Measurement of B0d - B0d-bar mixing rate from the time evolution of dilepton events at the Upsilon(4S)

TL;DR

This paper measures the B0d - B0d-bar mixing rate Delta-m_d using time evolution of dilepton events from Upsilon(4S) decays, providing the first such measurement at this energy level.

Contribution

It presents the first determination of Delta-m_d from time evolution measurements at the Upsilon(4S) resonance.

Findings

Delta-m_d = 0.463 +- 0.008 (stat) +- 0.016 (sys) ps^{-1}

First measurement of Delta-m_d from time evolution at Upsilon(4S)

Limits placed on CPT violation

Abstract

We report a determination of the B0d - B0d-bar mixing parameter Delta-m_d based on the time evolution of dilepton yields in Upsilon(4S) decays. The measurement is based on a 5.9 /fb data sample collected by the Belle detector at KEKB. The proper-time difference distributions for same-sign and opposite-sign dilepton events are simultaneously fitted to an expression containing Delta-m_d as a free parameter. Using both muons and electrons, we obtain Delta-m_d = 0.463 +- 0.008(stat.) +- 0.016(sys.) ps^{-1} This is the first determination of Delta-m_d from time evolution measurements at the Upsilon(4S). We also place limits on possible CPT violations.