Nuclear transparency effect of $π^{-}$-mesons in p+$^{12}$C- and d+$^{12}$C- interactions at 4.2A GeV/c

Abstract: The use of nuclear transparency effect of \pi^{-}-mesons in proton, and deuteron induced interactions with carbon nuclei at 4.2A GeV/c, to get information about the properties of nuclear matter, is presented in this work. Half angle (\theta_{1/2}) technique is used to extract information on nuclear transparency effect. The \theta_{1/2} divides the multiplicity of charged particles into two equal parts depending on their polar angle in the lab. frame in pp interactions. Particles with angle smaller than (incone particles) and greater than (outcone particles) \theta_{1/2} are considered separate. The average values of multiplicity, momentum and transverse momentum of the \pi^{-}-mesons are analyzed as a function of a number of identified protons in an event. We observed evidences in the data which could be considered as transparency effect. For quantitative analysis, the results are compared with cascade model. The observed effects are categorized into leading effect transparency and medium effect transparency. The transparency in the latter case could be the reason of collective interactions of grouped nucleons with the incident particles.