Physicists sharpen measurements of rare particle decay with 60% greater precision
Researchers using the BESIII detector have made the most precise measurement yet of how a charm-strange particle decays, reducing measurement uncertainty by more than half. The result provides a crucial benchmark for testing the Standard Model of physics and validates experimental techniques that will be essential for next-generation particle physics experiments.
Originaltitel: Improved measurement of the semileptonic decay <em>D<sub>s</sub></em><sup>+</sup> → <em>K</em><sup>0</sup><em>e</em><sup>+</sup>ν<sub>e</sub>
<p>Analyzing e<sup>+</sup>e<sup>-</sup> collision data corresponding to an integrated luminosity of 7.33 fb<sup>-1</sup> collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we measure the branching fraction of the semileptonic decay D<sub>s</sub><sup>+</sup> → K<sup>0</sup>e<sup>+</sup>ν<sub>e</sub>) to be (2.98 ± 0.23<sub>stat</sub> ± 0.12<sub>syst</sub>) x 10<sup>-3</sup>. Based on fit to the partial decay rates in various q<sup>2</sup> intervals, the product value of D<sub>s</sub><sup>+</sup> → K<sup>0</sup> hadronic form factor and Cabibbo-Kobayashi-Maskawa element is measured to be f<sub>+</sub><sup>K^0</sup>(0)|V<sub>cd</sub>| = 0.143 ± 0.011<sub>stat</sub> ± 0.003<sub>syst</sub>. With |V<sub>cd</sub>| = 0.22486 ± 0.00067 as an input, the hadronic form factor is evaluated to be f<sub>+</sub><sup>K^0</sup> = 0.636 ± 0.049<sub>stat</sub> ± 0.013<sub>syst</sub>. The branching fraction and form factor measurements are factors of 1.6 and 1.7 more precise than the previous world averages, respectively.</p>