Search for Muon-Hadron Interactions from Muonic X-rays

Abstract

I would like to report on a number of muonic X-ray experiments which were designed to investigate the muonnucleus interaction. In earlier days similar experiments were used as a test of the vacuum polarization effect of QED. With the advent of the unified electroweak interaction we expect muon-nucleon forces in addition to those of QED. One, of course, is the “heavy-light” interaction mediated by the vector boson Z^o. Due to the large mass of the Z^o the range of this force is, however, too short to result in a measurable energy shift in muonic atoms. An additional force would be mediated by the Higgs boson which also has definite coupling g to the leptons and to the quarks. In the minimal version of the theory (one Higgs doublet) we have

$$g^2 = m_f^2 \sqrt 2 G_F$$

(1)

where m_f is the fermion mass and G_F the Fermi coupling constant. The mass of the Higgs boson has a lower bound (under rather general assumptions) of about 10 GeV. This force is also extremely weak. One can enlarge the Higgs sector of the theory. In fact, most GUT’s and all supersymmetric models need at least two Higgs doublets. In such schemes there can be Higgs bosons much lighter than 10 GeV and their couplings to the fermions can be enhanced¹.