Revisiting D0-D0bar mixing using U-spin

TL;DR

This paper demonstrates that D0-D0bar mixing in the standard model is only second order in U-spin breaking, using U-spin symmetry to analyze cancellations among intermediate states affecting the mixing parameter.

Contribution

It introduces a U-spin symmetry approach to analyze D0-D0bar mixing, showing cancellations occur at first order within U-spin triplets, refining understanding of mixing mechanisms.

Findings

D0-D0bar mixing occurs only at second order in U-spin breaking.

Cancellations within U-spin triplets are valid to first order.

Illustrations include various meson pairs and states of four kaons and pions.

Abstract

We prove that $D^0$-$\bar D^0$ mixing in the standard model occurs only at second order in U-spin breaking. The U-spin subgroup of SU(3) is found to be a powerful tool for analyzing the cancellation of intermediate-state contributions to the $D^0$--$\od^0$ mixing parameter $y = \Delta \Gamma/(2 \Gamma)$. Cancellations due to states {\it within a single U-spin triplet} are shown to be valid to first order in U-spin breaking. Illustrations are given for triplets consisting of (a) pairs of charged pions and kaons; (b) pairs of neutral pseudoscalar members of the meson octet; (c) charged vector-pseudoscalar pairs, and (d) states of four charged kaons and pions.