Evidence for the h b(1P) meson in the decay ?(3S) →π 0h b(1P)

Abstract

Using a sample of 122×106 Υ(3S) events recorded with the BABAR detector at the PEP-II asymmetric-energy e +e - collider at SLAC, we search for the h b(1P) spin-singlet partner of the P-wave χ bJ(1P) states in the sequential decay Υ(3S) →π0h b(1P), h b(1P) →γη b(1S). We observe an excess of events above background in the distribution of the recoil mass against the π0 at mass 9902±4(stat)±2(syst)MeV/c2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.1σ, including systematic uncertainties. We obtain the value (4.3±1.1(stat) ±0.9(syst))×10 -4 for the product branching fraction B(Υ(3S)→π0h b)×B(h b→γη b). © 2011 American Physical Society.