measured at SLD an almost model independent limit on the decay width of the Z into unpredicted modes is derived. Assuming only that the \rm{Z} \rightarrow \ee and \rm{Z} \rightarrow \mumu decays can be selected cleanly a limit of \Gnew < 6.3 \MeV at 95\% confidence level is derived

A Laser Cavity for Polarised Positron Production?

LAL & DESYPolarised positrons in the ILC are attractive for physics reasons and polarised positron production with Compton scattering has the advantage that the source is independent from the electron arm. In this note some ideas are presented, how this might be achieved using storage devices like a laser cavity and an accumulator ring

Physics at Future Linear Colliders

This article summarises the physics at future linear colliders. It will be shown that in all studied physics scenarios a 1 TeV linear collider in addition to the LHC will enhance our knowledge significantly and helps to reconstruct the model of new physics nature has chosen.Comment: Invited talk at the Lepton Photon Symposium 2005, Upsala, Sweden, July 2005, V2: minor improvement

Corrections to Quark Asymmetries at LEP

The most precise measurement of the weak mixing angle sin^2(theta) at LEP is from the forward-backward asymmetry e+e- --> bbbar at the Z-pole. In this note the QED and electroweak radiative corrections to obtain the pole asymmetry from the measured asymmetry for b- and c-quarks have been calculated using ZFITTER, which has been amended to allow a consistent treatment of partial two-loop corrections for the b-quark final asymmetries. A total correction of dAfbb=0.0019+/-0.0002 and dAfbc=0.0064+/-0.0001 has been found, where the remaining theoretical uncertainty is much too small to explain the apparent discrepancy between sin^2(theta) obtained from Afbb and from the left-right asymmetry at SLD

Spin rotation schemes at the ILC for two interaction regions and positron polarization with both helicities

This note describes a spin rotation scheme for the ILC that allows the polarization spin vector of the electron and positron beams to be tuned independently for two Interaction Regions (IR). The correct spin direction for a particular IR can be selected by directing the beam into one of two parallel spin rotation beam lines located between the damping ring and the linac. With suitable fast kicker magnets, it is possible to rapidly switch between these parallel beam lines, so that polarized beams can be delivered to two IRs on a pulse train by pulse train basis. A similar scheme can be employed in the insertion beam line to the positron damping ring, to allow rapid helicity switching for polarized positrons

Studies for a Photon Collider at the ILC

One option at the International Linear Collider is to convert the electron beams into high energy photon beams by Compton scattering a few millimetres in front of the interaction region. Selected physics channels for this option have been analysed and technical issues have been studied. So far no showstoppers for this option have been found.Comment: V2: Minor changes, accepted by NI

Study of incoherent pair generation in the beam-beam interaction simulation program Guinea-Pig

Talk given at 2005 ALCPG & ILC Workshops - Snowmass, U.S.A., Aug. 14-27, 2005. Pulbished in the proceedings : www.slac.stanford.edu/econf/C0508141/proc/papers/ALCPG0933.PDFInternational audienceThis paper deals with two topics: the generation of incoherent pairs in two-beam-beam simulation programs, Guinea-Pig and CAIN, and the influence of the ILC beam parameter choices on the background in the micro-vertex detector (VD) induced by direct hits. One of the processes involved in incoherent pair creation (IPC) is equivalent to a four fermions interaction and its cross section can be calculated exactly with a dedicaded generator, BDK. A comparison of Guinea-Pig and CAIN results with BDK allows to identify and quantify the uncertainties on IPC background predictoins and to benchmark the Guinea-Pig calculation. Based on this simulation and different VD designs, the five currently suggested ILC beam parameter sets have been compared regarding IPC background induced in the VD by direct IPC hits. We emphasize that the high luminosity set, as it is currently defined, would constrain both the choices of magnetic field and VD inner layer radius

Recent Results from LEP at the Z on Electroweak and Heavy Flavour Physics

The four LEP experiments ALEPH, DELPHI, L3 and OPAL have collected about four million Z decays each between 1990 and 1995 at energies close to the Z-pole. Most of the data have been taken between 1992 and 1995 on the peak and at approximately $2 GeV$ above and below. Recent preliminary results, using a large fraction of the full statistics, are presented on electroweak and selected topics of b-physics