A-Dependence of the Relative Yields of Neutral Mesons in Pion–Nucleus Interactions at Plab = 7 GeV/c in the Hyperon-M Experiment

Abstract

The measurement results \(A\)-dependences of the relative yields of neutral mesons \({{\pi }^{0}}\), \(\omega (782)\), \({{f}_{2}}(1270)\) and \(K_{S}^{0}\) in relation to \(\eta \)-meson produced in \({{\pi }^{ + }}A\)-interactions at a momentum of 7 GeV/c are presented. The measurements were performed on six nuclear targets (Be, C, Al, Cu, Sn, Pb) in the Hyperon-M experiment at the U-70 accelerator complex. Mesons were identified by their photon decays using the LGD2 wide-aperture electromagnetic calorimeter. The yield ratios of the mesons under study to the yield \(\eta \)-mesons were measured in the beam fragmentation region (\({{x}_{F}} > 0.6\) in the center of mass system \(\pi N\)-reactions). It is shown that the relative yields of non-strange mesons (\({{\pi }^{0}}\), \(\omega (782)\), \({{f}_{2}}(1270)\)) decrease with increasing the mass number of the target nucleus. At the same time, the yield ratio \(K_{S}^{0}{\text{/}}\eta \) demonstrates a steady statistically significant increase with increasing \(A\). The obtained results are important for the study of hadron–nucleus interactions at intermediate energies, including testing and fine-tuning transport models such as GiBUU, PHSD, UrQMD, SMASH, regarding the influence of collective effects in the nucleus on the production of mesons with different quark compositions.