Uploaded August 2025 | Updated September 2026, 2 weeks ago
Speaker: Poulami Mondal (Indian Institute of Technology Kanpur)
Abstract: Despite the discovery of the Higgs boson with a mass around 125 GeV at the Large Hadron Collider (LHC), the underlying mechanism of electroweak symmetry breaking (EWSB) in the Standard Model (SM) remains elusive. Beyond the SM (BSM) particles with a higher representation of the SU (2)L gauge group leave an imprint on the EWSB mechanism that can be detected via SM-like Higgs couplings to the vector bosons and fermions. Among these higher multiplets, the scalar SU (2)L triplet extensions of the SM have various interesting phenomenological aspects at the LHC and future colliders. The Georgi-Machacek (GM) model is a triplet scalar extension of the SM that preserves custodial symmetry (CS) due to an explicit global SU(2)_ L X SU(2)_R symmetry in the scalar potential at tree-level. In contrast, we construct a triplet extended scalar sector without imposing a global SU(2)_L X SU(2)_R symmetry in the potential while still maintaining custodial symmetry at tree-level. This is referred to as the extended GM (eGM) model. We aim to identify the regions of parameter space in the GM and eGM models that are consistent with current LHC data. As a first step, we focus on theoretical constraints by computing next-to-leading-order (NLO) unitarity and bounded-from-below (BFB) conditions on the scalar potential’s quartic couplings. To robustly determine the regions compatible with experimental observations, and fully exploring the multidimensional parameter space, we perform global fits for both models. These fits combine the Higgs signal strengths and direct search limits from ATLAS and CMS at √s = 8 and 13 TeV, B-physics observables, and theoretical constraints arising from NLO unitarity and BFB conditions on the scalar potential. I will present the allowed ranges for the additional Higgs boson masses, their mass differences, and the constraints on the triplet VEVs for both models. Next we investigate whether the GM and eGM models can accommodate the recent excesses around 95 GeV reported by the CMS and ATLAS collaborations. In an era where several scalar excesses are observed at the LHC, we address a key question: how heavy an additional scalar resonance can be, within the GM or eGM model, while still accommodating the observed 95 GeV excess.
Speaker: Poulami Mondal (Indian Institute of Technology Kanpur)
Abstract: Despite the discovery of the Higgs boson with a mass around 125 GeV at the Large Hadron Collider (LHC), the underlying mechanism of electroweak symmetry breaking (EWSB) in the Standard Model (SM) remains elusive. Beyond the SM (BSM) particles with a higher representation of the SU (2)L gauge group leave an imprint on the EWSB mechanism that can be detected via SM-like Higgs couplings to the vector bosons and fermions. Among these higher multiplets, the scalar SU (2)L triplet extensions of the SM have various interesting phenomenological aspects at the LHC and future colliders. The Georgi-Machacek (GM) model is a triplet scalar extension of the SM that preserves custodial symmetry (CS) due to an explicit global SU(2)_ L X SU(2)_R symmetry in the scalar potential at tree-level. In contrast, we construct a triplet extended scalar sector without imposing a global SU(2)_L X SU(2)_R symmetry in the potential while still maintaining custodial symmetry at tree-level. This is referred to as the extended GM (eGM) model. We aim to identify the regions of parameter space in the GM and eGM models that are consistent with current LHC data. As a first step, we focus on theoretical constraints by computing next-to-leading-order (NLO) unitarity and bounded-from-below (BFB) conditions on the scalar potential’s quartic couplings. To robustly determine the regions compatible with experimental observations, and fully exploring the multidimensional parameter space, we perform global fits for both models. These fits combine the Higgs signal strengths and direct search limits from ATLAS and CMS at √s = 8 and 13 TeV, B-physics observables, and theoretical constraints arising from NLO unitarity and BFB conditions on the scalar potential. I will present the allowed ranges for the additional Higgs boson masses, their mass differences, and the constraints on the triplet VEVs for both models. Next we investigate whether the GM and eGM models can accommodate the recent excesses around 95 GeV reported by the CMS and ATLAS collaborations. In an era where several scalar excesses are observed at the LHC, we address a key question: how heavy an additional scalar resonance can be, within the GM or eGM model, while still accommodating the observed 95 GeV excess.
