Recent Tests of QCD at SLD

Abstract

We present selected results on strong interaction physics from the SLD experiment at the SLAC Linear Collider. We report on several new studies of 3-and 4-jet hadronic Z 0 decays, in which jets are identified as quark, antiquark or gluon. The 3-jet Z 0 → bbg rate is sensitive to the b-quark mass; prospects for measuring m b are discussed. The gluon energy spectrum is measured over the full kinematic range, providing an improved test of QCD and limits on anomalous bbg couplings. The parity violation in Z 0 → bbg decays is consistent with electroweak theory plus QCD. New tests of T-and CP-conservation at the bbg vertex are performed. A new measurement of the rate of gluon splitting into bb pairs yields g bb = 0.0031±0.0007(stat.)±0.0006(syst.) (Preliminary). We also present a number of new results on jet fragmentation into identified hadrons. The B hadron energy spectrum is measured over the full kinematic range using a new, inclusive technique, allowing stringent tests of predictions for its shape and a precise measurement of x B = 0.714 ± 0.005(stat.) ± 0.007(syst.) (Preliminary). A detailed study of correlations in rapidity y between pairs of identified π ± , K ± and p/p confirms that strangeness and baryon number are conserved locally, and shows local charge conservation between meson-baryon and strange-nonstrange pairs. Flavor-dependent long-range correlations are observed for all combinations of these hadron species, yielding new information on leading particle production. The first study of correlations using rapidities signed such that y > 0 corresponds to the quark direction provides additional new insights into fragmentation, including the first direct observation of baryon number ordering along the qq axis.