On the NuTeV anomaly and the asymmetry of the strange sea in the nucleon

Our recent theoretical analysis based on the flavor SU(3) chiral quark soliton model predicts fairly large particle-antiparticle asymmetry of the strange sea in the nucleon. We point out that the predicted magnitude of asymmetry is large enough to solely resolve the so-called NuTeV anomaly on the fundamental parameter $\sin^2 \theta_W$ in the standard model.Comment: 9 pages, 1 figure, revised final version to appear in Phys. Rev.

On the new COMPASS measurement of the deuteron spin-dependent structure function g1dg_1^d

Very recently, a new measurement of the deuteron spin-dependent structure function $g_1^d (x)$ was reported by the COMPASS group. A main change from the old SMC measurement is a considerable improvement of the statistical accuracy in the low $x$ region $0.004 < x < 0.03$. We point out that the new COMPASS data for $g_1^d (x)$ as well as their QCD fits for $\Delta \Sigma$ and $\Delta s + \Delta \bar{s}$ are all remarkably close to our theoretical predictions given several years ago based on the chiral quark soliton model.Comment: Errors in Fig.4 were corrected. Version accepted for publication in Physics Letters

Do we expect light flavor sea-quark asymmetry also for the spin-dependent distribution functions of the nucleon?

After taking account of the scale dependence by means of the standard DGLAP evolution equation, the theoretical predictions of the chiral quark soliton model for the unpolarized and longitudinally polarized structure functions of the nucleon are compared with the recent high energy data. The theory is shown to explain all the qualitative features of the experiments, including the NMC data for $F_2^p (x) - F_2^n (x)$, $F_2^n (x) / F_2^p (x)$, the Hermes and NuSea data for $\bar{d}(x) - \bar{u}(x)$, the EMC and SMC data for $g_1^p(x)$, $g_1^n(x)$ and $g_1^d(x)$. Among others, flavor asymmetry of the longitudinally polarized sea-quark distributions is a remarkable prediction of this model, i.e., it predicts that $\Delta \bar{d}(x) - \Delta \bar{u}(x) = C x^{\alpha} [ \bar{d}(x) - \bar{u}(x)]$ with a sizable negative coefficient $C \simeq -2.0$ (and $\alpha \simeq 0.12$) in qualitative consistency with the recent semi-phenomenological analysis by Morii and Yamanishi.Comment: 14pages, including 5 eps_figures with epsbox.sty, late

The nonperturbative origin of delta-function singularity in the chirally-odd twist-3 distribution function e(x)

We analytically prove that the existence of the delta-function singularity in the chirally-odd twist-3 distribution $e(x)$ of the nucleon is inseparably connected with the nonvanishing quark condensate as a signal of the spontaneous chiral symmetry breaking of the QCD vacuum. This singularity in $e(x)$, which would be observed as a sizable violation of the 1st moment sum rule, is then interpreted as giving a very rare case that the nontrivial vacuum structure of QCD manifests in an observable of a localized QCD excitation, i.e. the nucleon.Comment: 9 pages, 1 eps-figur

On the D-term of the nucleon generalized parton distributions

It is known that some of the deeply-virtual-Compton-scattering observables, for instance, the beam-charge asymmetry in the hard electroproduction of real photons on the nucleon, are extremely sensitive to the magnitude of D-term appearing in the parameterization of the generalized parton distributions. We report a theoretical analysis of both the isoscalar and isovector parts of the nucleon D-term within the framework of the chiral quark soliton model, without recourse to the derivative expansion type approximation used in previous works.Comment: 10 pages, 2 eps-figures, small improvements, version to appear in Phys. Lett.