The KLOE experiment's major physics goal is to measure the ~(et/e), with a precision of 10 -4, via both the traditional double ratio method and the kaons' quantum intefferometry. The experiment has started taking data at DA~NE, the C-factory at the Frascati National Laboratory (LNF) of INFN in Italy, beginning in April 1999. Integrated luminosity exceeding 100 pb -1 (10 s ¢'s) are expected to be delivered for end 1999/early 2000. A description of the detector's design and of its performances is presented. At the moment of writing the experiment has collected its first collisions for an integrated luminosity of 220 nb-1; the peak luminosity reached has been of 2 × 103°cm-2sec -1.
1. Introduction
The Frascati ¢ factory, DA~NE , is an e+e -collider optimized to operate at center of mass energy of Me with very high luminosity (Lp~ = 5 × 1032cm-2aec-1). The vector meson ¢ decays into K+K -49 %, KsKL 34 %, pTr 13 % and r/7 1.3 % of the time. Thus DAONE can be considered a factory of neutral and charged kaons. The neutral kaons are produced in collinear pairs, with momenta of N 110 MeV/c and in a pure quantum state (jPC = 1--), the same as that of the ¢ meson. Quantum intefferometry effects exist between the pairs of produced KsKL allowing the measurement of most of the CP and CPT violation parameters. This clean KsKL system also allows for efficient tagging; the observation of one kaon guarantees the existence of the other one with determined direction and identity. A pure Ks beam without using any regenerator is therefore available.
At design luminosity DAONE will produce, in one HEP physics year (10 r sec), 8.5 × 109