Quarkonia decays into two photons induced by the space-time   non-commutativity
  In this article we propose standard model strictly forbidden decay modes, quarkonia (QQ(1^{--}) = J/psi, Upsilon) decays into two photons, as a possible signature of the space-time non-commutativity. An experimental discovery of J/psi -> gamma gamma and/or Upsilon -> gamma gamma processes would certainly indicate a violation of the Landau-Pomeranchuk-Yang theorem and a definitive appearance of new physics. 
B. Melic, K. Passek-Kumericki, J. Trampetic