H. Outa

First results on 12ΛC production at DAΦNE

Lambda-hypernuclei are produced and studied, with the FINUDA spectrometer, for the first time at an e+e- collider: DAPHNE, the Frascati phi-factory. The slow negative kaons from phi(1020) decay are stopped in thin (0.2 g/cm^2) nuclear targets, and Lambda-hypernuclei formation is detected by measuring the momentum of the outgoing pi^-. A preliminary analysis on 12Lambda-C shows an energy resolution of 1.29 MeV FWHM on the hypernuclear levels, the best obtained so far with magnetic spectrometers at hadron facilities. Capture rates for the ground state and the excited ones are reported, and compared with previous experiments.

New results on mesonic weak decay of p-shell Lambda-hypernuclei

Abstract The FINUDA experiment performed a systematic study of the charged mesonic weak decay channel of p -shell Λ -hypernuclei. Negatively charged pion spectra from mesonic decay were measured with magnetic analysis for the first time for 7 Λ Li, 9 Λ Be, 11 Λ B and 15 Λ N. The shape of the π − spectra was interpreted through a comparison with pion distorted wave calculations that take into account the structure of both hypernucleus and daughter nucleus. Branching ratios Γ π − / Γ tot were derived from the measured spectra and converted to π − decay rates Γ π − by means of known or extrapolated total decay widths Γ tot of p -shell Λ -hypernuclei. Based on these measurements, the spin-parity assignment 1 / 2 + for 7 Λ Li and 5 / 2 + for 11 Λ B ground-state are confirmed and a spin-parity 3 / 2 + for 15 Λ N ground-state is assigned for the first time.

First observation of the hyper superheavy hydrogen HΛ6

Abstract Three candidate events of the neutron-rich hypernucleus H Λ 6 were uniquely identified in the FINUDA experiment at DAΦNE, Frascati, by observing π + mesons from the ( K stop − , π + ) production reaction on 6 Li targets, in coincidence with π − mesons from H Λ 6 → He 6 + π − weak decay. Details of the experiment and the analysis of its data are reported, leading to an estimate of ( 2.9 ± 2.0 ) ⋅ 10 − 6 / K stop − for the H Λ 6 production rate times the two-body π − weak decay branching ratio. The H Λ 6 binding energy with respect to H 5 + Λ was determined jointly from production and decay to be B Λ = ( 4.0 ± 1.1 ) MeV , assuming that 5 H is unbound with respect to H 3 + 2 n 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 ± 0.74 ) MeV here assigned to the 0 g.s. + → 1 + excitation. The consequences of this assignment to Λ hypernuclear dynamics are briefly discussed.

Proton spectra from Non-Mesonic Weak Decay of p-shell Λ-hypernuclei and evidence for the two-nucleon induced process

Abstract New spectra from the FINUDA experiment of the Non-Mesonic Weak Decay (NMWD) proton kinetic energy for Be Λ 9 , B Λ 11 , C Λ 12 , C Λ 13 , N Λ 15 and O Λ 16 are presented and discussed along with the published data on He Λ 5 and Li Λ 7 . Exploiting the large mass number range and the low energy threshold (15 MeV) for the proton detection of FINUDA, an evaluation of both Final State Interactions (FSI) and the two-nucleon induced NMWD contributions to the decay process has been done. Based on this evaluation, a linear dependence of FSI on the hypernuclear mass number A is found and for the two-nucleon stimulated decay rate the experimental value of Γ 2 / Γ p = 0.43 ± 0.25 is determined for the first time. A value for the two-nucleon stimulated decay rate to the total decay rate Γ 2 / Γ NMWD = 0.24 ± 0.10 is also extracted.

Correlated Lambda d pairs from the K(stop)(-)A ->Lambda d A ' reaction

Correlated Lambda d pairs emitted after the absorption of negative kaons at rest K-stop(-) A -> Lambda dA in light nuclei Li-6 and C-12 stop C are studied. A-hyperons and deuterons are found to be preferentially emitted in opposite directions. The Lambda d invariant mass spectrum of Li-6 shows a bump whose mass is3251 +/- 6 MeV/c(2). The bump mass (binding energy), width and yield are reported. The appearance of a bump is discussed in the realm of the [K3N] clustering process in nuclei. The experiment was performed with the FINUDA spectrometer at DA Phi DNE (LNF)

Measurement of the proton spectra from non-mesonic weak decay of 5ΛHe, 7ΛLi and 12ΛC

Abstract The results of a measurement of the proton spectra following the non-mesonic weak decay of 5ΛHe, 7ΛLi and 12ΛC are presented and discussed. The experiment was performed at the ( e + e − ) collider DAΦNE at Laboratori Nazionale di Frascati of INFN. It is the first measurement for 7ΛLi, and for all the spectra the lower limit on the energy of the protons is 15 MeV, never reached before. All the spectra show a similar shape, namely a peak at around 80 MeV as expected for the free Λ p → n p weak reaction, with a low energy rise that should be due to final state interactions and/or two-nucleon induced weak processes. The decay spectrum of 5ΛHe is somehow similar to the ones reported by previous measurements and theoretical calculations, but the same does not happen for the 12ΛC one.

Search for HΛ6 and HΛ7 with the (Kstop−,π+) reaction

The production of neutron rich

The A(K(stop)(-), pi(+/-)Sigma(-/+))A ' reaction on p-shell nuclei

Lambda

Correlated Λd pairs from the Kstop−A→ΛdA′ reaction

-hypernuclei via the (

Correlated Lambda d pairs from the K-(stop) A ---> Lambda d A-prime reaction

K^-_stop