Several examples of the production of electron-positron pairs were found in the interactions with emulsion of fragments resulting from the collision of 12 C and 22 Ne projectiles of 4.5 and 4.2 GeV/c per nucleon, respectively with emulsion nuclei. Taking into account the effect of the background, the results seem to suggest the existence of new neutral boson with mass 1.60 ±0.59 MeV/c and a lifetime (0.15±0.01)xl0~1 4 sec.

Photoemulsions were irradiated to 8.4, 9.6, 69 GeV/c protons and 4.2 GeV/c/nucleon l zC ions. Large stars, having a number of heavily ionizing particles n,>28, were selected for this study. These events represent the catastrophic destruction of AgBr emulsion nuclei. Multiplicity, angular and energy distributions of particles, produced in this case, were studied at different momenta and for different incident particles. It was shown that the products of complete destruction of heavy nuclei are nearly individual nucleons. The probability of this phenomenon increases with the projectile mass number. About half of nuclear matter is knocked out of the target nucleus with energy higher than 30 MeV/nucleon. The average multiplicity of s-particles ffs is weakly dependent on the target nucleus mass number whereas the average multiplicity of g-particles ~g is strongly dependent on it. The modified pre-equilibrium model gives a satisfactory description for the energy spectrum of the emitted slow protons.

An anomalously short mean free path of 10.93 ±2.00 cm is found for secondary Z = 2 fragments of 4.5^4-GeV/c 12 C projectiles at distances D ^ 2.5 cm from their production in nuclear emulsions. The largest contribution to this anomalous short-mean-free-path component comes from N h = 0 interactions of 12 C in emulsion.

No abstract

The multiplicity and pseudo-rapidity distributions of hadrons produced in Central collisions of 4.1A GeVc-' =Ne nuclei in nuclear emulsion are studied. The KNO scaled multiplicity distribution of the produced hadrons is compared with the predicted distributions according to the Lund model, dual parton model (DPM) and the negative binomial Ian,. The negative binomial method seems to ofer a hetter representation of the experimental data at 4.1 A CeV c-'. The energy density is calculated according to the Bjorken model and found to be less than the estimated energy density required for the transformation into the quark-gluon plasma phase.