Measurement of direct photon emission in K+→π+π0γ decay using stopped positive kaons

Abstract

The radiative decay K + → π + π 0 γ (K π2γ ) has been measured with stopped positive kaons. A K π2γ sample containing 4k events was analyzed, and the K π2γ branching ratio of the direct photon emission process was determined to be [6.1 ± 2.5(stat) ± 1.9(syst)]×10 −6 . No interference pattern with internal bremsstrahlung was observed.

Measurement of the direct emission and interference terms and search for CP violation in the decay K ±→π ± π 0 γ

“…It should be noted that NA48/2 has been able to keep the rate of wrong solutions for the odd photon to <0.1% while in other measurements [13][14][15][16][17][18][19] the wrong solutions fraction was always larger than 10%. The relative background contamination is < 10 −4 while in other experiments it is at the level of 10 −2 or larger.…”

“…7.2 the possibility of e being non zero will be investigated. Most of the previous experiments [13][14][15][16][17][18][19] have measured DE and INT terms in the kinematical region of 55 < T * π < 90 MeV, obtaining a value for the INT contribution compatible with zero. Therefore, the values quoted in these works for the DE branching ratio have been obtained from fits where the INT term has been set to zero.…”