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Observation of D^{0}→K_{1}(1270)^{-}e^{+}ν_{e}.

M Ablikim¹, M N Achasov², P Adlarson³

¹Institute of High Energy Physics, Beijing 100049, People's Republic of China.

Physical Review Letters

|October 8, 2021

Summary

This summary is machine-generated.

Researchers observed a new D0 meson decay, D0→K1(1270)−e+νe, using BESIII data. This study provides the first measurement of longitudinal polarization in this semileptonic decay.

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Area of Science:

Particle Physics
High Energy Physics
Quantum Chromodynamics

Background:

The Standard Model of particle physics describes fundamental particles and forces.
Semileptonic decays of D mesons provide crucial insights into electroweak interactions.
Understanding these decays aids in probing the properties of heavy quarks.

Purpose of the Study:

To report the first observation of the D0→K1(1270)−e+νe semileptonic decay.
To measure the branching fraction and longitudinal polarization of this decay.
To contribute to the understanding of D meson decay dynamics.

Main Methods:

Analysis of 2.93 fb⁻¹ e+e− collision data collected at a center-of-mass energy of 3.773 GeV using the BESIII detector.
Identification of the D0→K1(1270)−e+νe decay signature through signature reconstruction.
Statistical analysis to determine significance, branching fraction, and polarization.

Main Results:

Observation of the D0→K1(1270)−e+νe decay with a statistical significance greater than 10σ.
Measurement of the branching fraction for D0→K1(1270)−e+νe as (1.09±0.13±0.16+0.09)×10⁻³.
First determination of the longitudinal polarization fraction for D0→K1(1270)−e+νe as 0.50±0.19stat±0.08syst.

Conclusions:

The D0→K1(1270)−e+νe decay has been definitively observed.
The measured branching fraction and polarization provide valuable data for theoretical models.
This finding enhances our knowledge of heavy meson semileptonic decays.