Measurement of the B+ and B0 Lifetimes and Search for CP(T) Violation using Reconstructed Secondary Vertices

TL;DR

This paper measures B+ and B0 meson lifetimes and searches for CP and CPT violation effects using secondary vertex reconstruction in Z0 decays, providing precise lifetime ratios and no evidence of CP violation.

Contribution

It provides new precise measurements of B meson lifetimes and their ratio, and sets limits on CP and CPT violation effects in B hadron decays.

Findings

Measured B+ lifetime as 1.643 ps

Measured B0 lifetime as 1.523 ps

No evidence of CP or CPT violation found

Abstract

The lifetimes of the B+ and B0 mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic Z0 decays recorded at LEP. Z0 -> b bbar decays were tagged using displaced secondary vertices and high momentum electrons and muons. The lifetimes were then measured using well-reconstructed charged and neutral secondary vertices selected in this tagged data sample. The results are tau(B+) = 1.643 +- 0.037 +- 0.025 ps tau(B0) = 1.523 +- 0.057 +- 0.053 ps ratio tau(B+)/tau(B0) = 1.079 +- 0.064 +- 0.041 where in each case the first error is statistical and the second systematic. A larger data sample of 3.1 million hadronic Z0 decays has been used to search for CP and CPT violating effects by comparison of inclusive b and bbar hadron decays. No evidence for such effects is seen. The CP violation parameter Re(epsilon_B) is measured to be Re(epsilon_B) = 0.001 +- 0.014 +- 0.003 and the fractional difference between b and bbar hadron lifetimes is measured to be -0.001 +- 0.012 +- 0.008