Coherent Higgs-boson production in relativistic heavy-ion collisions

Coherent heavy-ion collisions at ultrarelativistic energies can be used as a powerful source for the two-photon production of new particles within or beyond the standard model. Although the coherency condition limits the mass range, for beam energies of few TeV/nucleon, particles with masses up to few hundred GeV will be produced with large cross sections similar to Z4 and low hadronic background. This can be achieved by accelerating, e.g., heavy ions at the CERN Large Hadron Collider and the Superconducting Super Collider (SSC) up to energies of 3.5--8 TeV/nucleon. Then the cross section for the production of a 200-GeV heavy Higgs boson in an 8-TeV/nucleon UU collision is 300 pb, and is larger than that expected from pp collisions at the SSC. Another example is the production of a H+H/sup -/ pair of charged Higgs bosons, predicted by the different extensions of the standard model. In a 1--10-TeV/nucleon gold-on-gold collision the cross section for M/sub H/sup +//=20 GeV is 0.3 nb--0.3 mb, compared to the cross section expected at the CERN e+e/sup -/ collider LEP of 1 pb--0.3 nb