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.
Lees, J., Poireau, V., Tisserand, V., Grauges, E., Palano, A., Eigen, G., et al. (2014). Bottomonium spectroscopy and radiative transitions involving the chi(bJ)(1P, 2P) states at BABAR. PHYSICAL REVIEW D, PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY, 90(11) [10.1103/PhysRevD.90.112010].
Bottomonium spectroscopy and radiative transitions involving the chi(bJ)(1P, 2P) states at BABAR
CARPINELLI, MassimoMembro del Collaboration Group
;
2014
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.