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Alternative experimental evidence for chiral restoration in excited baryons
- Publication Year :
- 2007
-
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 \pi channel. Hence those excited nucleons which are assumed from the spectroscopic patterns to be in approximate chiral multiplets must only "weakly" decay into the N \pi channel, (f_{N^*N\pi}/f_{NN\pi})^2 << 1. However, those baryons which have no chiral partner must decay strongly with a decay constant comparable with f_{NN\pi}. 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^*N\pi}/f_{NN\pi})^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 N\pi channel that is comparable with f_{NN\pi}. This gives an independent experimental verification of the chiral symmetry restoration scenario.<br />Comment: 4 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
- Subjects :
- Particle physics
Nuclear Theory
High Energy Physics::Lattice
Spontaneous symmetry breaking
Hadron
FOS: Physical sciences
General Physics and Astronomy
01 natural sciences
High Energy Physics - Experiment
Nuclear Theory (nucl-th)
High Energy Physics - Experiment (hep-ex)
Particle decay
High Energy Physics - Phenomenology (hep-ph)
0103 physical sciences
Nuclear Experiment (nucl-ex)
Exponential decay
010306 general physics
Nuclear Experiment
Physics
010308 nuclear & particles physics
High Energy Physics::Phenomenology
Vertex function
Baryon
High Energy Physics - Phenomenology
Excited state
Atomic physics
Nucleon
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....6258625c817cfcdd1259c54011c35bae