Observation of the Semileptonic Decay D^{0}→a_{0}(980)^{-}e^{+}ν_{e} and Evidence for D^{+}→a_{0}(980)^{0}e^{+}ν_{e}

Area of Science:

• Particle Physics
• High Energy Physics
• Quantum Chromodynamics

Background:

• The a0(980) meson is a poorly understood scalar meson with a complex internal structure.
• Semileptonic decays of D mesons provide a valuable probe for studying hadronic properties.
• Previous studies have not extensively explored the a0(980) meson in D0 semileptonic decays.

Purpose of the Study:

• To report the observation of D0 → a0(980)-e+νe and evidence for D+ → a0(980)0e+νe decays.
• To measure the absolute branching fractions for these newly observed decay modes.
• To contribute to the understanding of the nature of the a0(980) meson.

Main Methods:

• Analysis of a large dataset of electron-positron collision events (2.93 fb-1) collected at a center-of-mass energy of 3.773 GeV.
• Utilized the BESIII detector at the BEPCII collider.
• Performed event reconstruction and background suppression techniques to isolate signal events.

Main Results:

• Observed the decay D0 → a0(980)-e+νe with a significance of 6.4σ.
• Found evidence for the decay D+ → a0(980)0e+νe with a significance of 2.9σ.
• Determined absolute branching fractions: B(D0 → a0(980)-e+νe) × B(a0(980)- → ηπ-) = [1.33 ± 0.29(stat) ± 0.09(syst)] × 10-4 and B(D+ → a0(980)0e+νe) × B(a0(980)0 → ηπ0) = [1.66 ± 0.81(stat) ± 0.11(syst)] × 10-4.

Conclusions:

• This study presents the first measurement of a0(980) in D0 semileptonic decays.
• The results provide crucial data for theoretical models aiming to explain the structure of the a0(980) meson.
• These findings open a new avenue for investigating the properties of the enigmatic a0(980) states.