Observation of Bs-Bsbar Oscillations

TL;DR

This paper reports the first observation of Bs-Bsbar oscillations with high statistical significance, measuring the oscillation frequency and related CKM matrix element ratio using data from the Fermilab Tevatron.

Contribution

The study provides the first definitive measurement of Bs-Bsbar oscillation frequency and related parameters, confirming oscillations with over 5 sigma significance.

Findings

Measured Delta ms = 17.77 ± 0.10 (stat) ± 0.07 (syst) ps^-1

Determined |Vtd/Vts| = 0.2060 ± 0.0007 (exp) + 0.0081 - 0.0060 (theor)

Observed Bs-Bsbar oscillations with high statistical significance

Abstract

We report the observation of Bs-Bsbar oscillations from a time-dependent measurement of the Bs-Bsbar oscillation frequency Delta ms. Using a data sample of 1 fb^-1 of p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic Bs decays, 3100 partially reconstructed hadronic Bs decays, and 61500 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal for Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 8 X 10^-8, which exceeds 5 sigma significance. We measure Delta ms = 17.77 +- 0.10 (stat) +- 0.07 (syst) ps^-1 and extract |Vtd/Vts| = 0.2060 +- 0.0007 (exp) + 0.0081 - 0.0060 (theor).