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Constraining the heavy leptophilic neutral gauge bosons through the $Z\to\ell^+\ell^-$, $W^\pm\to\ell^\pmν_\ell$, and $h\to\ell^+\ell^-$ decays

Bibhabasu De, Amitabha Dey

Abstract

We consider the hypothetical possibility of neutral gauge bosons~($Z^\prime$) with flavor-specific leptophilic couplings. For such {\it New Physics}~(NP) interactions, the current experimental constraints are much relaxed in the heavy mass regime, particularly for masses $\geq \mathcal{O}(1)$ TeV. However, in the presence of a leptophilic $Z^\prime$, leptonic decay modes of the electroweak gauge bosons and Higgs can be corrected at the loop level. Using the existing upper bounds on the corresponding decay widths, we find that one can impose stronger exclusion limits on the interactions of a heavy $Z^\prime$. Future updates on the aforesaid decay channels can be used in complementarity with the proposed lepton colliders to probe even weaker leptophilic NP interactions at the TeV scale and beyond.

Constraining the heavy leptophilic neutral gauge bosons through the $Z\to\ell^+\ell^-$, $W^\pm\to\ell^\pmν_\ell$, and $h\to\ell^+\ell^-$ decays

Abstract

We consider the hypothetical possibility of neutral gauge bosons~() with flavor-specific leptophilic couplings. For such {\it New Physics}~(NP) interactions, the current experimental constraints are much relaxed in the heavy mass regime, particularly for masses TeV. However, in the presence of a leptophilic , leptonic decay modes of the electroweak gauge bosons and Higgs can be corrected at the loop level. Using the existing upper bounds on the corresponding decay widths, we find that one can impose stronger exclusion limits on the interactions of a heavy . Future updates on the aforesaid decay channels can be used in complementarity with the proposed lepton colliders to probe even weaker leptophilic NP interactions at the TeV scale and beyond.

Paper Structure

This paper contains 10 sections, 29 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. The Model : $\mathbb{G}_{\rm SM}\otimes U(1)_{L_i-L_j}$
  3. Present and Future Bounds
  4. Corrections to the SM Observables
  5. $\mathbf{W^\pm\to\ell^\pm\nu_\ell}$
  6. $\mathbf{Z\to\ell^+\ell^-}$
  7. $\mathbf{h\to\ell^+\ell^-}$
  8. New Exclusion Limits
  9. Conclusion
  10. $\mathcal{F}$-Functions

Figures (6)

  • Figure 1: Current experimental bounds (gray-shaded regions) and projected sensitivities (colored lines) in the heavy $Z^\prime_{ij}$ regime. The projected sensitivities corresponding to the HL-LHC and lepton colliders have been recast from Ref. Dasgupta:2023zrh.
  • Figure 2: One-loop correction to (a) $W\bar{\ell}\nu_\ell$ vertex and (b), (c) the corresponding leg correction diagrams in the presence of $Z^\prime$.
  • Figure 3: One-loop correction to (a) $Z\bar{\ell}\ell$ vertex and (b), (c) the corresponding leg correction diagrams in the presence of $Z^\prime$.
  • Figure 4: One-loop diagrams resulting in corrections to the (a) $h\bar{\ell}\ell$ vertex, and (b) lepton mass in the presence of $Z^\prime$.
  • Figure 5: Exclusion limits on (a) $Z^\prime_{e\mu}$, (b) $Z^\prime_{e\tau}$, and (c) $Z^\prime_{\mu\tau}$ gauge bosons obtained through the collective constraints on $\Delta\Gamma_{W\ell\nu_\ell}$, $\Delta\Gamma_{Z\ell\ell}$, and $\Delta\Gamma_{h\ell\ell}$ with $\ell=e$ (red), $\mu$ (yellow), and $\tau$ (blue). The solid gray bands show the current experimental bounds (LEP-2 and neutrino trident experiments) on the considered parameter spaces.
  • ...and 1 more figures