Observation of the Semileptonic Decay $D^0 \to a_0(980)^- e^+ \nu_e$ and Evidence for $D^+ \to a_0(980)^0 e^+ \nu_e$

TL;DR

This paper reports the first observation of the semileptonic decay $D^0 o a_0(980)^- e^+ u_e$ and provides evidence for $D^+ o a_0(980)^0 e^+ u_e$, measuring their branching fractions using BESIII data.

Contribution

First observation of $D^0 o a_0(980)^- e^+ u_e$ decay and evidence for $D^+ o a_0(980)^0 e^+ u_e$, with measured branching fractions and upper limits.

Findings

Observation of $D^0 o a_0(980)^- e^+ u_e$ with 6.4σ significance.

Evidence for $D^+ o a_0(980)^0 e^+ u_e$ with 2.9σ significance.

Measured branching fractions and an upper limit for the decays.

Abstract

Using an $e^+e^-$ collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of $D^0 \to a_0(980)^- e^+ \nu_e$ and evidence for $D^+ \to a_0(980)^0 e^+ \nu_e~$ with significances of $6.4\sigma$ and $2.9\sigma$, respectively. The absolute branching fractions are determined to be $\mathcal{B}(D^0 \to a_0(980)^- e^+ \nu_e)\times\mathcal{B}(a_0(980)^- \to \eta \pi^-) = (1.33_{-0.29}^{+0.33}({\rm stat})\pm0.09({\rm syst}))\times10^{-4}~$ and $\mathcal{B}(D^+ \to a_0(980)^0 e^+ \nu_e)\times\mathcal{B}(a_0(980)^0 \to \eta \pi^0) = (1.66_{-0.66}^{+0.81}({\rm stat})\pm0.11({\rm syst}))\times10^{-4}~$. An upper limit of $\mathcal{B}(D^+ \to a_0(980)^0 e^+ \nu_e)\times\mathcal{B}(a_0(980)^0 \to \eta \pi^0)<3.0\times10^{-4}~$ is also determined at the $90\%~$ confidence level.