N→Δtransition and proton polarizabilities from measurements ofp(γ→

Effective theory of theΔ(1232)resonance in Compton scattering off the nucleon

“…NLO effects can also be obtained by considering corrections from Σ (4) to the leading Delta self-energy Σ (3) . More complicated electromagnetic couplings and higher-order terms in Σ lead to effects of NNLO in the δ-expansion of O∆R graphs.…”

“…5, together with the counterterms necessary for their renormalization. Insertions from L (2) πN generate effects in Σ (4) . These effects include relativistic corrections to the leading heavy-baryon result Σ (3) .…”

“…This suggests that the extraction of polarizabilities from Compton data is a delicate process. PDG average [39] 12.0 ± 0.7 1.6 ± 0.6 LEGS [4] 11.8 ± 2.0 1.4 ± 1.5 MAMI [5] 11.9 ± 2.1 1.2 ± 1.4 Beane et al [20] 12.1 ± 1.6 3.2 ± 1.2 …”

“…III C indicates that at NLO we must include effects due to the O(δ 4 ) piece of Σ, Σ (4) . The heavy-baryon graphs which contribute to the O(ǫ 4 ) self-energy in a heavy-baryon calculation with explicit Deltas [40] are shown in Fig.…”

“…During the past decade a number of excellent experimental programs have been dedicated to these two processes (see Refs. [1][2][3][4][5] and [6][7][8][9][10], respectively). At low photon energies, these experiments probe the static properties of the nucleon, such as its electric charge, magnetic moment, and polarizabilities.…”