55 research outputs found
Measurement of the Nucleon F\u3csup\u3en\u3c/sup\u3eâ‚‚/F\u3csup\u3ep\u3c/sup\u3eâ‚‚ Structure Function Ratio by the Jefferson Lab MARATHON Tritium/Helium-3 Deep Inelastic Scattering Experiment
The ratio of the nucleon F2 structure functions, Fn2/Fp2, is determined by the MARATHON experiment from measurements of deep inelastic scattering of electrons from 3H and 3He nuclei. The experiment was performed in the Hall A Facility of Jefferson Lab using two high-resolution spectrometers for electron detection, and a cryogenic target system which included a low-activity tritium cell. The data analysis used a novel technique exploiting the mirror symmetry of the two nuclei, which essentially eliminates many theoretical uncertainties in the extraction of the ratio. The results, which cover the Bjorken scaling variable range 0.19 \u3c x \u3c 0.83, represent a significant improvement compared to previous SLAC and Jefferson Lab measurements for the ratio. They are compared to recent theoretical calculations and empirical determinations of the Fn2/Fp2 ratio
Comparing Proton Momentum Distributions in A = 2 and 3 Nuclei Via \u3csup\u3e2\u3c/sup\u3eH \u3csup\u3e3\u3c/sup\u3eH and \u3csup\u3e3\u3c/sup\u3eHe (e,e′p) Measurements
We report the first measurement of the (e, e\u27 p) reaction cross-section ratios for Helium-3 (3He), Tritium (3H), and Deuterium (d). The measurement covered a missing momentum range of 40 ≤ pmiss ≤ 550 MeV/c, at large momentum transfer ({Q2} ≈ 1.9 (GeV/c)2) and xB \u3e 1, which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with planewave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for 3He/d and 3H/d extend to just above the typical nucleon Fermi-momentum (kF ≈ 250 MeV/c) and differ from each other by ∼ 20%, while for 3He/3H they agree within the measurement accuracy of about 3%. At momenta above kF , the measured 3He/3H ratios differ from the calculation by 20% −50%. Final state interaction (FSI) calculations using the generalized Eikonal Approximation indicate that FSI should change the 3He/3H cross-section ratio for this measurement by less than 5%. If these calculations are correct, then the differences at large missing momenta between the 3He/3H experimental and calculated ratios could be due to the underlying NN interaction, and thus could provide new constraints on the previously loosely-constrained short-distance parts of the NN interaction
Constraints on the Onset of Color Transparency from Quasielastic ¹²C(e, e′p) up to Q² = (14.2 GeV /c)²
Quasielastic scattering on 12C(e,e′p) was measured in Hall C at Jefferson Lab for spacelike four-momentum transfer squared Q2 in the range of 8–14.2(GeV/c)2 with proton momenta up to 8.3GeV/c. The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high-momentum spectrometer and the new super-high-momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the 1s1/2 and 1p3/2 shell protons in 12C was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of color transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of color transparency
Density Changes in Low Pressure Gas Targets for Electron Scattering Experiments
A system of modular sealed gas target cells has been developed for use in
electron scattering experiments at the Thomas Jefferson National Accelerator
Facility (Jefferson Lab). This system was initially developed to complete the
MARATHON experiment which required, among other species, tritium as a target
material. Thus far, the cells have been loaded with the gas species 3H, 3He,
2H, 1H and 40Ar and operated in nominal beam currents of up to 22.5 uA in
Jefferson Lab's Hall A. While the gas density of the cells at the time of
loading is known, the density of each gas varies uniquely when heated by the
electron beam. To extract experimental cross sections using these cells,
density dependence on beam current of each target fluid must be determined. In
this study, data from measurements with several beam currents within the range
of 2.5 to 22.5 uA on each target fluid are presented. Additionally, expressions
for the beam current dependent fluid density of each target are developed.Comment: 8 pages, 12 figures, 4 table
First Measurement of the Ti (e,e′) X Cross Section at Jefferson Lab
