Nuclear physics topics will be investigated by the FINUDA (standing for
FIsica NUcleare a DA
ne) experiment
.
A nuclear physics experiment carried
out at a collider sounds contradictory itself, and indeed here the
uniqueness of the idea stands [4]: charged kaons from
decays are used as a monochromatic, slow (127 MeV/c), tagged,
background-free, high-counting rate beam on a thin target surrounding the beam
pipe. The possibility of stopping low-momentum monochromatic 
with a thin
(typically 
of 
) is unique of 
: 
's can
be stopped with minimal straggling very near the target surface,
so that outgoing
prompt pions do not cross any significant amount of target and do not undergo
any momentum degradation. This feature
provides unprecedented momentum resolution as long as very transparent
detectors are employed before and after the target.
The FINUDA detector is optimized to perform high-resolution studies of
hypernuclei production[5] and non-mesonic decays[6]
using a spectrometer
with the large acceptance typical of collider experiments.
Furthermore, differently from fixed target experiments, the direction of the
is competely tagged by the detection of the 
and viceversa.
Negative kaons stopping inside the
target produce a Y-hypernucleus 
via the process
where the momentum of the outgoing 
is directly
related to the level of
the hypernucleus formed (two body reaction).
In case of 
hypernuclei formation, the
following weak interaction 'decays'
are strongly favoured in medium heavy nuclei
with the nucleus undergoing the reactions
of interest in studying the validity of the 
rule[6].
Prompt pions and decay products are all detected with the same large acceptance spectrometer featuring state-of-the-art tracking, particle identification and neutron detection, good triggering capability.
Interesting similarities there exist in expected rates between FINUDA and the
proposed facility at the BNL AGS, where
the 
reaction, complementary to FINUDA's 
,
is studied with 
at rest,
both experiments with design energy resolution below 1MeV
fwhm, and a comparable hypernuclei production rate.
However, AGS operates with extracted beams at high rate (
stopped 
) and low geometrical acceptance (about 20 msr),
while FINUDA's flux, at initial 
luminosity,
is two orders of magnitudes lower, and the acceptance is 2 orders of magnitude
larger. The AGS choice of considering neutral prompt pions is dictated by their
use of thick targets, which worsens the resolution for emerging prompt charged
pions in a much larger extent than for neutral pions.
Figure 1: Cut-out view of the FINUDA spectrometer, showing also
a section of the 
beam pipe and compensating quadrupoles.
Following the initial idea [4], FINUDA was formally
proposed in May 1993 [7], rapidly approved and funded at the end
of 1993. A technical report[8] is to appear shortly as a LNF
preprint. For recent reviews, see [9],[10].