2014/06/18 by The NA Collaboration, 2 Collaboration
Engineering · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #Superconducting Materials and Applications
paper · pdf · doi:10.48550/arxiv.1406.4749
openalex publication_date 2014/06/18 · openalex created_date 2022/10/02 · openalex updated_date 2026/07/28
A sample of 65210 \mathrmK± → π0 π0 \mathrme± ν (Ke400) 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 (Mππ2,Meν2) and brings evidence for a cusp-like structure in the distribution of the squared π0 π0 invariant mass around 4mπ+2. Exploiting a model independent description of this form factor, the branching ratio, inclusive of radiative decays, is obtained using the \mathrmK± → π0 π0 π± decay mode as normalization. It is measured to be BR(Ke400) = (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 (Ke4+-) is also presented.