First measurement of polarizations in the decay $D^0 \to \omega \phi$

TL;DR

This paper reports the first observation of the decay $D^0 o \omega\phi$, measures its branching fraction, and finds that the vector mesons are transversely polarized, challenging existing theoretical models.

Contribution

First measurement of the decay $D^0 o \omega\phi$, including branching fraction and polarization analysis, providing new insights into charm meson decay dynamics.

Findings

Branching fraction measured as (6.48 ± 0.96 ± 0.40)×10^{-4}.

Decay exhibits predominantly transverse polarization.

Results challenge current theoretical expectations.

Abstract

Using a data sample corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at a center-of-mass energy $\sqrt{s}=3.773$ GeV by the BESIII detector, the decay $D^0 \to\omega\phi$ is observed for the first time. The branching fraction is measured to be $(6.48 \pm 0.96 \pm 0.40)\times 10^{-4}$ with a significance of $6.3 \sigma$, where the first and second uncertainties are statistical and systematic, respectively. An angular analysis reveals that the $\phi$ and $\omega$ mesons from the $D^0 \to \omega \phi$ decay are transversely polarized. The $95\%$ confidence level upper limit on longitudinal polarization fraction is set to be less than $0.24$, which is inconsistent with current theoretical expectations and challenges our understanding of the underlying dynamics in charm meson decays.