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See detailQUARK CONDENSATES, POMERON STRUCTURE AND DISTRIBUTION FUNCTIONS
Cudell, Jean-René ULg

in Tran Thanh Van, Jean (Ed.) Moriond 1989: Hadronic interactions (1989)

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See detailQuark model analysis of the Sivers function
Courtoy, Aurore ULg; Fratini, F.; Scopetta, S. et al

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2008), 78(3),

We develop a formalism to evaluate the Sivers function. The approach is well suited for calculations which use constituent quark models to describe the structure of the nucleon. A nonrelativistic ... [more ▼]

We develop a formalism to evaluate the Sivers function. The approach is well suited for calculations which use constituent quark models to describe the structure of the nucleon. A nonrelativistic reduction of the scheme is performed and applied to the Isgur-Karl model of hadron structure. The results obtained are consistent with a sizable Sivers effect and the signs for the u and d flavor contributions turn out to be opposite. This pattern is in agreement with the one found analyzing, in the same model, the impact parameter dependent generalized parton distributions. The Burkardt sum rule turns out to be fulfilled to a large extent. We estimate the QCD evolution of our results from the momentum scale of the model to the experimental one and obtain reasonable agreement with the available data. © 2008 The American Physical Society. [less ▲]

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See detailQuark model: recent issues
Stancu, Floarea ULg

Conference (2007)

In the first part I briefly survey recent issues in constituent quark models raised by the observation of unusual hadronic states. In particular I discuss the role of higher Fock components in the wave ... [more ▼]

In the first part I briefly survey recent issues in constituent quark models raised by the observation of unusual hadronic states. In particular I discuss the role of higher Fock components in the wave function of baryons and the possible interpretation of open charm and of new charmonium-type resonances as tetraquarks. In the second part I show support for the quark model dynamics obtained in a model independent way from the 1/Nc expansion approach of QCD which proved to be successful in describing baryon properties. [less ▲]

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See detailThe quark orbital angular momentum from Wigner distributions and light-cone wave functions
Lorce, Cédric ULg; Pasquini, Barbara; Xiong, Xiaonu et al

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2012), D85

We investigate the quark orbital angular momentum of the nucleon in the absence of gauge-field degrees of freedom, by using the concept of the Wigner distribution and the light-cone wave functions of the ... [more ▼]

We investigate the quark orbital angular momentum of the nucleon in the absence of gauge-field degrees of freedom, by using the concept of the Wigner distribution and the light-cone wave functions of the Fock-state expansion of the nucleon. The quark orbital angular momentum is obtained from the phase-space average of the orbital angular momentum operator weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. We also derive the light-cone wave-function representation of the orbital angular momentum. In particular, we perform an expansion in the nucleon Fock-state space and decompose the orbital angular momentum into the N-parton state contributions. Explicit expressions are presented in terms of the light-cone wave functions of the three-quark Fock state. Numerical results for the up and down quark orbital angular momenta of the proton are shown in the lightcone constituent quark model and the light-cone chiral quark-soliton model. [less ▲]

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See detailThe quark propagator from the Dyson-Schwinger equations: (I). The chiral solution
Cudell, Jean-René ULg; Gentles, A. J.; Ross, D. A.

in Nuclear Physics B (1995), 440

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See detailQuark transverse charge densities in the Delta(1232) from lattice QCD
Alexandrou, Constantia; Korzec, Tomasz; Giannis, Koutsou et al

in Nuclear Physics A (2009), A825

We extend the formalism relating electromagnetic form factors to transverse quark charge densities in the light-front frame to the case of a spin-3/2 baryon and calculate these transverse densities for ... [more ▼]

We extend the formalism relating electromagnetic form factors to transverse quark charge densities in the light-front frame to the case of a spin-3/2 baryon and calculate these transverse densities for the $\Delta (1232)$ isobar using lattice QCD. The transverse charge densities for a transversely polarized spin-3/2 particle are characterized by monopole, dipole, quadrupole, and octupole patterns representing the structure beyond that of a pure point-like spin-3/2 particle.We present lattice QCD results for the $\Delta$-isobar electromagnetic form factors for pion masses down to approximatively 350 MeV for three cases: quenched QCD, two-degenerate flavors of dynamicalWilson quarks, and three flavors of quarks using a mixed action that combines domain wall valence quarks and dynamical staggered sea quarks. We extract transverse quark charge densities from these lattice results and find that the $Delta$ is prolately deformed, as indicated by the fact that the quadrupole moment $G_{E2}(0)$ is larger than the value −3 characterizing a point particle and the fact that the transverse charge density in a $\Delta^+$ of maximal transverse spin projection is elongated along the axis of the spin. [less ▲]

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See detailQuark Wigner Distributions and Orbital Angular Momentum
Lorce, Cédric ULg; Pasquini, B.

