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Bottomonium spectroscopy and radiative transitions involving the chi_bJ(1P,2P) states at BABAR

Abstract : We use (121±1) million Υ(3S) and (98±1) million Υ(2S) mesons recorded by the BABAR detector at the PEP-II e+e− collider at SLAC to perform a study of radiative transitions involving the χbJ(1P,2P) states in exclusive decays with μ+μ−γγ final states. We reconstruct twelve channels in four cascades using two complementary methods. In the first we identify both signal photon candidates in the Electromagnetic Calorimeter (EMC), employ a calorimeter timing-based technique to reduce backgrounds, and determine branching-ratio products and fine mass splittings. These results include the best observational significance yet for the χb0(2P)→γΥ(2S) and χb0(1P)→γΥ(1S) transitions. In the second method, we identify one photon candidate in the EMC and one which has converted into an e+e− pair due to interaction with detector material, and we measure absolute product branching fractions. This method is particularly useful for measuring Υ(3S)→γχb1,2(1P) decays. Additionally, we provide the most up-to-date derived branching fractions, matrix elements and mass splittings for χb transitions in the bottomonium system. Using a new technique, we also measure the two lowest-order spin-dependent coefficients in the nonrelativistic QCD Hamiltonian.
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Submitted on : Friday, October 24, 2014 - 4:30:39 PM
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J. P. Lees, V. Poireau, V. Tisserand, N. Arnaud, M. Davier, et al.. Bottomonium spectroscopy and radiative transitions involving the chi_bJ(1P,2P) states at BABAR. Physical Review D, American Physical Society, 2014, 90 (11), pp.112010. ⟨10.1103/PhysRevD.90.112010⟩. ⟨in2p3-01077427⟩



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