Precision Determination of the Neutral Weak Form Factor of

We report a precise measurement of the parity-violating (PV) asymmetry A_{PV} in the elastic scattering of longitudinally polarized electrons from ^{48}Ca. We measure A_{PV}=2668±106(stat)±40(syst) parts per billion, leading to an extraction of the neutral weak form factor F_{W}(q=0.8733 fm^{-1})=0.1304±0.0052(stat)±0.0020(syst) and the charge minus the weak form factor F_{ch}-F_{W}=0.0277±0.0055. The resulting neutron skin thickness R_{n}-R_{p}=0.121±0.026(exp)±0.024(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.

Revealing the short-range structure of the mirror nuclei 3H and 3He.

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.

New Measurements of the Beam-Normal Single Spin Asymmetry in Elastic Electron Scattering over a Range of Spin-0 Nuclei.

We report precision determinations of the beam-normal single spin asymmetries (A_{n}) in the elastic scattering of 0.95 and 2.18 GeV electrons off ^{12}C, ^{40}Ca, ^{48}Ca, and ^{208}Pb at very forward angles where the most detailed theoretical calculations have been performed. The first measurements of A_{n} for ^{40}Ca and ^{48}Ca are found to be similar to that of ^{12}C, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤20. We also report A_{n} for ^{208}Pb at two new momentum transfers (Q^{2}) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A_{n} for nuclei containing ≲50 nucleons, but point to the need for further investigation to understand the unusual A_{n} behavior discovered for scattering off ^{208}Pb.

Measurement of the Nucleon F_{2}

The ratio of the nucleon F_{2} structure functions, F_{2}^{n}/F_{2}^{p}, is determined by the MARATHON experiment from measurements of deep inelastic scattering of electrons from ^{3}H and ^{3}He 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

Air-classified faba bean protein fraction as a substitute to soybean meal in pelleted and extruded broiler diets.

1. The hypothesis that air-classified faba bean protein fraction (FBP) can replace soybean meal (SBM) in pelleted or extruded broiler diets without adverse effect on performance or nutrient digestibility was tested.2. At 17 d of age, male broilers were randomly distriibuted among four dietary treatments consisting of either SBM or FBP (main dietary protein source) and pelleting or extrusion as processing methods. Treatments had 10 replicate pens containing five birds each.3. Compared to SBM, birds fed FBP had significantly lower feed intake, less weight gain and had poorer feed conversion.4. Pellet durability was high (above 92%) for all diets. In pelleted diets, FBP was harder than SBM whereas extruded diets had similar hardness. Pelleting increased water stability compared to extrusion. FBP diets were more water stable than the SBM diets.5. Gizzard content weight was 2.2-fold higher (P = 0.002) for birds given FBP compared to those fed SBM. The weight of the jejunum and ileum with contents was 1.4-fold lower for the FBP diets, and this effect was larger (P < 0.05) for the extruded FBP diet.6. Birds fed FBP diets had significantly higher nitrogen digestibility in the lower jejunum and ileum compared to those given SBM diets, while the starch digestibility coefficient was above 0.980 in all treatments.7. The high nutrient digestibility of FBP diets indicates that the poor performance of the FBP group was due to lower feed intake which was not explained by the differences in pellet durability or hardness. The reduced palatability of the FBP and the longer retention of the FBP diets in the upper gut are more likely to have depressed feed intake.

Accurate Determination of the Neutron Skin Thickness of

We report a precision measurement of the parity-violating asymmetry A_{PV} in the elastic scattering of longitudinally polarized electrons from ^{208}Pb. We measure A_{PV}=550±16(stat)±8(syst) parts per billion, leading to an extraction of the neutral weak form factor F_{W}(Q^{2}=0.00616 GeV^{2})=0.368±0.013. Combined with our previous measurement, the extracted neutron skin thickness is R_{n}-R_{p}=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of ^{208}Pb: ρ_{W}^{0}=-0.0796±0.0036(exp)±0.0013(theo) fm^{-3} leading to the interior baryon density ρ_{b}^{0}=0.1480±0.0036(exp)±0.0013(theo) fm^{-3}. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.

