V. Hepp

Investigation of short-lived isomeric states with half-lives in the μs and ms region

Abstract Unique experimental isotope assignments are presented for fifteen previously reported isomeric states with half-lives in the μsec and msec region. The isomers were produced by photonuclear reactions. The assigned activities are 49.5 μsec Sc 44m , 10.2 μsec Co 58m , 5.1 μsec Ge 69m , 17.5 μsec Ru 101m , 1.7 msec Ru 103m , 155 μsec Sn 115m , 49 μsec Hf 175m , 10.5 μsec Hf 176m , 8.3 μsec Hf 177m , 70 μsec Re 186m , 225 μsec Os 187m , 92 μsec Hg 203m , 21 μsec Hg 203m , 2.1 msec Tl 201m and 62 μsec Tl 204m . A few of these assignments have been previously suggested in the literature on a tentative basis. The isotope assignments of the following three short-lived activities remained ambiguous; 11.5 μsec Ru 100m or Tc 100m , 710 μsec Ru 101m or Tc 101m and 10.4 μsec Cd 109m or Ag 109m . In addition, a new 435 μsec isomeric state in Sc 43 and a new 18 μsec isomeric state in Hf 177 were discovered. Additional results include improved values for half-lived and gamma-ray energies for these isomeric transitions, and detailed measurements on the decay properties of some of the reported short-lived isomeric states. The multipolarities of a few of the observed transitions were determined.

On the Λp enhancement near ΣN threshold

Abstract New high statistics bubble chamber data on K−d → Λpπ− at incident K− momenta between 680 and 840 MeV/c were used to study the enhancement in the effective Λp mass near the ΣN threshold (∼2130 MeV). An analysis of the t-dependence of this effect shows that for minimum 4-momentum transfer |t| to the recoiling dibaryon system a narrow, symmetric peak with M = 2129.0 ± 0.4 MeV and Λ = 5.9 ± 1.6 MeV is observed. At larger negative t-values a broad asymmetric shoulder is seen with a sharp rise at ΣN threshold and extending to ∼2180 MeV. The broad structure is attributed to ΣN → Λp conversion. The dynamical origin of the peripherally produced narrow enhancement is discussed. The data favour strongly a 3S1 state like the deuteron. In a simple coupled channel formalism it is shown that its interpretation as a Λp resonance is acceptable, but the mass and width parameters in this formalism need not correspond to the mass and width of the observed peak. Since the enhancement is found to be very close to ∑+n threshold, an alternative explanation might be a threshold cusp in the elastic Λp scattering.

Inelastic Σ−p-interactions at low momenta☆

The total cross-sections for the two reactions Σ−p → Λn and Σ−p → Σ°n in the momentum intervall 105 ⩽pgS− ⩽ 165 MeV/c are presented. For the process Σ−p → Λn the differential cross-section and the Λ-polarization are given.

New information about the Kaon-nucleon-hyperon coupling constants g(KNΣ(1197)), g(KNΣ(1385)) and g(KNΛ(1405))

The reactions K − d→ Σ − p, K − d→ Σ − (1385)p, K − d→ Λ (1405)n and K − d→ Λ (1520)n have been studied at K − momenta between 686 and 844 MeV/ c in an experiment with the 81 cm Saclay bubble chamber at CERN. About 630 000 pictures have been analyzed. Partial and differential cross sections are presented. A one-nucleon-exchange model is used to extract the kaon-nucleon-hyperon coupling constants from these results. For g( K N Σ(1197)), g( K N Σ(1385)) and g( K N Λ(1405)) we find values which are compatible with the SU(3) predictions. The coupling constant g( K N Λ(1520)) obtained by our method agrees with that determined from the partial decay width for Λ(1520)→ K N .

Elastic σp-scattering at low momenta☆

Abstract Elastic σ ± p scattering cross sections and angular distributions are given in the momentum interval of 135–175 MeV/ c .

Radiative Σ± decays and search for neutral currents

AbstractThe decay modesΣ±→nπ±γ, Σ+→pγ,Σ+→pe+e}- were studied in the 81 cm Saclay hydrogen bubble chamber. In the radiative decayΣ±→nπ±γ only low momentum pions which stop in the chamber were accepted.We obtain the following branching ratios:(1)n

Determination of the Σ± → Λe±ν decay parameters

frac{{Gamma {text{(}}sum ^{text{ + }} to npi ^ + gamma , p_{pi + }^*< 110{text{ MeV/c)}}}}{{Gamma {text{(}}sum ^{text{ + }} to npi ^ + )}} = (2.7 pm 0.5) times 10^{ - 4} ,

Search for ΔQ=−ΔS transitions in Σ-hyperon decays

n(2)n