The non-mesonic decay of helium hypernuclei

Hypernuclear physics legacy and heritage of Dick Dalitz

“…A more conclusive proof for this suggestion would come from the observation of back-to-back Λ 3 He pairs in the two-body decay 4 Σ He → Λ+ 3 He. The branching ratio for this decay relative to the inclusive ΛX decay rate is perhaps a few percent, as may be argued by analogy with the approximately 8%(5%) branching ratio measured for the nonmesonic decay 4 Λ He( 5 Λ He) → n+ 3 He( 4 He) relative to the inclusive π − decay rate of 4 Λ He( 5 Λ He) [63,64]. Irrespective of whether or not the above conjecture of 4 Σ He production is correct for the FOPI-Detector GSI experiments, it would be a wise practice forK-nuclear bound state searches in heavy ion collisions to look first for known hypernuclear signals in order to determine their production rates as calibration and normalization standards.…”

Strangeness nuclear physics: a critical review on selected topics

“…The existing observations of two-body NMWD of Hypernuclei are very scarce and date back to bubble chamber [169] ≤ 0.24 4 Λ He, n and p spectra KEK-E508 [25] 0.27 ± 0.13 0.29 ± 0.13 12 Λ C, nn and np spectra FINUDA [26] 0.24±0.10 A =5-16, p spectra FINUDA [27] 0.21 ± 0.07stat +0.03 −0.02 sys A =5-16, np spectra and emulsion experiments [248][249][250]; in particular, reaction (67) has not yet been observed. The only existing calculation for the 4 Λ He two-body NMWD rates was performed long ago by Ref.…”

Exchange reactions with Dick Dalitz

“…Coremans et al [30], by combining emulsion data on helium hypernuclei with the bubble chamber result for 4 Λ He, were able to determine Q − for 5 Λ He but only after making a large correction for the undetectable decay mode 3 He + n + n. Values for Q − for Λ Be and 11 Λ B were given by Montwill et al [20] whereas a ballpark number was given for heavy spallation hypernuclei by Lagnaux et al [31]. These results are summarised in Table 3.…”

“…Moreover, the emulsion experiment, despite its limited statistics, does have the advantage that the protons in the spectrum are seen to come from hypernuclear decays. It should also be remarked that a considerable number, certainly in excess of 10%, of the so-called protons are in fact deuterons and tritons [30,36] Coremans et al [30] studied the non-mesonic decays of 5 Λ He and found the following partial decay rates with respect to the π − -mesonic rate for those decays which involve at most one neutron and these are presented in Table 4.…”