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 $J/\psi\rightarrow\mu^{+}\mu^{-}$ 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. 
A. Adare, C. Aidala, N.N. Ajitanand, Y. Akiba, R. Akimoto, M. Alfred,   V. Andrieux, K. Aoki, N. Apadula, Y. Aramaki, H. Asa...
hep-ex nucl-ex