ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2012, vol. 108, p. -
First observation of the P-wave spin-singlet bottomonium states h b(1P) and h b(2P)
We report the first observations of the spin-singlet bottomonium states h b(1P) and h b(2P). The states are produced in the reaction e +e -→h b(nP)π +π - using a 121.4fb -1 data sample collected at energies near the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e +e - collider. We determine M[h b(1P)]=(9898.2- 1.0-1.1+1.1+1.0)MeV/c2 and M[h b(2P)]=(10259.8±0.6-1.0+1.4)MeV/ c2, which correspond to P-wave hyperfine splittings ΔM HF=(+1. 7±1.5) and (+0.5-1.2+1.6)MeV/c2, respectively. The significances of the h b(1P) and h b(2P) are 5.5σ and 11.2σ, respectively. We find that the production of the h b(1P) and h b(2P) is not suppressed relative to the production of the Υ(1S), Υ(2S), and Υ(3S). © 2012 American Physical Society.