Measurement of the Bs-Bsbar Oscillation Frequency

TL;DR

This paper reports the first measurement of the Bs-Bsbar oscillation frequency Delta m_s using data from the Fermilab Tevatron, providing key insights into flavor oscillations and CKM matrix elements.

Contribution

It presents the first measurement of Delta m_s and the ratio |Vtd/Vts| using a large dataset of Bs decays from proton-antiproton collisions.

Findings

Measured Delta m_s = 17.31 ps^-1 with statistical and systematic uncertainties.

Found a 0.2% probability that the signal is a fluctuation, confirming oscillation detection.

Determined |Vtd/Vts| = 0.208 with experimental and theoretical uncertainties.

Abstract

We present the first measurement of the Bs-Bsbar oscillation frequency Delta m_s. We use 1 fb^-1 of data from p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3,600 fully reconstructed hadronic Bs decays and 37,000 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 consistent with Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs-Bsbar oscillations, we measure Delta m_s = 17.31^{+0.33}_{-0.18} (stat.) +- 0.07 (syst.) ps^-1 and determine |Vtd/Vts| = 0.208^{+0.001}_{-0.002} (exp.) ^{+0.008}_{-0.006} (theo.).