Evidence for single top quark production at D0

par Prof. Gordon WATTS (U.of Washington, Seattle)

lundi 14 mai 2007, 14:00 → 15:00 Europe/Paris

Amphithéâtre

The DØ Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron ppbar collider. We apply three multivariate analyses to separate signal from background in the same 0.9 fb-1 dataset, and measure: *Boosted Decision Trees* (DT) σ(ppbar→ tb + X, tqb + X) = 4.9 ± 1.4 pb *Matrix Elements* (ME) σ(ppbar→ tb + X, tqb + X) = 4.6 +1.8-1.5 pb *Bayesian Neural Networks* (BNN) σ(ppbar→ tb + X, tqb + X) = 5.0 ± 1.9 pb The DT result corresponds to a *3.4 standard deviation significance* from the background-only hypothesis. The ME and BNN measurements correspond to 2.9 and 2.4 standard deviations, respectively. We use the cross section measurement to directly determine the CKM matrix element that describes the /Wtb/ coupling and find 0.68 < |V_tb | ≤ 1 at 95% C.L. within the standard model.