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Probing $ΔL=2$ lepton number violating SMEFT operators at the same-sign muon collider

Subhaditya Bhattacharya, Soumyajit Datta, Abhik Sarkar

Abstract

We investigate lepton number violation (LNV) induced by $ΔL = 2$ dimension-seven Standard Model Effective Field Theory (SMEFT) operators in the context of same-sign muon colliders. Specifically, we study $μ^+ μ^+ \rightarrow W^+W^+/\;W^+qq'$ production at the $μ$TRISTAN at $\sqrt{s} =$ 2 TeV with an integrated luminosity of 1 ab$^{-1}$, using the final-state signature comprising two fat jets. This process is sensitive to eight distinct SMEFT operators, providing a unique avenue for testing LNV beyond the Standard Model. We determine the maximal sensitivity to these operators and compare our results with existing LHC constraints and future projections from the FCC. Our findings highlight the potential of same-sign muon colliders to serve as powerful probes of LNV and New Physics (NP) at the TeV scale.

Probing $ΔL=2$ lepton number violating SMEFT operators at the same-sign muon collider

Abstract

We investigate lepton number violation (LNV) induced by dimension-seven Standard Model Effective Field Theory (SMEFT) operators in the context of same-sign muon colliders. Specifically, we study production at the TRISTAN at 2 TeV with an integrated luminosity of 1 ab, using the final-state signature comprising two fat jets. This process is sensitive to eight distinct SMEFT operators, providing a unique avenue for testing LNV beyond the Standard Model. We determine the maximal sensitivity to these operators and compare our results with existing LHC constraints and future projections from the FCC. Our findings highlight the potential of same-sign muon colliders to serve as powerful probes of LNV and New Physics (NP) at the TeV scale.

Paper Structure

This paper contains 14 sections, 14 equations, 9 figures, 5 tables.

Table of Contents

  1. Introduction
  2. LNV operators in SMEFT
  3. Constraints on LNV operators
  4. $W^{+}W^{+}/\;W^{+}qq'$ production at $\mu$TRISTAN
  5. Collider analysis
  6. Projected sensitivities of operators
  7. One operator analysis
  8. Two operator analysis
  9. Comparison with FCC projections
  10. New Physics Implications
  11. Summary and Conclusion
  12. The Weinberg operator
  13. Validity of the effective field theory
  14. Additional sensitivity plots

Figures (9)

  • Figure 1: Feynman graphs corresponding to $W^{+}W^{+}/\, W^{+}qq'$ signal process at the $\mu$TRISTAN. Black square dot refers to the effective vertices arising from the dimension seven SMEFT operators.
  • Figure 2: Production cross section of $\mu^+ \mu^+ \rightarrow W^{+}W^{+}/\;W^{+}qq'$ process as a function of the WCs, $C_i/\Lambda^{3}$ (left), and EFT scale ($\Lambda$) with $C_i$ set to 1 (right), at the $\mu$TRISTAN $\sqrt{s} = 2$ TeV.
  • Figure 3: Kinematic distributions corresponding to EFT signals (colored) and the dominant SM background, $W^{+}W^{+}\overline{\nu}\,\overline{\nu}$ (black) at the $\mu$TRISTAN 2 TeV.
  • Figure 4: Left:$\chi^{2}$ sensitivity curves for the LNV operator coefficients corresponding to $W^+W^+/\;W^+qq'$ production at the $\mu$TRISTAN with $\sqrt{s} = 2$ TeV with $\mathfrak{L}_{\rm int} = 1$ ab$^{-1}$. The black dashed (dotted) horizontal line indicates the 95% (68%) C.L. exclusion limit. Right: 95% C.L. limits on operators as a function of integrated luminosity, $\mathfrak{L}_{\rm int}$.
  • Figure 5: Correlated 95% C.L. $\chi^{2}$ sensitivity contours for the LNV operator $\mathcal{O}_{LHD1}$ in combination with other operators, derived from $W^+W^+$ and $W^+qq'$ production at the $\mu$TRISTAN with $\sqrt{s} = 2$ TeV and an integrated luminosity of $\mathfrak{L}_{\rm int} = 1$ ab$^{-1}$.
  • ...and 4 more figures