• Accepted Paper

Generalized chiral U(1)B−L: Toward a less constrained Z′ and dark matter

Ranjeet Kumar and Hemant Kumar Prajapati

Phys. Rev. D - Accepted 3 November, 2026

DOI: https://doi.org/10.1103/d59r-yk66

Abstract

Extensions of the Standard Model by a U(1)X gauge symmetry predict a new Z′ boson, whose mass is severely constrained by high-mass dilepton resonance searches at the LHC. We show that these bounds can be relaxed by generalizing the chiral (B−L) charge assignment while preserving gauge anomaly cancellation. The resulting U(1)X charges are parameterized by two independent parameters, and an appropriate choice of these parameters suppresses the Z′ branching fraction into charged leptons, substantially weakening the dilepton constraints. The framework accommodates Dirac neutrino masses through a Dirac type-I seesaw mechanism and a stable singlet scalar DM candidate without requiring an additional discrete symmetry. We find that the modified charge assignment, although beneficial for collider phenomenology, introduces a tension between obtaining the observed relic abundance and satisfying direct detection limits when DM annihilation proceeds solely through the Z′ portal. The inclusion of scalar-mediated annihilation channels resolves this tension and opens up a broad viable parameter space, with DM masses ranging from $M_{\rm DM}\simeq 60~{\rm GeV}$ to $10~{\rm TeV}$. The resulting parameter space is consistent with the observed relic density, direct detection, collider, and electroweak precision constraints, demonstrating that a generalized chiral charge structure can simultaneously accommodate a less constrained Z′ sector, neutrino masses, and viable dark matter phenomenology.

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