G. Piragino

Antiproton Annihilation on Ag/Br Nuclei

The charged-prong multiplicity distribution of (, Ag/Br) annihilation events has been measured in photographic emulsion at incoming momenta of 500, 400, 300 MeV/c and at rest. In the light of INC model predictions, the results show that the low-multiplicity events are produced mainly by nuclear surface annihilations and the higher multiplicity events can be interpreted as annihilations occurred in deep nuclear matter.

Restriction on amount of antimatter in the early universe from\(\bar p^{ - 4} \)He reaction data-4He reaction data

SummaryA limit on the possible amount of antimatter in the early universe has been deduced fromnn

Elastic backward scattering of positive pions from 12C at 23, 29 and 35 MeV

bar p^{ - 4}

Escape of charged particles at stopping annihilation of antiprotons in the heavy nuclei of nuclear photoemulsion

nnHe reaction data obtained at 180 MeV.

New Improvement in Track Localization in Selfshunted Helium Streamer Chamber

Abstract In this article are displayed tests on the digitization and the reconstruction of nuclear events detected in a self-shunted streamer chamber, using a television system. The light emission from such events is enough to be detected without image intensifier, but the high dynamic range of the luminosity imposes the use of a multithreshold digitization. As a consequence, a software method is implemented to find the effective profile of the tracks.

Spin asymmetry A1(d) and the spin-dependent structure function g1(d) of the deuteron at low values of x and Q**2

Abstract The elastic scattering of positively charged pions at 23, 29 and 35 MeV scattering from 12 C has been measured at 161°, 168° and 176° scattering angles. The new measurements give a backward descending behaviour to the existing angular distribution at 30 MeV. The complete angular distribution is compared to a calculation based upon the only Ericson-Ericson-Lorentz-Lorenz effect and to the theoretical models of Landau and Thomas and of Stricker et al. for low-energy pion-nucleus scattering.

Light hyperfragments production in (p)over-bar annihilation at rest on nuclear emulsion

Abstract The energy distribution and polarization of photoneutrons from 51V, natural nickel, 55Mn and 59Co have been measured. The targets were irradiated with the γ-ray beam (Eγ max = 85 MeV) of the Turin synchrotron, and the photoneutrons were detected with a diffusion cloud chamber filled with helium. The usual interpretation of the photoneutron spectra in terms of evaporation with a small contribution of direct reaction is not in agreement with the experimental results for neutron energies lower than 1.5 MeV. Qualitative discussion of other models is given to explain the experimental indication of photoneutron polarization found for 55Mn and 59Co.

Localization of Charged Particle Tracks in a Selfshunted Helium Streamer Chamber

Abstract “Rare” annihilation channels for antiprotons stopping on heavy (Ag, Br) nuclei of photoemulsion, have been sought; 4872 stops of antiprotons on photoemulsion nuclei are analysed. Events of formation and decay of the hyperfragment Λ4H, escape of 8He and 8Li nuclei, one-prong stars with the mean range 79.5±5.1 μm of secondary slow “b” particles are found among the annihilation stars at p capture on nuclei (Ag, Br). The lower limits for the production probability of Λ4H and 8 He , 8 Li nuclei per antiproton stopping in the nuclei (Ag, Br) are W Λ 4 H ⩾2×10 −4 and W 8 He , 8 Li =(1.3±0.6)×10 −3 . The branching ratio for the production of one-prong stars with the secondary “b” particles is at least (1.3±0.6)×10−3. Possible mechanisms for a production of these events in annihilation processes are considered.