We measure ^{2}H(e,e^{'}p)n cross sections at 4-momentum transfers of Q^{2}=4.5±0.5 (GeV/c)^{2} over a range of neutron recoil momenta p_{r}, reaching up to ∼1.0 GeV/c. We obtain data at fixed ...neutron recoil angles θ_{nq}=35°, 45°, and 75° with respect to the 3-momentum transfer qover →. The new data agree well with previous data, which reached p_{r}∼500 MeV/c. At θ_{nq}=35° and 45°, final state interactions, meson exchange currents, and isobar currents are suppressed and the plane wave impulse approximation provides the dominant cross section contribution. We compare the new data to recent theoretical calculations, where we observe a significant discrepancy for recoil momenta p_{r}>700 MeV/c.
Here, a mass spectroscopy experiment with a pair of nearly identical high resolution spectrometers and a tritium target was performed in Hall A at Jefferson Lab. Utilizing the (e,e'K+) reaction, ...enhancements, which may correspond to a possible $\Lambda$nn resonance and a pair of ΣNN states, were observed with an energy resolution of about 1.21 MeV (σ), although greater statistics are needed to make definitive identifications. An experimentally measured Λnn state may provide a unique constraint in determining the Λn interaction, for which no scattering data exist. In addition, although bound A = 3 and 4 Σ hypernuclei have been predicted, only an A = 4 Σ hypernucleus ($^4_Σ$He) was found, utilizing the (K-,π-) reaction on a 4He target. The possible bound ΣNN state is likely a Σ0nn state, although this has to be confirmed by future experiments.
The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in 10B and 11B. Previous measurements of the EMC effect in A ...≤ 12 nuclei showed an unexpected nuclear dependence; 10B and 11B were measured to explore the EMC effect in this region in more detail. Results are presented for 9Be, 10B, 11B, and 12C at an incident beam energy of 10.6 GeV. The EMC effect in the boron isotopes was found to be similar to that for 9Be and 12C, yielding almost no nuclear dependence in the EMC effect in the range A = 4-12. This represents important, new data supporting the hypothesis that the the EMC effect depends primarily on the local nuclear density due to the cluster structure of these nuclei.
Quasi-elastic scattering on 12C(e,e'p) was measured in Hall C at Jefferson Lab for space-like 4-momentum transfer squared Q2 in the range of 8-14.2 (GeV/c)2 with proton momenta up to 8.3 GeV/c. Here ...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.
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.
In this work, we report a precise measurement of the parity-violating asymmetry $A_{\rm PV}$ in the elastic scattering of longitudinally polarized electrons from $^{48}{\rm Ca}$. We measure $A_{\rm ...PV} =2668\pm 106\ {\rm (stat)}\pm 40\ {\rm (syst)}$ parts per billion, leading to an extraction of the neutral weak form factor $F_{\rm W} (q=0.8733$ fm$^{-1}) = 0.1304 \pm 0.0052 \ {\rm (stat)}\pm 0.0020\ {\rm (syst)}$ and the charge minus the weak form factor $F_{\rm ch} - F_{\rm W} = 0.0277\pm 0.0055$. The resulting neutron skin thickness $R_n-R_p=0.121 \pm 0.026\ {\rm (exp)} \pm 0.024\ {\rm (model)}$~fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.
Here, a mass spectroscopy experiment with a pair of nearly identical high resolution spectrometers and a tritium target was performed in Hall A at Jefferson Lab. Utilizing the (e,e'K+) reaction, ...enhancements, which may correspond to a possible $\Lambda$nn resonance and a pair of ΣNN states, were observed with an energy resolution of about 1.21 MeV (σ), although greater statistics are needed to make definitive identifications. An experimentally measured Λnn state may provide a unique constraint in determining the Λn interaction, for which no scattering data exist. In addition, although bound A = 3 and 4 Σ hypernuclei have been predicted, only an A = 4 Σ hypernucleus ($^4_Σ$He) was found, utilizing the (K-,π-) reaction on a 4He target. The possible bound ΣNN state is likely a Σ0nn state, although this has to be confirmed by future experiments.
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