Abstract
We present the status of an ongoing analysis of the η → π+π−π0 Dalitz plot, as well as preliminary results for the Dalitz plot parameters. The analysis is based on data taken at the DAΦNE φ-factory with the KLOE detector.
Highlights
Nb j=1 j σi where Nb is the number of bins of the Dalitz plot, Ni is the number of data events in bin i, j is the efficency for bin j, S i j the smearing matrix from bin j to bin i, Ntjheory the theoretical number of events in bin j calculated with equation 3 and σi the error in bin i
The preliminary results are shown in table 1, compared to the results of the previous analysis
The fit is done with 143 degrees of freedom, resulting in χ2 = 164.2 and χ2ν = 1.148
Summary
The experimental decay width of η → π+π−π0 (Γexp = 296 ± 16 eV [1]) is not well described by leading or next to leading order Chiral Perturbation Theory (χPT) (ΓLO ∼ 70 eV, ΓNLO = 160 ± 50 eV). This points towards strong pion rescattering effects in the final state, which can be treated by means of dispersion relations [2]. More data is needed to understand the tension between experimental results and χPT calculations. The Monte Carlo description of the detector has been improved and any possible bias due to the event classification filter, that organizes data in different output files, is studied on prescaled, unclassified events
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