Two-photon physics capabilities of KLOE at DAΦNE

Summary  A feasibility study has been carried out for high-precision measurements of two-photon reactions leading to hadrons at the DAΦNE 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 ofL⋍5�1032 cm−2s−1, 100 times larger than the present available e+e− colliders. DAΦNE offers an excellent opportunity to study γγ 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 γγ→ππ. 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 γγ→ππ and other two-photon reactions. These provide new tests of the validity of chiral and other theories. 3) Formation of theC=+1 light pseudoscalar mesons, π0, η and η′. This allows the study of the $$q\bar q$$ and possibly gluonic inner structure of these mesons. For the π0 its measured radiative width will also improve the currently known lifetime. 4) The possibility to realize a double tagging at DAΦNE will allow reliable measurements of the currently little known total γγ→hadrons cross-section below 1 GeV, to be compared with several models. The physics program described abovecannot be realized without tagging the two-photon reactions to suppress the background from e+e− annihilation channels and other sources.