FRASCATI-DAFNE-DEAR (Frascati)

FRASCATI-DAFNE-DEAR (Frascati)
DAFNE EXOTIC ATOMS RESEARCH AT THE FRASCATI PHI-FACTORY
http://www.lnf.infn.it/esperimenti/dear/
HEP articles associated with FRASCATI-DAFNE-DEAR
DEAR

Spokesperson: Guaraldo, Carlo
Contact Email: Carlo.Guaraldo@lnf.infn.it
URL: http://www.lnf.infn.it/esperimenti/dear/

DEAR (DAFNE Exotic Atoms Research) is an experiment devoted to a precision measurement of the scattering lengths of the kaon-nucleon system, through a percent measurement of the Kalpha line shifts - due to strong interaction - in kaonic hydrogen and kaonic deuterium. In addition to the precise determination of low-energy parameters, a fundamental non-perturbative QCD quantity, such as the KN sigma term, undetermined up to now, will be measured. The sigma term is a quantity which gives an indication of the chiral symmetry breaking part in the total Hamiltonian for a nucleon state. Moreover, the KN sigma term is an extremely sensitive and direct measurement of the strangeness content of the proton. One can eventually extract the KN sigma term from accurate measurements of K- nucleon amplitudes at zero energy. This will be possible only with the DEAR experiment. DAFNE is a unique source of low momentum, monochromatic (127 MeV/c) K-, coming from the decay of the phi(1020) meson produced by the e+e- interactions. In the DEAR experimental set-up the K-, after being slowed down, stop inside a low temperature (25 K), pressurized (3 bar) gaseous hydrogen target and eventually form an exotic K-hydrogen atom in a high excited atomic level, which subsequently decays to the ground level, emitting characteristic X-rays. The selected conditions for the density of the hydrogen target reduce the Stark mixing and hence enhance the yield of the 2P-1S X-ray transition. The X-ray detectors will be CCD (Charge Coupled Devices), which offer high resolution and efficiency (140 eV and 60%, respectively, at 6.5 KeV), and, above all, unprecedented background suppression of ionizing particles, neutrons and gammas.