No abstract

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 energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is presented. These measurements were carried out at the Protvino accelerator using a 1 to 45 GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented.

We report on the effects of radiation on the light output of lead tungstate crystals. The crystals were irradiated by pure, intense high energy electron and hadron beams as well as by a mixture of hadrons, neutrons and gammas. The crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai (China). These studies were carried out at the 70-GeV proton accelerator in Protvino.