Observation of the Doubly Cabibbo-Suppressed Decay $D^+\to K^+\pi^+\pi^-\pi^0$ and Evidence for $D^+\to K^+\omega$

TL;DR

This paper reports the first observation of a doubly Cabibbo-suppressed decay of the D+ meson, measures its branching fraction, compares it to related decays, and finds evidence for another decay mode, with no CP violation observed.

Contribution

The study provides the first measurement of the branching fraction for D+→K+π+π−π0 and evidence for D+→K+ω, advancing understanding of charm meson decay dynamics and Cabibbo suppression effects.

Findings

First observation of D+→K+π+π−π0 decay.

Branching fraction measured as (1.13 ± 0.08 ± 0.03)×10⁻³.

Evidence for D+→K+ω decay with 3.3σ significance.

Abstract

Using $2.93 \rm fb^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay $D^+\to K^+\pi^+\pi^-\pi^0$ is reported. After removing decays that contain narrow intermediate resonances, including $D^+\to K^+\eta$, $D^+\to K^+\omega$, and $D^+\to K^+\phi$, the branching fraction of the decay $D^+\to K^+\pi^+\pi^-\pi^0$ is measured to be $(1.13 \pm 0.08_{\rm stat} \pm 0.03_{\rm syst})\times 10^{-3}$. The ratio of branching fractions of $D^+\to K^+\pi^+\pi^-\pi^0$ over $D^+\to K^-\pi^+\pi^+\pi^0$ is found to be $(1.81\pm0.15)$\%, which corresponds to $(6.28\pm0.52)\tan^4\theta_C$, where $\theta_C$ is the Cabibbo mixing angle. This ratio is significantly larger than the corresponding ratios for other doubly Cabibbo-suppressed decays. The asymmetry of the branching fractions of charge-conjugated decays $D^\pm\to K^\pm\pi^\pm\pi^\mp\pi^0$ is also determined, and no evidence of $CP$ violation is found. In addition, the first evidence of the $D^+\to K^+\omega$ decay, with a statistical significance of 3.3$\sigma$, is presented and its decay branching fraction is determined to be $({5.7^{+2.5}_{-2.1}}_{\rm stat}\pm0.2_{\rm syst})\times10^{-5}$.