Physicists Find No Signs of Exotic Particles in Rare Decay Study
An international team has completed the first detailed measurement of a rare particle decay, finding that the fundamental forces behave exactly as predicted by current theory. The result tightens constraints on theoretical models and rules out certain exotic physics scenarios, strengthening confidence in the Standard Model that underpins particle physics research funding and next-generation detector development.
Originaltitel: Test of Lepton Universality and Measurement of the Form Factors of <em>D</em><sup>0</sup> → <em>K</em>*(892)<sup>-</sup>μ<sup>+</sup>ν<sub>μ</sub>
<p>One of the main goals of studying semileptonic decays in flavor physics is to gain a better understanding of hadronic transitions in the nonperturbative region of Quantum Chromodynamics. This involves measuring Cabibbo-Kobayashi-Maskawa matrix elements, understanding form factors, and comparing them with theoretical predictions. We report a first study of the semileptonic decay D<sup>0</sup> → K<sup>-</sup>π<sup>0</sup>μ<sup>+</sup>ν<sub>μ</sub> by analyzing an e<sup>+</sup>e<sup>-</sup> annihilation data sample of 7.93 fb<sup>-1</sup> collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The absolute branching fraction of D<sup>0</sup> → K<sup>-</sup>π<sup>0</sup>μ<sup>+</sup>ν<sub>μ</sub> is measured for the first time, providing necessary input for extracting the c → <em>s</em> Cabibbo-Kobayashi-Maskawa matrix element through this process. This measurement allows us to test lepton flavor universality, with no indication of violation found. Furthermore, a series of hadronic form factors have been determined and compared with theoretical predictions, which will impose stricter constraints on theoretical models.</p>