Measurement ofB0B¯0mixing at the Fermilab Tevatron Collider

Abstract

The ${\mathit{B}}^0$ B¯ ${}_{}{}^0{}_{}{}^{}$ average mixing parameter χ has been extracted from eμ and ee events produced in pp¯ collisions at √s =1.8 TeV. In a sample of 900 eμ events, the like-sign to opposite-sign charge ratio R is measured to be 0.556±0.048(stat${)}_{\mathrm{-}0.042}^{+0.035\mathrm{}}$(syst). In the absence of mixing, the expected value of R would be 0.23±0.06. The corresponding number for 212 ee events is 0.573±0.116(stat)±0.047(syst) with an expected nonmixing value of 0.24±0.07. The observed excess in R leads to a combined determination of χ=0.176±0.031(stat+syst) ±0.032 (model), where the last uncertainty is due to Monte Carlo modeling.