Effects of the quantityσTSon the spin structure functions of nucleons in the resonance region (original) (raw)

Generalized sum rules for spin dependent structure functions of the nucleon

Journal of Physics G, 2001

The Drell-Hearn-Gerasimov and Bjorken sum rules are special examples of dispersive sum rules for the spin-dependent structure function G 1 (ν, Q 2) at Q 2 = 0 and ∞. We generalize these sum rules through studying the virtualphoton Compton amplitudes S 1 (ν, Q 2) and S 2 (ν, Q 2). At small Q 2 , we calculate the Compton amplitudes at leading-order in chiral perturbation theory; the resulting sum rules can be tested by data soon available from Jefferson Lab. For Q 2 > > Λ 2 QCD , the standard twist-expansion for the Compton amplitudes leads to the well-known deep-inelastic sum rules. Although the situation is still relatively unclear in a small intermediate-Q 2 window, we argue that chiral perturbation theory and the twist-expansion alone already provide strong constraints on the Q 2-evolution of the G 1 (ν, Q 2) sum rule from Q 2 = 0 to Q 2 = ∞.

Sum rules and moments of the nucleon spin structure functions

Arxiv preprint nucl-ex/0509007, 2005

Abstract: The nucleon has been used as a laboratory to investigate its own spin structure and Quantum Chromodynamics. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data ...

Q2 dependence of the spin structure function in the resonance region

Physical Review D, 1994

In this paper, we show what we can learn from the CEBAF experiments on spin-structure functions, and the transition from the Drell-Hearn-Gerasimov sum rule in the real photon limit to the spin dependent sum rules in the deep inelastic scattering, and how the asymmetry A 1 (x, Q 2) approaches the scaling limit in the resonance region. The spin structure function in the resonance region alone can not determine the spin-dependent sum rule due to the kinematic restriction of the resonance region. The integral 1 0 A 1 (x,Q 2)F 2 (x,Q 2) 2x(1+R(x,Q 2)) dx is estimated from Q 2 = 0 to 2.5 GeV 2. The result shows that there is a region where both contributions from the baryon resonances and the deep inelastic scattering are important, thus provides important information on the 1 high twist effects on the spin dependent sum rule.

The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Nucleon

Annual Review of Nuclear and Particle Science, 2004

▪ The Gerasimov-Drell-Hearn sum rule is one of several dispersive sum rules that connect the Compton scattering amplitudes to the inclusive photoproduction cross sections of the target under investigation. Being based on such universal principles as causality, unitarity, and gauge invariance, these sum rules provide a unique testing ground to study the internal degrees of freedom that hold the system together. The present article reviews these sum rules for the spin-dependent cross sections of the nucleon by presenting an overview of recent experiments and theoretical approaches. The generalization from real to virtual photons provides a microscope of variable resolution: At small virtuality of the photon, the data sample information about the long-range phenomena, which are described by effective degrees of freedom (Goldstone bosons and collective resonances), whereas the primary degrees of freedom (quarks and gluons) become visible at the larger virtualities. Through a rich body...

Q2-dependence of the nucleon's G1 structure function sum rule

Physics Letters B, 1994

We study the Q 2 variation of the first moment of the nucleon's spin-dependent structure function G 1. As Q 2 → 0 the moment is determined by the low energy theorem for Compton scattering. In the deep-inelastic region the moment is calculated using twist expansion to order 1/Q 2. Based on these limits, we construct a formula which smoothly interpolates between the two regions.

Nucleon spin structure at low momentum transfers

Physical Review D, 2010

The generalized Gerasimov-Drell-Hearn (GDH) sum rule is known to be very sensitive to QCD radiative and power corrections. We improve the previously developed QCD-inspired model for the Q 2 -dependence of the GDH sum rule. We take into account higher order radiative and higher twist power corrections extracted from precise Jefferson Lab data on the lowest moment of the spin-dependent proton structure function Γ p 1 (Q 2 ) and on the Bjorken sum rule Γ p−n 1 (Q 2 ). By using the singularity-free analytic perturbation theory we demonstrate that the matching point between chiral-like positive-Q 2 expansion and QCD operator product 1/Q 2 -expansion for the nucleon spin sum rules can be shifted down to rather low Q ≃ Λ QCD leading to a good description of recent proton, neutron, deuteron and Bjorken sum rule data at all accessible Q 2 .

Measurements of the Q2-dependence of the proton and neutron spin structure functions g1p and g1n

2000

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Measurements of the Q 2 dependence of the proton and neutron spin structure functions g p _1 and g n _1

The spin-dependent structure function of the proton and a test of the Bjorken sum rule

Physics Letters B, 2010

The inclusive double-spin asymmetry, A p 1 , has been measured at COMPASS in deepinelastic polarised muon scattering off a large polarised NH 3 target. The data, collected in the year 2007, cover the range Q 2 > 1 (GeV/c) 2 , 0.004 < x < 0.7 and improve the statistical precision of g p 1 (x) by a factor of two in the region x < 0.02. The new proton asymmetries are combined with those previously published for the deuteron to extract the non-singlet spin-dependent structure function g N S 1 (x, Q 2 ). The isovector quark density, ∆q 3 (x, Q 2 ), is evaluated from a NLO QCD fit of g N S 1 . The first moment of ∆q 3 is in good agreement with the value predicted by the Bjorken sum rule and corresponds to a ratio of the axial and vector coupling constants |g A /g V | = 1.28±0.07(stat.)±0.10(syst.).