Measurement of spin density matrix elements in the reaction yp ->K^+L(1520) using CLAS at Jefferson Lab

Abstract

This work presents a measurement of the spin density matrix elements of the Λ(1520) in the reac- tion γp → K + Λ(1520). The elements measured are ρ 11 , Re( ρ 31 ), and Re( ρ 3 − 1 ). The spin density matrix elements, together with differential cross sections, can provide information about the pro- duction mechanism of the Λ(1520). The data used is from the g11a run period, collected at the CLAS detector at Jefferson Lab. The Λ(1520) was detected via the pK − decay mode, and three topologies, p ( K + ) K − , pK + ( K − ), and pK + K − , were studied to maximize kinematic coverage. The measurements cover the center-of-mass energy range from 2.04 GeV to 2.82 GeV and almost the full range of the production angle. These are the first measurements of these quantities over much of this kinematic region, and the large dataset allows us to use much finer binning than all previous measurements. These measurements do not match predictions from existing models and can provide the basis for a better theoretical understanding of Λ(1520) photoproduction.