Measurement of the $\Lambda_b$ polarization and angular parameters in $\Lambda_b\to J/\psi\, \Lambda$ decays from pp collisions at $\sqrt{s}=$ 7 and 8 TeV
An analysis of the bottom baryon decay Λb→J/ψ(→μ+μ-)Λ(→pπ-) is performed to measure the Λb polarization and three angular parameters in data from pp collisions at s=7 and 8 TeV, collected by the CMS experiment at the Large Hadron Collider. The Λb polarization is measured to be 0.00±0.06(stat)±0.06(syst) and the parity-violating asymmetry parameter is determined to be 0.14±0.14(stat)±0.10(syst). The measurements are compared to various theoretical predictions, including those from perturbative quantum chromodynamics.
Bakhshiansohi, H., Bondu, O., Brochet, S., Bruno, G., Caputo, C., Caudron, A., David, P., De Visscher, S., Delaere, C., Delcourt, M., François, B., Giammanco, A., Komm, M., Krintiras, G., Lemaitre, V., Magitteri, A., Mertens, A., Musich, M., Piotrzkowski, K., et al. (2018). Measurement of the $\Lambda_b$ polarization and angular parameters in $\Lambda_b\to J/\psi\, \Lambda$ decays from pp collisions at $\sqrt{s}=$ 7 and 8 TeV. Physical Review D, D97, 72010. https://doi.org/10.1103/PhysRevD.97.072010 (Original work published 2018)