Hadronic $D_s$ decays

The CLEO-c experiment at the CESR $e^+ e^-$ collider has collected a large sample of $D_s^\pm D_s^{\mp *}$ events at $E_{cm} \sim 4.17$~GeV. By exploiting the pair production of these charmed mesons, we can determine their absolute hadronic branching fractions without reference to the total luminosity of the sample. Here we report preliminary measurements of major $D_s^+$ hadronic branching fractions, in particular ${\mathcal B}(D_s^+ \to \phi \pi^+)$.