Radiative corrections: from medium to high energy experiments.

Radiative corrections are crucial for modern high-precision physics experiments, and are an area of active research in the experimental and theoretical community. Here we provide an overview of the state of the field of radiative corrections with a focus on several topics: lepton-proton scattering, QED corrections in deep-inelastic scattering, and in radiative light-hadron decays. Particular emphasis is placed on the two-photon exchange, believed to be responsible for the proton form-factor discrepancy, and associated Monte-Carlo codes.

X17 Discovery Potential in the γN→e^{+}e^{-}N Process at Electron Scattering Facilities.

We propose a direct search for the X17 particle, which was conjectured to explain the ATOMKI ^{8}Be and ^{4}He anomalies, through the dilepton photoproduction process on a nucleon in the photon energy range below or around the pion production threshold. For the scenarios of either pseudoscalar, vector, or axial-vector quantum numbers of the conjectured X17, we use existing constraints to estimate the X17 signal process. For dilepton invariant mass resolutions which have been achieved in previous experiments, a signal-to-background ratio of up to an order of magnitude is found for a neutron target, and, in particular, for the pseudoscalar and vector X17 scenarios.

Lepton Universality Test in the Photoproduction of e^{-}e^{+} Versus μ^{-}μ^{+} Pairs on a Proton Target.

In view of the significantly different proton charge radius extracted from muonic hydrogen Lamb shift measurements as compared to electronic hydrogen spectroscopy or electron-scattering experiments, we study in this Letter the photoproduction of a lepton pair on a proton target in the limit of very small momentum transfer as a way to provide a test of the lepton universality when extracting the proton charge form factor. By detecting the recoiling proton in the γp→l^{-}l^{+}p reaction, we show that a measurement of a ratio of e^{-}e^{+}+μ^{-}μ^{+} over e^{-}e^{+} cross sections with an absolute precision of 7×10^{-4} would allow for a test to distinguish, at the 3σ level, between the two different proton charge radii currently extracted from muonic and electronic observables.

Generalized parton distributions in the valence region from deeply virtual Compton scattering.

This work reviews the recent developments in the field of generalized parton distributions (GPDs) and deeply virtual Compton scattering in the valence region, which aim at extracting the quark structure of the nucleon. We discuss the constraints which the present generation of measurements provide on GPDs, and examine several state-of-the-art parametrizations of GPDs. Future directions in this active field are discussed.

Transverse beam spin asymmetries at backward angles in elastic electron-proton and quasielastic electron-deuteron scattering.

We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for Q² = 0.22 GeV²/c² and 0.63 GeV²/c² at beam energies of 362 and 687 MeV, respectively.

Search for effects beyond the born approximation in polarization transfer observables in e(over→)p elastic scattering.

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, G(E)/G(M), obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic H(e[over →],e(')p[over →]) reaction for three different beam energies at a Q(2)=2.

Sum rules for light-by-light scattering.

We derive a set of sum rules for the light-by-light scattering and fusion: γγ→all, and verify them in lowest order QED calculations. A prominent implication of these sum rules is the superconvergence of the helicity-difference total cross section for photon fusion, which in the hadron sector reveals an intricate cancellation between the pseudoscalar and tensor mesons. An experimental verification of superconvergence of the polarized photon fusion into hadrons is called for, but will only be possible at e+ e- and γγ colliders with both beams polarized.

Light-front interpretation of proton generalized polarizabilities.

We extend the recently developed formalism to extract light-front quark charge densities from nucleon form factor data to the deformations of these quark charge densities when applying an external electric field. We show that the resulting induced polarizations can be extracted from proton generalized polarizabilities. The available data for the generalized electric polarizability of the proton yield a pronounced structure in its induced polarization at large transverse distances, which will be pinned down by forthcoming high precision virtual Compton scattering experiments.

Two-photon exchange in elastic electron-proton scattering: a QCD factorization approach.

