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The vertex y + 3~ has been investigated in the reaction of pion pair production by pions in the nuclear Coulomb field, rii-+ ( Z , A 1-r-+no+ (2, A ) , in the region of low-invariant-mass r -T O pairs. The experiment has been carried out in the 40-GeV pion beam of the I H E P accelerator (Serpukhov) with the SIGMA spectrometer. We have measured for the first time the cross section of the reaction in the region of momentum transfer squared q 2 < 2 X 1 0 -' (~e V / c )~, U / Z ' = 1.63k0.2310.13 nb, and the y -3 r coupling constant F'"= 12.9k0.9iO. 5 G~V P ' , where the first (second) error is statistical (systematic). The obtained result agrees with the calculations based on the Wess-Zumino-Witten effective Lagrangian. The hypothesis of chiral anomalies and the color-SU(3) quark symmetry are confirmed.

The pion radiative scattering rtZ~ ~rZ7 at 40 GeV was investigated. Coulomb scattering -i.e. pion Compton-effect -dominates for small fourmomentum transfers in this reaction. In our previous paper we found the pion polarizability to be /3~= -~=(-6.8 _+ 1.4). 10 -~3 cm 3, where we assume following the theory that the sum of electrical and magnetic polarizabilities (7 + fl.)~-0. More complete analysis of our data is done in order to test this assumption. The result for (c~ +ft.) is in agreement with theoretical predictions.

The nrc ~ production in nuclear Coulomb field at threshold has been studied for the first time experimentally. The cross section of the reaction n-+(A,Z)--+n-+n o +(A,Z)at 40GeV on C, A1, Fe nuclei has been determined for small 4-momentum transfers t < 2.10-3 (GeV/c)2 and invariant mass of n-n ~ S<10 m~. The obtained result is in agreement with Adler's PCAC anomaly and colour SU(3) theory.

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