When protons and neutrons (nucleons) are bound into atomic nuclei, they are close enough to feel significant attraction, or repulsion, from the strong, short-distance part of the nucleon-nucleon ...interaction. These strong interactions lead to hard collisions between nucleons, generating pairs of highly energetic nucleons referred to as short-range correlations (SRCs). SRCs are an important but relatively poorly understood part of nuclear structure1-3, and mapping out the strength and the isospin structure (neutron-proton (np) versus proton-proton (pp) pairs) of these virtual excitations is thus critical input for modelling a range of nuclear, particle and astrophysics measurements3-5. Two-nucleon knockout or 'triple coincidence' reactions have been used to measure the relative contribution of np-SRCs and pp-SRCs by knocking out a proton from the SRC and detecting its partner nucleon (proton or neutron). These measurements6-8 have shown that SRCs are almost exclusively np pairs, but they had limited statistics and required large model-dependent final-state interaction corrections. Here we report on measurements using inclusive scattering from the mirror nuclei hydrogen-3 and helium-3 to extract the np/pp ratio of SRCs in systems with a mass number of three. We obtain a measure of the np/pp SRC ratio that is an order of magnitude more precise than previous experiments, and find a marked deviation from the near-total np dominance observed in heavy nuclei. This result implies an unexpected structure in the high-momentum wavefunction for hydrogen-3 and helium-3. Understanding these results will improve our understanding of the short-range part of the nucleon-nucleon interaction.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The electromagnetic form factors of the proton and neutron encode information on the spatial structure of their charge and magnetization distributions. While measurements of the proton are relatively ...straightforward, the lack of a free neutron target makes measurements of the neutron's electromagnetic structure more challenging and more sensitive to experimental or model-dependent uncertainties. Various experiments have attempted to extract the neutron form factors from scattering from the neutron in deuterium, with different techniques providing different, and sometimes large, systematic uncertainties. We present results from a novel measurement of the neutron magnetic form factor using quasielastic scattering from the mirror nuclei \(^3\)H and \(^3\)He, where the nuclear effects are larger than for deuterium but expected to largely cancel in the cross-section ratios. We extracted values of the neutron magnetic form factor for low-to-modest momentum transfer, \(0.6<Q^2<2.9\) GeV\(^2\), where existing measurements give inconsistent results. The precision and \(Q^2\) range of this data allow for a better understanding of the current world's data, and suggest a path toward further improvement of our overall understanding of the neutron's magnetic form factor.
Inclusive electron scattering at carefully chosen kinematics can isolate
scattering from short-range correlations (SRCs), produced through hard,
short-distance interactions of nucleons in the ...nucleus. Because the two-nucleon
(2N) SRCs arise from the same N-N interaction in all nuclei, the cross section
in the SRC-dominated regime is identical up to an overall scaling factor, and
the A/2H cross section ratio is constant in this region. This scaling behavior
has been used to identify SRC dominance and to map out the contribution of SRCs
for a wide range of nuclei. We examine this scaling behavior at lower momentum
transfers using new data on $^2$H, $^3$H, and $^3$He which show that the
scaling region is larger than in heavy nuclei. Based on the improved scaling,
especially for $^3$H/$^3$He, we examine the ratios at kinematics where
three-nucleon SRCs may play an important role. The data for the largest initial
nucleon momenta are consistent with isolation of scattering from 3N-SRCs, and
suggest that the very-highest momentum nucleons in $^3$He have a nearly
isospin-independent momentum configuration, or a small enhancement of the
proton distribution.
Nature 609, 41-45 (2022) When protons and neutrons (nucleons) are bound into atomic nuclei, they are
close enough together to feel significant attraction, or repulsion, from the
strong, ...short-distance part of the nucleon-nucleon interaction. These strong
interactions lead to hard collisions between nucleons, generating pairs of
highly-energetic nucleons referred to as short-range correlations (SRCs). SRCs
are an important but relatively poorly understood part of nuclear structure and
mapping out the strength and isospin structure (neutron-proton vs proton-proton
pairs) of these virtual excitations is thus critical input for modeling a range
of nuclear, particle, and astrophysics measurements. Hitherto measurements used
two-nucleon knockout or ``triple-coincidence'' reactions to measure the
relative contribution of np- and pp-SRCs by knocking out a proton from the SRC
and detecting its partner nucleon (proton or neutron). These measurementsshow
that SRCs are almost exclusively np pairs, but had limited statistics and
required large model-dependent final-state interaction (FSI) corrections. We
report on the first measurement using inclusive scattering from the mirror
nuclei $^3$H and $^3$He to extract the np/pp ratio of SRCs in the A=3 system.
We obtain a measure of the np/pp SRC ratio that is an order of magnitude more
precise than previous experiments, and find a dramatic deviation from the
near-total np dominance observed in heavy nuclei. This result implies an
unexpected structure in the high-momentum wavefunction for $^3$He and $^3$H.
Understanding these results will improve our understanding of the short-range
part of the N-N interaction.
Inclusive electron scattering at carefully chosen kinematics can isolate scattering from short-range correlations (SRCs), produced through hard, short-distance interactions of nucleons in the ...nucleus. Because the two-nucleon (2N) SRCs arise from the same N-N interaction in all nuclei, the cross section in the SRC-dominated regime is identical up to an overall scaling factor, and the A/2H cross section ratio is constant in this region. This scaling behavior has been used to identify SRC dominance and to map out the contribution of SRCs for a wide range of nuclei. We examine this scaling behavior at lower momentum transfers using new data on \(^2\)H, \(^3\)H, and \(^3\)He which show that the scaling region is larger than in heavy nuclei. Based on the improved scaling, especially for \(^3\)H/\(^3\)He, we examine the ratios at kinematics where three-nucleon SRCs may play an important role. The data for the largest initial nucleon momenta are consistent with isolation of scattering from 3N-SRCs, and suggest that the very-highest momentum nucleons in \(^3\)He have a nearly isospin-independent momentum configuration, or a small enhancement of the proton distribution.
When protons and neutrons (nucleons) are bound into atomic nuclei, they are close enough together to feel significant attraction, or repulsion, from the strong, short-distance part of the ...nucleon-nucleon interaction. These strong interactions lead to hard collisions between nucleons, generating pairs of highly-energetic nucleons referred to as short-range correlations (SRCs). SRCs are an important but relatively poorly understood part of nuclear structure and mapping out the strength and isospin structure (neutron-proton vs proton-proton pairs) of these virtual excitations is thus critical input for modeling a range of nuclear, particle, and astrophysics measurements. Hitherto measurements used two-nucleon knockout or ``triple-coincidence'' reactions to measure the relative contribution of np- and pp-SRCs by knocking out a proton from the SRC and detecting its partner nucleon (proton or neutron). These measurementsshow that SRCs are almost exclusively np pairs, but had limited statistics and required large model-dependent final-state interaction (FSI) corrections. We report on the first measurement using inclusive scattering from the mirror nuclei \(^3\)H and \(^3\)He to extract the np/pp ratio of SRCs in the A=3 system. We obtain a measure of the np/pp SRC ratio that is an order of magnitude more precise than previous experiments, and find a dramatic deviation from the near-total np dominance observed in heavy nuclei. This result implies an unexpected structure in the high-momentum wavefunction for \(^3\)He and \(^3\)H. Understanding these results will improve our understanding of the short-range part of the N-N interaction.
