Measurement of the parity-violating asymmetry parameter α b and the helicity amplitudes for the decay Λ 0b → J/ψ Λ 0 with the ATLAS detector

Aad, G. and Abajyan, T. and Abbott, B. and Abdallah, J. and Khalek, S. A. and Abdinov, O. and Aben, R. and Abi, B. and Abolins, M. and AbouZeid, O. S. and Abramowicz, H. and Abreu, H. and Abulaiti, Y. and Acharya, B. S. and Adamczyk, L. and Adams, D. L. and Adelman, J. and Adomeit, S. and Adye, T. and Agatonovic-Jovin, T. and Aguilar-Saavedra, J. A. and Agustoni, M. and Ahlen, S. P. and Ahmad, A. and Ahmadov, F. and Aielli, G. and Akesson, T. P. A. and Akimoto, G. and Akimov, A. V. and Albert, J. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2014) Measurement of the parity-violating asymmetry parameter α b and the helicity amplitudes for the decay Λ 0b → J/ψ Λ 0 with the ATLAS detector. PHYSICAL REVIEW D, 89 (9). ISSN 2470-0010

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Abstract

A measurement of the parity-violating decay asymmetry parameter, α b, and the helicity amplitudes for the decay Λ 0b → J/ψ ( µ + µ −)Λ 0 (pπ − ) is reported. The analysis is based on 1400 Λ 0b and Λ¯ 0b 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 Λ 0b and Λ¯ 0b samples under the assumption of CP conservation, the value of α b 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.

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