Study of the [formula omitted] decay by the NA62 experiment

C Lazzeroni,V Obraztsov,J Engelfried,B Renk,M Napolitano,M Sozzi,F Petrucci,M Fiorini,N Molokanova,A Sergi,D Di Filippo,M Veltri,S Movchan,M Hita-Hochgesand,B Peyaud,M Misheva,M Moulson,A Zinchenko,I Mannelli,V Falaleev,V Kekelidze,F Ambrosino,A Cotta Ramusino,C Cerri,P Cenci,R Arcidiacono,B Hallgren,G Lamanna,D Madigozhin,D Coward,V Kurshetsov,S Giudici,O Yushchenko,A Winhart,M Serra,A Romano,P Rubin,A Bizzeti,E Gersabeck,A Salamon,M Lenti,S Goy Lopez,S Venditti,P Valente,A Antonelli,K Kleinknecht,Yu Potrebenikov,T Numao,S Bifani,G Ruggiero,V Duk,A Norton,G Anzivino,W Baldini,E Leonardi,S Gallorini,E Iacopini,H Wahl,R Fantechi,B Bloch-Devaux,G Collazuol,S Balev,G Saracino,L Litov,N Doble,M Piccini,E Gushchin,K Eppard,L Dilella,A Fucci,S Kholodenko,R Winston,L Gatignon,S Shkarovskiy,M Raggi,P Massarotti,F Costantini,R Wanke,A Peters,P Dalpiaz,F Bucci,G Dellacasa,V Kozhuharov,A Ceccucci,V Semenov,R Piandani,F Retière,A Gianoli,M Savrié,E Goudzovski,G Pierazzini,A Maier,T Spadaro,P Riedler,V Palladino,F Marchetto,E Imbergamo,C Biino,G D’agostini ,M Pepé ,H O Danielsson ,P L Frabetti ,В.н Болотов

doi:10.1016/j.physletb.2014.03.016

Abstract

A study of the dynamics of the rare decay K±→π±γγ has been performed on a sample of 232 decay candidates, with an estimated background of 17.4±1.1 events, collected by the NA62 experiment at CERN in 2007. The results are combined with those from a measurement conducted by the NA48/2 Collaboration at CERN. The combined model-independent branching ratio in the kinematic range z=(mγγ/mK)2>0.2 is BMI(z>0.2)=(0.965±0.063)×10−6, and the combined branching ratio in the full kinematic range assuming a Chiral Perturbation Theory description is B(Kπγγ)=(1.003±0.056)×10−6. A detailed comparison of the results with the previous measurements is performed.

Highlights

Experimental studies of radiative non-leptonic kaon decays allow crucial tests of Chiral Perturbation Theory (ChPT) describing weak low energy processes: the first non-trivial contribution to their decay rates stems from next-to-leading order ChPT
A sample of 232 K ± → π ±γ γ (Kπγ γ) decay candidates with an estimated background contamination of 17.4 ± 1.1 events collected with minimum bias trigger conditions by the NA62 experiment at CERN in 2007 has been analyzed
Measurements performed separately for K + and K − decays are consistent within 1.5 standard deviations: BM+I(z > 0.2) = (1.010 ± 0.098stat) × 10−6, BM−I(z > 0.2) = (1.417 ± 0.256stat) × 10−6

Summary

Introduction

Experimental studies of radiative non-leptonic kaon decays allow crucial tests of Chiral Perturbation Theory (ChPT) describing weak low energy processes: the first non-trivial contribution to their decay rates stems from next-to-leading order ChPT. The Kπγ γ decay can be described by two kinematic variables: z= (q1 + q2) m2K = mγ γ mK. The allowed region of the kinematic variables is [3]. 5 Present address: Sezione dell’INFN di Perugia, I-06100 Perugia, Italy. 8 at Dipartimento di Fisica, Università di Modena e Reggio Emilia, I-41125. 9 at Dipartimento di Fisica, Università di Firenze, I-50019 Sesto Fiorentino, Italy. At Istituto di Fisica, Università di Urbino, I-61029 Urbino, Italy Funded by the German Federal Minister for Education and Research (BMBF) under contract 05HA6UMA. Present address: Sezione dell’INFN di Pisa, I-56100 Pisa, Italy. Present address: Dipartimento di Fisica dell’Università e Sezione dell’INFN di Padova, I-35131 Padova, Italy. 16 Present address: Dipartimento di Fisica dell’Università di Torino, I-10125 Torino, Italy.

Results

Discussion

Conclusion