Unpolarized Distribution Research Articles

FLAVOR DEPENDENCE OF UNPOLARIZED TMDS FROM SEMI-INCLUSIVE PION PRODUCTION

Recent data from semi-inclusive deep inelastic scattering collected by the HERMES collaboration allow for the first time to discuss how the transverse-momentum dependence of unpolarized distribution and fragmentation functions is affected by the flavor of the involved partons. A model built with flavor-dependent Gaussian transverse-momentum distributions fits data better than the same flavor-independent model. The current analysis is performed for totally unpolarized scattering of leptons off protons and deuterons, with detected pions in the final state. There are convincing indications of flavor dependence in the fragmentation functions, while for parton distribution functions the evidence is weaker.

Symmetry breaking effect on determination of polarized and unpolarized parton distributions

We perform a new extraction for unpolarized and polarized parton distribution functions considering a flavor decompositions for sea quarks and applying very recent deep inelastic scattering (DIS) and semi inclusive deep inelastic scattering (SIDIS) data in the fixed flavor number scheme (FFNS) framework. In the new symmetry breaking scenario the light quark and antiquark densities are extracted separately and new parametrization forms are determined for them. The heavy flavors contribution, including charm and bottom quarks, are also taken to be account for unpolarized distributions.

Unpolarized Release of Vaccinia Virus and HIV Antigen by Colchicine Treatment Enhances Intranasal HIV Antigen Expression and Mucosal Humoral Responses

The induction of a strong mucosal immune response is essential to building successful HIV vaccines. Highly attenuated recombinant HIV vaccinia virus can be administered mucosally, but even high doses of immunization have been found unable to induce strong mucosal antibody responses. In order to solve this problem, we studied the interactions of recombinant HIV vaccinia virus Tiantan strain (rVTT-gagpol) in mucosal epithelial cells (specifically Caco-2 cell layers) and in BALB/c mice. We evaluated the impact of this virus on HIV antigen delivery and specific immune responses. The results demonstrated that rVTT-gagpol was able to infect Caco-2 cell layers and both the nasal and lung epithelia in BALB/c mice. The progeny viruses and expressed p24 were released mainly from apical surfaces. In BALB/c mice, the infection was limited to the respiratory system and was not observed in the blood. This showed that polarized distribution limited antigen delivery into the whole body and thus limited immune response. To see if this could be improved upon, we stimulated unpolarized budding of the virus and HIV antigens by treating both Caco-2 cells and BALB/c mice with colchicine. We found that, in BALB/c mice, the degree of infection and antigen expression in the epithelia went up. As a result, specific immune responses increased correspondingly. Together, these data suggest that polarized budding limits antigen delivery and immune responses, but unpolarized distribution can increase antigen expression and delivery and thus enhance specific immune responses. This conclusion can be used to optimize mucosal HIV vaccine strategies.

Optical field-strength generalized polarization of multimode single photon states in integrated directional couplers

A quantum analysis of the generalized polarization properties of multimode single photon states is presented. It is based on the optical field-strength probability distributions in such a way that generalized polarization is understood as a significant confinement of the probability distribution along certain regions of the multidimensional optical field-strength space. The analysis is addressed to multimode integrated waveguiding devices, such as N × N integrated directional couplers, whose modes fulfil a spatial modal orthogonality relationship. For that purpose a definition of the quantum generalized polarization degree in a N-dimensional space, based on the concept of distance to an unpolarized N-dimensional Gaussian distribution, is proposed. The generalized polarization degree of pure and mixture multimode single photon states and also of some multi-photon states such as coherent and chaotic ones, is evaluated and analyzed.

Nucleon and pion distribution functions in the valence region

An experimental and theoretical perspective is provided on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain, namely, Bjorken $x\ensuremath{\gtrsim}0.4$. This domain is a key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. The focus is on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the standard model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, an explanation that an upgraded Jefferson Laboratory facility is well suited to provide new data on the nucleon is provided, while a future electron-ion collider could provide essential new data for the mesons. There is also great potential in using Drell-Yan interactions, at FNAL, CERN, J-PARC, and GSI, to push into the large-$x$ domain for both mesons and nucleons. Furthermore, it is argued that explanation, in contrast to modeling and parametrization, requires a widespread acceptance of the need to adapt theory: to the lessons learnt already from the methods of nonperturbative quantum-field theory and a fuller exploitation of those methods.

Optical field-strength polarization of two-mode single-photon states

We present a quantum analysis of two-mode single-photon states based on the probability distributions of the optical field strength (or position quadrature) in order to describe their quantum polarization characteristics, where polarization is understood as a significative confinement of the optical field-strength values on determined regions of the two-mode optical field-strength plane. We will show that the mentioned probability distributions along with the values of quantum Stokes parameters allow us to characterize the polarization of a two-mode single-photon state, in an analogous way to the classical case, and to distinguish conceptually between mixture and partially polarized quantum states; in this way, we propose a simple definition of the quantum polarization degree based on the recent concept of distance measure to an unpolarized distribution, which gives rise to a depolarization degree equivalent to an overlapping between the probability distribution of the quantum state and a non-polarized two-mode Gaussian distribution. The work is particularly intended to university physics teachers and graduate students as well as to physicists and specialists concerned with the issue of optical polarization.

