Sea Polarization Research Articles

Sea ice small-scale surface roughness estimation based on AMSR-E observations

In this article, the retrieval of a sea ice small-scale surface roughness parameter using a proposed model is investigated at several Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) channels (6.9, 10.7, and 89 GHz) over the Arctic oceans. The AMSR-E 89 GHz observations with a spatial resolution of approximately 6 km × 4 km, nearly three times the resolution of the currently operational radiometer SSM/I 85 GHz (15 km × 13 km), are fully exploited to retrieve the total and multiyear (MY) ice concentrations through the utilization of the ARTIST sea ice (ASI) and polarization corrected temperature (PCT) algorithms, respectively. To improve the accuracy of the retrieved ice concentration, a tie-point adaption scheme was used to obtain daily adaptable tie-points for the two ice concentration algorithms. A sea ice small-scale roughness parameter was then calculated with the model proposed by Hong for the above-mentioned three frequencies. At lower frequencies, such as 6.9 and 10.7 GHz, roughness estimates are available for all ice types. However, estimates at 89 GHz are physically illegitimate over the wintertime MY ice cover. The model estimates at the two low frequencies were further studied over a protracted period (2003–2010). The annual time series of the averaged estimate over the Arctic sea ice were found to exhibit a slightly decreasing trend (−2.1 × 10−3 and −1.9 × 10−3 cm year−1 for 6.9 and 10.7 GHz, respectively). Meanwhile, the winter time series showed an increasing trend whereas the summer time series showed a remarkably decreasing trend, which indicates more serious melting activity occurring over the Arctic ice.

Effects of Dirac sea polarization on hadronic properties: A chiral SU(3) approach

The effect of vacuum fluctuations on the in-medium hadronic properties is investigated using a chiral SU(3) model in the nonlinear realization. The effect of the baryon Dirac sea is seen to modify hadronic properties and in contrast to a calculation in mean field approximation it is seen to give rise to a significant drop of the vector meson masses in hot and dense matter. This effect is taken into account through the summation of baryonic tadpole diagrams in the relativistic Hartree approximation (RHA), where the baryon self energy is modified due to interactions with both the non-strange $(\sigma)$ and the strange $(\zeta)$ scalar fields.

Transverse momentum in semi-inclusive polarized deep inelastic scattering and the spin-flavor structure of the proton

The nonvalence spin-flavor structure of the proton extracted from semi-inclusive measurements of polarized deep inelastic scattering depends strongly on the transverse momentum of the detected hadrons which are used to determine the individual polarized sea distributions. This physics may explain the recent HERMES observation of a positively polarized strange sea through semi-inclusive scattering, in contrast with the negative strange sea polarization deduced from inclusive polarized deep inelastic scattering.

Breit-interaction correction to the hyperfine constant of an externalselectron in a many-electron atom

Correction to the hyperfine constant $A$ of an external $s\ensuremath{-}\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{o}\mathrm{n}$ in many-electron atom caused by the Breit interaction is calculated analytically: $\ensuremath{\delta}A/A=0.68Z{\ensuremath{\alpha}}^{2}.$ The physical mechanism for this correction is polarization of the internal electronic shells (mainly ${1s}^{2}$ shell) by the magnetic field of the external electron. This mechanism is similar to the polarization of vacuum considered by Karplus and Klein [Phys. Rev. 85, 972 (1952)] long time ago. The similarity is the reason why in both cases (Dirac sea polarization and internal atomic shells polarization) the corrections have the same dependence on the nuclear charge and fine-structure constant. In conclusion we also discuss $Z{\ensuremath{\alpha}}^{2}$ corrections to the parity violation effects in atoms.

Measurement of polarized quark distributions at HERMES

Preliminary results for inclusive and semi-inclusive hadron asymmetries are presented for 3He and 1H targets, measured in 1995 and 1996 at the HERMES experiment. Under the assumption of spin-independent fragmentation, these asymmetries may be used to extract the polarizations of individual quark flavors. The extraction requires a knowledge of unpolarized parton distributions, an understanding of the fragmentation process, a precise description of the HERMES spectrometer, and an assumption about the sea polarization. Preliminary results for the uv, dv, and averaged sea quark polizations are presented.

Polarized parton distribution functions reexamined.

