Coherent Higgs-boson production in relativistic heavy-ion collisions

Ccoherent 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 $\sim Z^4$ 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 $\mathrm{pp}$ collisions at the SSC. Another example is the production of a $H^{+}{H}^{-}$ 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 $M_{H^{+}}=20\mathrm{}$ GeV is 0.3 nb-0.3 mb, compared to the cross section expected at the CERN $e^{+}{e}^{-}$ collider LEP of 1 pb-0.3 nb.