Deep-inelastic scattering and the operator product expansion in lattice QCD

We discuss the determination of deep-inelastic hadron structure in lattice QCD. By using a fictitious heavy-quark, direct calculations of the Compton scattering tensor can be performed in Euclidean space that allow the extraction of the moments of structure functions. This overcomes issues of operator mixing and renormalization that have so far prohibited lattice computations of higher moments. This approach is especially suitable for the study of the twist-two contributions to isovector quark distributions, which is practical with current computing resources. While we focus on the isovector unpolarized distribution, our method is equally applicable to other quark distributions and to generalized parton distributions. By looking at matrix elements such as (where V{sup {mu}} and A{sup {nu}} are vector and axial-vector heavy-light currents) within the same formalism, moments of meson distribution amplitudes can also be extracted.

THE KINETIC INTERPRETATION OF THE DGLAP EQUATION, ITS KRAMERS–MOYAL EXPANSION AND POSITIVITY OF HELICITY DISTRIBUTIONS

According to a rederivation — due to Collins and Qiu — the DGLAP equation can be reinterpreted (in leading order) in a probabilistic way. This form of the equation has been used indirectly to prove the bound |Δ f(x, Q)| < f(x, Q) between polarized and unpolarized distributions, or positivity of the helicity distributions, for any Q. We reanalyze this issue by performing a detailed numerical study of the positivity bounds of the helicity distributions. To obtain the numerical solution we implement an x-space based algorithm for polarized and unpolarized distributions to next-to-leading order in αs, which we illustrate. We also elaborate on some of the formal properties of the Collins–Qiu form and comment on the underlying regularization, introduce a Kramers–Moyal expansion of the equation and briefly analyze its Fokker–Planck approximation. These follow quite naturally once the master version is given. We illustrate this expansion both for the valence quark distribution qV and for the transverse spin distribution h1.

QUARK–ANTIQUARK ASYMMETRY OF THE NUCLEON STRANGE SEA

The possible asymmetry of the s- and [Formula: see text]-quark distributions in the nucleon is investigated on the basis of the flavor SU(3) chiral quark soliton model. We find that the asymmetry is much larger for the longitudinally polarized distribution functions than for the unpolarized ones. A preliminary comparison with the CCFR data for the unpolarized s-quark distribution and with the LSS fits of the longitudinally polarized distribution functions is encouraging.

PHENOMENOLOGY OF THE FLAVOR-ASYMMETRY IN THE LIGHT-QUARK SEA OF THE NUCLEON

A phenomenological ansatz for the flavor-asymmetry of the light sea distributions of the nucleon, based on the Pauli exclusion principle, is proposed. This ansatz is compatible with the measured flavor-asymmetry of the unpolarized sea distributions, [Formula: see text], of the nucleon. A prediction for the corresponding polarized flavor-asymmetry is presented and shown to agree with predictions of (chiral quark–soliton) models which successfully reproduced the flavor-asymmetry of the unpolarized sea.

ANALYZING POWERS IN INCLUSIVE PION PRODUCTION AT HIGH ENERGY AND THE NUCLEON SPIN STRUCTURE

Analyzing powers in inclusive pion production in high energy transversely polarized proton–proton collisions are studied theoretically in the framework of the quark recombination model. Calculations by assuming the SU(6) spin-flavor symmetry for the nucleon structure disagree with the experiments. We solve this difficulty by taking into account the realistic spin distribution functions of the nucleon, which differs from the SU(6) expectation at large x, with a perturbative QCD constraint on the ratio of the unpolarized valence distributions, u/d→5 as x→ 1. We also discuss the kaon spin asymmetry and find AN(K+)=-AN(K0) in the polarized proton–proton collisions at large x F .

Nucleon parton distributions in the chiral theory of nucleon

Abstract At large Nc the nucleon can be viewed as a soliton of the effective chiral lagrangian. This picture of nucleons allows a consistent nonperturbative calculation of the leading-twist parton distributions at a low normalization point. We derive general formulae for the polarized and unpolarized distributions in the chiral quark-soliton model. The consistency of the approach is demonstrated by checking the baryon number, isospin and total momentum sum rules, as well as the Bjorken sum rule. We present results for the quark and antiquark distributions and find reasonable agreement with parametriza-tions of the data at a low normalization point. In particular, we obtain a sizeable fraction of antiquaries, in agreement with the phenomenological analysis.

