A search for the exclusive production of the $Z_c^{pm}(3900)$ hadron by virtual photons has been performed in the channel $Z_c^{pm}(3900)rightarrow J/psi pi^{pm}$. The data cover the range from 7 GeV to 19 GeV in the centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio $BR(Z_c^{pm}(3900)rightarrow J/psi pi^{pm} )times sigma_{ gamma~N rightarrow Z_c^{pm}(3900)~ N} /sigma_{gamma~N rightarrow J/psi~ N}$ of $3.7times10^{-3}$ has been established at the confidence level of 90%.
Download