Null Tests and Lepton Universality in $\Xi_{cc}$ Baryon Decays

TL;DR

This paper develops a precise framework using symmetry and effective field theory to analyze $ ext{Xi}_{cc}$ baryon decays, enabling sensitive tests of short-distance physics and potential new physics beyond the Standard Model.

Contribution

It introduces null tests and lepton universality ratios in $ ext{Xi}_{cc}$ decays, providing novel probes of nonfactorizable QCD effects and short-distance charged-current interactions.

Findings

Constructed a null combination of decay widths sensitive to nonfactorizable QCD dynamics.

Identified the $R_{ ext{Xi}_c}^{ ext{mu e}}$ ratio as a clean probe of short-distance interactions.

Showed $ ext{Xi}_{cc}$ decays can constrain new physics scales beyond the reach of current experiments.

Abstract

We develop a precision framework for doubly charmed baryon decays based on symmetry-protected observables and effective-field-theory diagnostics. In nonleptonic $\Xi_{cc}$ decays, we construct a null combination of widths that vanishes in the heavy-diquark factorization limit, providing a direct probe of nonfactorizable QCD dynamics. For semileptonic decays, we identify the light-lepton universality ratio $R_{\Xi_c}^{\mu e}$ as an observable in which leading hadronic normalization cancels at the amplitude level, yielding direct sensitivity to short-distance charged-current interactions. Percent-level precision probes $|C_{V_L}^{\mu}|\sim \mathcal{O}(10^{-2})$, whereas $\mathcal{O}(10^{-1})$ deformations induce order-one deviations. Scalar contributions remain parametrically suppressed. Combining baryonic and mesonic inputs, we show that $\Xi_{cc}$ decays constrain the same short-distance interaction with complementary scaling, lifting degeneracies inherent to meson-only analyses. Mapping to a charged-vector benchmark demonstrates sensitivity to multi-TeVnew-physics scales. These results establish doubly charmed baryons as an independent probe of charged-current interactions beyond the Standard Model.