A new measurement of the K ± → π ±γγ decay at the NA48/2 experiment

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 $K^\pm\to\pi^\pm\gamma\gamma$ from these data sets based on 149 decay candidates with an estimated background of $15.5\pm0.7$ events is reported. The model-independent branching ratio in the kinematic range $z=(m_{\gamma\gamma}/m_K)^2>0.2$ is measured to be ${\cal B}_{\rm MI}(z>0.2) = (0.877 \pm 0.089) \times 10^{-6}$, and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be ${\cal B}(K_{\pi\gamma\gamma}) = (0.910 \pm 0.075) \times 10^{-6}$

A new measurement of the K \ub1 \u2192 \u3c0 \ub1\u3b3\u3b3 decay at the NA48/2 experiment

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 \ub1 \u2192 \u3c0 \ub1\u3b3\u3b3 from these data sets based on 149 decay candidates with an estimated background of 15.5 \ub1 0.7 events is reported. The model-independent branching ratio in the kinematic range z=(m\u3b3\u3b3/mK)2>0.2 is measured to be BMI(z>0.2)=(0.877\ub10.089) 710-6, and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be B(K\u3c0\u3b3\u3b3)=(0.910\ub10.075) 710-6. \ua9 2014 The Authors