CERN Accelerating science

Published Articles
Title	Tests of Chiral Perturbation Theory with $K_{e4}$ decays at CERN NA48/2 experiment
Author(s)	Balev, Spasimir (CERN) ; Bloch-Devaux, Brigitte (Turin U.)
Collaboration	NA48/2
Publication	2014
Number of pages	3
In:	PoS EPS-HEP2013 (2013) 133
In:	EPS-HEP 2013 European Physical Society Conference on High Energy Physics, Stockholm, Sweden, 18 - 24 Jul 2013, pp.133
DOI	10.22323/1.180.0133
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN SPS ; NA48-2
Abstract	The NA48/2 collaboration has accumulated the largest sampl es to date of semi-leptonic charged kaon decays in the K + − e4 (K ± → π + π − e ± ν ) and K 00 e4 ( K ± → π 0 π 0 e ± ν ) modes. From 1.1 million K + − e4 decays, form factors in the S- and P-wave have been extensive ly studied. Branching ratio and form factors have been measured at unprecedented precis ion. From ∼ 66000 K 00 e4 decays, preliminary values of the Branching ratio and form factor ha ve been obtained at a percent level precision. The comparison of Branching ratio and form facto r values in both K e4 modes sheds new light on isospin symmetry breaking effects. Form factor measurements are major inputs to the study of low energy QCD and are powerful tests of Chiral Pe rturbation Theory predictions

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