Probing New Physics and CP Violation in $ν_τn \to Λ_c τ^- (π^- ν_τ)$ and $\barν_τp \to Λτ^+ (π^+ \barν_τ)$
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| Formato: | Preprint |
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2026
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| author | Hernández, E. Nieves, J. Sobczyk, J. E. |
| author_facet | Hernández, E. Nieves, J. Sobczyk, J. E. |
| contents | We study the processes $ν_τn \to Λ_c τ^- (π^- ν_τ)$ and $\barν_τp \to Λτ^+ (π^+ \barν_τ)$, with particular emphasis on the pion energy and angular distributions, as a possible signal for lepton flavor universality violation, and in general of physics beyond the Standard Model (SM), as well as a sensitive probe of the $τ$ polarization vector. We work within an effective low-energy extension of the SM with all dimension-six four-fermion operators. In this framework, complex Wilson coefficients which encode new physics can generate CP-violating contributions. We propose an observable that provides a genuine CP-odd signal due to its sensitivity to particular transverse components of the $τ$ polarization vector. Namely, we show that the asymmetry in the azimuthal-angle distribution of the pion in the decay $τ^\pm\to π^\pm ν_τ$ constitutes a smoking-gun prediction of such a beyond the SM scenario. We estimate the strength of this effect extrapolating nucleon-hyperon form factors recently obtained from lattice QCD calculations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_19397 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Probing New Physics and CP Violation in $ν_τn \to Λ_c τ^- (π^- ν_τ)$ and $\barν_τp \to Λτ^+ (π^+ \barν_τ)$ Hernández, E. Nieves, J. Sobczyk, J. E. High Energy Physics - Phenomenology Nuclear Theory We study the processes $ν_τn \to Λ_c τ^- (π^- ν_τ)$ and $\barν_τp \to Λτ^+ (π^+ \barν_τ)$, with particular emphasis on the pion energy and angular distributions, as a possible signal for lepton flavor universality violation, and in general of physics beyond the Standard Model (SM), as well as a sensitive probe of the $τ$ polarization vector. We work within an effective low-energy extension of the SM with all dimension-six four-fermion operators. In this framework, complex Wilson coefficients which encode new physics can generate CP-violating contributions. We propose an observable that provides a genuine CP-odd signal due to its sensitivity to particular transverse components of the $τ$ polarization vector. Namely, we show that the asymmetry in the azimuthal-angle distribution of the pion in the decay $τ^\pm\to π^\pm ν_τ$ constitutes a smoking-gun prediction of such a beyond the SM scenario. We estimate the strength of this effect extrapolating nucleon-hyperon form factors recently obtained from lattice QCD calculations. |
| title | Probing New Physics and CP Violation in $ν_τn \to Λ_c τ^- (π^- ν_τ)$ and $\barν_τp \to Λτ^+ (π^+ \barν_τ)$ |
| topic | High Energy Physics - Phenomenology Nuclear Theory |
| url | https://arxiv.org/abs/2601.19397 |