Evaluation of the E2/M1 ratio in the $N\to Δ(1232)$ transition from the $ \vecγ \vec{p} \to p π^0 $ reaction
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| Format: | Preprint |
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2023
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| author | Mornacchi, E. Pedroni, P. Afzal, F. Wunderlich, Y. Abt, S. Achenbach, P. Annand, J. R. M. Arends, H. J. Bashkanov, M. Biroth, M. Beck, R. Borisov, N. Braghieri, A. Briscoe, W. J. Cividini, F. Collicott, C. Denig, A. Dolzhikov, A. S. Downie, E. Fegan, S. Fix, A. Ghosal, D. Gorodnov, I. Gradl, W. Gurevich, D. Heijkenskjoeld, L. Hornidge, D. Huber, G. M. Kashevarov, V. L. Kay, S. J. D. Korolija, M. Lazarev, A. Livingston, K. Lutterer, S. MacGregor, I. J. D. Manley, D. M. Martel, P. P. Miskimen, R. Mocanu, M. Mullen, C. Neganov, A. Neiser, A. Oberle, M. Ostrick, M. Otte, P. B. Paudyal, D. Powell, A. Rostomyan, T. Sokhoyan, V. Spieker, K. Steffen, O. Strakovsky, I. I. Thiel, M. Thomas, A. Usov, Yu. A. Wagner, S. Watts, D. P. Werthmueller, D. Wettig, J. Witthauer, L. Wolfes, M. Zachariou, N. |
| author_facet | Mornacchi, E. Pedroni, P. Afzal, F. Wunderlich, Y. Abt, S. Achenbach, P. Annand, J. R. M. Arends, H. J. Bashkanov, M. Biroth, M. Beck, R. Borisov, N. Braghieri, A. Briscoe, W. J. Cividini, F. Collicott, C. Denig, A. Dolzhikov, A. S. Downie, E. Fegan, S. Fix, A. Ghosal, D. Gorodnov, I. Gradl, W. Gurevich, D. Heijkenskjoeld, L. Hornidge, D. Huber, G. M. Kashevarov, V. L. Kay, S. J. D. Korolija, M. Lazarev, A. Livingston, K. Lutterer, S. MacGregor, I. J. D. Manley, D. M. Martel, P. P. Miskimen, R. Mocanu, M. Mullen, C. Neganov, A. Neiser, A. Oberle, M. Ostrick, M. Otte, P. B. Paudyal, D. Powell, A. Rostomyan, T. Sokhoyan, V. Spieker, K. Steffen, O. Strakovsky, I. I. Thiel, M. Thomas, A. Usov, Yu. A. Wagner, S. Watts, D. P. Werthmueller, D. Wettig, J. Witthauer, L. Wolfes, M. Zachariou, N. |
| contents | A new data set for the helicity-dependent differential cross section of the single-meson photoproduction reaction $γp \to p π^{0}$ was obtained for the photon energy interval 150-400 MeV. The experiment was performed at the A2 tagged photon facility of the Mainz Microtron MAMI using a circularly polarized photon beam and a longitudinally polarized proton target. The reaction products were detected with the large acceptance Crystal Ball/TAPS calorimeter covering 97\% of the full solid angle. These new results, obtained with a fine energy and polar angle binning, greatly increase both the existing quantity and quality of the data available for this observable. A moment analysis, based on a finite expansion in Legendre polynomials, was applied to these data by using a bootstrap-based fitting method to correctly account for their systematic uncertainties. From the resulting decomposition of the differential cross sections, the $E2/M1$ ratio for the $N\to Δ(1232)$ transition was determined to be $[-2.38 \pm 0.16{\hbox{ (stat.+sys.)}} \pm 0.10 {\hbox{ (model)}}] \%$. Combining this value with previous results also allowed us to evaluate the most precise available estimate of the $E2/M1$ ratio to be used for all further reference and model comparisons. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2312_08211 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Evaluation of the E2/M1 ratio in the $N\to Δ(1232)$ transition from the $ \vecγ \vec{p} \to p π^0 $ reaction Mornacchi, E. Pedroni, P. Afzal, F. Wunderlich, Y. Abt, S. Achenbach, P. Annand, J. R. M. Arends, H. J. Bashkanov, M. Biroth, M. Beck, R. Borisov, N. Braghieri, A. Briscoe, W. J. Cividini, F. Collicott, C. Denig, A. Dolzhikov, A. S. Downie, E. Fegan, S. Fix, A. Ghosal, D. Gorodnov, I. Gradl, W. Gurevich, D. Heijkenskjoeld, L. Hornidge, D. Huber, G. M. Kashevarov, V. L. Kay, S. J. D. Korolija, M. Lazarev, A. Livingston, K. Lutterer, S. MacGregor, I. J. D. Manley, D. M. Martel, P. P. Miskimen, R. Mocanu, M. Mullen, C. Neganov, A. Neiser, A. Oberle, M. Ostrick, M. Otte, P. B. Paudyal, D. Powell, A. Rostomyan, T. Sokhoyan, V. Spieker, K. Steffen, O. Strakovsky, I. I. Thiel, M. Thomas, A. Usov, Yu. A. Wagner, S. Watts, D. P. Werthmueller, D. Wettig, J. Witthauer, L. Wolfes, M. Zachariou, N. Nuclear Experiment A new data set for the helicity-dependent differential cross section of the single-meson photoproduction reaction $γp \to p π^{0}$ was obtained for the photon energy interval 150-400 MeV. The experiment was performed at the A2 tagged photon facility of the Mainz Microtron MAMI using a circularly polarized photon beam and a longitudinally polarized proton target. The reaction products were detected with the large acceptance Crystal Ball/TAPS calorimeter covering 97\% of the full solid angle. These new results, obtained with a fine energy and polar angle binning, greatly increase both the existing quantity and quality of the data available for this observable. A moment analysis, based on a finite expansion in Legendre polynomials, was applied to these data by using a bootstrap-based fitting method to correctly account for their systematic uncertainties. From the resulting decomposition of the differential cross sections, the $E2/M1$ ratio for the $N\to Δ(1232)$ transition was determined to be $[-2.38 \pm 0.16{\hbox{ (stat.+sys.)}} \pm 0.10 {\hbox{ (model)}}] \%$. Combining this value with previous results also allowed us to evaluate the most precise available estimate of the $E2/M1$ ratio to be used for all further reference and model comparisons. |
| title | Evaluation of the E2/M1 ratio in the $N\to Δ(1232)$ transition from the $ \vecγ \vec{p} \to p π^0 $ reaction |
| topic | Nuclear Experiment |
| url | https://arxiv.org/abs/2312.08211 |