Measurement of the Branching Ratio and Asymmetry of the DecayΞ°→Σ°γ

Abstract

The KTeV CollaborationWe have studied the rare weak radiative hyperon decay Ξ • → Σ • γ in the KTeV experiment at Fermilab. We have identified 4045 signal events over a background of 804 events. The dominant Ξ • → Λπ • decay, which was used for normalization, is the only important background source. An analysis of the acceptance of both modes yields a branching ratio ofBy analyzing the final state decay distributions, we have also determined that the Σ • emission asymmetry parameter for this decay is αΞΣ = −0.63 ± 0.09.

New precise measurements of the and decay asymmetries

“…The first result is a factor of three more precise than the previous measurement by NA48 [10] while the latter is of similar accuracy as the KTeV measurement [11], and both are in very good agreement with the previous measurements.…”

“…Measurements of Ξ 0 decay asymmetries have been performed by the NA48 experiment, which has obtained a value of α Ξ 0 →Λγ = −0.78 ± 0.19 using 730 reconstructed events [10], and by the KTeV collaboration, which found α Ξ 0 →Σ 0 γ = −0.63± 0.09 from more than 4000 events [11].…”

Rare Kaon and Hyperon Decays in Na48 Experiment

“…These values agree with previous measurements by NA48 on Ξ 0 → Λγ [2] and KTeV on Ξ 0 → Σγ [3], but are much more precise. In particular the result on Ξ 0 → Λγ is of high theoretical interest, as it confirms the large negative value of the decay asymmetry, which is difficult to accommodate for quark and vector meson dominance models.…”

hyperon decay modes with the hyperCP experiment at Fermilab

“…A large decay sample can be useful for more than just the BR measurement. The subsequent decay of the Ξ − can tell us about the decay itself by using its analyzing power to look for an asymmetry in the decay [4], similar to that done with other hyperon radiative decays [5].…”