Generalized structure functions are derived for tau decays including tensor beyond-SM contributions, enabling maximal model-independent use of data for CP/T violation studies.
Semileptonic decays of light quarks beyond the Standard Model
5 Pith papers cite this work. Polarity classification is still indexing.
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abstract
We describe non-standard contributions to semileptonic processes in a model independent way in terms of an SU(2)_L X U(1)_Y invariant effective lagrangian at the weak scale, from which we derive the low-energy effective lagrangian governing muon and beta decays. We find that the deviation from Cabibbo universality, \Delta_CKM = |V_ud|^2 + |V_us|^2 + |V_ub|^2 - 1, receives contributions from four effective operators. The phenomenological bound of \Delta_CKM = -1E-4 +- 6E-4 provides strong constraints on all four operators, corresponding to an effective scale greater than 11 TeV (90% CL). Depending on the operator, this constraint is at the same level or better then the Z pole observables. Conversely, precision electroweak constraints alone would allow universality violations as large as \Delta_CKM = -0.01 (90% CL). An observed nonzero \Delta_CKM at this level could be explained in terms of a single four-fermion operator which is relatively poorly constrained by electroweak precision measurements.
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representative citing papers
Calculates O(α α_s) scheme-conversion coefficients for semileptonic weak operators in MOM/SMOM schemes using projectors that eliminate pure-QCD artifacts and yield reduced scale dependence.
Lattice QCD yields the scalar and tensor form factors for Λ→pℓν̄ℓ as functions of q², providing a model-independent input to constrain non-standard charged-current interactions via the predicted R^{μe} ratio compared to experiment.
Doubly charmed baryon decays provide symmetry-protected null tests for nonfactorizable QCD and lepton-universality ratios sensitive to new physics at multi-TeV scales.
Workshop summary discussing the sensitivity of precision beta-decay experiments to new physics.
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Generalized structure functions in semileptonic tau decays
Generalized structure functions are derived for tau decays including tensor beyond-SM contributions, enabling maximal model-independent use of data for CP/T violation studies.
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Semileptonic weak Hamiltonian to $\mathcal{O}(\alpha \alpha_s(\mu_{\mathrm{Lattice}}))$ in momentum-space subtraction schemes
Calculates O(α α_s) scheme-conversion coefficients for semileptonic weak operators in MOM/SMOM schemes using projectors that eliminate pure-QCD artifacts and yield reduced scale dependence.
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Scalar and Tensor Form Factors for $\Lambda \rightarrow p\ell \bar{\nu}_\ell$ from Lattice QCD
Lattice QCD yields the scalar and tensor form factors for Λ→pℓν̄ℓ as functions of q², providing a model-independent input to constrain non-standard charged-current interactions via the predicted R^{μe} ratio compared to experiment.
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Null Tests and Lepton Universality in $\Xi_{cc}$ Baryon Decays
Doubly charmed baryon decays provide symmetry-protected null tests for nonfactorizable QCD and lepton-universality ratios sensitive to new physics at multi-TeV scales.
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Precision Beta Decay as a Probe of New Physics
Workshop summary discussing the sensitivity of precision beta-decay experiments to new physics.