0000000000207945
AUTHOR
Jose Manuel Alarcón
Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: II. Spin polarizabilities and moments of polarized structure functions
We examine the polarized doubly-virtual Compton scattering (VVCS) off the nucleon using chiral perturbation theory ($\chi$PT). The polarized VVCS contains a wealth of information on the spin structure of the nucleon which is relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of the polarized VVCS amplitudes $S_1(\nu, Q^2)$ and $S_2(\nu, Q^2)$, and the corresponding polarized spin structure functions $g_1(x, Q^2)$ and $g_2(x,Q^2)$. Our results for the moments of polarized structure functions, partially related to different spin polarizabilities, are compared to other th…
The role of the $\Delta(1232)$-resonance in covariant baryon chiral perturbation theory
We stress, on theoretical and phenomenological grounds, the importance of the $\Delta(1232)$-resonance in a chiral effective field theory approach applied to the study of $\pi N$ scattering. We show how its inclusion as a dynamical degree of freedom allow us to obtain reliably valuable information from $\pi N$ scattering data.
Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: The subtraction function and moments of unpolarized structure functions
The forward doubly-virtual Compton scattering (VVCS) off the nucleon contains a wealth of information on nucleon structure, relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of low-energy VVCS in chiral perturbation theory ($\chi$PT). Here we focus on the unpolarized VVCS amplitudes $T_1(\nu, Q^2)$ and $T_2(\nu, Q^2)$, and the corresponding structure functions $F_1(x, Q^2)$ and $F_2(x,Q^2)$. Our results are confronted, where possible, with "data-driven" dispersive evaluations of low-energy structure quantities, such as nucleon polarizabilities. We find significant dis…
Low energy structure of the nucleon from chiral effective field theory
We present some updated results regarding the scalar and electromagnetic structure of the nucleon obtained by the relativistic formulation of chiral effective field theory with baryons. We compare them with previous determinations available in the literature, and show their relevance for searches of physics beyond the standard model in the low energy frontier. An accurate knowledge of the structure of the nucleon is important to improve our understanding of the funda- mental interactions and provide theoretical estimations of some important quantities with a small uncertainty. This is specially relevant for experiential searches of physics be- yond the standard model in the low energy front…
Moments of nucleon structure functions at next-to-leading order in baryon chiral perturbation theory
We obtain leading- and next-to-leading-order predictions of chiral perturbation theory for several prominent moments of nucleon structure functions. These parameter-free results turn out to be in overall agreement with the available empirical information on nearly all of the considered moments, in the region of low momentum transfer $({Q}^{2}l0.3\phantom{\rule{4pt}{0ex}}{\mathrm{GeV}}^{2})$. Especially surprising is the situation for the spin polarizability ${\ensuremath{\delta}}_{LT}$, which thus far was not reproducible in chiral perturbation theory for proton and neutron simultaneously. This problem, known as the ``${\ensuremath{\delta}}_{LT}$ puzzle,'' is not seen in the present calcula…
Improved description of the pion-nucleon scattering phenomenology in covariant baryon chiral perturbation theory
We highlight some of the recent advances in the application of chiral effective field theory (chiral EFT) with baryons to the $\pi N$ scattering process. We recall some problems that cast doubt on the applicability of chiral EFT to $\pi N$ and show how the relativistic formalism, once the $\Delta(1232)$-resonance is included as an explicit degree of freedom, solves these issues. Finally it is shown how this approach can be used to extract the $\sigma$-terms from phenomenological information.
Low-energy symmetries of QCD and the structure of the nucleon
Abstract We present some updated results regarding the scalar and electromagnetic structure of the nucleon obtained by the relativistic formulation of chiral effective field theory with baryons. We compare them with previous determinations available in the literature, and show their relevance for searches of physics beyond the standard model in the low energy frontier.
Gold-plated moments of nucleon structure functions in baryon chiral perturbation theory
We obtain leading- and next-to-leading order predictions of chiral perturbation theory for several prominent moments of nucleon structure functions. These free-parameter free results turn out to be in overall agreement with the available empirical information on nearly all of the considered moments, in the region of low-momentum transfer ($Q^2 < 0.3$ GeV$^2$). Especially surprising is the situation for the spin polarizability $\delta_{LT}$, which thus far was not reproducible in chiral perturbation theory for proton and neutron simultaneously. This problem, known as the "$\delta_{LT}$ puzzle," is not seen in the present calculation.