Recent QCD-related studies with the BaBar detector

Abstract

We report some of the most recent results in studying different aspects of QCD with about $500$~fb$^{−1}$ of data collected by the BaBar experiment at the $e^+e^-$ $B$-factory PEP-II. Among these, we present a high precision measurement of the mass difference between the $D^{*+}(2010)$ and $D^{+}$ mesons using the decay chain $D^{* +}(2010)\rightarrow D^+\pi^0$, with $D^+\rightarrow K^-\pi^+\pi^+$. This result is then combined with a previous BaBar measurement of $m(D^{* +}(2010)) - m(D^0)$ to extract the mass difference between the charged and neutral $D$ mesons. We obtain results that are approximately five times more precise than the present world averages. We also report on the search for a $B$-meson decay to four baryons, $B^0\rightarrow p p \bar{p} \bar{p}$, which can help to shed light on the experimental discrepancy between the inclusive branching fraction of all $B$ meson decay modes with at least a couple of baryons in the final state, measured by ARGUS to be $(6.8\pm0.6)\%$ , and the sum of exclusive baryonic channels. Finally, we present a measurement of the spectral function for the $\tau^-\rightarrow K^-K_S\nu_\tau$ decay, which can be used to determine the hadronic contribution to the muon $g-2$ due to the vacuum polarization.