Speaker
Description
The investigation of N and Δ excitations, as well as the quest for missing baryonic resonances, remains a central challenge in today’s hadron spectroscopy. Traditional approaches utilizing unpolarized γp cross section measurements are limited in their spectroscopic utility due to the broad width of baryonic intermediate states and their consequent overlap in the mass spectrum. An alternative avenue for exploration lies in the study of polarization variables, which are intimately linked to partial wave amplitudes, offering valuable insights into amplitude interference. This pursuit is significantly enhanced by experimental setups featuring both polarized beams and targets, which provide measurements of cross section asymmetries in different relative polarization states. The g14 experiment, conducted at CLAS (Jefferson Lab, USA) during 2011-2012, provided such conditions, employing a circularly polarized photon beam (momentum range: 0.6-2.3 GeV/c) interacting with a longitudinally polarized HD target. This presentation will discuss the results of beam-helicity and target-spin asymmetry measurements in two-pion photoproduction from these data. The two-pion channel, being the primary contributor to the total cross section, can potentially provide useful information for the investigation of intermediate states; in particular, about those located in the second resonance mass region, whose decay lead to an exclusive final state comprising two pions and a nucleon. The latest findings will be showcased and compared against previous results from CLAS and other experiments.
