A search for decay η′ → 4 π0 with GAMS-4π setup

isospin violation mocks *new* physics: π0 − η, η ′ mixing

Test of charge conjugation invariance in the decay of the η meson into π+π−π0

In this work we present the preliminary results of the analysis of the pp → ppη → ppπ+π−π0 reaction aiming to test the charge conjugation symmetry C in strong interactions. Based on approximately 105 identified η → π+π−π0 decay events we have extracted asymmetry parameters sensitive to C symmetry violation for different isospin values of the final state and we have established that all are cons...

The decay η ′ c → η

The decay η ′ c → η c π π. Abstract It is pointed out that the decay of the recently observed charmonium η ′ c resonance, η ′ c → η c π π is simply related to the well studied decay ψ ′ → J/ψ π π and can thus be used for absolute normalization of other decay modes of the η ′ c. The total rate of the discussed decay should be approximately three to four times the corresponding rate for the ψ ′ r...

Chiral expansions of the π0 decay amplitude

We consider the anomaly dominated process of a neutral pion decaying into two photons and present the computation of the amplitude up to NNLO in the two-flavour chiral expansion. We show that the result is renormalizable and that chiral logarithms are present at this order, unlike the case at lower orders. Their influence turns out to be very small for physical pion masses. We also discuss the ...

Searching for η → γγγ decay

Data collected by the KLOE experiment in years 2001/2002 for a total integrated luminosity of 410 pb−1, corresponding to 17 million of produced η’s from the Φ → ηγ radiative decay, have been analyzed to look for the C-violating decay η → γγγ. The signal is searched in events with 4 photons in the final state by using the spectrum of the most energetic photon. The background is evaluated from th...