Measurement of the parity-violating asymmetry parameter αb and the helicity amplitudes for the decay Λ<sup>0</sup>b →j /ψ Λ<sup>0</sup> with the ATLAS detector

Alconada Verzini, María Josefina; Alonso, Francisco; Anduaga, Xabier Sebastián; Dova, María Teresa; Monticelli, Fernando Gabriel; Tripiana, Martín Fernando; The ATLAS Collaboration

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Measurement of the parity-violating asymmetry parameter αb and the helicity amplitudes for the decay Λ⁰b →j /ψ Λ⁰ with the ATLAS detector

2014

Tipo de documento: Articulo

Resumen

A measurement of the parity-violating decay asymmetry parameter, αb, and the helicity amplitudes for the decay Λ⁰b→J/ψ(μ+μ-)Λ⁰(pπ-) is reported. The analysis is based on 1400 Λ⁰b and Λ⁰¯b baryons selected in 4.6 fb-1 of proton-proton collision data with a center-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. By combining the Λb0 and Λ⁰¯b samples under the assumption of CP conservation, the value of αb is measured to be 0.30±0.16(stat)±0.06(syst). This measurement provides a test of theoretical models based on perturbative QCD or heavy-quark effective theory.