Experimental bounds on the coupling strength of torsion potentials

We examine the experimental implications of a recent suggestion by Kaempffer that the coupling strength G^' for a propagating torsion potential need not be the same as the Newtonian gravitational coupling strength G. We allow the torsion potential to transform either as a six-tensor, or as a pseudoscalar. In neutrino-electron and neutrino-nucleon scattering, we find that pseudoscalar exchange does not contribute, while exchange of the six-tensor closely simulates exchange of a Z⁰. Agreement of data with Weinberg-Salam neutral current theory is preserved if 4πG^'<0.14GFc²², where GF is the Fermi μ decay constant. If we demand that emission of torsion quanta not destroy the energy balance in helium-burning stars, we get a much stronger bound 4πG^'<5×10^-19GFc²². This bound applies to both cases, pseudoscalar as well as six-tensor. It may be rewritten G^'<1(1.5×10¹² GeV)² in natural units. For comparison, G=1(1.2×10¹⁹ GeV)².