The carbon footprint of proposed $${\mathrm{e}}^+{\mathrm{e}}^-$$ Higgs factories

Abstract

The energy consumption of any of the $${\mathrm{e}}^+{\mathrm{e}}^-$$ e + e - Higgs factory projects that can credibly operate immediately after the end of LHC, namely three linear colliders (CLIC, operating at $$\sqrt{s}\,=\,380$$ s = 380 GeV; and ILC and $${\mathrm{C}}^3$$ C 3 , operating at $$\sqrt{s}\,=\,250$$ s = 250 GeV) and two circular colliders (CEPC and FCC-ee, operating at $$\sqrt{s}\,=\,240$$ s = 240 GeV), will be everything but negligible. Future Higgs boson studies may therefore have a significant environmental impact. This note proposes to include the carbon footprint for a given physics performance as a top-level gauge for the design optimisation and, eventually, the choice of the future facility. The projected footprints per Higgs boson produced, evaluated using the 2021 carbon emission of available electricity, are found to vary by a factor 100 depending on the considered Higgs factory project.

Future e+e- and hadron colliders

“…Concerning the aspects of the green colliders, the detailed comparisons of carbon footprint of future Higgs boson studies through Higgs factories have been given in Ref. [4]. As for the staging possibilities of circular electron positron colliders, proton proton colliders are the ideal options for these machines, such as CEPC and FCC 𝑒𝑒 , to use the same tunnels to build the hadron colliders to reach the center of mass energy up to 100TeV with SppC and FCC ℎℎ .…”