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2011), D84

We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse ... [more ▼]

We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. We focus the discussion on the distributions of unpolarized/longitudinally polarized quark in an unpolarized/longitudinally polarized nucleon. In this way, we can study the role of the orbital angular momentum of the quark in shaping the nucleon and its correlations with the quark and nucleon polarizations. The quark orbital angular momentum is also calculated from its phase-space average weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. The corresponding results obtained within different light-cone quark models are compared with alternative definitions of the quark orbital angular momentum, as given in terms of generalized parton distributions and transverse-momentum dependent parton distributions. [less ▲]

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See detailQuartier nègre: nouveau monde et nouveau code
Demoulin, Laurent ULg

in Traces (2012), 20

Le roman Quartier nègre de Simenon est lu ici à la lumière de l'essai de Goffman La Mise en scène de la vie quotidienne.

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See detailQuartiere non è un quartiere : Racconto con foto quasi immaginarie
Curreri, Luciano ULg

Book published by Amos (2013)

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See detailLes quartiers 'ghettos' : des étiquettes collées sur des phénomènes complexes?
Ruelle, Christine ULg

Conference given outside the academic context (2014)

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See detailLes quartiers durables : processus de production et reproductibilité
Marique, Anne-Françoise ULg

Master's dissertation (2009)

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See detailLes quartiers urbains existants peuvent-ils devenir des "quartiers durables" et surtout, comment? L'expérience du projet SUN dans le quartier St-Léonard (Liège).
Ruelle, Christine ULg; Stangherlin, Gregor

in Cahiers Nouveaux (Les) (2012), n°84

L'article retrace brièvement la démarche de recherche-action menée dans le cadre du projet Interreg IVA SUN, qui avait pour objectif d'explorer les pistes d'action publique possibles afin de soutenir la ... [more ▼]

L'article retrace brièvement la démarche de recherche-action menée dans le cadre du projet Interreg IVA SUN, qui avait pour objectif d'explorer les pistes d'action publique possibles afin de soutenir la transition des quartiers urbains vers un développement durable. [less ▲]

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See detailQuartiles d'une série statistique univariée : quelles définitions ?
Henry, Valérie ULg

in Losanges (2010), 7

Sur base d'une étude comparative de la littérature sur le sujet, nous proposons une définition du premier quartile qui permette de rester en cohérence avec la définition de celui-ci pour une variable ... [more ▼]

Sur base d'une étude comparative de la littérature sur le sujet, nous proposons une définition du premier quartile qui permette de rester en cohérence avec la définition de celui-ci pour une variable quantitative dont les données ont été réparties en classes. [less ▲]

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See detailIl quarto musicista
Emmanuel, François; Ricciardi, Stefania ULg

Book published by San Paolo (2003)

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See detailQuasar Candidates in a Large Field Centered around NGC450 and the Discovery of a New Very Interesting Pair of Quasars
Swings, Jean-Pierre ULg; Surdej, Jean ULg; Henry, A. et al

in Revista Mexicana de Astronomia y Astrofisica, vol. 10 (1985), 10

Abstract image available at: http://esoads.eso.org/abs/1985RMxAA..10...91S

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See detailQuasar Host Orientation and Polarization: Insights into the Type 1/Type 2 Dichotomy
Borguet, Benoît ULg; Hutsemekers, Damien ULg; Letawe, Géraldine ULg et al

in Revista Mexicana de Astronomía y Astrofísica (2008), 32

We investigate correlations between the optical linear polarization position angle and the orientation of the host galaxy/extended emission of Type 1 and Type 2 Radio-Loud (RL) and Radio-Quiet (RQ ... [more ▼]

We investigate correlations between the optical linear polarization position angle and the orientation of the host galaxy/extended emission of Type 1 and Type 2 Radio-Loud (RL) and Radio-Quiet (RQ) quasars. We have used high resolution Hubble Space Telescope (HST) data and deconvolution process to obtain a good determination of the host galaxy orientation. With these new measurements and a compilation of data from the literature, we find a significant correlation between the polarization position angle and the position angle of the major axis of the host galaxy/extended emission. The correlation appears different for Type 1 and Type 2 objects and depends on the redshift of the source. Interpretations in the framework of the unification model are discussed. [less ▲]

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See detailQuasar induced galaxy formation: a new paradigm?
Elbaz, David; Jahnke, Knud; Pantin, eric et al

in Astronomy and Astrophysics (2009), 507

Aims: We discuss observational evidence that quasars play a key role in the formation of galaxies, starting from the detailed study of the quasar HE0450-2958 and extending the discussion to a series of ... [more ▼]

