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Milner, R. G.

Publications and source records attributed to Milner, R. G..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

First Measurement of Deeply Virtual Compton Scattering on the Neutron with Detection of the Active Neutron

Measuring deeply virtual Compton scattering (DVCS) on the neutron is one of the necessary steps to understand the structure of the nucleon in terms of generalized parton distributions (GPDs). Neutron targets play a complementary role to transversely polarized proton targets in the determination of the GPD E . This poorly known and poorly constrained GPD is essential to obtain the contribution of the quarks’ angular momentum to the spin of the nucleon. DVCS on the neutron was measured for the first time selecting the exclusive final state by detecting the neutron, using the Jefferson Lab longitudinally polarized electron beam, with energies up to 10.6 GeV, and the CLAS12 detector. The extracted beam-spin asymmetries, combined with DVCS observables measured on the proton, allow a clean quark-flavor separation of the imaginary parts of the Compton form factors H and E . Published by the American Physical Society 2024

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

The two-photon exchange experiment at DESY

We propose a new measurement of the ratio of positron-proton to electron-proton elastic scattering at DESY. The purpose is to determine the contributions beyond single-photon exchange, which are essential for the Quantum Electrodynamic (QED) description of the most fundamental process in hadronic physics. By utilizing a 20 cm long liquid hydrogen target in conjunction with the extracted beam from the DESY synchrotron, we can achieve an average luminosity of 2.12 x 10 35 cm –2 •s –1 (≈ 200 times the luminosity achieved by OLYMPUS). The proposed two-photon exchange experiment (TPEX) entails a commissioning run at a beam energy of 2 GeV, followed by measurements at 3 GeV, thereby providing new data up to Q 2 = 4.6 (GeV/c) 2 (twice the range of current measurements). We present and discuss the proposed experimental setup, run plan, and expectations.

Physics↗
DOE OSTI2023

Metastability exchange optical pumping of 3 He at low pressure and high magnetic field

We report systematic studies on metastability exchange optical pumping of 3 He nuclei have been performed at Jefferson Lab using a 1-torr sealed cell at magnetic fields from 2 to 4 T. The effects of the discharge intensity, pump laser power and pumping transition schemes on achievable nuclear polarization and pumping rate have been investigated. A maximum steady-state nuclear polarization of about 75% has been obtained. This work provides a baseline for the development of the novel polarized 3 He target for CLAS12 at Jefferson Lab.

47 OTHER INSTRUMENTATION↗
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

Observation of Azimuth-Dependent Suppression of Hadron Pairs in Electron Scattering off Nuclei

Here, we present the first measurement of dihadron angular correlations in electron-nucleus scattering. The data were taken with the CLAS detector and a 5.0 GeV electron beam incident on deuterium, carbon, iron, and lead targets. Relative to deuterium, the nuclear yields of charged-pion pairs show a strong suppression for azimuthally opposite pairs, no suppression for azimuthally nearby pairs, and an enhancement of pairs with large invariant mass. These effects grow with increased nuclear size. The data are qualitatively described by the GIBUU model, which suggests that hadrons form near the nuclear surface and undergo multiple scattering in nuclei. These results show that angular correlation studies can open a new way to elucidate how hadrons form and interact inside nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Measurement of R = σ L / σ T and the separated longitudinal and transverse structure functions in the nucleon-resonance region

Here we report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q 2 < 5.5 GeV 2 . The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R = $\sigma_{L} /\sigma _{T}$ data are presented here, along with the first separate values of the inelastic structure functions F 1 and F L in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q 2 = 1 GeV 2 in the separated structure functions independently.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

A concept for polarized 3 He targets for high luminosity scattering experiments in high magnetic field environments

In this work, we present the conceptual design of a polarized 3 He target to be used for high luminosity scattering experiments within high magnetic field environments. This two-cell target will take advantage of advancements in optical pumping techniques at high magnetic field to create 60% longitudinally polarized 3 He gas in a pumping cell within a uniform magnetic field above 1 T. By transferring the polarized gas to a cryogenic target cell, the gas density is increased to create a target thickness suitable for high luminosity applications. We discuss the general design of this scheme, and plans for its application in Jefferson Lab’s CLAS12 detector.

3He polarization↗
DOE OSTI2020

Measurement of Møller scattering at 2.5 MeV

Møller scattering is one of the most fundamental processes in QED, and a variety of modern experiments require its knowledge to high precision. A recent calculation considered the radiative process at low energy, where the electron mass cannot be neglected. To test the calculation, an experiment was carried out using the Van de Graaff accelerator at the MIT High Voltage Research Laboratory. Momentum spectra at three scattering angles are reported here and compared to simulation, based on our previous calculation. In this work, good agreement between the measurements and our calculation is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