2025/11/14 by Paolo Crivelli, Crivelli, Paolo, Josu Hernandez-Garcia +7
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #hep-ph
paper · pdf · doi:10.48550/arxiv.2511.11801
published as JHEP 07 (2026) 31 · v1: 11 pages, 6 figures, 1 table. v2 - JHEP: minor changes implemented. 12 pages, 6 figures, 1 table
arxiv created 2026/07/30 · arxiv updated 2026/07/31
We analyze how NA64μ can contribute to the global SMEFT program demonstrating that it can probe two effective four lepton operators completely unbounded so far and break one of the current flat directions. Furthermore, we also study an extension of SMEFT that includes fermion singlets of the SM gauge group in the low energy field content. This effective field theory, usually dubbed νSMEFT, is well motivated by the observation of light neutrino masses and leptonic mixing. We find that NA64μ can constrain three unbounded four fermion operators of the νSMEFT. We derive the current leading bounds on these operators and compute the future sensitivity. Our results fill the gap between the current experimental program and a possible future muon collider able to probe this type of New Physics.