Evidence for Δ(2200)7/2− from photoproduction and consequence for chiral-symmetry restoration at high mass

Abstract

We report a partial-wave analysis of new data on the double-polarization variable E for the reactions γp→π+n and γp→π0p and of further data published earlier. The analysis within the Bonn–Gatchina (BnGa) formalism reveals evidence for a poorly known baryon resonance, the one-star Δ(2200)7/2−. This is the lowest-mass Δ⁎ resonance with spin-parity JP=7/2−. Its mass is significantly higher than the mass of its parity partner Δ(1950)7/2+ which is the lowest-mass Δ⁎ resonance with spin-parity JP=7/2+. It has been suggested that chiral symmetry might be restored in the high-mass region of hadron excitations, and that these two resonances should be degenerate in mass. Our findings are in conflict with this prediction.

Keywords

• Partial-wave analysis
• Baryon resonance
• Photoproduction
• Chiral symmetry