The FINUDA experiment is installed by the DAφNE φ factory at Laboratori Nazionali di Frascati, and was devised for high resolution hypernuclear physics studies exploiting the K- produced in the decay of the φ(1020) meson produced in the e+e- collision. The hypernuclei are formed through the K- + AZ → AΛZ + π- reaction: by measuring the formation momentum the energy levels of the produced AΛZ hypenucleus can be determined. The very small kinetic energy of the kaons lets them stop in very thin targets (~0.1 g/cm2) minimizing this way the energy straggling of the pion and allowing high resolution studies to be performed over an angular range of ~2π.
The FINUDA program foresees a high statistics study of several hypernuclear species whose formation occurs in eight solid targets, placed according to a cylindric geometry along the beam interaction region. In the two data takings performed so far, in 2003-2004 and in 2006-2007, 6Li, 7Li, 9Be, 12C, 13C, 16O, 27Al and 51V targets were used, in different experimental configurations. The apparatus is a magnetic spectrometer devised for the simultaneous detection both of the π- emitted in the hypernucleus formation and of all the particles emitted in its decay, as well as all the particles produced in the interaction of a K- (or a K+) in the targets (π, protons, deuterons, tritons and positive muons from the Kmu2 decay). For this reaction, FINUDA proved to be a very good device not only for hypernuclear physics investigations, but also for the study of a wide scenario of phenomena linked to the K- induced interactions on nucleons and nuclei, and the dynamics of their absorption.
The produced particles are detected inside a cylindrical volume (1 m radius, 2 m long) immersed in a 1 T solenoidal magnetic field, by means of four different kinds of detectors: two series of silicon microstrip detectors determine the reaction vertex (stopping point of a K- in the target) and allow the particles crossing them to be identified by means of their ionization energy loss, two series of low mass planar drift chambers and a set of six layers of straw tubes detectors allow the charged particle trajectories to be reconstructed in the tracking volume, and an external scintillator hodoscope allows neutrons to be detected. The latter, together with an internal hodoscope, cylindrical as well and located just beyond the beam pipe, delivers the trigger signal for the experiment. Every part of the apparatus has been built with light materials in order to minimize at best the multiple scattering effects on the particles during their travel through the apparatus; for the same reason the tracking region is filled by Helium gas, which allows scattering effects to be minimized at most, which would imply a worsening of the resolution on the momentum measurements.
Two data takings were performed so far, in 2003-2004 and in 2006-2007, in which an integrated luminosity of, respectively, 192 pb-1 and 954 pb-1was collected.
FINUDA is an International Collaboration with the participation of about 60 researchers belonging to the following italian and foreign institutions: Bari (Dip. Interateneo di Fisica e INFN), Brescia (Dip. di Meccanica e INFN), Laboratori Nazionali di Frascati dell'INFN, Pavia (Dip. Fisica Nucleare e Teorica e INFN), Torino (Dip. di Fisica Generale, Dip. di Fisica Sperimentale, Dip. di Fisica del Politecnico, INAF-IFSI e INFN), Trieste (Dipartimento di Fisica e INFN), University of Victoria e TRIUMF (Canada), University of Seoul (Korea), G.S.I. (Germany), University of Kyoto, KEK e RIKEN (Japan), Univerity of Teheran (Iran), JINR (Russia)
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