Measurement of the $\mathrm{{\rm Y}}$ polarizations in $pp$ collisions at $\sqrt{s}$=7 and 8TeV

The polarization of the $\mathrm{{\rm Y}}(1S)$, $\mathrm{{\rm Y}}(2S)$ and $\mathrm{{\rm Y}}(3S)$mesons, produced in $pp$ collisions at centre-of-mass energies $\sqrt{s}$=7 and 8TeV, is measured using data samples collected by the LHCb experiment, corresponding to integrated luminosities of 1 and 2fb${}^{-1}$, respectively. The measurements are performed in three polarization frames, using $\mathrm{{\rm Y}}\to {\mu }^{+}{\mu }^{-}$ decays in the kinematic region of the transverse momentum $p_T(\mathrm{{\rm Y}})<30GeV\mathrm{/}c$, and rapidity $2.2<y(\mathrm{{\rm Y}})<4.5$. No large polarization is observed.