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Register a new userGeneralized polarizability of neutral pions of the process $e^- e^+ to pi^0pi^0gamma$ in NJL model
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Differential distributions in the $pi_0pi_0gamma$ system created in the annihilation channel of an electron-positron collision are considered. The energy fractions of the pions (Dalitz-plot) distribution are presented in a general form and in approximation of intermediate vector mesons (excited and ordinary ones).It is pointed out that in relevant experiments the generalized polarizability of the neutral pion can be measured. Numerical illustrations are presented.
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The cross section of the $e^+e^-toomegapi^0topi^0pi^0gamma$ reaction was measured by the SND detector at VEPP-2M $e^+e^-$ collider in the energy range from threshold up to 1.4 GeV. Results of the cross section fitting by the sum of $rho$, $rho^{prime}$ and $rho^{primeprime}$ contributions are presented.
We analyze a 37 pb$^{-1}$ data sample collected with the SND detector at the VEPP-2000 $e^+e^-$ collider in the center-of-mass energy range 1.05--2.00 GeV and present an updated measurement of the $e^+e^- to omega pi^0 to pi^0pi^0gamma$ cross section. In particular, we correct the mistake in radiative correction calculation made in our previous measurement based on a part of the data. The measured cross section is fitted with the vector meson dominance model with three $rho$-like states and used to test the conserved vector current hypothesis in the $tau^-toomegapi^- u_{tau}$ decay.
Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of $sqrt{s}=4.23$, 4.26, and 4.36~GeV, we observe $EEto pphc$ for the first time. The Born cross sections are measured and found to be about half of those of $EEto pi^+pi^-h_c$ within less than 2$sigma$. In the $pi^0h_c$ mass spectrum, a structure at 4.02~GeV/$c^2$ is found. It is most likely to be the neutral isospin partner of the $zcp^{pm}$ observed in the process of $EEto pi^+pi^-h_c$ is found. A fit to the $pi^0 h_c$ invariant mass spectrum, with the width of the $zcpn$ fixed to that of its charged isospin partner and possible interferences with non-$zcpn$ amplitudes neglected, gives a mass of ($4023.9pm 2.2 pm 3.8$)~MeV/$c^2$ for the $zcpn$, where the first error is statistical and the second systematic.
The process $e^+e^- to pi^0gamma$ has been studied in the experiment with the SND detector at the VEPP-2M $e^+e^-$ collider. The $e^+e^- to pi^0gamma$ cross section has been measured in the center-of-mass energy range from 0.60 to 1.38 GeV. The cross section is well described by the vector meson dominance model. From the fit to the cross section data we have determined the branching fractions $B(rhotopi^0gamma)=(4.20pm0.52)times10^{-4}$, $B(omegatopi^0gamma)=(8.88pm0.18)%$, $B(phitopi^0gamma)=(1.367pm0.072)times10^{-3}$, and the relative phase between the $rho$ and $omega$ amplitudes $varphi_{rho}=(-12.7pm4.5)^circ$. Our data on the process $e^+e^- to pi^0gamma$ are the most accurate to date.
The process $e^+e^- to pi^0gamma$ is studied with the SND detector at the VEPP-2000 $e^+e^-$ collider. Basing on data with an integrated luminosity of 41 pb$^{-1}$ recorded in 2010-2012 we measure the $e^+e^- to pi^0gamma$ cross section in the center-of-mass energy range from 1.075 up to 2 GeV. In the range 1.4-2.0 GeV the process $e^+e^- to pi^0gamma$ is studied for the first time.
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