The ratio Rη = Γ (η →π+π−γ )/Γ (η →π+π−π0) has been measured by analysing 22 million φ → ηγ decays collected by the KLOE experiment at DANE, corresponding to an integrated luminosity of 558 pb−1. The η→π+π−γ proceeds both via the ρ resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, Rη = 0.1856±0.0005stat ±0.0028syst, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the η→π+π−γ decay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter α is α = (1.32±0.08stat +0.10−0.09 syst±0.02theo) GeV−2.
Measurement of Gamma(eta -> pi(+)pi(-)gamma)/Gamma(eta -> pi(+)pi(-)pi(0)) with the KLOE detector
GIARDINA, Giorgio 42;MANDAGLIO, GIUSEPPE;
2012-01-01
Abstract
The ratio Rη = Γ (η →π+π−γ )/Γ (η →π+π−π0) has been measured by analysing 22 million φ → ηγ decays collected by the KLOE experiment at DANE, corresponding to an integrated luminosity of 558 pb−1. The η→π+π−γ proceeds both via the ρ resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, Rη = 0.1856±0.0005stat ±0.0028syst, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the η→π+π−γ decay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter α is α = (1.32±0.08stat +0.10−0.09 syst±0.02theo) GeV−2.Pubblicazioni consigliate
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