The pion-mass dependence of the nucleon mass within the covariant SU (2) baryon chiral perturbation theory both without and with explicit ∆ (1232) degrees of freedom up to order p 4 is investigated. By fitting to a comprehensive set of lattice QCD data in 2 and 2+1 flavors from several collaborations, for pion masses Mπ < 420 MeV, we obtain low energy constants of natural size and compatible with pion nucleon scattering data. Our results are consistent with the rather linear pion-mass dependence showed by lattice QCD. In the 2 flavor case we have also performed simultaneous fits to nucleon mass and σπN data. As a result of our analysis, which encompasses the study of finite volume corrections and discretization effects, we report a value of σπN = 41(5)(4) MeV in the 2 flavor case and σπN = 52(3)(8) MeV for 2+1 flavors, where the inclusion of the ∆ (1232) resonance changes the results by around 9 MeV. In the 2 flavor case we are able to set independently the scale for lQCD data, given by a Sommer scale of r0 = 0.493(23) fm.

The octet-baryon axial-vector charges and the g1/f1 ratios measured in the semileptonic hyperon decays are studied up to O(p 3 ) using the covariant baryon chiral perturbation theory with explicit decuplet contributions. We clarify the role of different low-energy constants and find a good convergence for the chiral expansion of the axial-vector charges of the baryon octet, g1(0), with O(p 3 ) corrections typically around 20% of the leading ones. This is a consequence of strong cancellations between different next-to-leading order terms. We show that considering only non-analytic terms is not enough and that analytic terms appearing at the same chiral order play an important role in this description. The same effects still hold for the chiral extrapolation of the axial-vector charges and result in a rather mild quark-mass dependence. As a result, we report a determination of the leading order chiral couplings, D = 0.623(61)(17) and F = 0.441 (47)(2), as obtained from a completely consistent chiral analysis up to O(p 3 ). Furthermore, we note that the appearance of an unknown low-energy constant precludes the extraction of the proton octet-charge from semileptonic decay data alone, which is relevant for an analysis of the composition of the proton spin. * Electronic address: ledwig@ific.uv.es † Electronic address: jmartincamalich@ucsd.edu ‡ Electronic address: lisheng.geng@buaa.edu.cn § Electronic address: vicente@ific.uv.es 1 In the SU (2) version of BχPT, only the combination D + F is accessible, which is at leading order equal to the AV charge of the nucleon g A = 1.2701 (25) × g V as measured in neutron β-decay [5].

We examine the electromagnetic properties of the ∆(1232) resonance within the self-consistent chiral quark-soliton model. In particular we present the ∆ form factors of the vector-current GE0(Q 2 ), GE2(Q 2 ) and GM1(Q 2 ) for a momentum-transfer range of 0 ≤ Q 2 ≤ 1 GeV 2 . We apply the symmetry-conserving quantization of the soliton and take 1/Nc rotational corrections into account. Values for the magnetic moments of all decuplet baryons as well as for the N −∆ transition are given. Special interest is also given to the electric quadrupole moment of the ∆.

An expansion of the electromagnetic form factors of the nucleon and ∆(1232) in small momentum transfer and pion mass is performed in a manifestly-covariant EFT framework consistent with chiral symmetry and analyticity. We present the expressions for the nucleon and ∆(1232) electromagnetic form factors, charge radii, and electromagnetic moments in the framework of SU(2) baryon chiral perturbation theory, with nucleon and ∆-isobar degrees of freedom, to next-to-leading order. Motivated by the results for the proton electric radius obtained from the muonic-hydrogen atom and electron-scattering process, we extract values for the second derivative of the electric form factor which is a genuine prediction of the p 3 BχPT. The chiral behavior of radii and moments is studied and compared to that obtained in the heavy-baryon framework and lattice QCD. The chiral behavior of ∆(1232)-isobar properties exhibits cusps and singularities at the threshold of ∆ → πN decay, and their physical significance is discussed. *

We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider 1/N c rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: κ u T = 3.56 and κ d T = 1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be κ s T = 0.2 ∼ −0.2, that is compatible with zero. We also calculate the corresponding form factors κ q T (Q 2 ) up to a momentum transfer Q 2 ≤ 1 GeV 2 at a renormalization scale of 0.36 GeV 2 .