Measurement of $\psi (2S)$ polarisation in $pp$ collisions at $\sqrt{s}=7$ TeV

LHCb collaboration, R. Aaij, B. Adeva +693

The polarisation of prompt $\psi (2S)$ mesons is measured by performing an angular analysis of $\psi (2S)\to {\mu }^{+}{\mu }^{-}$ decays using proton-proton collision data, corresponding t…