Large high energy accelerators provide tools for investigation at the frontiers of our knowledge in subnuclear physics by probing the ultimate constituents of matter within always smaller space-time regions, and by generating new patterns of matter at always increasing energies. A complementary approach to the understanding of the fundamental properties of nature is the study at a very high degree of precision of rare phenomena, which clarify critical items of the theories and open the possibility of discriminating between different models of the physical reality.

In order to follow the latter line of research in subnuclear physics, we need accelerators capable of delivering beams of extremely high intensity and accurate energy calibration; in this way a wide variety of data even on the most rare phenomena can be obtained.

The italian National Institute for Nuclear Physics (INFN) is realising in the Frascati National Laboratory the first of this special kind of accelerators, dedicated to the an abundant production of Phi particles coming from the annihilation of electrons and positrons at the energy of the Phi resonance.

The Phi particle is unstable and decays in a very short time into other lower energy particles, the most interesting being K mesons. This kind of particles showed up, right at their discovery in 1947, such unexpected features that a new physical entity, called "strangeness", was introduced to explain them.

The study of neutral K mesons led to the discovery of a unique phenomenon, the violation of a fundamental symmetry of nature, which is strictly respected in any other reaction: the CP symmetry, which states that any reaction must not change if it undergoes a simultaneous mirror reflection and change of all particles into their antiparticles. The detailed measurement of the fundamental parameters of CP violation and its inclusion into a coherent conceptual framework is one of the most challenging open problems in physics, and it represents the Main Research Program at DAFNE.

The extremely precise study of the different decays of Phi and K mesons at DAFNE will deliver clear experimental information on many critical items of the subnuclear world and of the forces which drive the interactions between its constituents. The KLOE collaboration has been set up to follow this line of research on DAFNE.

However, CP violation and K meson physics are not the only goals of the DAFNE Project: the abundant production of K mesons opens a wide range of experiments in nuclear physics, with unique characteristics of energy resolution and kind of observable reactions. A second experiment, FINUDA, will be installed on one of the two interaction straights of the DAFNE Main Rings to perform studies on the spectroscopy and decay modes of hypernuclei, e.g. special nuclei, where a nucleon is replaced by a baryon made up of "strange" quarks (Lambda, Sigma, Csi). The "strangeness" degree of freedom adds a new dimension to our knowledge of the nuclear world, by creating new dynamic systems whose spectroscopy can show up symmetries which are forbidden in ordinary nuclei. In DAFNE, Lambda hypernuclei will be produced by stopping K mesons of known energy inside nuclear targets.

Due to the very large stored current, DAFNE is also an intersting high flux source of synchrotron radiation in the UV and soft X-ray wavelength region. The project of installing a small number of synchrotron radiation beamlines from the bending magnets and wigglers of the DAFNE Main Rings has also been approved. 

M.Preger 19 MAR 1997