May 7, LR asymmetry


-SLD still seems to have best sin(theta)w measurement (well but maybe not, given new (2018) LHC results)
-ATLAS has pretty good (2018) measurement with error +/- 0.00024 


SLD vs LEP
-SLD had polarized beams, LEP did not
-LEP could recirculate electrons: higher lumi
-in the end SLD got ~1,000,000 Z’s vs 10,000,000 Z’s at LEP
(-LHC gets ~70,000,000 Z’s per year at current instantaneous lumi)


SLD
-Didn’t really need muon spectrometer to get accurate muon pT measurement (bending radius of ~40 GeV particle)


Beam
-transverse aspect ratio = ellepticallness of beamspot
-Use compton scattering to measure polarization of beam-> uses spin-helicity structure of QED
-You can also measure polarization of electron beam with iron foil: magnetic field in iron manipulates stationary e- states for Moller scattering (compton scattering is typically more precise)


Damping Rings and Focussing
-To focus beam, you need dissipative forces (squeezing without friction means wider pT spread of electrons).  Damping rings use synchrotron radiation.  They must flip electron spin transverse of circular motion to avoid too much spin precession in the damping rings


Tagging events
-require “9 clusters”, which more or less correspond to particles.  Think like jets