Alternative experimental evidence for chiral restoration in excited baryons

Abstract

Given existing empirical spectral patterns of excited hadrons it has been suggested that chiral symmetry is approximately restored in excited hadrons at zero temperature/density (effective symmetry restoration). If correct, this implies that mass generation mechanisms and physics in excited hadrons is very different as compared to the lowest states. One needs an alternative and independent experimental information to confirm this conjecture. Using very general chiral symmetry arguments it is shown that strict chiral restoration in a given excited nucleon forbids its decay into the N πchannel. Hence those excited nucleons which are assumed from the spectroscopic patterns to be in approximate chiral multiplets must only "weakly" decay into the N πchannel, (f_{N^*Nπ}/f_{NNπ})^2 << 1. However, those baryons which have no chiral partner must decay strongly with a decay constant comparable with f_{NNπ}. Decay constants can be extracted from the existing decay widths and branching ratios. It turnes out that for all those well established excited nucleons which can be classified into chiral doublets N_+(1440) - N_-(1535), N_+(1710) - N_-(1650), N_+(1720) - N_-(1700), N_+(1680) - N_-(1675), N_+(2220) - N_-(2250), N_+(?) - N_-(2190), N_+(?) - N_-(2600), the ratio is (f_{N^*Nπ}/f_{NNπ})^2 ~ 0.1 or much smaller for the high-spin states. In contrast, the only well established excited nucleon for which the chiral partner cannot be identified from the spectroscopic data, N(1520), has a decay constant into the Nπchannel that is comparable with f_{NNπ}. This gives an independent experimental verification of the chiral symmetry restoration scenario.

arXiv comment4 pp. A new footnote with an alternative proof of impossibility of parity doublet decay into pi + N is added. To appear in Phys. Rev. Lett

References in corpus (17)

• Chiral Symmetry of Baryons
• Nucleon Resonance Transition Couplings to Vector Mesons
• Restoration of chiral and $U(1{)}_A$ symmetries in excited hadrons
• Parity doublets and chiral symmetry restoration in baryon spectrum
• Chiral Symmetry Realization for Even- and Odd-parity Baryon Resonances
• Chiral multiplets versus parity doublets in highly excited baryons
• Does one observe chiral symmetry restoration in baryon spectrum?
• Chiral multiplets of excited mesons
• SU(2)_L * SU(2)_R and U(1)_A restorations high in the hadron spectrum and what it tells us about
• Parity Doubling Among the Baryons
• Chiral symmetry restoration and the string picture of hadrons
• Chiral symmetry patterns of excited mesons with the Coulomb-like linear confinement
• Parity Doubling and SU(2)_L x SU(2)_R Restoration in the Hadron Spectrum
• Chiral and U(1)_A restorations high in the hadron spectrum, semiclassical approximation and large N_c
• Effective restoration of chiral symmetry in excited mesons
• Chiral QCD: Baryon dynamics
• On Goldstone bosons decoupling from high-lying hadrons

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