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.
ChPT test at NA48 and NA62 experiment at CERN / Piandani, Roberto; Ambrosino, Fabio; Capussela, Tiziana; Massarotti, Paolo; Mirra, Marco; Saracino, Giulio; Et, A. l.. - In: NUCLEAR AND PARTICLE PHYSICS PROCEEDINGS. - ISSN 2405-6014. - 258-259:(2015), pp. 75-79. (Intervento presentato al convegno 17th International Conference in Quantum Chromodynamics QCD, 2014 tenutosi a Montpellier, France nel 30 Jun-04 Jul 2014) [10.1016/j.nuclphysbps.2015.01.017].
ChPT test at NA48 and NA62 experiment at CERN
AMBROSINO, FABIO;CAPUSSELA, TIZIANA;MASSAROTTI, PAOLO;MIRRA, MARCO;SARACINO, GIULIO;
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
