Reappraisal of constraints on Z′ models from unitarity and direct searches at the LHC

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In a truly model-independent approach, we reexamine a minimal extension of the Standard Model (SM) through the introduction of an additional U(1) symmetry leading to a new neutral gauge boson (Z′), allowing its kinetic mixing with the hypercharge gauge boson. An SM neutral scalar is used to spontaneously break this extra symmetry, leading to the mass of the Z′. Except for three right-handed neutrinos, no other fermions are added. We use the current LHC Drell-Yan data to put model-independent constraints in the parameter space of three quantities, namely, MZ′, the Z-Z′ mixing angle (αz), and the extra U(1) effective gauge coupling (gx′), which absorb all model dependence. We impose additional constraints from unitarity and low-energy neutrino-electron scattering. However, limits extracted from direct searches turn out to be most stringent. We obtain MZ′>4.4 TeV and |αz|<0.001 at 95% C.L., when the strength of the additional U(1) gauge coupling is the same as that of the SM SU(2)L.


  • Triparno Bandyopadhyay
  • Gautam Bhattacharyya
  • Dipankar Das
  • Amitava Raychaudhuri
Externa organisationer
  • University of Calcutta
  • Saha Institute of Nuclear Physics

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Annan fysik
TidskriftPhysical Review D
StatusPublished - 2018 aug 1
Peer review utfördJa
Externt publiceradJa