A new measurement of the K plus or minus arrow right pi plus or minus gamma gamma K plus or minus arrow right pi plus or minus gamma gamma decay at the NA48/2 experiment

• Published in: Physics letters. B 2014-03, Vol.730, p.141-148
• Main Authors: Batley, J R, Kalmus, G, Lazzeroni, C, Munday, D J, Slater, M W, Wotton, SA, Arcidiacono, R, Bocquet, G, Cabibbo, N, Ceccucci, A, Cundy, D, Falaleev, V, Fidecaro, M, Gatignon, L, Gonidec, A, Kubischta, W, Norton, A, Maier, A, Patel, M, Peters, A, Balev, S, Frabetti, P L, Gersabeck, E, Goudzovski, E, Hristov, P, Kekelidze, V, Kozhuharov, V, Litov, L, Madigozhin, D, Molokanova, N, Polenkevich, I, Potrebenikov, Yu, Stoynev, S, Zinchenko, A, Monnier, E, Swallow, E, Winston, R, Rubin, P, Walker, A, Baldini, W, Ramusino, ACotta, Dalpiaz, P, Damiani, C, Fiorini, M, Gianoli, A, Martini, M, Petrucci, F, Savrie, M, Scarpa, M, Wahl, H, et. al
• Format: Article
• Language: English
• Subjects: Decay; Decay rate; Dynamic mechanical properties; Elementary particles; Kinematics; Mathematical models; Perturbation theory
• ISSN: 0370-2693
• DOI: 10.1016/j.physletb.2014.01.038

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 plus or minus arrow right pi plus or minus gamma gamma K plus or minus arrow right pi plus or minus gamma gamma from these data sets based on 149 decay candidates with an estimated background of 15.5 plus or minus 0.715.5 plus or minus 0.7 events is reported. The model-independent branching ratio in the kinematic range z=(m gamma gamma /mK)2>0.2z=(m gamma gamma /mK)2>0.2 is measured to be BMI(z>0.2)=(0.877 plus or minus 0.089)10-6BMI(z>0.2)=(0.877 plus or minus 0.089)10-6, and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be B(K pi gamma gamma )=(0.910 plus or minus 0.075)10-6B(K pi gamma gamma )=(0.910 plus or minus 0.075)10-6.