Energy dependence of forward 1S0 diproton production in the pp -> pp pi0 reaction

TL;DR

This study measures the energy dependence of forward 1S0 diproton production in proton-proton collisions, revealing a broad peak around 0.6-0.8 GeV and a minimum at 1.4 GeV, with implications for understanding nucleon interactions.

Contribution

First detailed measurement of the energy dependence of forward 1S0 diproton production in pp collisions across a wide energy range.

Findings

Broad peak in cross section at 0.6-0.8 GeV likely linked to Delta(1232) excitation

Minimum in cross section observed at 1.4 GeV

Significant suppression of spin-singlet final state compared to spin-isospin partner reaction

Abstract

The pp -> {pp}_s pi0 differential cross section has been measured with the ANKE spectrometer at COSY-Juelich for seven proton beam energies T_p between 0.5 and 1.97 GeV. By selecting proton pairs with an excitation energy of less than 3 MeV it is ensured that the final {pp}_s system is in the 1S0 state. In the measured region of theta_{pp}^{cm} < 18 deg, the data reveal a forward dip for T_p =< 1.4 GeV whereas a forward peaking is seen at 1.97 GeV. The energy dependence of the forward cross section shows a broad peak in the 0.6-0.8 GeV region, probably associated with Delta(1232) excitation, and a minimum at 1.4 GeV. Some of these features are similar to those observed for the spin-isospin partner reaction, pp -> d pi+. However, the ratio of the forward differential cross sections of the two reactions shows a significant suppression of single pion production associated with a spin--singlet final nucleon pair.