Angular decay coefficients of $J/psi$ mesons at forward rapidity from $p+p$ collisions at $sqrt{s}=510$ GeV

We report the first measurement of the full angular distribution for inclusive $J/psirightarrowmu^{+}mu^{-}$ decays in $p$$+$$p$ collisions at $sqrt{s}=510$ GeV. The measurements are made for $J/psi$ transverse momentum $2<p_{T}<10$ GeV/$c$ and rapidity $1.2<y<2.2$ in the Helicity, Collins-Soper, and Gottfried-Jackson reference frames. In all frames the polar coefficient $lambda_{theta}$ is strongly negative at low $p_{T}$ and becomes close to zero at high $p_{T}$, while the azimuthal coefficient $lambda_{phi}$ is close to zero at low $p_{T}$, and becomes slightly negative at higher $p_{T}$. The frame-independent coefficient $tilde{lambda}$ is strongly negative at all $p_{T}$ in all frames. The data are compared to the theoretical predictions provided by nonrelativistic quantum chromodynamics models.