232 research outputs found
Hypernuclear spectroscopy with K at rest on Li, Be, C and O
The FINUDA experiment collected data to study the production of hypernuclei
on different nuclear targets. The hypernucleus formation occurred through the
strangeness-exchange reaction K^-_{stop} + \; ^AZ \rightarrow \; ^A_{\Lambda}Z
+ \pi^-. From the analysis of the momentum of the emerging , binding
energies and formation probabilities of Li, Be,
C and O have been measured and are here
presented. The behavior of the formation probability as a function of the
atomic mass number A is also discussed.Comment: Accepted for publication in PL
Production of H and H with the (K,) reaction
The production of neutron rich -hypernuclei via the
(,) reaction has been studied using data collected with the
FINUDA spectrometer at the DANE -factory (LNF). The analysis of the
inclusive momentum spectra is presented and an upper limit for the
production of H and H from Li and Li, is
assessed for the first time.Comment: 11 pages, 3 figures. Accepted for publication in PL
The reaction on p-shell nuclei
This letter is concerned with the study of the reaction in p-shell nuclei, i.e., , ,
and . The emission rates are
reported as a function of . These rates are discussed in comparison with
previous findings. The ratio in p-shell nuclei is
found to depart largely from that on hydrogen, which provides support for large
in-medium effects possibly generated by the sub-threshold . The
continuum momentum spectra of prompt pions and free sigmas are also discussed
as well as the missing mass behavior and the link with the
reaction mechanism. The apparatus used for the investigation is the FINUDA
spectrometer operating at the DANE -factory (LNF-INFN, Italy).Comment: 14 pages, 5 figures, accepted for publication in Phys. Lett.
A study of the proton spectra following the capture of in Li and C with FINUDA
Momenta spectra of protons emitted following the capture of in Li
and C have been measured with 1% resolution. The C spectrum is
smooth whereas for Li a well defined peak appears at about 500 MeV/. The
first observation of a structure in this region was identified as a strange
tribaryon or, possibly, a -nuclear state. The peak is correlated with a
coming from decay in flight, selected by setting momenta
larger than 275 MeV/. The could be produced, together with a 500
MeV/ proton, by the capture of a in a deuteron-cluster substructure of
the Li nucleus. The capture rate for such a reaction is (1.62\pm
0.23_{stat} ^{+0.71}_{-0.44}(sys))%/K^-_{stop}, in agreement with the existing
observations on He targets and with the hypothesis that the Li nucleus
can be interpreted as a cluster.Comment: 21 pages, 10 figures. Accepted for publication in NP
Correlated pairs from the reaction
Correlated pairs emitted after the absorption of negative kaons
at rest in light nuclei and are
studied. -hyperons and deuterons are found to be preferentially
emitted in opposite directions. The invariant mass spectrum of
shows a bump whose mass is 32516 MeV/c. The bump mass (binding
energy), width and yield are reported. The appearance of a bump is discussed in
the realm of the [] clustering process in nuclei. The experiment was
performed with the FINUDA spectrometer at DANE (LNF).Comment: 13 pages, 5 figures, accepted for publication in Phys. Lett.
Evidence for 6{\Lambda}H
Evidence for the neutron-rich hypernucleus 6{\Lambda}H is presented from the
FINUDA experiment at DA{\Phi}NE, Frascati, studying ({\pi}+, {\pi}-) pairs in
coincidence from the K- +6Li \rightarrow 6 H+{\pi}+ production reaction
followed by 6{\Lambda}H \rightarrow 6He + {\pi}- weak decay. The production
rate of 6{\Lambda}H undergoing this two-body {\pi}- decay is determined to be
(2.9\pm2.0)\cdot10-6/K-. Its binding energy, evaluated jointly from production
and decay, is B{\Lambda}(6{\Lambda}H) = (4.0\pm1.1) MeV with respect to
5H+{\Lambda}. A systematic difference of (0.98 \pm 0.74) MeV between B{\Lambda}
values derived separately from decay and from production is tentatively
assigned to the 6{\Lambda}H 0+g.s. \rightarrow 1+ excitation.Comment: 5 pages, 3 figure
An improved determination of the two--nucleon induced non mesonic weak decay of -hypernuclei
The decay of -hypernuclei without pion emission, known as Non
Mesonic Weak Decay (NMWD), gives an effective tool to investigate S=1
four-baryon interactions. It was theoretically suggested that the two-nucleon
induced mechanism could play a substantial role in reproducing the observed
NMWD decay rates and nucleon spectra, but at present no direct evidence of such
a mechanism has been obtained. The FINUDA experiment, exploiting the
possibility to detect both charged and neutral particles coming from the
hypernucleus decay, has allowed us to deduce the relative weight of the two
nucleon induced decay rate to the total NMWD rate. The value of
/=0.24
has been deduced, with an error reduced by a factor more than two compared with
the previous assessment.Comment: 10 pages, 3 figure
First observation of the hyper superheavy hydrogen 6{\Lambda}H
Three candidate events of the neutron-rich hypernucleus 6{\Lambda}H were
uniquely identified in the FINUDA experiment at DA{\Phi}NE, Frascati, by
observing {\pi}+ mesons from the (K-stop,{\pi}+) production reaction on 6Li
targets, in coincidence with {\pi}-mesons from 6{\Lambda}H \rightarrow
6He+{\pi}- weak decay. Details of the experiment and the analysis of its data
are reported, leading to an estimate of (2.9\pm2.0)\cdot10-6/K- stop for the
6{\Lambda}H production rate times the two-body {\pi}- weak decay branching
ratio. The 6{\Lambda}H binding energy with respect to 5H + {\Lambda} was
determined jointly from production and decay to be B{\Lambda} = (4.0 \pm 1.1)
MeV, assuming that 5H is unbound with respect to 3H + 2n by 1.7 MeV. The
binding energy determined from production is higher, in each one of the three
events, than that determined from decay, with a difference of (0.98 \pm 0.74)
MeV here assigned to the 0+g.s. \rightarrow 1+ excitation. The consequences of
this assignment to {\Lambda} hypernuclear dynamics are briefly discussed.Comment: 20 pages, 8 figures, version matching published Nuclear Physics A
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