The muon g-2 and the bounds on the Higgs boson mass

After a brief review of the muon g - 2 status, we analyze the possibility that the present discrepancy between experiment and the standard model (SM) prediction may be due to hypothetical errors in the determination of the hadronic leading-order contribution to the latter. In particular, we show how an increase of the hadroproduction cross section in low-energy e(+)e(-) collisions could bridge the muon g - 2 discrepancy, leading however to a decrease on the electroweak upper bound on M-H, the SM Higgs boson mass. That bound is currently M-H less than or similar to 150 GeV (95% C.L.) based on the preliminary top quark mass M-t = 172.6(1.4) GeV and the recent determination Delta alpha((5))(had)(M-Z) = 0.027 68(22), while the direct-search lower bound is M-H > 114.4 GeV (95% C.L.). By means of a detailed analysis we conclude that this solution of the muon g - 2 discrepancy is unlikely in view of current experimental error estimates. However, if this turns out to be the solution, the 95% C.L. upper bound on M-H is reduced to about 130 GeV which, in conjunction with the experimental lower bound, leaves a narrow window for the mass of this fundamental particle.