The reaction n p -> d π⁰ measured at CLAS as a probe of Nucleon-Delta Attraction

The CLAS detector setup, previously located in Hall B of Jefferson Lab, has been used to investigate secondary scattering reactions. In the first step, neutrons are produced via the photoproduction reaction γ p -> π⁺ n, which is tagged via detection of the π⁺ in CLAS. The neutrons then propagate through the 40-cm long liquid hydrogen target, and some of these neutrons undergo a secondary scattering reaction. The exclusive reaction n p -> d π⁰ is seen via detection of a deuteron in CLAS, coincident with the tagged π⁺. Cross sections from this reaction show a resonant peaking at a center-of-mass energy, W, corresponding to a resonant nucleon-delta system, which decays to a bound deuteron and a neutral pion. These data provide new information that can be used to extract details of the nuclear force in the N-Δ system.