Understanding the 1P- and 2S-wave nucleon resonances within the extended Lee-Friedrichs Model
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| Format: | Preprint |
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2026
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| _version_ | 1866914498651095040 |
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| author | Zhou, Yu-Hui Zhong, Hui-Hua Zhou, Zhi-Yong Zhong, Xian-Hui |
| author_facet | Zhou, Yu-Hui Zhong, Hui-Hua Zhou, Zhi-Yong Zhong, Xian-Hui |
| contents | We present a unified desciption of the low-lying $1P$- and $2S$-wave nucleon resonance within the framework of an extended Lee-Friedrichs scheme. By incorporating the coupled-channel dynamics between bare quark-model states and the $πN$, $πΔ$ and $ηN$ meson-baryon continua, we examine the mass shifts and structural properties of these excited states. We demonstrate that when the model parameters are calibrated to match the $1P$-wave spectrum and their widths, the pole associated with the bare $2S$ state is naturally shifted downward to the mass region of physical Roper resonance--$N(1440)$, thereby offering a dynamical explanation for the long-standing level-inversion problem. An approximate analysis of compositeness and elementariness reveals that the Roper resonance contains a significant meson-baryon continuum states, consistent with the picture of a bare core heavily dressed by meson-baryon cloud. Simultaneously, the pole positions and properties of five $1P$-wave resonances--$N(1535)$, $N(1650)$, $N(1520)$, $N(1700)$ and $N(1675)$ are successfully reproduced. Our results highlight the essential role of coupled-channel effects in shaping the nucleon spectrum and provide a consistent microscopic insight into the interplay between internal quark degrees of freedom and external hadronic fields. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_21697 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Understanding the 1P- and 2S-wave nucleon resonances within the extended Lee-Friedrichs Model Zhou, Yu-Hui Zhong, Hui-Hua Zhou, Zhi-Yong Zhong, Xian-Hui High Energy Physics - Phenomenology We present a unified desciption of the low-lying $1P$- and $2S$-wave nucleon resonance within the framework of an extended Lee-Friedrichs scheme. By incorporating the coupled-channel dynamics between bare quark-model states and the $πN$, $πΔ$ and $ηN$ meson-baryon continua, we examine the mass shifts and structural properties of these excited states. We demonstrate that when the model parameters are calibrated to match the $1P$-wave spectrum and their widths, the pole associated with the bare $2S$ state is naturally shifted downward to the mass region of physical Roper resonance--$N(1440)$, thereby offering a dynamical explanation for the long-standing level-inversion problem. An approximate analysis of compositeness and elementariness reveals that the Roper resonance contains a significant meson-baryon continuum states, consistent with the picture of a bare core heavily dressed by meson-baryon cloud. Simultaneously, the pole positions and properties of five $1P$-wave resonances--$N(1535)$, $N(1650)$, $N(1520)$, $N(1700)$ and $N(1675)$ are successfully reproduced. Our results highlight the essential role of coupled-channel effects in shaping the nucleon spectrum and provide a consistent microscopic insight into the interplay between internal quark degrees of freedom and external hadronic fields. |
| title | Understanding the 1P- and 2S-wave nucleon resonances within the extended Lee-Friedrichs Model |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2601.21697 |