Multiplicity characteristics of the produced shower particles in backward direction-target and projectile dependence

Abstract

In the present paper a detailed investigation of the multiplicity distribution of the produced shower particles in the backward hemisphere ( $$\theta _{\mathrm {Lab}} \ge 90^{\circ }$$ ) in nuclear emulsion track detector has been carried out. The present study involves interactions of $$^{\mathrm {16}}\hbox {O}$$ and $$^{\mathrm {32}}\hbox {S}$$ projectiles with CNO, AgBr and composite emulsion target at 4.5 AGeV/c. We have compared our results with the results obtained from the analysis of modified Fritiof model. Present study reveals that the production of single shower particle is the most dominant production mode of shower particles in the backward direction. This probability increases with the increase of target mass. The percentage of events having backward shower particles remains almost independent of the projectile beam. But it increases with the increase of target size. Average multiplicity of the shower particles in the backward direction reflects a weaker dependence on the mass number of the projectile beam. Multiplicity distribution of backward shower particles for both experimental and modified Fritiof model can be described by an expression $$\mathrm {P}_{\mathrm {N}} = {\mathrm {P}_{\mathrm {s}}\mathrm {N}_{\mathrm {B}}}^{-{\uplambda }_{\mathrm {B}}}$$ . The fitting parameter $${\uplambda }_{\mathrm {B}}$$ decreases as the target size increases. The decay constant has lower value for the heavier projectile. Higher order multiplicity moments and scaled variance of multiplicity distribution for the backward shower particles showed strong target dependence. Multiplicity distributions of the backward shower particles violate KNO scaling law. Modified Fritiof model failed to reproduce the various features of the multiplicity distribution.