Measurement of the e⁺e^- → Z → bb forward-backward asymmetry and the B⁰B⁰ mixing parameter using prompt leptons

Abstract

The time-integrated <math><mtext>B</mtext><msup><mi></mi><mn>0</mn></msup><mtext>B</mtext><mtext>̄</mtext><msup><mi></mi><mn>0</mn></msup></math> mixing parameter and the forward-backward charge asymmetry in the process <math><mtext>e</mtext><msup><mi></mi><mn>+</mn></msup><mtext>e</mtext><msup><mi></mi><mn>−</mn></msup><mtext>→b</mtext><mtext>b</mtext><mtext>̄</mtext></math> are measured in hadronic Z events containing prompt muons or electrons, collected by the L3 experiment in the years 1990 to 1995. The total sample of 3.3 milion hadronic Z events with a mean centre-of-mass energy of 91.26 GeV yields: A^b_FB=0.0960±0.0066(stat.)±0.0033(sys.), χ_b=0.1192±0.0068(stat.)±0.0051(sys.). This asymmetry measurement together with measurements at energies away from the Z pole energy yield a pole asymmetry and corresponding effective electroweak mixing angle of: A^0,b_FB=0.1015±0.0064(stat.)±0.0035(sys.), <math><mtext>sin</mtext><msup><mi></mi><mn>2</mn></msup><mtext>θ</mtext><mtext>̄</mtext><msub><mi></mi><mn><mtext>W</mtext></mn></msub><mtext>=0.2318±0.0013</mtext></math>.