Kaonic X-ray experiments at DAFNE using SIDDHARTA

Abstract

on behalf of the SIDDHARTA collaborationThe KN system at rest makes a sensitive testing ground for chiral SU(3) symmetry in QCD, especially for the explicit symmetry breaking induced by the relatively large mass of the strange quark. At the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati we study kaonic atoms, taking advantage of the low-energy kaons from Φ-mesons decaying nearly at rest. The low-energy antikaon-nucleon interaction in kaonic hydrogen and kaonic deuterium can be investigated under favorable conditions. The DEAR (DAΦNE Exotic Atom Research) experiment at LNF delivered the most precise data on kaonic hydrogen up to now. DEAR and its follow-up experiment SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research by Timing Application) are using X-ray spectroscopy of kaonic atoms to measure the strong interaction induced shift and width of the ground state. SID-DHARTA will be the first experiment on kaonic deuterium ever, and kaonic hydrogen will be remeasured with greatly improved precision. From the shift and width in K − p and K − d the isospin-dependent antikaon-nucleon scattering lengths can be determined, quantities essential as constraints for low-energy QCD.

Low-energy antikaon nucleon interaction physics revisited

“…In fig. 4 the preliminary values for ε 1s and Γ 1s of SIDDHARTA are shown which are compatible with the final values which will be published soon [24]. From these values the K − p scattering PoS(Bormio 2011)063 length can be deduced (see equation below).…”

Precision measurements with kaonic atoms – from DEAR to SIDDHARTA

“…5). With this coincidence method [26] we will suppress the continuous background, as well as fluorescence X-rays by almost three orders of magnitude compared to the DEAR case. Silicon Drift Detectors (SDDs) [27,28] fulfill all the requirements we are looking for, except one: There were no large-area devices were available up to now (available sizes up to 10 mm 2 , first prototypes produced with an active area of 30 mm 2 ).…”

“…The cryogenic target cell will consist of a thin walled aluminum body with side windows and entrance window made out of thin Kapton foils. The SDD detector will be placed around the target with a total active detector area of about 200 cm 2 [26].…”