Search for the rare decay K+ -> pi+ gamma

TL;DR

This study searched for a rare, forbidden decay of K+ into pi+ gamma using the E787 detector, setting a new upper limit on its branching ratio due to no observed events.

Contribution

First experimental search for the forbidden decay K+ -> pi+ gamma, establishing an upper limit on its branching ratio at 3.6 x 10^{-7}.

Findings

No events observed in the targeted kinematic region.

Set an upper limit on the decay's branching ratio.

Improves constraints on rare kaon decay processes.

Abstract

We have performed a search for the angular-momentum forbidden decay K+ -> pi+ gamma with the E787 detector at BNL. No events were observed in the pi+ kinematic region around 227 MeV/c. An upper limit on the branching ratio for the decay is determined to be 3.6 x 10^{-7} at 90% confidence level.