The photoproduction of strangeness in gammaP → Delta K+pi+pi-- with CLAS at Jefferson Lab

The available information about strange excited mesons is limited and most of the observed states have been reported but not confirmed. While the low mass region (1.0 - 1.5 GeV) has been extensively studied in the past and states such as the K1(1270), K1(1400), and K*(1410) have been confirmed by a handful of experiments, little is known about the spin-parity structure of resonances in the higher K+ pi+ pi- mass region (1.5-2.0 GeV). Past experiments have used hadron beams to gain access to the K+ pi+ pi- system, and have provided extensive information about strange states that made mapping their spectrum possible. Except for the K*(892), none of the excited strange states has been photoproduced before. We perform a partial wave analysis on a photoproduced K+ pi+ pi- system produced off a Lambda baryon using the CLAS detector at Jefferson Lab. Using a photon beam incident of a liquid hydrogen target, we are able to reconstruct 16K events of the gamma p -> Lambda K+ pi+ pi- topology. Results from initial data selection confirmed the dominance of two decay modes for a K+ pi+ pi- resonance: the K*(892)pi+ and the rho(770)K+. A PWA was carried out in the helicity formalism using the reflectivity basis in the isobar model to parametrize the decay amplitudes of the resonances. Resonating structures are found in the 1+S wave primarily coupling to K*(892)pi+ with a mass of 1.35 GeV/c2 and to rho(770)K with a lower mass structure around 1.33 GeV/c2 and a higher mass resonance around 1.73 GeV/c2. The 1-P also exhibited a significant resonating behavior with a mass of 1.43 GeV/c2 coupling primarily to the K*(892)pi+ decay mode. Also observed, an enhancement around 1.49 GeV/c2 in the 2+D wave strongly coupling to K*2 (1430)pi+, and an enhancement in the 2-S wave around 1.76 GeV/c2 coupling primarily to K*2 (1430)pi+.