Aims: We discuss observational evidence that quasars play a key role in the formation of galaxies, starting from the detailed study of the quasar HE0450-2958 and extending the discussion to a series of converging evidence that radio jets may trigger galaxy formation. Methods: We use mid infrared imaging with VISIR at the ESO-VLT to model the mid to far infrared energy distribution of the system and the stellar population of the companion galaxy using optical VLT-FORS spectroscopy. The results are combined with optical, CO, radio continuum imaging from ancillary data. Results: The direct detection with VISIR of the 7 kpc distant companion galaxy of HE0450-2958 allows us to spatially separate the sites of quasar and star formation activity in this composite system made of two ultra-luminous infrared galaxies (ULIRGs), where the quasar generates the bulk of the mid infrared light and the companion galaxy powered by star formation dominates in the far infrared. No host galaxy has yet been detected for this quasar, but the companion galaxy stellar mass would bring HE0450-2958 in the local MBH - Mstar-bulge relation if it were to merge with the QSO. This is bound to happen because of their close distance (7 kpc) and low relative velocity ( 60-200 km s-1). We conclude that we may be witnessing the building of the MBH - Mstar-bulge relation, or at least of a major event in that process. The star formation rate ( 340 Mȯ yr-1), age (40-200 Myr) and stellar mass ( [5-6]×10^10 Mȯ) are consistent with jet-induced formation of the companion galaxy. We suggest that HE0450-2958 may be fueled by fresh material from cold gas accretion from intergalactic filaments. We map the projected galaxy density surrounding the QSO as a potential tracer of intergalactic filaments and discuss a putative detection. Comparison to other systems suggest that an inside-out formation of quasar host galaxies and jet-induced galaxy formation may be a common process. Two tests are proposed for this new paradigm: (1) the detection of offset molecular gas or dust emission with respect to the position of distant QSOs; (2) the delayed formation of host galaxies as a result of QSO activity, hence the two step building of the M_BH/Mstar-bulge ratio. [less ▲]

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See detailQuasar pairs with arcminute angular separations
Zhdanov, V. I.; Surdej, Jean ULg

in Astronomy and Astrophysics (2001), 372

We use the Véron-Cetty & Véron (\cite {veron}) catalog (VV) of 13 213 quasars to investigate their possible physical grouping over angular scales 10arcsec <=Delta theta <= 1000arcsec . We first estimate ... [more ▼]

We use the Véron-Cetty & Véron (\cite {veron}) catalog (VV) of 13 213 quasars to investigate their possible physical grouping over angular scales 10arcsec <=Delta theta <= 1000arcsec . We first estimate the number of quasar pairs that would be expected in VV assuming a random distribution for the quasar positions and taking into account observational selection effects affecting heterogeneous catalogs. We find in VV a statistically significant (>3sigma ) excess of pairs of quasars with similar redshifts (Delta z<= 0.01) and angular separations in the 50arcsec -100arcsec range, corresponding to projected linear separations (0.2-0.5) Mpc/h[SUB]75[/SUB] (Omega[SUB]M[/SUB] =1, Omega[SUB]Lambda[/SUB] =0) or (0.4-0.7) Mpc/h[SUB]75[/SUB] (Omega[SUB]M[/SUB] =0.3, Omega[SUB]Lambda[/SUB] = 0.7). There is also some excess in the 100arcsec -600arcsec range corresponding to (1-5) Mpc in projected linear separations. If most of these quasar pairs do indeed belong to large physical entities, these separations must represent the inner scales of huge mass concentrations (cf. galaxy clusters or superclusters) at high redshifts; but it is not excluded that some of the pairs may actually consist of multiple quasar images produced by gravitational lensing. Of course, a fraction of these pairs could also arise due to random projections of quasars on the sky. The list of 11 pairs of quasars with redshift differences Delta z<= 0.02 and angular separations 50arcsec <= Delta theta <= 100arcsec is presented in order to stimulate further observational studies and to better understand the astrophysical and cosmological significance of these interesting objects. [less ▲]

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See detailQuasar polarization (Hutsemekers 1998)
Hutsemekers, Damien ULg

Textual, factual or bibliographical database (1997)

The table contains optical polarization data for a sample of 170 moderate to high-redshift quasars (1 data file).

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See detailQuasar polarization (Hutsemekers+ 1998)
Hutsemekers, Damien ULg; Lamy, H.; Remy, Marc

Textual, factual or bibliographical database (1998)

Table 2 contains optical (V) polarimetric measurements for 42 optically selected QSOs including 29 broad absorption line QSOs. Table 3 contains a series of spectral indices characterizing the broad ... [more ▼]

Table 2 contains optical (V) polarimetric measurements for 42 optically selected QSOs including 29 broad absorption line QSOs. Table 3 contains a series of spectral indices characterizing the broad absorption line QSOs. (2 data files). [less ▲]

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