Kinematic distributions and nuclear effects of $J/\psi$ production in 920 GeV fixed-target proton-nucleus collisions

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Measurements of the kinematic distributions of $J/\psi$ mesons produced in $p-$C, $p-$Ti and $p-$W collisions at $\sqrt{s}=41.6 \mathrm{GeV}$ in the Feynman-$x$ region $-0.34 < x_{F} < 0.14$ and for transverse momentum up to $p_T = 5.4 \mathrm{GeV}/c$ are presented.

• The $x_F$ and $p_T$ dependencies of the nuclear suppression parameter, $\alpha$, are also given.
• The results are based on $2.4 \cdot 10^{5}$ $J/\psi$ mesons in both the $e^+ e^-$ and $\mu^{+}\mu^{-}$ decay channels.
• The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory.