Description
Proton leading scalar and spin polarisabilities from proton Compton scattering data Timon Esser, Franziska Hagelstein, and Vadim Lensky We present the results of a partial wave analysis of the global real Compton scattering (RCS) database, extracting the leading scalar and spin polarisabilities of the proton. Exploring the nucleon using electromagnetic probes reveals a fine and intricate interplay between its various structural properties. As an example, the nucleon polarisabilities encode the two-photon response, such as measured in RCS [1, 2]. On the other hand, their precise knowledge is very important for the analysis of atomic spectra, especially in muonic atoms [3], which serves to constrain the details of the nucleon charge distribution such as the charge radius. The polarisabilities are introduced as the coefficients in the low-energy expansion (LEX) of the RCS amplitudes, and can, in principle, be extracted using the LEX to analyse the RCS data [1, 4]. However, the energies where quality experimental data are available are too high to use the LEX for an analysis, forcing one to use a more sophisticated framework such as effective field theories [5, 6], disperson relations [7], or partial wave analysis [8]. We use the latter framework here, include the most recent RCS data from MAMI [9] and HIGS [10], and introduce a few further modifications in the formalism. The results of our refined analysis are presented in this contribution. [1] D. Babusci et al. In: Phys. Rev. C 58 (1998). [2] H. W. Griesshammer et al. In: Prog. Part. Nucl. Phys. 67 (2012). [3] B. R. Holstein et al. In: Phys. Rev. C 61 (2000). [4] N. Krupina et al. In: Phys. Lett. B 782 (2018). [5] N. Krupina et al. In: Phys. Rev. Lett. 110.26 (2013). [6] V. Lensky et al. In: Phys. Rev. C 89.3 (2014). [7] X. Li et al. In: Phys. Rev. Lett. 128 (2022). [8] E. Mornacchi et al. In: Phys. Rev. Lett. 128.13 (2022). [9] E. Mornacchi et al. In: Phys. Rev. Lett. 129.10 (2022). [10] K. Pachucki et al. In: Rev. Mod. Phys. 96.1 (2024)