Observation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:msubsup><mml:mi>B</mml:mi><mml:mi>s</mml:mi><mml:mn>0</mml:mn></mml:msubsup></mml:math>–<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"><mml:msubsup><mml:mover accent="true"><mml:mi>B</mml:mi><mml:mo>¯</mml:mo></mml:mover><mml:mi>s</mml:mi><mml:mn>0</mml:mn></mml:msubsup></mml:math> Oscillations

Abstract

We report the observation of Bs0–B¯s0 oscillations using 1 fb−1 of data from pp¯ collisions with the CDF II detector at the Fermilab Tevatron. We measure the probability, as a function of proper decay time, that the Bs0 decays with the same, or opposite, flavor as its flavor at production, which is determined using opposite-side and same-side flavor identification methods. We find a signal consistent with Bs0–B¯s0 oscillations, with a significance greater than 5σ. We measure Δms=17.77±0.10(stat)±0.07(syst)ps−1.