Distortions of the spectra of cumulative mesons by multiscattering in nuclei

Abstract

The quantitative estimates of multiscattering distortions of momentum spectra for cumulative pions and kaons in p + A → π(K±) + X reaction at angles close to 180° are reported. The calculations for C, Al, Mo, W nuclei were made by using Monte Carlo simulation on the basis of the intranuclear cascade model. The fluctuon model of cumulative particles generation was used to give initial momentum and angular distributions of mesons. Multiscattering on the intranuclear nucleons causes the difference between the initial and observed (distorted by FSI-final state interactions in nuclei) meson spectra, which increases with increasing of atomic number. Due to the rescattering and absorption of pions and kaons by intranuclear nucleons their absolute yields decrease by about 2-5 times in the momentum range p = 0.3-1 GeV/c for medium and heavy nuclei. The relative distortions of the slope parameters of the momentum spectra are 3-10%. The correction of cross sections with account of FSI leads to the amplification of A-dependences for π, K± and to their bringing together. Taking into account FSI is also important when the ratios of particles yield of different types are considered. The K+ /K− -ratio corrections can reach a factor of about 3. Obtained values of distortions effects for cumulative reactions demonstrate evidently the necessity to account of FSI for data obtained in experiments with nuclei at momenta of reaction products <1-2 GeV/c.