Measurement of Compton Scattering at MAMI for the Extraction of the Electric and Magnetic Polarizabilities of the Proton

(A2 Collaboration at MAMI)

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A precise measurement of the differential cross sections dσ/dω and the linearly polarized photon beam asymmetry ς3 for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: αE1=10.99±0.16±0.47±0.17±0.34, βM1=3.14±0.21±0.24±0.20±0.35; in units of 10-4 fm3 where the errors are statistical, systematic, spin polarizability dependent, and model dependent.

Original languageEnglish
Article number132503
Number of pages6
JournalPhysical Review Letters
Issue number13
Publication statusPublished - 1 Apr 2022

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Funding Information:
The authors wish to acknowledge the outstanding support of the accelerator group and operators of MAMI. We also wish to acknowledge and thank J. McGovern, V. Pascalutsa, and B. Pasquini for providing us with their theory codes, together with H. Grießhammer and M. Vanderhaegen for the theoretical contributions and support. This project has received funding from the European Unions Horizon 2020 research and innovation program under Grant Agreement No. 824093. This work has been supported by the U.K. STFC (ST/L005719/1, ST/P004458/1, ST/T002077/1,ST/P004385/2, ST/V002570/1, ST/P004008/1 and ST/L00478X/2) grants, the Deutsche Forschungsgemeinschaft (SFB443, SFB/TR16, and SFB1044), DFG-RFBR (Grant No. 09-02-91330), Schweizerischer Nationalfonds (Contracts No. 200020-175807, No. 200020-156983, No. 132799, No. 121781, No. 117601), the U.S. Department of Energy (Offices of Science and Nuclear Physics, Awards No. DE-SC0014323, No. DEFG02-99-ER41110, No. DE-FG02-88ER40415, No. DEFG02-01-ER41194) and National Science Foundation (Grants No. NSF OISE-1358175; No. PHY-1039130, No. PHY-1714833, No. PHY-2012940, No. IIA-1358175), INFN (Italy), and NSERC of Canada (Grant No. FRN-SAPPJ2015-00023).

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