Engineering topics

Lenisa, P. [INFN; Università di Ferrara]

Publications and source records attributed to Lenisa, P. [INFN; Università di Ferrara].

4 records

DOE OSTI2025

Suppression of neutral-pion production in deep-inelastic scattering off nuclei with the CLAS detector

We present the first threefold differential measurement for neutral-pion multiplicity ratios produced in semi-inclusive deep-inelastic electron scattering on carbon, iron, and lead nuclei normalized to deuterium from CLAS at Jefferson Lab. We found that the neutral-pion multiplicity ratio is maximally suppressed for the leading hadrons (energy fraction 𝑧 → 1), suppression varying from 25% in carbon up to 75% in lead. An enhancement of the multiplicity ratio at low 𝑧 and high 𝑝$^2_𝑇$ is observed, suggesting an interconnection between these two variables. This behavior is qualitatively similar to the previous twofold differential measurement of charged pions by the HERMES Collaboration and, recently, by CLAS Collaboration. The largest enhancement was observed at high 𝑝$^2_𝑇$ for heavier nuclei, namely, iron and lead, while the smallest enhancement was observed for the lightest nucleus, carbon. This behavior suggests a competition between partonic multiple scattering, which causes enhancement, and hadronic inelastic scattering, which causes suppression.

color confinement↗

DOE OSTI2025

Measurement of single- and double-polarization observables in the photoproduction of 𝜋 + ⁢𝜋 − meson pairs off the proton using CLAS at Jefferson Laboratory

The photoproduction of 𝜋 + ⁢𝜋 − meson pairs off the proton has been studied in the reaction 𝛾⁢𝑝→𝑝⁢𝜋 + ⁢𝜋 − using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the beam and target asymmetries, 𝐼 𝑠,𝑐 and 𝑃 𝑥,𝑦 , have been measured along with the beam-target double-polarization observables, 𝑃$^{𝑠,𝑐}_{𝑥,𝑦}$, using a transversely polarized target with center-of-mass energies ranging from 1.51 GeV up to 2.04 GeV. These data and additional 𝜋⁢𝜋 photoproduction observables from CLAS and experiments elsewhere were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from 𝑠-channel resonance production are observed in addition to 𝑡-channel exchange processes. The data indicate significant contributions from 𝑁* and Δ* resonances in the third and fourth resonance regions.

QCD phenomenology↗

DOE OSTI2025

Photoproduction of two charged pions off protons in the resonance region

Photoproduction of charged pions pairs off protons is studied within the invariant masses of the final state hadrons from 1.6 to 2.4 GeV at the Thomas Jefferson National Accelerator Facility with the CLAS detector. The total and differential cross sections and spin-density matrix elements are presented for the isobars pρ 0 (770), Δ(1232) ++ π − , and Δ(1232) 0 π + . The data are included in the Bonn-Gatchina coupled-channel analysis and provide the information necessary to determine the branching fractions of Nρ(770) decays for most known N* and Δ* resonances. For the first time, the Nρ branching ratios are obtained here from an event-based likelihood to γp → π + π − p.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2025

Dihadron azimuthal correlations in deep-inelastic scattering off nuclear targets

We measured the nuclear dependence of the di-pion azimuthal correlation function in deepinelastic scattering (DIS) using the CEBAF Large Acceptance Spectrometer (CLAS) and a 5 GeV electron beam. As the nuclear-target size increases, transitioning from deuterium to carbon, iron, and lead, the correlation function broadens monotonically. Its shape exhibits a significant dependence on kinematics, including the transverse momentum of the pions and the difference in their rapidity. None of the various Monte-Carlo event generators we evaluated could fully replicate the observed correlation functions and nuclear effects throughout the entire phase space. As the first study of its kind in DIS experiments, this research provides an important baseline for enhancing our understanding of the interplay between the nuclear medium and the hadronization process in these reactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