Measurement of the Spectroscopy of Orbitally Excited B Mesons at LEP

TL;DR

This study measures the properties of orbitally excited B mesons, including their masses and decay widths, using data from Z decays at LEP, providing new insights into heavy meson spectroscopy.

Contribution

It presents the first measurements of masses, decay widths, and production rates of orbitally excited B mesons at LEP, including evidence for a new excited state.

Findings

Masses and widths of B_1^* and B_2^* states determined.

Evidence for an excited B-meson state around 5.9-6.0 GeV.

Branching fractions of l=1 B-meson states measured.

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\pi mass spectrum in the region 5.6-5.8 GeV is interpreted as resulting from the decay B_u,d^** -> B^(*)\pi, 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.