Higgs boson production in partonic and electromagnetic interactions with heavy ions

Abstract

Higgs boson production in partonic and electromagnetic (photon-photon) interactions of light- and heavy-ions (A-A) at the LHC and future colliders is summarized. Parton-induced cross sections --including gluon-gluon, vector-boson fusion, and associated W, Z, t processes-- are computed at NNLO with MCFM 8.0 using nuclear parton distribution functions. Photon-photon cross sections are computed with MadGraph 5.0 for ultraperipheral A-A interactions with both ions surviving the collision. In the center-of-mass energy range $\sqrt{s} \approx 5$--100 TeV, the ratio of electromagnetic-to-partonic Higgs cross sections is $\rm R_{e.m./parton} \approx 10^{-5}$--10$^{-4}$. At FCC energies, this ratio is 10--100 times larger in A-A than in p-p thanks to the strong nuclear coherent $\gamma$ fluxes. The feasibility of Higgs boson measurements at LHC, HE-LHC, and FCC, in the most-favourable $H\to\gamma\gamma,b\bar{b}$ decay channels in partonic and e.m. interactions respectively, is determined taking into account standard acceptance and efficiency losses on the final states, plus selection criteria to minimize the respective continuum backgrounds. Whereas $3\sigma$ evidence for partonic and e.m. Higgs production requires about $\times$35 and $\times$200 ($\times$7 and $\times$30) larger integrated luminosities than those expected for a nominal 1-month run at the LHC (HE-LHC), a $5\sigma$ observation of both production modes is warranted in just one month at the FCC.