Study of azimuthal correlations in the target fragmentation region in p, d, He, C+C, Ta and C+Ne, Cu collisions at momenta of 4.2, 4.5 and 10 A GeV/c

Abstract

Azimuthal correlations between the same type of particles (protons or pions) in the target fragmentation region was studied in d, He, C+C, Ta (4.2A GeV/c, C+Ne, Cu (4.5A GeV/c) and p+C, Ta (10 GeV/c) interactions. The data were obtained from the SKM-200-GIBS streamer chamber and from the Propane Bubble Chamber (PBL-500) systems utilized at JINR. Study of multiparticle azimuthal correlations offers unique information about space-time evolution of the interactions. Azimuthal correlations were investigated by using correlation function $ C(\Delta\phi) = \mathrm{d} N/\mathrm{d} (\Delta\phi)$ , where $ \Delta\phi$ represents the angle between the sums of transverse momenta vectors for particles emitted in the forward and backward hemispheres. For protons “back-to-back” (“negative”) azimuthal correlations were observed in the above-mentioned interactions. The absolute values of the correlation coefficient $ \vert\xi\vert$ --the slope parameter of $ C(\Delta\phi)$, strongly depend on the mass number of the target ($ A_{T}$) nuclei in the nucleon-nucleus and nucleus-nucleus collisions. Namely, $ \vert\xi\vert$ decreases with increase of $ A_T$ in p+C and p+Ta collisions, while $ \vert\xi\vert$ initially decreases from d+C to C+Ne and then almost does not change with increase of $ A_P$, $ A_T$ in (d+He)Ta, C+Cu and C+Ta collisions. For pions “back-to-back” correlations were obtained for light targets (C, Ne), and “side-by-side” (“positive”) correlations for heavy targets (Cu, Ta). The $ \vert\xi\vert$ insignificantly changes with increase of the momenta per nucleon and almost does not change with increase of $ A_P$ and $ A_T$. Models used for description of the data, the Ultra relativistic Quantum Molecular Dynamic (UrQMD) and Quark-Gluon String Model (QGSM), satisfactorily describe the obtained experimental results.