Ruling out Color Transparency in Quasielastic

Quasielastic ^{12}C(e,e^{'}p) scattering was measured at spacelike 4-momentum transfer squared Q^{2}=8, 9.4, 11.4, and 14.2 (GeV/c)^{2}, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q^{2} dependence, up to proton momenta of 8.5 GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q^{2} scales in exclusive (e,e^{'}p) reactions. These results impose strict constraints on models of color transparency for protons.

Experimental sleep restriction increases latency jitter in pain elicited cortical responses.

OBJECTIVE: Previous studies have shown increased pain scores to painful stimulation after experimental sleep restriction, but reduced or unchanged magnitude of the event related potentials (ERPs) when averaged in the time-domain. However, some studies found increased response magnitude when averaging in the time-frequency domain. The aim of this study was to determine whether ERP-latency jitter may contribute to this discrepancy. METHODS: Ninety painful electrical stimuli were given to 21 volunteers after two nights of 50% sleep restriction and after two nights of habitual sleep. ERPs were analyzed in the time-domain (N2-and P2-peaks) and time-frequency domain (power spectral density). We quantified latency jitter by the mean consecutive difference (MCD) between single-trial peak latencies and by phase locking value (PLV) across trials. RESULTS: P2-MCD increased from 20.4 ± 2.1 ms after habitual sleep to 24.3 ± 2.2 ms after sleep restriction (19%, p = 0.038) and PLV decreased from 0.582 ± 0.015 after habitual sleep to 0.536 ± 0.015 after sleep restriction (7.9%, p = 0.009). We found no difference for N2-MCD. CONCLUSIONS: Our results indicate that partial sleep restriction increase latency jitter in cortical responses to experimental pain. SIGNIFICANCE: Latency jitter may contribute to the discrepancies between ERP-responses in the time-frequency domain and time-domain. Latency jitter should be considered when ERPs are analyzed.

Interactions between starch source and gelatinisation degree on performance and small intestinal digestion in broiler chickens.

1. A 2 × 2 factorial arrangement was used to test the hypothesis that, in pelleted diets, legume starch is digested less rapidly and to a lesser extent than cereal starch, and that increased gelatinisation through extrusion would eliminate the differences between the starch sources. In addition, the trial examined whether a lower ratio of starch to nitrogen disappearance rate (SNDR) could improve feed conversion ratio (FCR).2. At 17 d of age, male broilers were randomly distributed among four dietary treatments, consisting of either wheat or faba bean starch-rich fraction (FBS) as the sole starch source and pelleting or extrusion as processing methods. Each treatment had 10 replicate pens containing five birds each.3. Extrusion resulted in a more extensive starch gelatinisation compared to pelleting, as expected.4. No difference in weight gain at 29 d of age was observed between birds fed starch sources. However, birds fed wheat tended (P = 0.080) to have better FCR than those fed FBS, while the effect of processing methods was insignificant. Thus, there was no interaction between starch source and processing method on FCR.5. In pelleted diets, FBS had lower and slower starch digestibility compared to wheat in all intestinal segments (P < 0.05). The interaction between starch source and processing method in all intestinal segments (P < 0.001) demonstrated that FBS responded more to gelatinisation through extrusion than did wheat. Thus, differences in starch digestibility between the wheat and FBS were eliminated with extrusion.6. Feeding extruded diets significantly increased the upper jejunal expression of GLUT1, GLUT2 and SGLT1 compared to pelleted diets, which suggested that glucose absorption was less likely to be a limiting factor for starch utilisation.7. Pelleting resulted in a lower ratio (P < 0.001) of SNDR compared to extrusion (on average 1.4-fold) but did not improve FCR.

Probing the Deuteron at Very Large Internal Momenta.

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 q[over →]. 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.

