Analysis of the data on differential cross sections and spin density matrix elements for $γp \to ρ^0 p$
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| Format: | Preprint |
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2025
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| author | Wang, Ai-Chao Wei, Neng-Chang Huang, Fei |
| author_facet | Wang, Ai-Chao Wei, Neng-Chang Huang, Fei |
| contents | The newly published data on spin density matrix elements from the GlueX Collaboration, along with the previously released differential cross-section data from the CLAS Collaboration and the other two experiments for the $γp \to ρ^0 p$ reaction, are systematically investigated using an effective Lagrangian approach within the tree-level Born approximation. The model combines contributions from $t$-channel meson exchanges ($π$, $η$, and $f_2$), $s$-channel nucleon ($N$) and nucleon resonance ($N^\ast$) exchanges, $u$-channel $N$ exchange, and a generalized contact term to construct the scattering amplitudes. Regge propagators are employed for $t$-channel amplitudes to incorporate the contributions from mesons with various spins lying on the same trajectories. The analysis shows that the background contributions, dominated by the $f_2$-trajectory exchange, provide a satisfactory description of the data in the high-energy and forward-angle regions. The inclusion of specific nucleon resonances, such as $N(2100)1/2^{+}$, $N(2060)5/2^{-}$, or $Δ(2000)5/2^{+}$, significantly improves the description of the differential cross-section data at near-perpendicular scattering angles in the low-energy region. Predictions of photon beam and target nucleon asymmetries are provided, offering valuable insights to discriminate reaction mechanisms when corresponding data become available in the future. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_11499 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Analysis of the data on differential cross sections and spin density matrix elements for $γp \to ρ^0 p$ Wang, Ai-Chao Wei, Neng-Chang Huang, Fei High Energy Physics - Phenomenology The newly published data on spin density matrix elements from the GlueX Collaboration, along with the previously released differential cross-section data from the CLAS Collaboration and the other two experiments for the $γp \to ρ^0 p$ reaction, are systematically investigated using an effective Lagrangian approach within the tree-level Born approximation. The model combines contributions from $t$-channel meson exchanges ($π$, $η$, and $f_2$), $s$-channel nucleon ($N$) and nucleon resonance ($N^\ast$) exchanges, $u$-channel $N$ exchange, and a generalized contact term to construct the scattering amplitudes. Regge propagators are employed for $t$-channel amplitudes to incorporate the contributions from mesons with various spins lying on the same trajectories. The analysis shows that the background contributions, dominated by the $f_2$-trajectory exchange, provide a satisfactory description of the data in the high-energy and forward-angle regions. The inclusion of specific nucleon resonances, such as $N(2100)1/2^{+}$, $N(2060)5/2^{-}$, or $Δ(2000)5/2^{+}$, significantly improves the description of the differential cross-section data at near-perpendicular scattering angles in the low-energy region. Predictions of photon beam and target nucleon asymmetries are provided, offering valuable insights to discriminate reaction mechanisms when corresponding data become available in the future. |
| title | Analysis of the data on differential cross sections and spin density matrix elements for $γp \to ρ^0 p$ |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2502.11499 |