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Sfienti, C.

Publications and source records attributed to Sfienti, C..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

High-resolution hypernuclear decay pion spectroscopy at MAMI and future

Hypernuclear decay pion spectroscopy was established in 2012 at MAMI as a mass spectroscopy method for light hypernuclei. A monochromatic pion peak from $^4_Λ$H was successfully observed, and the Λ binding energy was determined to be B Λ = 2.157±0.005(stat.)±0.077(syst.) MeV in the 2014 run. In 2022, an upgrade experiment for $^3_Λ$H spectroscopy was conducted using a newly developed Li target. The absolute electron beam energy will be measured by the synchrotron radiation interferometry, which will be applied with the spectrometer calibration to improve the systematic error. The decay pion spectroscopy is planned to be performed at JLab Hall-C, which would significantly increase the statistics thanks to the higher energy beam, the better K + identification, and the faster data acquisition system. This experiment has been submitted as a Letter of Intent in JLab PAC51. The upgraded decay pion spectroscopy method is expected to provide new, accurate hypernuclear data, which will contribute to the advancement of our understanding of hypernuclear physics

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

First Measurement Using Elliptically Polarized Photons of the Double-Polarization Observable E for γ p → p π 0 and γ p → n π +

We report the measurement of the helicity asymmetry E for the p π 0 and n π + final states using, for the first time, an elliptically polarized photon beam in combination with a longitudinally polarized target at the Crystal Ball experiment at MAMI. The results agree very well with data that were taken with a circularly polarized photon beam, showing that it is possible to simultaneously measure polarization observables that require linearly (e.g., G ) and circularly polarized photons (e.g., E ) and a longitudinally polarized target. The new data cover a photon energy range 270–1400 MeV for the p π 0 final state (230–842 MeV for the n π + final state) and the full range of pion polar angles, θ , providing the most precise measurement of the observable E . A moment analysis gives a clear observation of the p η cusp in the p π 0 final state. Published by the American Physical Society 2024

Physics↗
DOE OSTI2022

Low- Q 2 elastic electron-proton scattering using a gas jet target

In this paper, we describe an experiment measuring low-Q 2 elastic electron-proton scattering using a newly developed cryogenic supersonic gas jet target in the A1 three-spectrometer facility at the Mainz Microtron. Here, we measured the proton electric form factor within the four-momentum transfer range of 0.01 ≤ Q 2 ≤ 0.045 (GeV/c) 2 . The experiment showed consistent results with the existing measurements. The data we collected demonstrated the feasibility of the gas jet target and the potential of future scattering experiments using high-resolution spectrometers with this gas jet target.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Theoretical analysis of the extraction of neutron skin thickness from coherent π 0 photoproduction off nuclei

Background: Coherent π⁢ 0 photoproduction on heavy nuclei has been suggested as a reliable tool to infer neutron skin thicknesses. To this aim, various experiments have been performed, especially on 208 Pb. Purpose: Here, we analyze the sensitivity of that reaction process to the nucleonic density, and especially to the neutron skin thickness, for 12 C, 40 Ca, and 208 Pb, for which reliable data exist, and on 116,124 Sn, for which measurements have been performed in Mainz. We study also the role played by the π 0 -nucleus final-state interaction. Methods: A model of the reaction is developed at the impulse approximation considering either plane waves or distorted waves to describe the π 0 -nucleus scattering in the outgoing channel. Results: Our calculations are in good agreement with existing data, especially for 208 Pb. The sensitivity of the theoretical cross sections to the choice of the nucleonic density is small and below the experimental resolution. Conclusions: Coherent π 0 photoproduction is mostly an isoscalar observable that bares no practical sensitivity to the neutron skin thickness. To infer that structure observable it should be coupled to other reaction measurements, such as electron scattering, or by comparing experiments performed on isotopes of the same chemical element.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Single $\pi ^0$ production off neutrons bound in deuteron with linearly polarized photons

The quasifree γ → d → π 0 n(p) photon beam asymmetry, Σ, has been measured at photon energies, E γ , from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49° to 148°. In this kinematic region, polarization observables are sensitive to contributions from the Δ(1232) and N(1440) resonances. The extracted values of Σ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn–Gatchina analyses; while a revised SAID fit, including the new Σ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict π 0 n photoproduction observables, based on fits to published data in the channels π 0 p, π + n and π – p.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

The proton charge radius extracted from the initial-state radiation experiment at MAMI

Abstract We report on a comprehensive reinterpretation of the existing cross-section data for elastic electron-proton scattering obtained by the initial-state radiation technique, resulting in a significantly improved accuracy of the extracted proton charge radius. By refining the external energy corrections we have achieved an outstanding description of the radiative tail, essential for a detailed investigation of the proton finite-size effects on the measured cross sections. This development, together with a novel framework for determining the radius, based on a regression analysis of the cross sections employing a polynomial model for the form factor, led us to a new value for the charge radius, which is $$(0.878 \pm 0.011_\mathrm {stat.}\pm 0.031_\mathrm {sys.}\pm 0.002_\mathrm {mod.})\,\mathrm {fm}$$ ( 0.878 ± 0 . 011 stat . ± 0 . 031 sys . ± 0 . 002 mod . ) fm

Physics↗
DOE OSTI2020

Measuring the surface thickness of the weak charge density of nuclei

The present PREX-II and CREX experiments are measuring the rms radius of the weak charge density of Pb 208 and Ca 48 . We discuss the feasibility of a new parity violating electron scattering experiment to measure the surface thickness of the weak charge density of a heavy nucleus. Additionally, once PREX-II and CREX have constrained weak radii, an additional parity violating measurement at a momentum transfer near 0.76 fm - 1 for Pb 208 or 1.28 fm - 1 for Ca 48 can determine the surface thickness.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