Activation of the Urokinase Plasminogen Activator/Urokinase Plasminogen Activator Receptor System and Redistribution of E-Cadherin Are Associated with Hepatocyte Growth Factor-Induced Motility of Pancreas Tumor Cells Overexpressing Met

Because hepatocyte growth factor (HGF) is a potent mitogen for normal human exocrine pancreas cells (NPCs) in vitro, we have analyzed the expression of HGF and its receptor, Met, in NPC and pancreas cancer cells and studied its effects in vitro. Using immunohistochemistry, Northern blotting, and reverse transcription-polymerase chain reaction, we examined the expression of HGF and Met in normal pancreas and pancreas cancer. Scatter assays, wound-healing assays, and migration through transwell filters were used to study HGF-stimulated motility of IMIM-PC-2 cancer cells. In tumors, HGF is mainly detected in stromal cells, whereas Met is overexpressed in cancer cells with an unpolarized distribution. In vitro, HGF stimulates motogenesis but not proliferation in cancer cells. Cell motility is accompanied by a rapid decrease in the cytoskeleton-bound E-cadherin, an acceleration of cellular adhesion to the substrate, an up-regulation of urokinase plasminogen activator (u-PA) RNA and protein, and a change in the solubility and proteolysis of the u-PA receptor. Cell motility is significantly reduced by inhibitors of u-PA proteolytic activity such as antibodies neutralizing u-PA activity, plasminogen activator inhibitor 1, and amiloride. These results show that a paracrine loop of HGF activation may participate in the development or progression of pancreas cancer. In vitro, the HGF-stimulated motogenesis of pancreas cancer cells involves the activation of the u-PA/u-PA receptor proteolytic system, suggesting its role in the invasive stages of tumor progression.

Light-cone wavefunctions at small x

There exist an infinite number of exact small momentum fraction-$x$ boundary conditions on light-cone wavefunctions of bound states in gauge theory. They are necessary for finite expectation values of the invariant mass operator and relate components of the wavefunction from different Fock sectors. We illustrate their consequences by analyzing the small-$x$ quark Regge behavior of a heavy large-$N$ meson, finding power-law rise of unpolarized distributions. The polarized distribution changes sign and then vanishes with minus the unpolarized Regge intercept.

Nucleon parton distributions at low normalization point in the large Nc limit

At large N c the nucleon can be viewed as a soliton of the effective chiral lagrangian. This picture of nucleons allows for a consistent non-perturbative calculation of the leading-twist parton distributions at a low normalization point. We derive general formulae for the polarized and unpolarized distributions (singlet and non-singlet) in the chiral quark-soliton model. The consistency of our approach is demonstrated by checking the baryon number, isospin and total momentum sum rules, as well as the Bjorken sum rule. We present numerical estimates of the quark and antiquark distributions and find reasonable agreement with parameterizations of the data at a low normalization point. In particular, we obtain a sizeable fraction of antiquarks, in agreement with the phenomenological analysis.

Diffusely scattered second harmonic generation from a silver film due to surface plasmons

We have measured the surface normal scattering of optical second harmonic generation (SHG) from a silver film due to excitation of surface plasmons. Previous researchers reported a narrow angular (∼0.5°) p-polarized SHG distribution. Instead we observe a broad (∼90°) unpolarized distribution both for smooth and roughened silver films.

PARTON DISTRIBUTIONS IN THE NUCLEON AND THE PAULI PRINCIPLE

The Pauli principle is used, together with some deep inelastic scattering data, to guide us in making reasonable assumptions for various polarized parton distributions in terms of unpolarized distributions. We relate the violation of the Gottfried and Ellis-Jaffe sum rules and we anticipate a substantial violation of the Bjorken sum rule.

The strangeness content of the proton can only be small

It has recently been claimed that the explicit introduction of a so-called “non-perturbative” contribution to the spin-dependent strange-quark distribution in the proton sea may avoid positivity bounds obtained from very precise data presently available for the corresponding unpolarised distributions. We show that the unusual large- x B behaviour, ∼ (1 − x) 5, required for such avoidance is entirely incompatible with that displayed by the existing deep-inelastic neutrino data, ∼ (1 − x) 10. Thus we demonstrate the untenability of this scenario for the avoidance of the positivity bound on the magnitude of the strange-quark contribution to the proton-spin sum-rule. Such a bound leads to a marked disagreement between predictions based on the light-cone expansion in perturbative QCD and experimental measurements.

Gauge vector boson pair production at $$\bar p$$ p collider energies

Within the standardSU(2)×U(1) model differential cross sections and angular distributions of all polarization states are studied for all channels of gauge vector boson pairs accessible in hadron hadron collisions,W+W−,Z0Z0,Zγ,ZW, γW. The zero in the unpolarized angular distribution ofq\(\bar q\)→Wγ reported theoretically by Mikaelian et al. [1] is confirmed. The origin of this zero is studied which was discovered by Brown, Mikaelian, Samuel, and Shadev. None of the other channels exhibits a zero in the unpolarized angular distribution, but strong minima at cosΘ=0 are predicted for\(q_i \bar q_j \to Z\gamma \) and\(q_i \bar q_j \to ZW^ + \). These are of different origin than the Mikaelian zero. Simple structure functions suggest that these minima are seen inp\(\bar p\) collisions.

Scale-breaking polarised quark and gluon distributions

The authors present scale-breaking polarised and unpolarised parton distribution functions obtained by solving the Altarelli-Parisi equations (1977) numerically. For valence quarks analytical parametrisations for these distributions are given. The sea-quark distributions become polarised with increasing Q2 even for unpolarised input distributions at Q02. They apply these distributions for the calculation of weak vector-boson signals in hadron jet production cross sections and parity-violating spin asymmetries in pp and pp collisions at collider energies.