The NA48/2 experiment at CERN collected two data samples with minimum bias trigger conditions in 2003 and 2004. A measurement of the rate and dynamic properties of the rare decay K ± → π ± γγ from these data sets based on 149 decay candidates with an estimated background of 15.5 ± 0.7 events is reported. The model-independent branching ratio in the kinematic range z=(mγγ/mK)2>0.2 is measured to be BMI(z>0.2)=(0.877±0.089)×10-6, and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be B(Kπγγ)=(0.910±0.075)×10-6. © 2014 The Authors.
Batley, J. R., Kalmus, G., Lazzeroni, C., Munday, D. J., Slater, M. W., Wotton, S. A., … Widhalm, L. (2014). A new measurement of the K ± → π ± γγ decay at the NA48/2 experiment. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 730, 141–148. https://doi.org/10.1016/j.physletb.2014.01.038