Properties of the Λ(1520) resonance from high-precision electroproduction data

High-resolution spectrometer measurements of the reaction H(e,e′K+)X at small Q2 are used to extract the mass and width of the Λ(1520). We investigate the influence of various assumptions used in the extraction. The width appears to be more sensitive to the assumptions than the mass. To reach a width uncertainty about 1 MeV or better, one needs to know the structure of the non-resonant background. Based on the new Jefferson Lab Hall A data, our final values for the Breit-Wigner parameters are M=1520.4±0.6(stat.)±1.5(syst.) MeV, Γ=18.6±1.9(stat.)±1(syst.) MeV. We also estimate, for the first time, the pole position for this resonance and find that both the pole mass and width seem to be smaller than their Breit-Wigner values.