2-PHOTON PHYSICS CAPABILITIES OF KLOE AT DA-PHI-NE

A feasibility study has been carried out for high-precision measurements of two-photon reactions leading to hadrons at the DAPHINE electron-positron collider. This new facility will operate at a c.m. energy of 1.02 GeV and up to a maximum of 1.5 GeV. It will have a luminosity of L congruent-to 5 .10(32) cm-2 s-1, 100 times larger than the present available e+e- colliders. DAPHINE offers an excellent opportunity to study gammagamma reactions at low energy with high statistics, using the KLOE detector equipped with electron tagging facilities as described in this report. Among the various topics that one may address in these studies, we concentrate on the following: 1) Precision measurements of the polarizabilities of charged and neutral pions via the two-photon reactions gammagamma --> pipi. These will allow tests of chiral theories and chiral perturbation techniques, as well as other theoretical approaches. 2) Measurements for the first time of the azimuthal correlations of the gammagamma --> pipi and other two-photon reactions. These provide new tests of the validity of chiral and other theories. 3) Formation of the C = + 1 light pseudoscalar mesons, pi0, eta and eta'. This allows the study of the qqBAR and possibly gluonic inner structure of these mesons. For the pi0 its measured radiative width will also improve the currently known lifetime. 4) The possibility to realize a double tagging at DAPHINE will allow reliable measurements of the currently little known total gammagamma --> hadrons cross-section below 1 GeV, to be compared with several models. The physics program described above cannot be realized without tagging the two-photon reactions to suppress the background from e+e- annihilation channels and other sources.