The first observation of the decay K+ → π+γγ is reported. A total of 31 events was observed with an estimated background of 5.1 ± 3.3. events in the π+ momentum range from 100 to 180 MeV/c. The corresponding partial branching ratio, B(K+ → π+γγ, 100 MeV/c < Pπ+ < 180 MeV/c), is [6.0 ± 1.5(stat) ± 0.7(stat) × 10−7. No K+ → π+γγ decay was observed in the π+ momentum region greater than 215 MeV/c. The observed π+ momentum spectrum is compared with the predictions of chiral perturbation theory.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)