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Renormalization-group-improved constraints on dimension-7 baryon-number-violating operators

Yi Liao, Xiao-Dong Ma, Xiang Zhao

Abstract

We study constraints on dimension-7 SMEFT baryon-number-violating operators from nucleon decays by incorporating full renormalization group (RG) running effects. At high new physics scales, we demonstrate that RG running effects help set stringent bounds on all 297 Wilson coefficients compared to the tree-level analysis in which only coefficients involving the first and second fermion generations could be constrained. Our findings highlight that the RG running effects through Yukawa mixings are particularly important for indirectly probing operators involving the second and third generation fermions.

Renormalization-group-improved constraints on dimension-7 baryon-number-violating operators

Abstract

We study constraints on dimension-7 SMEFT baryon-number-violating operators from nucleon decays by incorporating full renormalization group (RG) running effects. At high new physics scales, we demonstrate that RG running effects help set stringent bounds on all 297 Wilson coefficients compared to the tree-level analysis in which only coefficients involving the first and second fermion generations could be constrained. Our findings highlight that the RG running effects through Yukawa mixings are particularly important for indirectly probing operators involving the second and third generation fermions.

Paper Structure

This paper contains 14 sections, 27 equations, 2 figures, 5 tables.

Table of Contents

  1. Introduction
  2. Formalism for $\Delta(B+L)=0$ nucleon decays in SMEFT
  3. SMEFT dim-7 BNV operators
  4. LEFT operators
  5. Matching onto the LEFT
  6. Chiral matching
  7. RG-improved analysis of nucleon decays
  8. Solving the RG equations
  9. Constraints at a higher new physics scale
  10. Summary
  11. Matching the derivative operator $\mathcal{O}^{prst}_{\bar{L}QdDd}$ onto the LEFT
  12. Chiral Lagrangian
  13. Constraints on the dimensionless Wilson coefficients
  14. An illustrative example

Figures (2)

  • Figure 1: Diagrams for the contact (left) and non-contact (right) contributions to two-body nucleon decays into a meson and a lepton. The cyan blob (black square) represents the insertion of a BNV (usual) chiral vertex.
  • Figure 2: Limits on the effective scales $\Lambda_{\tt eff} =|C_7^i({\Lambda_{\tt NP})}|^{-1/3}$ of dim-7 SMEFT BNV operators in both the up-quark and down-quark flavor bases, derived from experimental bounds on two-body nucleon decays summarized in \ref{['tab:exp_bound']}. The light (dark) regions show the constraints with (without) SMEFT RG running effects. For $\mathcal{O}_{\bar{e}ddDd}^{p333}$, the black dashed and red solid arcs represent the results in the up- and down-quark flavor bases, respectively. Here, $p=1,~2,~3$ refers to the lepton generation.