Abstract
The Σ0 and Λ hyperons are close relatives of the neutron, being related by flavour SU(3) symmetry. This allows to estimate an upper limit for the electric dipole transition moment (EDTM) of the Σ0-Λ transition, based on the experimental knowledge of the upper limit of the neutron electric dipole moment. The three-body decay could show an angular asymmetry due to the interference of parity violating and conserving amplitudes in both the first and second step of the decay chain . This angular asymmetry, which will be measured at e.g. PANDA for both particle and antiparticle decays, is determined in this work from the Σ0-Λ EDTM, where a CP violating QCD theta-vacuum-angle term has been included. It turns out to be below any experimental resolution that one can expect in the foreseeable future. Any experimental significance would therefore point to physics beyond the Standard Model.
Highlights
The three-body decay Σ0 → γpπ− could show an angular asymmetry due to the interference of parity violating and conserving amplitudes in both the first and second step of the decay chain Σ0 → Λγ → γpπ−. This angular asymmetry, which will be measured at e.g. PANDA for both particle and antiparticle decays, is determined in this work from the Σ0-Λ electric dipole transition moment (EDTM), where a conjugation parity (CP) violating QCD theta-vacuum-angle term has been included
The amount of charge conjugation parity (CP) symmetry violation predicted by the Standard Model (SM) is not enough to explain the baryon asymmetry observed in our universe
Using eq(15) together with the experimental upper limit of the neutron Electric dipole moments (EDMs) [11], |denxp| ≤ 2.9 × 10−26 e cm, we obtain an upper limit for the Σ0-Λ EDTM:
Summary
The amount of charge conjugation parity (CP) symmetry violation predicted by the Standard Model (SM) is not enough to explain the baryon asymmetry observed in our universe. This allows to estimate an upper limit for the electric dipole transition moment (EDTM) of the Σ0-Λ transition, based on the experimental knowledge of the upper limit of the neutron electric dipole moment. The three-body decay Σ0 → γpπ− could show an angular asymmetry due to the interference of parity violating and conserving amplitudes in both the first and second step of the decay chain Σ0 → Λγ → γpπ−.
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