The target normal single-spin asymmetry in inclusive electron-nucleon scattering is studied in the low-energy regime that includes the Δ resonance. The particular interest in the asymmetry resides in ...that it is driven by two-photon exchange effects. It probes the spin-dependent absorptive part of the two-photon exchange amplitude, which is free of infrared and collinear singularities and represents the most pristine expression of two-photon exchange dynamics. The study presented here uses the 1/Nc expansion of QCD, which combines the N and Δ through the emergent SU(4) spin-flavor symmetry in the baryon sector and allows for a systematic construction of the transition EM currents. The analysis includes the first subleading corrections in the 1/Nc expansion and presents results for elastic and inelastic final states. The asymmetry is found to be in the range 10-3 - 10-2. The Δ resonance plays an important role as an intermediate state in the elastic asymmetry and as a final state in the inclusive asymmetry.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Baryon chiral perturbation theory (BChPT) combined with the 1/Nc expansion is applied to the SU(3) vector currents. In terms of the ξ power counting linking the low-energy and 1/Nc expansions ...according to O(ξ) = O(p) = O(1/Nc), the study is carried out to next-to-next-to-leading order, and it includes SU(3) breaking corrections to the |ΔS| = 1 vector charges, charge radii, and magnetic moments and radii. The results are obtained for generic Nc, allowing for investigating the various scalings in Nc.
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We calculate the target normal single-spin asymmetry caused by two-photon exchange in inclusive electron-nucleon scattering in the resonance region. Our analysis uses the 1/Nc expansion of low-energy ...QCD and combines N and Δ intermediate and final states using the contracted SU(4) spin-flavor symmetry. The normal spin asymmetry obtained in leading-order accuracy in 1/Nc has magnitude ∼10−2 and different sign in ep and en scattering. It can be measured in electron scattering at lab energies ∼0.5–1.5 GeV and provides a clean probe of two-photon exchange dynamics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Baryon chiral perturbation theory (BChPT) combined with the 1 / Nc expansion is applied to the SU ( 3 ) vector currents. In terms of the ξ power counting linking the low-energy and 1 / Nc expansions ...according to O ( ξ ) = O ( p ) = O ( 1 / Nc ) , the study is carried out to next-to-next-to-leading order, and it includes SU ( 3 ) breaking corrections to the | Δ S | =1 vector charges, charge radii, and magnetic moments and radii. The results are obtained for generic Nc , allowing for investigating the various scalings in Nc .
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Baryon Chiral Perturbation Theory combined with the $1/N_c$ expansion is implemented for three flavors. Here, Baryon masses, vector charges and axial vector couplings are studied to one-loop and ...organized according to the $\xi$-expansion, in which the $1/N_c$ and the low energy power countings are linked according to $1/N_c={\cal{O}}(\xi)={\cal{O}}(p)$. The renormalization to ${\cal{O}}(\xi^3)$ necessary for the mentioned observables is provided, along with applications to the baryon masses and axial couplings as obtained in lattice QCD calculations.
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Baryon masses and nucleon σ terms are studied with the effective theory that combines the chiral and 1/Nc expansions for three flavors. In particular the connection between the deviation of the ...Gell-Mann–Okubo relation and the σ term associated with the scalar density u¯u+d¯d−2s¯s is emphasized. The latter is at lowest order related to a mass combination whose low value has given rise to a σ term puzzle. It is shown that while the nucleon σ terms have a well behaved low energy expansion, that mass combination is affected by large higher order corrections non-analytic in quark masses. Adding to the analysis lattice QCD baryon masses, it is found that σπN=69(10) MeV and σs has natural magnitude within its relatively large uncertainty.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We calculate the target normal single-spin asymmetry caused by two-photon exchange in inclusive electron-nucleon scattering in the resonance region. Our analysis uses the 1/$N_c$ expansion of ...low-energy QCD and combines $\textit{N}$ and Δ intermediate and final states using the contracted $\textit{SU}$(4) spin-flavor symmetry. The normal spin asymmetry obtained in leading-order accuracy in 1/$N_c$ has magnitude ~10-2 and different sign in $\textit{ep}$ and $\textit{en}$ scattering. It can be measured in electron scattering at lab energies ~0.5-1.5 GeV and provides a clean probe of two-photon exchange dynamics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Baryon chiral perturbation theory combined with the 1/Nc expansion is implemented for three flavors. Baryon masses, vector charges and axial vector couplings are studied to one-loop and organized ...according to the ξ-expansion, in which the 1/Nc and the low-energy power countings are linked according to 1/Nc=O(ξ)=O(p). The renormalization to O(ξ3) necessary for the mentioned observables is provided, along with applications to the baryon masses and axial couplings as obtained in lattice QCD calculations.
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We analyze Regge trajectories in terms of the 1/Nc expansion of QCD. Neglecting spin–orbit contributions to the large Nc baryon mass operator, we consider the evolution of the spin-flavor singlet ...component of the masses with respect to the angular momentum. We find two distinct and remarkably linear Regge trajectories for symmetric and for mixed symmetric spin-flavor multiplets.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We study the photoproduction helicity amplitudes of negative parity baryons in the context of the 1/Nc expansion of QCD. A complete analysis to next-to-leading order is carried out. The results show ...sub-leading effects to be within the magnitude expected from the 1/Nc power counting. They also show significant deviations from the quark model, in particular the need for 2-body effects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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