The hard-gluonic contribution to the first moment of the polarized proton structure function $g_1^p(x)$ is dependent of the factorization convention chosen in defining the quark spin density and the hard cross section for photon-gluon scattering. Two extremes of interest, namely gauge-invariant and chiral-invariant factorization schemes, are considered. We show that in order to satisfy the positivity constraint for sea and gluon polarizations, the polarized valence quark distributions should fully account for the observed $g_1^p(x)$ at $x\gsim 0.2\,$. This together with the first-moment and perturbative QCD constraints puts a pertinent restriction on the shape of $\Delta u_v(x)$ and $\Delta d_v(x)$. The spin-dependent sea distribution in the gauge-invariant factorization scheme is extracted from the data of $g_1^p(x)$. It is shown in the chiral invariant scheme that it is possible to interpret the $g_1^p(x)$ data with anomalous gluonic contributions, yet a best least $\chi^2$ fit to the data implies a gluon spin distribution which violates the positivity condition $|\Delta G(x)|\leq G(x)$. We then propose a more realistic set of parton spin distributions with sea polarization and with a moderate value of $\Delta G$. The polarized parton distributions in this work are presented in the next-to-leading order of QCD at the scale $Q^2=10\,{\rm GeV}^2\,$. Predictions for the polarized structure functions $g_1^n(x)$ of the neutron and $g_1^d(x)$ of the deuteron are given.

Electromagnetic form factors of the nucleon in the chiral quark soliton model

In this paper we present the derivation as well as the numerical results for the electromagnetic form factors of the nucleon within the chiral quark soliton model in the semiclassical quantization scheme. The model is based on semibosonized SU(2) Nambu -- Jona-Lasinio lagrangean, where the boson fields are treated as classical ones. Other observables, namely the nucleon mean squared radii, the magnetic moments, and the nucleon--$\Delta$ splitting are calculated as well. The calculations have been done taking into account the quark sea polarization effects. The final results, including rotational $1/N_c$ corrections, are compared with the existing experimental data, and they are found to be in a good agreement for the constituent quark mass of about 420 MeV. The only exception is the neutron electric form factor which is overestimated.

Model for the Q2 dependence of polarized structure functions.

We present an update of a phenomenological model for the spin-dependent structure functions ${\mathit{g}}_{1}$(x,${\mathit{Q}}^{2}$) of the proton and neutron. This model is based on a broken SU(6) wave function parametrized by the unpolarized structure functions. The two free parameters of the model are chosen to satisfy the Bjorken and Ellis-Jaffe sum rules. The model respects isospin symmetry and has zero strange sea polarization. Using new values for F/D from hyperon \ensuremath{\beta} decay the resulting ${\mathit{Q}}^{2}$-dependent asymmetries ${\mathit{A}}_{1}$ are in perfect agreement with the existing data. Therefore we do not see any evidence for a ``spin crisis.'' With two choices for ${\mathit{g}}_{2}$ the ${\mathit{Q}}^{2}$ dependence of ${\mathit{A}}_{1}$(x,${\mathit{Q}}^{2}$) and ${\mathit{A}}_{2}$(x,${\mathit{Q}}^{2}$) \ensuremath{\surd}${\mathit{Q}}^{2}$/M is predicted and shown to be small for both cases.

Strange Sea Polarization in the Proton and a Constituent Quark Model

The valence-quark and q q -sea polarizations in the polarized proton are calculated in the frame­ work of a constituent quark model. It is pointed out that the configuration mixing of the symmetric three-quark state with the quark-diquark state gives a good fit to existing data on the strange sea polarization in the proton. Recently, the Spin Muon Collaboration (SMC) reported on the measurement of the spin-dependent structure function of the deuteron 1 > and pointed out that its first moment is smaller than the prediction of the Ellis-Jaffe sum rule 2 > as already found by the European Muon Collaboration (EMC). 3 > Namely, they conclude that the quarks do not carry the spin of the nucleon and the strange sea polarization is large and negative. On the other hand, the SLAC group (E142) 4 > reported the opposite result from the measurement at Q 2 =2 GeV 2 , i.e., the guarks carry half the nucleon spin and the strange sea polarization is consistent with the one expected by the naive parton model. 2 > This apparent discrepancy is an open question. In this paper, we calculate the valence-quark and qq-sea polarizations in the polarized proton in the framework of a constituent quark model. 5 >,G> It is shown that the amount of the strange sea polarization is strongly dependent on the structure of constituents and the SUA3) symmetry breaking parameter in the qq sea polarization. It is pointed out that the configuration mixing of the simple three-quark state with the quark-diquark state gives a good fit to existing data on the strange sea polarization in the proton below Q 2 =12 GeV 2 • We allow a distinction between the valence and sea quarks in the proton with positive helicity. For the up- and down-quark polarizations, we write Llu=Lluv+ Llus and Lld=Lldv+Llds where Llu(Lld) denotes the polarization carried by the u quark (d quark). The subscripts V and S denote valence and sea, respectively. We introduce the valence-quark spin l:v(=Lluv+Lldv).7) We assume the isospin invariance of the sea-quark with respect to the up- and down-quark but the broken SUf(3) symmetry so that

Strange Sea Polarization in the Proton and a Constituent Quark Model

The valence-quark and qq-sea polarizations in the polarized proton are calculated in the frame-work of a constituent quark model. It is pointed out that the configuration mixing of the symmetric three-quark state with the quark-diquark state gives a good fit to existing data on the strange sea polarization in the proton.

