Speaker
Description
Employing the heavy quark expansion model with the kinetic scheme, we evaluate $\alpha_S(m_c^2)$, the strong coupling constant at the charm quark mass $m_c$ with data on inclusive semileptonic decays of charmed mesons. Using the experimental values of semileptonic decay widths of the $D^0$ and the $D^+$, the value of $\alpha_{s}(m_c^{2})$ is determined to be $0.445\pm0.009\pm0.114$, where the first uncertainty is experimental and the second systematic. This reported $\alpha_{s}(m_c^{2})$ is in good agreement with the value of $\alpha_{s}(m_c^{2})$ calculated by running $\alpha_S(m_Z^2)$ at the $Z^0$ boson mass $m_Z$ with the renormalization group evolution equation. In addition, values of $\alpha_{s}(m_c^{2})$ obtained individually from each of the $D^0$, $D^+$, and $D_s^+$ mesons are found to be consistent being of the same origin. The outcome of this work determined the $\alpha_{s}$ at $m_c=1.37$GeV, which is the first measurement of this quantity below the $\tau$ mass. The measurement represents a new approach to determine $\alpha_{s}(m_c^{2})$, and indicates that an important feature of Quantum Chromo-Dynamics, asymptotic freedom, is still valid at the energy scale of charm quark mass. This measurement can help to further understand strong interaction, and probe possible new physics.