To probe CP violation in the leptonic sector using GeV energy neutrino beams in current and future experiments using argon detectors, precise models of the complex underlying neutrino and antineutrino interactions are needed. The E12-14-012 experiment at Jefferson Lab Hall A was designed to perform a combined analysis of inclusive and exclusive electron scatterings on both argon (N=22) and titanium (Z=22) nuclei using GeV-energy electron beams. The measurement on titanium nucleus provides essential information to understand the neutrino scattering on argon, large contribution to which comes from scattering off neutrons. Here we report the first experimental study of electron-titanium scattering as double-differential cross section at beam energy E=2.222 GeV and electron-scattering angle θ=15.541^{∘}, measured over a broad range of energy transfer, spanning the kinematical regions in which quasielastic scattering and delta production are the dominant reaction mechanisms. The data provide valuable new information needed to develop accurate theoretical models of the electromagnetic and weak cross sections of these complex nuclei in the kinematic regime of interest to neutrino experiments.National Science Foundation (U.S.) (CAREER Grant PHY-1352106
First Measurement of the Ti Cross Section at Jefferson Lab
To probe CP violation in the leptonic sector using GeV energy neutrino beams
in current and future experiments using argon detectors, precise models of the
complex underlying neutrino and antineutrino interactions are needed. The
E12-14-012 experiment at Jefferson Lab Hall A was designed to perform a
combined analysis of inclusive and exclusive electron scatterings on both argon
() and titanium () nuclei using GeV energy electron beams. The
measurement on titanium nucleus provides essential information to understand
the neutrino scattering on argon, large contribution to which comes from
scattering off neutrons. Here we report the first experimental study of
electron-titanium scattering as double differential cross section at beam
energy GeV and electron scattering angle deg,
measured over a broad range of energy transfer, spanning the kinematical
regions in which quasielastic scattering and delta production are the dominant
reaction mechanisms. The data provide valuable new information needed to
develop accurate theoretical models of the electromagnetic and weak cross
sections of these complex nuclei in the kinematic regime of interest to
neutrino experiments.Comment: 6 pages, 5 figures. Version published in Physical Review
Measurement of the Ar(e,e p) and Ti(e,e p) cross sections in Jefferson Lab Hall A
The E12-14-012 experiment, performed in Jefferson Lab Hall A, has collected
exclusive electron-scattering data (e,ep) in parallel kinematics using
natural argon and natural titanium targets. Here, we report the first results
of the analysis of the data set corresponding to beam energy of 2,222 MeV,
electron scattering angle 21.5 deg, and proton emission angle -50 deg. The
differential cross sections, measured with 4% uncertainty, have been
studied as a function of missing energy and missing momentum, and compared to
the results of Monte Carlo simulations, obtained from a model based on the
Distorted Wave Impulse Approximation.Comment: 14 pages, 8 figures (submitted to PRC
Measurement of the Cross Sections for Inclusive Electron Scattering in the E12-14-012 Experiment at Jefferson Lab
The E12-14-012 experiment performed at Jefferson Lab Hall A has collected inclusive electron-scattering data for different targets at the kinematics corresponding to beam energy 2.222 GeV and scattering angle 15.54°. Here we present a comprehensive analysis of the collected data and compare the double-differential cross sections for inclusive scattering of electrons, extracted using solid targets (aluminum, carbon, and titanium) and a closed argon-gas cell. The data extend over broad range of energy transfer, where quasielastic interaction, Δ-resonance excitation, and inelastic scattering yield contributions to the cross section. The double-differential cross sections are reported with high precision (∼3%) for all targets over the covered kinematic range
First Measurement of the EMC Effect in B and B
The nuclear dependence of the inclusive inelastic electron scattering cross
section (the EMC effect) has been measured for the first time in B and
B. Previous measurements of the EMC effect in nuclei showed
an unexpected nuclear dependence; B and B were measured to
explore the EMC effect in this region in more detail. Results are presented for
Be, B, B, and C at an incident beam energy of
10.6~GeV. The EMC effect in the boron isotopes was found to be similar to that
for Be and C, yielding almost no nuclear dependence in the EMC
effect in the range . This represents important, new data supporting
the hypothesis that the EMC effect depends primarily on the local nuclear
environment due to the cluster structure of these nuclei.Comment: Submitted to PR
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