$\mathrm{{\rm Y}}(nS)$ polarizations in $pp$ collisions at $\sqrt{s}=$ 7 and 8 TeV by the LHCb collaboration

A polarization measurement carried out for the $\mathrm{{\rm Y}}(1S)$, $\mathrm{{\rm Y}}(2S)$ and $\mathrm{{\rm Y}}(3S)$ mesons produced in pp collisions at $\sqrt{s}=$ 7 and 8 TeV is presented. Data samples used for the polarization measurement were collected by the LHCb experiment during the 2011 and 2012 data taking runs with integrated luminosities of 1 and 2 fb${}^{-1}$, respectively. The measurement has been performed in three polarization frames, using an angular distribution analysis of the $\mathrm{{\rm Y}}\to {\mu }^{+}{\mu }^{-}$ decays in the kinematic region of the $\mathrm{{\rm Y}}$ transverse momentum $p_T^{\mathrm{{\rm Y}}}<30$ GeV/c and rapidity $2.2<y^{\mathrm{{\rm Y}}}<4.5$. No large polarization is observed.