U(1)_A symmetry in two-doublet models, U bosons or light scalars, and   psi and Upsilon decays
  psi and Upsilon decays may be used to search for light neutral spin-1 or spin-0 bosons associated with a broken extra-U(1) symmetry, local or global, acting axially on quarks and leptons, as may be present in supersymmetric theories with a lambda H_1 H_2 S superpotential term. Recent data on Upsilon --> gamma + invisible neutral constrain an axial, pseudoscalar or scalar coupling to b to f_bA < 4 10^-7 m_U(MeV)/ sqrt B_inv, f_bP < 4 10^-3/ sqrt B_inv or f_bS < 6 10^-3/ sqrt B_inv, respectively. This also constrains, from universality properties, couplings to electrons to f_eA < 4 10^-7 m_U(MeV)/ sqrt B_inv, f_eP < 4 10^-7/ sqrt B_inv or f_eS < 6 10^-7/ sqrt B_inv. The pseudoscalar a (possibly traded for a light gauge boson, or scalar particle) should then be, for invisible decays of the new boson, for > 96 % singlet and < 4 % doublet, for tan beta > 1. Or, more generally, < 4 % /(tan^2 beta B_inv) doublet, which implies a very small rate for the corresponding psi decay, B (psi --> gamma + neutral) B_inv <~ 10^-6/ tan^4 beta. Similar results are obtained for new spin-1 or spin-0 neutral bosons decaying into mu+ mu-. 
Pierre Fayet