Measurement of the Lambda(b) polarization and angular parameters in Lambda(b) -> J/psi Lambda decays from pp collisions at root s=7 and 8 TeV

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American Physical Society

An analysis of the bottom baryon decay ({\Lambda }{b}\to J/\psi \left(\to {\mu }^{+}{\mu }^{-}\right)\Lambda \left(\to p{\pi }^{-}\right)) is performed to measure the ({\Lambda }{b}) polarization and three angular parameters in data from (pp) collisions at (\sqrt{s}=7) and 8 TeV, collected by the CMS experiment at the Large Hadron Collider. The ({\Lambda }_{b}) polarization is measured to be (0.00±0.06\left(\mathrm{stat}\right)±0.06\left(\mathrm{syst}\right)) and the parity-violating asymmetry parameter is determined to be (0.14±0.14\left(\mathrm{stat}\right)±0.10\left(\mathrm{syst}\right)). The measurements are compared to various theoretical predictions, including those from perturbative quantum chromodynamics.

WEAK DECAYS, Astronomy & Astrophysics, Physics, Particles & Fields, Physics
Sirunyan, A. M., Tumasyan, A., Adam, W., Ambrogi, F., Asilar, E., Bergauer, T., Brandstetter, J., Brondolin, E., Dragicevic, M., Erö, J., Escalante Del Valle, A., Flechl, M., Friedl, M., Frühwirth, R., Ghete, V. M., Grossmann, J., Hrubec, J., Jeitler, M., … König, A. (2018). Measurement of the Λb polarization and angular parameters in Λb→J/ψΛ decays from pp collisions at s=7 and 8 TeV. In Physical Review D (Vol. 97, Issue 7). American Physical Society (APS).