First measurement using elliptically polarized photons of the double-polarization observable E for γp→pπ0 and γp→nπ+

Afzal, F. et al. (2024) First measurement using elliptically polarized photons of the double-polarization observable E for γp→pπ0 and γp→nπ+. Physical Review Letters, 132(12), 121902. (doi: 10.1103/PhysRevLett.132.121902) (PMID:38579200)

Abstract

We report the measurement of the helicity asymmetry E for the pπ0 and nπ+ final states using, for the first time, an elliptically polarized photon beam in combination with a longitudinally polarized target at the Crystal Ball experiment at MAMI. The results agree very well with data that were taken with a circularly polarized photon beam, showing that it is possible to simultaneously measure polarization observables that require linearly (e.g., G) and circularly polarized photons (e.g., E) and a longitudinally polarized target. The new data cover a photon energy range 270–1400 MeV for the pπ0 final state (230–842 MeV for the nπ+ final state) and the full range of pion polar angles, θ, providing the most precise measurement of the observable E. A moment analysis gives a clear observation of the pη cusp in the pπ0 final state.

• Item Type: Articles
• Additional Information: This work was supported by Schweizerischer Nationalfonds (No. 200020-156983, No. 132799, No. 121781, No. 117601), Deutsche Forschungsgemeinschaft (No. SFB443, No. SFB1044, No. SFB/TR16), the INFN-Italy, the European Community-Research Infrastructure Activity under FP7 programme (Hadron Physics, grant agreement No. 227431), the U.K. Science and Technology Facilities Council Grants No. ST/J000175/1, No. ST/G008604/1, No. ST/G008582/1, No. ST/J00006X/1, No. ST/V001035/1, No. ST/V002570/1, No. ST/P004385/2, No. ST/T002077/1, and No. ST/L00478X/2, the Natural Sciences and Engineering Research Council (NSERC, FRN: SAPPJ-2015-00023), Canada. This material is based upon work also supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics Research Division, under Awards No. DE-FG02-99-ER41110, No. DE-FG02-88ER40415, No. DE-FG02-01-ER41194, No. DE-SC0014323, and No. DE-SC0016583 and by the National Science Foundation, under Grants No. PHY-1039130 and No. IIA-1358175.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gardner, Mr Simon and Powell, Ms Abby and Mullen, Mr Christopher and Macrae, Mr Roddy and Livingston, Dr Kenneth and Hurck, Dr Peter and MacGregor, Professor Ian and Annand, Dr John and Glazier, Dr Derek
• Authors: Afzal, F., Spieker, K., Hurck, P., Abt, S., Achenbach, P., Adlarson, P., Ahmed, Z., Akondi, C. S., Annand, J.R.M., Arends, H.J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W.J., Cividini, F., Collicott, C., Costanza, S., Denig, A., Dieterle, M., Downie, E.J., Drexler, P., Fegan, S., Gardner, S., Ghosal, D., Glazier, D.I., Gorodnov, I., Gradl, W., Gurevich, D., Heijkenskjöld, L., Hornidge, D., Huber, G.M., Kashevarov, V.L., Kay, S.J.D., Korolija, M., Krusche, B., Lazarev, A., Livingston, K., Lutterer, S., MacGregor, I.J.D., Macrae, R.G., Manley, D.M., Martel, P.P., Miskimen, R., Mocanu, M., Mornacchi, E., Mullen, C., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P.B., Paudyal, D., Pedroni, P., Powell, A., Reicherz, G., Rostomyan, T., Sfienti, C., Sokhoyan, V., Steffen, O., Strakovsky, I.I., Strub, T., Supek, I., Thiel, A., Thiel, M., Thomas, A., Usov, Y. A., Wagner, S., Walford, N.K., Watts, D.P., Werthmüller, D., Wettig, J., Witthauer, L., Wolfes, M., and Zachariou, N.
• Subjects: Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review Letters
• Publisher: American Physical Society
• ISSN: 0031-9007
• Copyright Holders: Copyright © 2024 American Physical Society
• First Published: First published in Physical Review Letters 132(12):121902
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
162724		Study of Strongly Interacting Matter	Guenther Rosner	European Commission (EC)	227431	P&S - Physics & Astronomy
165582		Nuclear Physics Group	David Ireland	Science and Technology Facilities Council (STFC)	ST/J000175/1	P&S - Physics & Astronomy
162615		Illuminating strongly interacting matter	Ian Macgregor	Science and Technology Facilities Council (STFC)	ST/G008604/1	P&S - Physics & Astronomy