Increasing levels of rapeseed expeller meal in diets for pigs: effects on protein and energy metabolism.

The heavy reliance on imported soybean meal (SBM) as a protein source makes it necessary for the European pig industry to search for alternatives and to develop pigs that perform efficiently when fed such ingredients. Digestion and metabolism are major physiological processes contributing to variation in feed efficiency. Therefore, an experiment was conducted to assess the effects of replacing SBM with increasing levels of rapeseed meal (RSM) in diets for young pigs on apparent total tract digestibility (ATTD) of energy and nutrients, nitrogen (N) balance, energy metabolism and carbohydrate, protein and fat oxidation. Four diets were fed to 32 pigs (22.7±4.1 kg initial BW) for three weeks. The diets consisted of a control cereal grain-SBM basal diet and three test diets where SBM and wheat were partially replaced with 10%, 20%, and 30% of expeller RSM. Increasing level of RSM in the diets linearly reduced ATTD of organic matter, CP, total carbohydrates, dietary fiber and energy. Utilization of digested nitrogen (DN) for N retention and total N excretion were not affected by RSM inclusion, however, RSM inclusion induced a shift in N excretion from urine to feces. Despite a linear increase in liver to metabolic BW ratio, heat production and utilization of metabolizable energy (ME) for retention were not affected by increasing RSM inclusion. In conclusion, replacing SBM with up to 30% of expeller RSM in nutritionally balanced diets for young pigs reduced the ATTD of most nutrients and energy, but did not affect N and energy retention in the body or efficiency of utilization of DN or ME for retention.

Publisher's Note: JLab Measurements of the

This corrects the article DOI: 10.1103/PhysRevLett.119.162501.

JLab Measurements of the

The charge and magnetic form factors, F_{C} and F_{M}, respectively, of ^{3}He are extracted in the kinematic range 25 fm^{-2}≤Q^{2}≤61 fm^{-2} from elastic electron scattering by detecting ^{3}He recoil nuclei and scattered electrons in coincidence with the two High Resolution Spectrometers of the Hall A Facility at Jefferson Lab. The measurements find evidence for the existence of a second diffraction minimum for the magnetic form factor at Q^{2}=49.3 fm^{-2} and for the charge form factor at Q^{2}=62.0 fm^{-2}. Both minima are predicted to exist in the Q^{2} range accessible by this Jefferson Lab experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the three-body nuclear problem.

Skin conductance as a pain assessment tool during chest tube removal: An observational study.

BACKGROUND: Skin conductance variability to assess pain has shown varying results. Skin conductance responses per second (SCR) during a standardized painful stimulus in awake adults may give further understanding of the method's validity. The purpose of this study was to validate the SCR with the visual analogue scale (VAS) for pain (P-VAS) and anxiety (A-VAS) during chest tube removal (CTR). METHODS: Ninety-five patients receiving epidural or non-epidural treatment, scheduled for CTR, were studied. Pain or anxiety was considered when VAS > 30 mm; the SCR cut-off value reflecting pain was ≥0.2 SCR. RESULTS: SCR values could not be recorded in eight cases before CTR, six cases during CTR and seven cases after CTR. CTR induced increases in SCR, P-VAS and A-VAS (p < 0.001). Seventy-seven percent of all pairs of P-VAS and SCR values were well-classified; P-VAS ≤ 30 mm and SCR < 0.2 or P-VAS > 30 mm and SCR ≥ 0.2. SCR obtained before CTR differentiates between patients with and without pain during CTR in all patients (p = 0.04) and in the subgroup of non-anxious patients (p = 0.02), but not in the subgroup of anxious patients. SCR obtained during CTR had similar values in patients with and without pain in all patients and in the subgroup of anxious patients, but in the subgroup of non-anxious patients SCR during CTR differentiates patients with and without pain (p = 0.009). CONCLUSIONS: SCR increases during painful procedures. Preprocedural SCR may help predict reported pain in patients exposed to painful procedures. SCR during CTR differentiates between patients with and without pain only in non-anxious patients. SIGNIFICANCE: Preprocedural SCR may help predict reported pain in patients exposed to painful procedures. Procedural SCR accuracy improves in a subgroup of non-anxious patients. P-VAS is influenced by anxiety different from SCR.

