Measurements of Lifetimes and a Limit on the Lifetime Difference in the Neutral D-Meson System

TL;DR

This paper reports the first direct measurement constraint on the decay-width difference in the neutral D-meson system using lifetime measurements of specific decay modes, providing insights into D0-D0bar mixing.

Contribution

It provides the first direct experimental constraint on the decay-width difference Delta Gamma in the D0-D0bar system based on lifetime measurements.

Findings

Decay-width difference Delta Gamma = 0.04 +/- 0.14 +/- 0.05 ps^-1

Lifetimes measured: tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps

Results relate to D-meson mixing measurements.

Abstract

Using the large hadroproduced charm sample collected in experiment E791 at Fermilab, we report the first directly measured constraint on the decay-width difference Delta Gamma for the mass eigenstates of the D0-D0bar system. We obtain our result from lifetime measurements of the decays D0 --> K-pi+ and D0 --> K-K+, under the assumption of CP invariance, which implies that the CP eigenstates and the mass eigenstates are the same. The lifetime of D0 --> K-K+ (the CP-even final state is \tau_KK = 0.410 +/- 0.011 +/- 0.006 ps, and the lifetime of D0 --> K-pi+ (an equal mixture of CP-odd and CP-even final states is tau_Kpi = 0.413 +/- 0.003 +/- 0.004 ps. The decay-width difference is Delta Gamma = 2(Gamma_KK - Gamma_Kpi) = 0.04 +/- 0.14 +/- 0.05 ps^-1. We relate these measurements to measurements of mixing in the neutral D-meson system.