QCD Tests using beam polarization

The SLC(L?) provides an electron beam with high longitudinal polarization. The magnitude of the polarization has increased over the years(L:pol history) from 22% in the 1992 run to 77% in the 1994-5 run. The sign of the polarization is determined randomly for each beam pulse. The Electroweak Standard Model predicts that the Z0 should decay preferentially into qq pairs in which the q is left-handed and the qbar right handed. The quark therefore prefers to follow the electron beam direction when the beam is left-polarized. The predicted distribution of the angle between the electron and quark directions for 77% polarization is:

We make use of this angular preference to separate quark jets from antiquark jets, which go in the opposite direction. The polarization of the quark depends on it's production angle:

so we can use this to look for propagation of the spin of the initial quark.

First Measurement of the T-odd Triple Product in Z0-->qqg Events

Tony Johnson