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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:57 |
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Conference: Bucharest University Faculty of Physics 2005 Meeting
Section: Nuclear and Elementary Particles Physics
Title:
Kaonic atoms measured by DEAR experiment at DAFNE
Authors:
D.L. Sirghi, F. Sirghi on behalf of DEAR/SIDDHARTA Collaboration
Affiliation:
Institute of Physics and Nuclear Engineering ``Horia Hulubei``, IFIN-HH,
Particle Physics Department, P.O. Box MG-6, R-76900 Magurele, Bucharest, Romania
INFN, Laboratori Nazionali di Frascati, C. P. 13, Via E. Fermi 40, I-00044, Frascati, Italy
E-mail
sirghi@lnf.infn.it
Keywords:
kaonic atoms; charged kaon mass
Abstract:
The DAFNE electron-positron collider at the Frascati National Laboratories, Italy has made available a unique “beam" of negative kaons providing so unprecedented conditions for the study of the low-energy kaon-nucleon interaction, a field still largely unexplored.
The DEAR (DAFNE Exotic Atom Research) experiment at DAFNE and its successor SIDDHARTA (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) aims at a precise determination of the isospin dependent antikaon-nucleon scattering lengths, through a percent level measurement of the K_alpha line shift and width in kaonic hydrogen, and a similar, being the first one in the same time, measurement of kaonic deuterium.
The principle of the DEAR experiment is: low-momentum negative kaons produced in the decay of the phi-mesons at DAFNE leave the beam pipe, are degraded in energy to a few MeV, enter a gaseous target and are stopped in the gas. The stopped kaons are captured in an outer orbit of the gaseous atoms, forming the exotic kaonic atoms. The kaons cascade down and some of them will reach the ground state. The energy of the x rays emitted in these transitions is measured with a CCD (Charge-Coupled Device) detector.
In the first phase of the experiment, dedicated to the calibration and optimization of the setup, the experiment collected data on gaseous kaonic nitrogen: for the first time a pattern of three transitions was measured, and the corresponding yields obtained.
In 2002, DEAR performed the most precise measurement ever obtained on the energy of the x rays emitted in the transitions to the ground state of kaonic hydrogen. The DEAR precision was limited by a signal/background ratio of about 1/70.
SIDDHARTA collaboration is developing a new set of large area, triggerabile X ray Silicon Drift Detector (SDD), which will improve the background rejection, allowing accomplishing the proposed objectives. Moreover, SIDDHARTA will deepen the scientific program, by measuring kaonic helium (related to the deeply bound kaonic nuclear states). Feasibility studies of other types of exotic atoms (sigmonic ones) are underway.
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