Measurement of J/ψ polarization in pp collisions at $\sqrt{s}=7\ \mathrm{TeV}$

An angular analysis of the decay <i>J</i>/<i>ψ</i>→<i>μ</i>⁺<i>μ</i>^- is performed to measure the polarization of prompt <i>J</i>/<i>ψ</i> mesons produced in <i>pp</i> collisions at [Formula: see text]. The dataset corresponds to an integrated luminosity of 0.37 fb^-1 collected with the LHCb detector. The measurement is presented as a function of transverse momentum, <i>p</i>_T, and rapidity, <i>y</i>, of the <i>J</i>/<i>ψ</i> meson, in the kinematic region 2<<i>p</i>_T<15 GeV/<i>c</i> and 2.0<<i>y</i><4.5.