Overview of SLD Data Analysis

The physics studies performed at LEP and SLD in e+e- collisions at the Z mass energy have been an exceedingly rich source of new information in the 90's. Several unique features of the detector and accelerator make the SLD/SLC data competitive with LEP in spite of the large discrepancy in data sample size. These features include: The polarization allows numerous tests of the standard model that are not possible at LEP. In addition the forward-backward asymmetry of quark-antiquark production from the decay of polarized Zs allows the tagging of the quark flavor at its origin, an important ingredient of many heavy quark studies as well as numerous measurements in QCD.

With the addition of the data from the 1997-1998 run, SLD's measurement of the Weinberg angle from the Z production asymmetry ALR has become the single most precise measurement of sin2qW in the world. In the figure below, the leftmost two results are SLD measurements from ALR and from the forward-backward left-right double asymmetry AFBLR.  The remaining six values are LEP determinations in which the results of all four LEP experiements are combined for each technique.
 
Weak Mixing Angle Results as of the 1999 Lepton-Photon Symposium

To emphasize the power of analysis techniques that exploit polarized electron beams, it should be emphasized that each of the 4 LEP experiments has a data sample that is a factor of ~25 larger that of SLD.

The measurements using leptons are in reasoanble internal agreement, as are those using hadrons. However there appears to be a systematic difference between the leptonic and hadronic results. In particular, there is a 3 sigma disagreement between the two most precise measurements, the SLD result from ALR using leptons, and those using the b-quark forward-backward asymmetry. This may be due to deviations in the Z to b-quark coupling which affect the quark measurements, but not the lepton measurement.

Other electroweak analyses have also progressed. With the full data set, SLD has made the most precise single measurements of Rc, Ab, Ac, and As. The result for Rb will also be in this class once the most recent data is included. The heavy-quark asymmetries Ab and Ac are each measured using several different techniques. It is projected that once all techniques are combined we will have results for these quantities that rival or exceed, in precision, the average of all four LEP experiments.

Much of the work in the Heavy Flavors working group is centered on B+ and B0 meson lifetimes, the heavy quark asymmetries discussed above, and B mixing. These analyses all rely heavily on the polarized electron beam in order to "tag" the hemisphere flavor as b or b-bar. Averaged over the detector acceptance, this tag is nearly 100% efficient and ~73% pure. The inclusive topological vertexing technique pioneered at SLD has enabled us to make very precise measurements of B meson lifetimes. We currently have the best single measurements of B+ and B0 lifetimes, and our B+/B0 lifetime ratio (in which many common systematic errors cancel) is currently at 1.030 +0.028/-0.027 (stat) +- 0.026, which is less than 1 sigma above the unity prediction of the spectator model. Other work has been on the measurements of B(b®DDX) and B(b®l)/B(b®c®l), which is discussed below. The primary focus of the mixing subgroup continues to be on Bs mixing. As of late 1999,  SLD has excluded at 95% C.L. the regions DmS<5.2 ps-1 and 11.3< DmS<14.2 ps-1. As a result of the new SLD contribution to the 1999 Lepton-Photon Symposium, the 95% C.L. lower limit on DmS increased from 12.4 to 14.2 ps-1. Further improvements are expected as additional Bs decay modes are included in the SLD result.

Much of the work in SLD's QCD group has been on "heavy flavor QCD". Using the new data, a new measurement of the B fragmentation function is being submitted for publication. Also, with the additional data, a new measurement of the gluon energy in bbg events has been made; from which limits on anomalous couplings in the QCD Lagrangian can be set. Utilizing the particle identification system, a lengthy article on identified particle production in Z ® light quark pairs, ccbar, and bbbar events has been published in Physical Review D. Ken Baird has contributed heavily to this publication.

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