The REDTOP Experiment

The REDTOP (Rare Eta/Eta’ Decays To Observe new Physics) collaboration is proposing the construction of a super η/η′ factory with the goal of exploring Physics Beyond the Standard Model, and, in particular, the Dark Sector, in the MeV-GeV energy regime. The Standard model quantum numbers of the η/η′ systems make such mesons almost unique in the particle universe, and are shared (except for parity) only by the Higgs and the vacuum. At present REDTOP is the only proposed meson factory exploring rare flavor-conserving decays and New Physics in the MeV-GeV mass range.

The experiment proposes to produce order of 1014 η mesons and ~1012 η′ mesons in a three-year running period. A proton beam of 1.8 (~4) GeV impinging on low-Z thin targets is necessary to reach that goal. At such energies, the η/η′ will be produced almost at rest in the laboratory. Therefore, an hermetic, collider style, detector with high sensitivity and granularity is required to detect the rare decays portending to BSM physics. In order to cope with the high interaction rate and a large background from hadronic scattering of the proton beam, novel detector technologies are being proposed. The main components of the apparatus are: 1) a super-light, Si-pixel vertex detector; 2) an ac-LGAD Central Tracker; 3) a Time of Flight detector with resolution better than 50 ps; 4) a dual-readout, ADRIANO2 EM calorimeter; 5) a dual-readout hadronic calorimeter.

The REDTOP collaboration has recently presented to the HEP Community the physics case for a super h/h’-factory. The collaboration is now forming with the intent of submitting a formal proposal to a hosting laboratory, before the end of 2024 (Fermilab, GSI, and HIAF are the best candidates at the moment). I would like to invite new groups, especially from European institutions, to join the Collaboration. All five detector components would benefit from a larger effort. One in particular, the vertex detector has no groups at all contributing to the R&D and to the design, as the final technology, Si-pixel, was only recently chose.

More information on REDTOP can be found in the White Paper for Snowmass2021: https://arxiv.org/abs/2203.07651 or on the experiment website: https://redtop.fnal.gov.