We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer Q(2). It is shown that the leading two-photon exchange amplitude behaves as 1/Q(4), and can be expressed in a model independent way in terms of the leading twist nucleon distribution amplitudes. Using several models for the nucleon distribution amplitudes, we provide estimates for existing data and for ongoing experiments.

Targeting nanoparticles to M cells with non-peptidic ligands for oral vaccination.

The presence of RGD on nanoparticles allows the targeting of beta1 integrins at the apical surface of human M cells and the enhancement of an immune response after oral immunization. To check the hypothesis that non-peptidic ligands targeting intestinal M cells or APCs would be more efficient for oral immunization than RGD, novel non-peptidic and peptidic analogs (RGD peptidomimitic (RGDp), LDV derivative (LDVd) and LDV peptidomimetic (LDVp)) as well as mannose were grafted on the PEG chain of PCL-PEG and incorporated in PLGA-based nanoparticles. RGD and RGDp significantly increased the transport of nanoparticles across an in vitro model of human M cells as compared to enterocytes.

Effect of tape stripping and adjuvants on immune response after intradermal DNA electroporation.

Purpose: DNA vaccines require both efficient delivery methods and appropriate adjuvants. Based on their mechanisms of action, we hypothesised that some adjuvants could enhance vaccine immunogenicity or direct the response towards Th1 profile after intradermal DNA electroporation.

Methods: After intradermal electroporation of plasmid DNA encoding luciferase, mice received hyaluronidase, imiquimod, monophosphoryl lipid A or were tape stripped in order to modulate the immune response against the encoded protein.

Empirical transverse charge densities in the nucleon and the nucleon-to-delta transition.

Using only the current empirical information on the nucleon electromagnetic form factors we map out the transverse charge density in proton and neutron as viewed from a light front moving towards a transversely polarized nucleon. These charge densities are characterized by a dipole pattern, in addition to the monopole field corresponding with the unpolarized density. Furthermore, we use the latest empirical information on the N-->Delta transition form factors to map out the transition charge density which induces the N-->Delta excitation.

Optimisation of intradermal DNA electrotransfer for immunisation.

The development of DNA vaccines requires appropriate delivery technologies. Electrotransfer is one of the most efficient methods of non-viral gene transfer. In the present study, intradermal DNA electrotransfer was first optimised.

Measurement of deeply virtual compton scattering with a polarized-proton target.

The longitudinal target-spin asymmetry AUL for the exclusive electroproduction of high-energy photons was measured for the first time in ep-->e;'pgamma. The data have been accumulated at JLab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH3 target.

Two-photon-exchange effects in the electroexcitation of the delta resonance.

We examine the two-photon exchange contribution to the eN --> edelta(1232) --> epiN process with the aim of a precision study of the ratios of electric quadrupole (E2) and Coulomb quadrupole (C2) to the magnetic dipole (M1) gamma*Ndelta transitions. We relate the two-photon exchange amplitude to the N --> delta generalized parton distributions and obtain a quantitative estimate of the two-photon effects. The two-photon exchange corrections to the C2/M1 ratio depend strongly on whether this quantity is obtained from an interference cross section or from the Rosenbluth-type cross sections, in similarity with the elastic, eN --> eN, process.

Electromagnetic nucleon-to-delta transition in chiral effective-field theory.

We perform a relativistic chiral effective-field theory calculation of pion electroproduction off the nucleon (e- N --> e- N(pi)) in the delta(1232)-resonance region. After fixing the three low-energy constants, corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) gammaNdelta couplings, our calculation provides a prediction for the momentum transfer and pion-mass dependence of the gammaNdelta form factors. The prediction for the pion-mass dependence resolves the discrepancy between the recent lattice QCD results and the experimental value for the "C2/M1 ratio" at low Q2.

Magnetic moment of the delta(1232) resonance in chiral effective-field theory.

