Abstract
A sample of 65210 K ± → π 0 π 0 e ± ν (K 00e4 ) decay candidates with 1% background contamination has been collected in 2003-2004 by the NA48/2 collaboration at the CERN SPS. A study of the differential rate provides the first measurement of the hadronic form factor variation in the plane (M 2 ππ , M 2 eν ) and brings evidence for a cusp-like structure in the distribution of the squared π 0 π 0 invariant mass around \( 4{m}_{\pi^{+}}^2 \). Exploiting a model independent description of this form factor, the branching ratio, inclusive of radiative decays, is obtained using the K ± → π 0 π 0 π ± decay mode as normalization. It is measured to be BR(K 00e4 ) = (2.552 ± 0.010stat ± 0.010syst ± 0.032ext) × 10−5, which improves the current world average precision by an order of magnitude while the 1.4% relative precision is dominated by the external uncertainty from the normalization mode. A comparison with the properties of the corresponding mode involving a π + π − pair (K + −e4 ) is also presented.
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This study is dedicated to the memory of our colleague and friend Spasimir Balev (1979-2013).
ArXiv ePrint: 1406.4749
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The NA48/2 collaboration., Batley, J.R., Kalmus, G. et al. Detailed study of the K ± → π 0 π 0 e ± ν (K 00e4 ) decay properties. J. High Energ. Phys. 2014, 159 (2014). https://doi.org/10.1007/JHEP08(2014)159
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DOI: https://doi.org/10.1007/JHEP08(2014)159