arXiv subjects

N. D'Hose

Publications and source records attributed to N. D'Hose.

6 recordsLinked to original sources

arXiv2022

ATHENA Detector Proposal -- A Totally Hermetic Electron Nucleus Apparatus proposed for IP6 at the Electron-Ion Collider

ATHENA has been designed as a general purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider. Careful technology choices provide fine tracking and momentum resolution, high performance electromagnetic and hadronic calorimetry, hadron identification over a wide kinematic range, and near-complete hermeticity. This article describes the detector design and its expected performance in the most relevant physics channels. It includes an evaluation of detector technology choices, the technical challenges to realizing the detector and the R&D required to meet those challenges.

physics.ins-det↗

arXiv2021

An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab

Positron beams, both polarized and unpolarized, are identified as essential ingredients for the experimental programs at the next generation of lepton accelerators. In the context of the hadronic physics program at Jefferson Lab (JLab), positron beams are complementary, even essential, tools for a precise understanding of the electromagnetic structure of nucleons and nuclei, in both the elastic and deep-inelastic regimes. For instance, elastic scattering of polarized and unpolarized electrons and positrons from the nucleon enables a model independent determination of its electromagnetic form factors. Also, the deeply-virtual scattering of polarized and unpolarized electrons and positrons allows unambiguous separation of the different contributions to the cross section of the lepto-production of photons and of lepton-pairs, enabling an accurate determination of the nucleons and nuclei generalized parton distributions, and providing an access to the gravitational form factors. Furthermore, positron beams offer the possibility of alternative tests of the Standard Model of particle physics through the search of a dark photon, the precise measurement of electroweak couplings, and the investigation of charged lepton flavor violation. This document discusses the perspectives of an experimental program with high duty-cycle positron beams at JLab.

nucl-ex↗

arXiv2015

Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton

Double-polarization observables in the reaction $\vec{e}p \rightarrow e'\vec{p'}γ$ have been measured at $Q^2=0.33 (GeV/c)^2$. The experiment was performed at the spectrometer setup of the A1 Collaboration using the 855 MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil proton polarimeter. From the double-polarization observables the structure function $P_{LT}^\perp$ is extracted for the first time, with the value $(-15.4 \pm 3.3 (stat.)^{+1.5}_{-2.4} (syst.)) GeV^{-2}$, using the low-energy theorem for Virtual Compton Sattering. This structure function provides a hitherto unmeasured linear combination of the generalized polarizabilities of the proton.

nucl-ex↗

arXiv2008

A new measurement of the structure functions $P_{LL}-P_{TT}/epsilon$ and $P_{LT}$ in virtual Compton scattering at $Q^2=$ 0.33 (GeV/c)$^2$

The cross section of the $ep \to e' p' γ$ reaction has been measured at $Q^2 = 0.33$ (GeV/c)$^2$. The experiment was performed using the electron beam of the MAMI accelerator and the standard detector setup of the A1 Collaboration. The cross section is analyzed using the low-energy theorem for virtual Compton scattering, yielding a new determination of the two structure functions $P_LL}-P_{TT}/epsilon$ and $P_{LT}$ which are linear combinations of the generalized polarizabilities of the proton. We find somewhat larger values than in the previous investigation at the same $Q^2$. This difference, however, is purely due to our more refined analysis of the data. The results tend to confirm the non-trivial $Q^2$-evolution of the generalized polarizabilities and call for more measurements in the low-$Q^2$ region ($\le$ 1 (GeV/c)$^2$).

nucl-ex↗

arXiv2007

Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2

The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p γ) and (e p \to e p π^0) in the $Δ(1232)$ resonance region at $Q^2=$ 0.35 (GeV/c)$^2$. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some $γ^{(*)} N \to πN$ multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels ($γ$ and $π^0$) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization.

hep-ph↗

arXiv2006

Monte Carlo simulation of virtual Compton scattering below pion threshold

This paper describes the Monte Carlo simulation developed specifically for the VCS experiments below pion threshold that have been performed at MAMI and JLab. This simulation generates events according to the (Bethe-Heitler + Born) cross section behaviour and takes into account all relevant resolution-deteriorating effects. It determines the `effective' solid angle for the various experimental settings which are used for the precise determination of photon electroproduction absolute cross section.

physics.data-an↗