Measurement of the $\Upsilon$ polarization in $pp$ collisions at $\sqrt{s}$=7 and 8TeV

The LHCb collaboration
Aaij, Roel , Adeva, Bernardo , Adinolfi, Marco , Ajaltouni, Ziad , Akar, Simon , Albrecht, Johannes , Alessio, Federico , Alexander, Michael , Alfonso Albero, Alejandro , Ali, Suvayu
JHEP 12 (2017) 110, 2017.

Abstract
The polarization of the $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(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 $\Upsilon\to\mu^+\mu^-$ decays in the kinematic region of the transverse momentum $p_{T}(\Upsilon)<30GeV/c$, and rapidity $2.2<y(\Upsilon)<4.5$. No large polarization is observed.

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