The BESIII Collaboration, an international research group working with the Beijing Spectrometer III (BESIII), has published its latest study on charm meson semileptonic decays in Physical Review Letters.

The paper, First Observation of D0(+)→¯Kωe+νe and Determination of the Branching Fraction of ¯K1(1270) → ¯Kω, highlights significant advancements in particle physics.

Professor Sun Liang’s team from Wuhan University’s School of Physics and Technology led this work, utilizing data collected from electron-positron collisions at a center-of-mass energy of 3.773 GeV.

By combining these results with previous measurements of D0(+)→K-π+π-(0)e+νe by the BESIII Collaboration and assuming these decays are mediated entirely through the ¯K1(1270) resonance, the team determined the combined branching fraction B(¯K1(1270) → ¯Kω) = (8.4±1.4±0.5) percent, marking the most precise result from collider experiments to date.

A particularly noteworthy aspect of this research is the innovative method used to measure the mass of the ¯K1(1270) meson through a single vector-pseudoscalar decay channel, employing a novel approach to simulate signal line shapes.

This method received high praise from Physical Review Letters, which noted its potential to set a new standard in the field: “This analysis goes beyond common practice, hopefully setting a new standard in this regard.”

The findings are expected to advance understanding of ¯K1(1270) related decays, such as B →Kωγ and B →Kωℓ+ℓ-, and provide crucial insights for refining theoretical descriptions of the ¯K1(1270) meson.