212 research outputs found
Constrained fit of the valence transversity distributions from dihadron production
We present a constrained analysis of the valence transversity Parton
Distribution Functions from dihadron production in semi-inclusive DIS. While
usual extractions of the transversity distributions rely explicitly on the
fulfilment of the Soffer bounds, the present analysis releases that implicit
restriction to implement further explicit constraints through the Lagrange
multipliers method. The results are quantitatively comparable to previous
analyses in the kinematical range of data ; the qualitative impact of the
chosen fitting strategy translates into an increased flexibility in the
functional form.Comment: 15 figures, hunsrt.bst included. Style modification
Partonic Picture of GTMDs
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions — the generalized transverse momentum distributions — that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that twist three contributions to deeply virtual Compton scattering provide observables related to orbital angular momentum
Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azymuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments
Observables for Quarks and Gluons Orbital Angular Momentum Distributions
We discuss the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term – Ji decomposition – or a canonical term – Jaffe-Manohar decomposition. Orbital angular momentum has been connected in each decomposition to a different observable, a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and a twist three Generalized Parton Distribution (GPD) for the kinetic term. While the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments
Transverse-Momentum Distributions and Spherical Symmetry
Transverse-momentum dependent parton distributions (TMDs) are studied in the
framework of quark models. In particular, quark model relations among TMDs are
reviewed and their physical origin is discussed in terms of rotational-symmetry
properties of the nucleon state in its rest frame.Comment: 8 pages, 2 figures, prepared for the workshop "30 years of strong
interactions", Spa, Belgium, 6-8 April 201
Confinement, the gluon propagator and the interquark potential for heavy mesons
The interquark static potential for heavy mesons described by a massive One
Gluon Exchange interaction obtained from the propagator of the truncated
Dyson-Schwinger equations does not reproduced the expected Cornell potential. I
show that no formulation based on a finite propagator will lead to confinement
of quenched QCD. I propose a mechanism based on a singular nonperturbative
coupling constant which has the virtue of giving rise to a finite gluon
propagator and (almost) linear confinement. The mechanism can be slightly
modified to produce the screened potentials of unquenched QCD.Comment: 12 pages and 7 figure
Dietary supplementation of cystinotic mice by lysine inhibits the megalin pathway and decreases kidney cystine content.
peer reviewedMegalin/LRP2 is a major receptor supporting apical endocytosis in kidney proximal tubular cells. We have previously reported that kidney-specific perinatal ablation of the megalin gene in cystinotic mice, a model of nephropathic cystinosis, essentially blocks renal cystine accumulation and partially preserves kidney tissue integrity. Here, we examined whether inhibition of the megalin pathway in adult cystinotic mice by dietary supplementation (5x-fold vs control regular diet) with the dibasic amino-acids (dAAs), lysine or arginine, both of which are used to treat patients with other rare metabolic disorders, could also decrease renal cystine accumulation and protect cystinotic kidneys. Using surface plasmon resonance, we first showed that both dAAs compete for protein ligand binding to immobilized megalin in a concentration-dependent manner, with identical inhibition curves by L- and D-stereoisomers. In cystinotic mice, 2-month diets with 5x-L-lysine and 5x-L-arginine were overall well tolerated, while 5x-D-lysine induced strong polyuria but no weight loss. All diets induced a marked increase of dAA urinary excretion, most prominent under 5x-D-lysine, without sign of kidney insufficiency. Renal cystine accumulation was slowed down approx. twofold by L-dAAs, and totally suppressed by D-lysine. We conclude that prolonged dietary manipulation of the megalin pathway in kidneys is feasible, tolerable and can be effective in vivo
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