Jim Virdee (Imperial)

LEP3: A High-Luminosity e+e− Higgs & Electroweak Factory in the LHC Tunnel

Abstract:

We support FCC-ee and FCC-hh as the preferred option for CERN’s future, as it addresses two key recommendations of European Strategy for Particle Physics (ESPP) 2019. The guidance for the ESPP 2025 requests, in addition to the preferred option, the inclusion of “prioritised alternatives to be pursued if the chosen preferred option turns out not to be feasible or competitive”. In response to this request we propose reusing the existing LHC tunnel for an electron-positron collider, called LEP3, as a back-up alternative if the FCC cannot proceed.

It is desirable that any back-up to FCC should present fewer technical and/or financial difficulties than those associated with the preferred option, as well as have good physics potential. To minimise the possibility of such difficulties, the LEP3 strategy is to re-use, as much as possible, the existing infrastructure of CERN, utilise maximally the R&D already carried out for FCC-ee, minimising the cost and keeping the required financing within the envelope of the pluriannual budget of CERN. LEP3 offers the possibility of carrying out high-precision studies of Z, W, and Higgs bosons below the t-t threshold. It offers potential physics performance comparable or superior to other fallback options at a lower cost while supporting continued R&D towards a next-generation energy frontier machine that should have the objective of increasing by an order of magnitude the constituent centre-of-mass energy with respect to that provided by the LHC.

LEP3 is not intended to compete with the FCC-ee.