We perform a relativistic chiral effective-field theory calculation of the radiative pion photoproduction (gammap--> pi(0)pgamma(')) in the Delta-resonance region, to next-to-leading order in the "delta expansion." This work is aimed at a model-independent extraction of the Delta(+) magnetic moment from new precise measurements of this reaction. It also predicts the chiral behavior of Delta's magnetic moment, which can be used to extrapolate the recent lattice QCD results to the physical point.

Partonic calculation of the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer.

We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer through the scattering off a parton in the proton. We relate the two-photon exchange amplitude to the generalized parton distributions which appear in hard exclusive processes. We find that when taking the polarization transfer determinations of the form factors as input, adding in the 2-photon correction does reproduce the Rosenbluth cross sections.

Measurement of the generalized polarizabilities of the proton in virtual Compton scattering at Q2=0.92 and 1.76 GeV2.

We report a virtual Compton scattering study of the proton at low c.m. energies.

How to reconcile the Rosenbluth and the polarization transfer methods in the measurement of the proton form factors.

The apparent discrepancy between the Rosenbluth and the polarization transfer methods for the ratio of the electric to magnetic proton form factors can be explained by a two-photon exchange correction which does not destroy the linearity of the Rosenbluth plot. Though intrinsically small, of the order of a few percent of the cross section, this correction is accidentally amplified in the case of the Rosenbluth method.

CD8+ T lymphocytes regulating Th2 pathology escape neonatal tolerization.

Transplantation tolerance induced by neonatal injection of semiallogeneic spleen cells is associated in several strain combinations with a pathological syndrome caused by Th2 differentiation of donor-specific CD4(+) T lymphocytes. We investigated the role of host CD8(+) T cells in the regulation of this Th2 pathology. IgE serum levels and eosinophilia significantly increased in BALB/c mice neonatally injected with (A/J x BALB/c)F(1) spleen cells when CD8(+) T cells were depleted by administration of anti-CD8 mAb or when beta(2)-microglobulin-deficient mice were used as recipients.

Double deeply virtual Compton scattering off the nucleon.

We study the double deeply virtual Compton scattering (DDVCS) process off the nucleon, through the scattering of a space-like virtual photon with large virtuality resulting in the production of a time-like virtual photon, decaying into an e(+)e(-) pair. This process is expressed in the Bjorken regime in terms of generalized parton distributions (GPDs), and it is shown that by varying the invariant mass of the lepton pair, one can directly extract the GPDs from the observables. We give predictions for the DDVCS cross section and beam helicity asymmetry and discuss its experimental feasibility.

Generalized spin polarizabilities of the nucleon in heavy-baryon chiral perturbation theory at order Omicron(p(4)).

We present the first heavy-baryon chiral perturbation theory calculation at order Omicron(p(4)) for the spin-dependent amplitudes for virtual Compton scattering off the nucleon and extract the Omicron(p(4)) results for the generalized spin polarizabilities of the nucleon.

Hypereosinophilic syndrome induced by neonatal immunization against MHC class II alloantigen: critical role of IL-4.

A significant proportion of patients with the hypereosinophilic syndrome suffer from oligoclonal expansion of type 2 helper T lymphocytes (Th2). Herein, we first provide evidence that mice immunized at birth against a single MHC class II alloantigen develop pathological features mimicking this variant of the hypereosinophilic syndrome. Indeed, C57BL / 6 mice injected at birth with (C57BL/ 6 x bm12)F1 spleen cells displayed T lymphocytes producing high levels of IL-5 and IL-13, increased blood eosinophil counts, eosinophilic infiltrates in various tissues, hyperplasia of lymphoid tissues, as well as serum hyperIgE.

Hard exclusive electroproduction of decuplet baryons in the large N(c) limit.

The cross sections and transverse spin asymmetries in the hard exclusive electroproduction of decuplet baryons are calculated in the large N(c) limit and found to be comparable to that of octet baryons. Large N(c) selection rules for the production amplitudes are derived, leading to new sensitive tests of the spin aspects of the QCD chiral dynamics both in the nonstrange and strange sectors. Importance of such studies for the reliable extraction of the pion form factor from pion electroproduction is explained.