The new published measurements of the K± → π± γγ decay with minimum bias data samples collected by the two experiments NA48/2 and NA62 are discussed. The results include a model independent decay rate measurement and fits to Chiral Perturbation Theory (ChPT) description. The model independent branching ratio in the kinematic range z = (mγγ/mK)2 > 0.2, obtained by combining the NA48/2 and NA62 results, is BMI = (0.965 ± 0.63) × 10-6. The combined branching ratio in the full kinematic range assuming a ChPT description is BChPT = (1.003±0.056)×10-6. The uncertainties are dominated by the statistical errors. The data support the ChPT prediction for a cusp in the di-photon invariant mass spectrum at the two pion threshold and are in agreement with both O(p4) and O(p6) ChPT predictions. © 2015 Elsevier B.V.
ChPT test at NA48 and NA62 experiment at CERN / Piandani, R., Ambrosino, F., Antonelli, A., Anzivino, G., Arcidiacono, R., Baldini, W., Balev, S., Batley, J.R., Behler, M., Bifani, S., Biino, C., Bizzeti, A., Bloch-Devaux, B., Bocquet, G., Bolotov, V., Bucci, F., Cabibbo, N., Calvetti, M., Cartiglia, N., Ceccucci, A., et al.. - In: NUCLEAR AND PARTICLE PHYSICS PROCEEDINGS. - ISSN 2405-6014. - 258:(2015), pp. 75-79. (17th International Conference in Quantum Chromodynamics (QCD) Montpellier, FRANCE JUN 30-JUL 04, 2014) [10.1016/j.nuclphysbps.2015.01.017].
ChPT test at NA48 and NA62 experiment at CERN
Bizzeti A.;
2015
Abstract
The new published measurements of the K± → π± γγ decay with minimum bias data samples collected by the two experiments NA48/2 and NA62 are discussed. The results include a model independent decay rate measurement and fits to Chiral Perturbation Theory (ChPT) description. The model independent branching ratio in the kinematic range z = (mγγ/mK)2 > 0.2, obtained by combining the NA48/2 and NA62 results, is BMI = (0.965 ± 0.63) × 10-6. The combined branching ratio in the full kinematic range assuming a ChPT description is BChPT = (1.003±0.056)×10-6. The uncertainties are dominated by the statistical errors. The data support the ChPT prediction for a cusp in the di-photon invariant mass spectrum at the two pion threshold and are in agreement with both O(p4) and O(p6) ChPT predictions. © 2015 Elsevier B.V.Pubblicazioni consigliate

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