Dev, P. S. BhupalP. S. BhupalDevGoswami, SrubabatiSrubabatiGoswamiPachhar, DebashisDebashisPachharShukla, Saurabh K.Saurabh K.Shukla2026-01-292026-01-292026-01-011126-670810.1007/JHEP01(2026)0612-s2.0-105027520334https://repository.iitgn.ac.in/handle/IITG2025/34192We discuss the role of heavy scalar fields in mediating neutrinoless double beta decay (0νββ) within the SU(5) Grand Unified Theory framework, extended suitably to include neutrino mass. In such a minimal realistic SU(5) setup for fermion masses, the scalar contributions to 0νββ are extremely suppressed as a consequence of the proton decay bound. We circumvent this problem by imposing a discrete Z3 symmetry. However, the scalar contributions to 0νββ remain suppressed in this SU(5) × Z3 model due to the neutrino mass constraint. We find that the 0νββ contribution can be enhanced by extending the scalar sector with an additional 15-dimensional scalar representation with suitable Z3 charge. Such an extension not only yields realistic fermion mass spectra but also leads to experimentally testable predictions in upcoming ton-scale 0νββ searches, which can be used as a sensitive probe of the new scalars across a broad range, from LHC-accessible scales up to ∼ 1010 GeV.en-USBaryon/Lepton Number ViolationGrand UnificationSpecific BSM PhenomenologyArticlehttps://link.springer.com/content/pdf/10.1007/JHEP01(2026)061.pdf1029-8479WOS:001661444600001