Precision Measurement of the p(e,e

New results are reported from a measurement of π^{0} electroproduction near threshold using the p(e,e^{'}p)π^{0} reaction. The experiment was designed to determine precisely the energy dependence of s- and p-wave electromagnetic multipoles as a stringent test of the predictions of chiral perturbation theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the ϕ_{π}^{*} and θ_{π}^{*} angles in the pπ^{0} center of mass was obtained for invariant energies above threshold from 0.5 up to 15 MeV. The 4-momentum transfer Q^{2} coverage ranges from 0.05 to 0.155 (GeV/c)^{2} in fine steps. A simple phenomenological analysis of our data shows strong disagreement with p-wave predictions from ChPT for Q^{2}>0.07 (GeV/c)^{2}, while the s-wave predictions are in reasonable agreement.

JLab measurement of the 4He charge form factor at large momentum transfers.

The charge form factor of 4He has been extracted in the range 29 fm(-2) ≤ Q2 ≤ 77 fm(-2) from elastic electron scattering, detecting 4He recoil nuclei and electrons in coincidence with the high resolution spectrometers of the Hall A Facility of Jefferson Lab. The measurements have uncovered a second diffraction minimum for the form factor, which was predicted in the Q2 range of this experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the few-body problem.

Role of steps in the dissociative adsorption of water on rutile TiO2(110).

The water-TiO(2) interaction is of paramount importance for many processes occurring on TiO(2), and the rutile TiO(2)(110)-(1×1) surface has often been considered as a test case. Yet, no consensus has been reached whether the well-studied surface O vacancies on the terraces are the only active sites for water dissociation on rutile TiO(2)(110)-(1 × 1), or whether another channel for the creation of H adatoms exists. Here we use high-resolution scanning tunneling microscopy and density functional theory calculations to tackle this long-standing question. Evidence is presented that a second water dissociation channel exists on the surfaces of vacuum-annealed TiO(2)(110) crystals that is associated with the ⟨111⟩ step edges. This second water dissociation channel can be suppressed by blocking of the ⟨111⟩ step edges using ethanol.

Reduced step edges on rutile TiO2(110) as competing defects to oxygen vacancies on the terraces and reactive sites for ethanol dissociation.

The rutile TiO2(110) surface is the most studied surface of titania and considered as a prototype of transition metal oxide surfaces. Reactions on flat TiO2(110)-(1×1) surfaces are well studied, but the processes occurring on the step edges have barely been considered. Based on scanning tunneling microscopy studies, we here present experimental evidence for the existence of O vacancies along the [11¯1](R) step edges (O(S) vac.'s) on rutile TiO(2)(110). Both the distribution of bridging O vacancies on the terraces and temperature-programed reaction experiments of ethanol-covered TiO(2)(110) point to the existence of the O(S) vac.'s. Based on experiments and density functional theory calculations, we show that O(S) vac.'s are reactive sites for ethanol dissociation via O-H bond scission. Implications of these findings are discussed.

Search for a new gauge boson in electron-nucleus fixed-target scattering by the APEX experiment.

We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'→ e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.

Direct evidence for ethanol dissociation on rutile TiO2(110).

We have studied the interaction of ethanol with reduced TiO(2)(110)-(1 × 1) by high-resolution scanning tunneling microscopy (STM) measurements and density functional theory calculations. The STM data revealed direct evidence for the coexistence of molecularly and dissociatively adsorbed ethanol species on surface Ti sites. In addition, we found evidence for dissociation of ethanol at bridge-bonded O vacancies. The density functional theory calculations support these findings and rationalize the distinct diffusion behaviors of molecularly and dissociatively adsorbed ethanol species, as revealed in time-lapsed STM images.