Measurements of the absolute branching fractions of $D^0\to\gamma \bar K^{*0}$ and $D^0\to\gamma \phi$

TL;DR

This study reports the first measurements of absolute branching fractions for the radiative decays of D0 mesons to gamma and vector mesons, using BESIII data, confirming previous averages and testing CP symmetry.

Contribution

First measurement of absolute branching fractions for D0→γK*0̄ and D0→γϕ decays, providing new experimental data for these rare processes.

Findings

Branching fraction for D0→γK*0̄ is (3.81 ± 0.18 ± 0.20)×10⁻⁴.

Branching fraction for D0→γϕ is (2.51 ± 0.44 ± 0.11)×10⁻⁵.

CP asymmetry measured is consistent with zero, indicating no CP violation.

Abstract

By analyzing a sample of 20.3 fb$^{-1}$ of $e^+e^-$ annihilation data collected at the center-of-mass energy of 3.773~GeV with the BESIII detector, we have made a first measurement of the absolute branching fractions of the radiative decays $D^0\to\gamma \bar K^{*0}$ and $D^0\to\gamma\phi$ to be $(3.81 \pm 0.18_{\rm stat.} \pm 0.20_{\rm syst.})\times 10^{-4}$ and $(2.51 \pm 0.44_{\rm stat.} \pm 0.11_{\rm syst.})\times 10^{-5}$, respectively. The statistical significances of $D^0\to\gamma \bar K^{*0}$ and $D^0\to\gamma \phi$ are $26.8\sigma$ and $7.9\sigma$, respectively. The obtained branching fractions are consistent with the corresponding world average values. In addition, the measured $C\!P$ asymmetry $\mathcal{A}_{C\!P}(D^0\to\gamma \bar K^{*0})=(-0.7\pm5.0_{\rm stat.} \pm4.1_{\rm syst.})\%$ is consistent with $C\!P$ conservation.