Effective Field Theory Effects on Type-II Seesaw Collider Searches: Reinterpretation and HL-LHC Prospects (TH Seminar)

by Subham Saha (Institute of Physics, Bhubaneswar)

Tuesday 1 Dec 2026, 11:00 → 12:00 Europe/Paris

LPSC

The Type-II seesaw mechanism provides an elegant explanation for tiny Majorana neutrino masses by extending the Standard Model with an SU(2)_L scalar triplet. We present a reinterpretation of LHC multi-lepton search for the doubly charged scalar within an effective field theory (EFT) framework, investigating two effective operators that modify scalar pair production and decay, respectively. After validating the experimental selection criteria in the canonical model, we analyse relevant signal regions and perform a statistical reinterpretation using the HistFitter framework, employing same-sign dilepton invariant-mass distributions as the key observable. Our results demonstrate that these operators can significantly alter the inferred exclusion limits: the pair-production operator strengthens the mass reach to approximately 1600 GeV, compared with 1050 GeV in the canonical scenario, while the decay operator modifies the signal topology and can substantially weaken the sensitivity. We also explore representative ultraviolet (UV) completions that can generate these effective interactions and discuss the discovery prospects of the doubly charged scalar at the High-Luminosity LHC (HL-LHC), highlighting the implications for future collider searches.