학술논문
Measurement of Compton scattering at MAMI for the extraction of the electric and magnetic polarizabilities of the proton
Document Type
Working Paper
Author
A2 Collaboration; Mornacchi, E.; Martel, P. P.; Abt, S.; Achenbach, P.; Adlarson, P.; Afzal, F.; Ahmed, Z.; 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.; Dolzhikov, A. S.; Downie, E. J.; Drexler, P.; Fegan, S.; Gardner, S.; Ghosal, D.; Glazier, D. I.; Gorodnov, I.; Gradl, W.; Günther, M.; Gurevich, D.; Heijkenskjöld, L.; Hornidge, D.; Huber, G. M.; Käser, A.; Kashevarov, V. L.; Kay, S. J. D.; Korolija, M.; Krusche, B.; Lazarev, A.; Livingston, K.; Lutterer, S.; MacGregor, I. J. D.; Manley, D. M.; Miskimen, R.; Mocanu, M.; Mullen, C.; Neganov, A.; Neiser, A.; Ostrick, M.; Paudyal, D.; Pedroni, P.; Powell, A.; Rostomyan, T.; Sokhoyan, V.; Spieker, K.; Steffen, O.; Strakovsky, I.; Strub, T.; Thiel, M.; Thomas, A.; Usov, Yu. A.; Wagner, S.; Watts, D. P.; Werthmüller, D.; Wettig, J.; Wolfes, M.; Zachariou, N.
Source
Subject
Language
Abstract
A precise measurement of the differential cross-sections $d\sigma/d\Omega$ and the linearly polarized photon beam asymmetry $\Sigma_3$ for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost $4\pi$ 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 set-up. 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: \begin{align*} &{}\alpha_{E1} = 10.99 \pm 0.16 \pm 0.47 \pm 0.17 \pm 0.34 &{}\beta_{M1} = 3.14 \pm 0.21 \pm 0.24 \pm 0.20 \pm 0.35 \end{align*} in units of $10^{-4}$\,fm$^3$ where the errors are statistical, systematic, spin polarizability dependent and model dependent.