Direct measurement of B(D_s^+ → φX^+)

The absolute inclusive branching fraction of D_s^+→φX^+ has been measured from data collected by the BES detector at a center-of-mass energy of 4.03 GeV, corresponding to an integrated luminosity of 22.3 pb^(-1). At this energy, direct pair production e^+e^-→D_s^+D_s^- has been observed. We have selected D_s candidate events by reconstructing five hadronic decay modes D_s^+→φπ^+, K^(0*)K^+, K^0K^+, f0^(π+) and K^0K^-π^+π^+ and have searched for inclusive φ’s in the recoiling D_s^-. We observed three recoiling φ’s in the 166.4 ± 31.8 D_s candidate events, which leads to the absolute branching fraction B(D_s^+→φX^+)=(17.8(-7.2 -6.3)^(+15.1+0.6)) % and B(D_s-6.3+→φπ-6.3+)=(3.6_(-1.6 -1.3)(^_3.1+0.4) %. [S0556-2821(97)02423-5]