Papers by Giovanni Angelini

Physics Letters B, 2021
High-momentum configurations of nucleon pairs at short-distance are probed using measurements of ... more High-momentum configurations of nucleon pairs at short-distance are probed using measurements of the 12 C(e, e p) and 12 C(e, e pN) reactions (where N is either n or p), at high-Q 2 and xB > 1.1. The data span a missing-momentum range of 300-1000 MeV/c and are predominantly sensitive to the transition region of the strong nuclear interaction from a Tensor to Scalar interaction. The data are well reproduced by theoretical calculations using the Generalized Contact Formalism with both chiral and phenomenological nucleon-nucleon (N N) interaction models. This agreement suggests that the measured high missing-momentum protons up to 1000 MeV/c predominantly belong to short-ranged correlated (SRC) pairs. The measured 12 C(e, e pN) / 12 C(e, e p) and 12 C(e, e pp) / 12 C(e, e pn) cross-section ratios are consistent with a decrease in the fraction of proton-neutron SRC pairs and increase in the fraction of proton-proton SRC pairs with increasing missing momentum. This confirms the transition from an isospin-dependent tensor N N interaction at ∼ 400 MeV/c to an isospin-independent scalar interaction at high-momentum around ∼ 800 MeV/c as predicted by theoretical calculation.
Physical Review Letters, 2019

We report the first beam spin asymmetry (BSA) measurement of incoherent deeply virtual Compton sc... more We report the first beam spin asymmetry (BSA) measurement of incoherent deeply virtual Compton scattering (DVCS) off ^4He. The data were accumulated using a 6 GeV longitudinally polarized electron beam incident on a pressurized ^4He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle (ϕ) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The Q^2, x_B, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20% to 40%, indicating possible medium modification of its partonic structure. This measurement opens a new avenue for studying the structure of bound nucleons and for exploring the origin of the EMC effect using the framework of the generalized parton distributions.

Physical Review C, 2022
Background: Energetic quarks in nuclear deep-inelastic scattering propagate through the nuclear m... more Background: Energetic quarks in nuclear deep-inelastic scattering propagate through the nuclear medium. Processes that are believed to occur inside nuclei include quark energy loss through medium-stimulated gluon bremsstrahlung and intra-nuclear interactions of forming hadrons. More data are required to gain a more complete understanding of these effects. Purpose: To test the theoretical models of parton transport and hadron formation, we compared their predictions for the nuclear and kinematic dependence of pion production in nuclei. Methods: We have measured charged-pion production in semi-inclusive deep-inelastic scattering off D, C, Fe, and Pb using the CLAS detector and the CEBAF 5.014 GeV electron beam. We report results on the nuclearto-deuterium multiplicity ratio for π + and π − as a function of energy transfer, four-momentum transfer, and pion energy fraction or transverse momentum-the first three-dimensional study of its kind. Results: The π + multiplicity ratio is found to depend strongly on the pion fractional energy z, and reaches minimum values of 0.67 ± 0.03, 0.43 ± 0.02, and 0.27 ± 0.01 for the C, Fe, and Pb targets, respectively. The z dependences of the multiplicity ratios for π + and π − are equal within uncertainties for C and Fe targets but show differences at the level of 10% for the Pb-target data. The results are qualitatively described by the GiBUU transport model, as well as with a model based on hadron absorption, but are in tension with calculations based on nuclear fragmentation functions. Conclusions: These precise results will strongly constrain the kinematic and flavor dependence of nuclear effects in hadron production, probing an unexplored kinematic region. They will help to reveal how the nucleus reacts to a fast quark, thereby shedding light on its color structure, transport properties, and on the mechanisms of the hadronization process.
Physical Review Letters, 2019

Few-Body Systems, 2018
The Jefferson Lab (JLab) CLAS12 detector will provide a worldleading facility for the study of el... more The Jefferson Lab (JLab) CLAS12 detector will provide a worldleading facility for the study of electron-nucleon scattering. The CLAS12 physics program is very broad and includes studies on quarks dynamics as well as studies on the meson and baryon spectroscopy with quasi-real photoproduction in a large variety of final states. The particle identification will be complemented by a Ring Imaging Cherenkov Detector (RICH), that will provide separation of kaons from protons and pions in the momentum range between 3-8 GeV/c allowing the study of pion and kaon electroproduction in semi-inclusive deep inelastic scattering as well as studying double and triple strange baryons. In this article, we will focus on the new technologies developed for the RICH, especially on the complex optical system, that allows to reduce the photo-detection area. Particular attention is given to the characterization of the surface in relationship with the simulation capability of GEANT4.
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Papers by Giovanni Angelini