Measurement of the spectroscopy of orbitally excited B mesons at LEP

Abstract We measure the masses, decay widths and relative production rate of orbitally excited B mesons using 1.25 million hadronic Z decays recorded by the L3 detector. B-meson candidates are inclusively reconstructed and combined with charged pions produced at the primary event vertex. An excess of events above the expected background in the B π mass spectrum in the region 5.6–5.8 GeV is interpreted as resulting from the decay B ∗∗ u , d → B (∗) π , where B ∗∗ u , d denotes a mixture of l =1 B-meson states containing a u or a d quark. A fit to the mass spectrum yields the masses and decay widths of the B 1 ∗ and B 2 ∗ spin states, as well as the branching fraction for the combination of l =1 states. In addition, evidence is presented for the existence of an excited B-meson state or mixture of states in the region 5.9–6.0 GeV.