K+Σ− photoproduction within an isobar model
We used an isobar model to study the K+Σ− photoproduction reaction on a neutron target with focus on the resonance region. In order to achieve a reasonable agreement with the data, we included spin-3/2 and spin-5/2 nucleon resonances in a consistent formalism together with a Δ resonance and two kaon...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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EDP Sciences
2022-01-01
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| Series: | EPJ Web of Conferences |
| Online Access: | https://www.epj-conferences.org/articles/epjconf/pdf/2022/15/epjconf_hyp2022_02009.pdf |
| _version_ | 1811308812273975296 |
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| author | Skoupil Dalibor Bydžovský Petr Cieplý Aleš Petrellis Dimitrios Zachariou Nicholas |
| author_facet | Skoupil Dalibor Bydžovský Petr Cieplý Aleš Petrellis Dimitrios Zachariou Nicholas |
| author_sort | Skoupil Dalibor |
| collection | DOAJ |
| description | We used an isobar model to study the K+Σ− photoproduction reaction on a neutron target with focus on the resonance region. In order to achieve a reasonable agreement with the data, we included spin-3/2 and spin-5/2 nucleon resonances in a consistent formalism together with a Δ resonance and two kaon resonances on top of the Born terms. The free parameters of the model were adjusted to the data from the CLAS and LEPS Collaborations on differential cross sections and photon beam asymmetry. The cornerstone of this analysis was an upgrade of the fitting method. Previously, we used only the plain χ2 minimization, which could not prevent us from overfitting the data. We, therefore, introduced a regularization method, the least absolute selection shrinkage operator (LASSO), which, together with information criteria, restricts the number of nonzero parameters and prevents us from overfitting the data. In our analysis, we arrived at two models, fit M, whose parameters were fitted with the MINUIT code only, and fit L, where we used the more advanced LASSO. Both models describe the data in a similar way and we observe only slight differences in the dσ/dΩ data description at very forward angles where the fit M is flat whereas the fit L produces two broad peaks, and in the photon beam asymmetries above 2 GeV at backward kaon angles where the fit M produces a bump. Surprisingly, no hyperon resonances are needed for the correct data description in these models. On the other hand, the N(1720)3/2+ nucleon resonance was found to be very important in both models. |
| first_indexed | 2024-04-13T09:30:57Z |
| format | Article |
| id | doaj.art-3722927807e2455b9958f58cbc521da6 |
| institution | Directory Open Access Journal |
| issn | 2100-014X |
| language | English |
| last_indexed | 2024-04-13T09:30:57Z |
| publishDate | 2022-01-01 |
| publisher | EDP Sciences |
| record_format | Article |
| series | EPJ Web of Conferences |
| spelling | doaj.art-3722927807e2455b9958f58cbc521da62022-12-22T02:52:15ZengEDP SciencesEPJ Web of Conferences2100-014X2022-01-012710200910.1051/epjconf/202227102009epjconf_hyp2022_02009K+Σ− photoproduction within an isobar modelSkoupil Dalibor0Bydžovský Petr1Cieplý Aleš2Petrellis Dimitrios3Zachariou Nicholas4Nuclear Physics Institute, Czech Academy of SciencesNuclear Physics Institute, Czech Academy of SciencesNuclear Physics Institute, Czech Academy of SciencesNuclear Physics Institute, Czech Academy of SciencesUniversity of YorkWe used an isobar model to study the K+Σ− photoproduction reaction on a neutron target with focus on the resonance region. In order to achieve a reasonable agreement with the data, we included spin-3/2 and spin-5/2 nucleon resonances in a consistent formalism together with a Δ resonance and two kaon resonances on top of the Born terms. The free parameters of the model were adjusted to the data from the CLAS and LEPS Collaborations on differential cross sections and photon beam asymmetry. The cornerstone of this analysis was an upgrade of the fitting method. Previously, we used only the plain χ2 minimization, which could not prevent us from overfitting the data. We, therefore, introduced a regularization method, the least absolute selection shrinkage operator (LASSO), which, together with information criteria, restricts the number of nonzero parameters and prevents us from overfitting the data. In our analysis, we arrived at two models, fit M, whose parameters were fitted with the MINUIT code only, and fit L, where we used the more advanced LASSO. Both models describe the data in a similar way and we observe only slight differences in the dσ/dΩ data description at very forward angles where the fit M is flat whereas the fit L produces two broad peaks, and in the photon beam asymmetries above 2 GeV at backward kaon angles where the fit M produces a bump. Surprisingly, no hyperon resonances are needed for the correct data description in these models. On the other hand, the N(1720)3/2+ nucleon resonance was found to be very important in both models.https://www.epj-conferences.org/articles/epjconf/pdf/2022/15/epjconf_hyp2022_02009.pdf |
| spellingShingle | Skoupil Dalibor Bydžovský Petr Cieplý Aleš Petrellis Dimitrios Zachariou Nicholas K+Σ− photoproduction within an isobar model EPJ Web of Conferences |
| title | K+Σ− photoproduction within an isobar model |
| title_full | K+Σ− photoproduction within an isobar model |
| title_fullStr | K+Σ− photoproduction within an isobar model |
| title_full_unstemmed | K+Σ− photoproduction within an isobar model |
| title_short | K+Σ− photoproduction within an isobar model |
| title_sort | k σ photoproduction within an isobar model |
| url | https://www.epj-conferences.org/articles/epjconf/pdf/2022/15/epjconf_hyp2022_02009.pdf |
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