Study of the reaction γp → K⁺Λ(1520) at photon energies up to 2.65 GeV

Abstract

The reaction γp → K ⁺ Λ(1520) was measured in the energy range from threshold to 2.65 GeV with the SAPHIR detector at the electron stretcher facility ELSA in Bonn. The Λ(1520) production cross-section was analyzed in the decay modes pK ⁻, $n\bar K^0$, Σ ^± π ^∓, and Λπ ⁺ π ⁻ as a function of the photon energy and the squared four-momentum transfer t . While the cross-sections for the inclusive reactions rise steadily with energy, the cross-section of the process γp → K ⁺ Λ(1520) peaks at a photon energy of about 2.0 GeV, falls off exponentially with t , and shows a slope flattening with increasing photon energy. The angular distributions in the t-channel helicity system indicate neither a K nor a K ^* exchange dominance. Rather, the rapid change of the angular distribution with energy suggests that, in addition to t -channel K and K^* exchange, amplitudes for formation of nucleon resonances in the s-channel play an important role.