Proton spin in the valon model.

The valon model description of the proton is used to calculate contributions of the constituents of the proton to its spin. It is shown that the results of the model calculation agree rather well with the EMC results. It is conjectured that in probing the nucleon with high ${\mathit{Q}}^{2}$ one actually probes its valon structure. It is further conjectured that the valence quark contribution to the proton spin cancels out the sea contribution, and gluons almost exclusively carry the spin of the proton. Our results satisfy various theoretical constraints on the sea polarization.

Can Magnetic Moment of Nucleons Be Correlated with Quark Distribution Functions?

We show that the magnetic moment of nucleons should not be correlated with the quark distribution functions, Δq. The assumption inherent in such correlations is that the strange sea polarization is zero in a proton.

Can Magnetic Moment of Nucleons Be Correlated with Quark Distribution Functions?

We show that the magnetic moment of nucleons should not be correlated with the quark distribution functions, Llq. The assumption inherent in such correlations is that the strange sea polarization is zero in a proton.

Polarizations of Sea and Gluon in the Proton and Valence Quark Spins

Recently, the European Muon Collaboration (EMC) measured the polarized structure function of the proton g/(x, Q2).1) The EMC found that the value of the first moment of g/(x, Q2) is smaller than the one expected by the naive quark modeL) The result has been investigated by means of various approaches. However, the sign. and magnitude of the sea and gluon polarizations are not clear. For example, Kobayakawa et aL) suggest the positive sea and positive gluon polarizations, while Cheng et aL) do the negative sea and negative gluon polarizations. Also, many authors),6) have discussed the negative sea and positive gluon polarizations. It is important to clarify the relations among their results. In this paper, we investigate the sea and gluon polarizations in the proton by considering the effect of the anomaly7) and the broken flavour-SU(3) (SUA3)) sea. It is pointed out that the sign and magnitude of the sea and gluon contributions demanded by the experimental data, are strongly correlated to the amount of the spins carried by valence quarks and the SUA3) symmetry breaking parametenwhen combined with the data of neutron and hyperon beta decays.S),9) Also, we calculate the magnitude of the valence quark spins in a framework of a constituent quark model,6) as an example. We consider the polarized parton distributions in a proton with positive helicity. Let us introduce the helicity-weighted quark and gluon densities Llq(x, Q2), Llg(x, Q2) and their polarizations (first moments) Llq( Q2), Llg( Q2) at Q2 Ge V:

Nucleon electric form factors and quark sea polarization in the Nambu-Jona-Lasinio model

The nucleon electric form factors are extracted from the semiclassically quantized solitonic solution of the Nambu-Jona-Lasinio model. To this end the model is solved self-consistently in the SU(2) sector with scalar coupling using the zero-boson and one-quark loop approximation on the chiral circle. Charge distributions, squared radii and the Coulomb energy splitting are calculated as well. For constituent masses around M=400 MeV one obtaine good agreement with the experimental data of the proton. The tail of the neutron charge distribution is made of polarized sea quarks.

Spin asymmetry in proton-proton collisions as a probe of sea and gluon polarization in a proton.

Quark and gluon spin densities in a proton are phenomenologically parametrized based on the European Muon Collaboration (EMC) data and on some plausible theoretical arguments. Four different characteristic values of gluon and sea polarizations suggested by various theoretical conjectures are considered. The sea polarization in a proton is probed by measuring the spin-spin asymmetry ${A}_{\mathrm{LL}}^{\mathrm{DY}}$ in the Drell-Yan process, while the helicity asymmetry ${A}_{\mathrm{LL}}^{\ensuremath{\gamma}}$ in direct photon production at high ${p}_{T}$ is employed to test the gluon spin content. Helicity asymmetries in both processes are quite sizable. ${A}_{\mathrm{LL}}^{\mathrm{DY}}$ is positive and of order ${10}^{\ensuremath{-}1}$ if the sea is polarized opposite to the proton spin, as suggested by the EMC data. However, even in the absence of the sea polarization at the EMC energies, we find ${A}_{\mathrm{LL}}^{\mathrm{DY}}$ to be large and negative. Experimental measurements of ${A}_{\mathrm{LL}}^{\mathrm{DY}}$ and ${A}_{\mathrm{LL}}^{\ensuremath{\gamma}}$ together will not only provide a clean probe of sea and gluon polarizations, but also test whether the combination $\ensuremath{\Delta}s\ensuremath{-}(\frac{{\ensuremath{\alpha}}_{s}}{4\ensuremath{\pi}})\ensuremath{\Delta}G$ inferred from the EMC data is valid, i.e., whether gluons contribute to the spin-dependent structure function ${g}_{1}^{p}(x,{Q}^{2})$ via the triangular anomaly.