A MEASUREMENT OF THE B(S)0 MESON MASS

Strange beauty mesons B(s)0 have been reconstructed through exclusive hadronic final states, using the data collected in 1992 by the DELPHI experiment at the LEP collider. The analysis relies on the combined use of accurate tracking and of the hadron identification capabilities of DELPHI. Three B(s)0 decay candidates have been selected over a negligible background using the D(s)- pi+, D(s)- a1+ (1260) and J/ psi phi decay modes, with identified kaons in the final state. The B(s)0 meson mass is measured to be m(b)s = (5374 +/- 16 +/- 2) MeV/c2.