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.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
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 APV=550±16(stat)±8(syst) parts per ...billion, leading to an extraction of the neutral weak form factor FW(Q2=0.00616 GeV2)=0.368±0.013 . Combined with our previous measurement, the extracted neutron skin thickness is Rn−Rp=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of 208 Pb: ρW0=− 0.0796 ± 0.0036 ( exp ) ± 0.0013 ( theo ) fm−3 leading to the interior baryon density ρb0 = 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.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
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.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
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 thus demonstrating the validity of theoretical calculations for nuclei with Z~\(\leq20\). 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 \(Z\leq 20\) nuclei. These data confirm our basic understanding of the underlying dynamics that govern \(A_n\) for nuclei containing \(\lesssim 50\) nucleons, but point to the need for further investigation to understand the unusual \(A_n\) behaviour discovered for scattering off \(^{208}\)Pb.
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.
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 \(A_{PV}=550\pm 16 {\rm ...(stat)}\pm 8\ {\rm (syst)}\) parts per billion, leading to an extraction of the neutral weak form factor \(F_W(Q^2 = 0.00616\ {\rm GeV}^2) = 0.368 \pm 0.013\). Combined with our previous measurement, the extracted neutron skin thickness is \(R_n-R_p=0.283 \pm 0.071\)~fm. The result also yields the first significant direct measurement of the interior weak density of \(^{208}\)Pb: \(\rho^0_W = -0.0796\pm0.0036\ {\rm (exp.)}\pm0.0013\ {\rm (theo.)}\ {\rm fm}^{-3}\) leading to the interior baryon density \(\rho^0_b = 0.1480\pm0.0036\ {\rm (exp.)}\pm0.0013\ {\rm (theo.)}\ {\rm fm}^{-3}\). 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.
Lithium iodide has been studied extensively as a redox-mediator to reduce the charging overpotential of Li–oxygen (Li–O
2
) batteries. Ambiguities exist regarding the influence of lithium iodide on ...the reaction product chemistry and performance of lithium–oxygen batteries. In this work, we examined the role of lithium iodide on the reduction product chemistry under two conditions: (i) mixing KO
2
with lithium salts and (ii) discharging Li–oxygen batteries at high and low overpotentials, in the presence of an ether-based electrolyte with different ratios of H
2
O : LiI. The addition of iodide to electrolytes containing water was found to promote the formation of LiOOH·H
2
O, LiOH·H
2
O and LiOH at the expense of Li
2
O
2
. At low H
2
O : LiI ratios (lower than 5), LiOH instead of Li
2
O
2
was formed, which was accompanied by the oxidation of iodide to triodide while at high H
2
O : LiI ratios (12, 24, 134), a mixture of Li
2
O
2
, LiOOH·H
2
O and LiOH·H
2
O was observed and no triiodide was detected. The reaction between peroxide Li
2
O
2
and/or superoxide LiO
2
with H
2
O to form LiOH is facilitated by increased water acidity by strong I
−
–H
2
O interactions as revealed by
1
H NMR and FT-IR measurements. This mechanism of LiOH formation in the presence of LiI and H
2
O was also found upon Li–O
2
cell discharge, which is critical to consider when developing LiI as a redox mediator for Li–O
2
batteries.
Lithium iodide has been studied extensively as a redox-mediator to reduce the charging overpotential of Li-oxygen (Li-O
2
) batteries. Ambiguities exist regarding the influence of lithium iodide on ...the reaction product chemistry and performance of lithium-oxygen batteries. In this work, we examined the role of lithium iodide on the reduction product chemistry under two conditions: (i) mixing KO
2
with lithium salts and (ii) discharging Li-oxygen batteries at high and low overpotentials, in the presence of an ether-based electrolyte with different ratios of H
2
O : LiI. The addition of iodide to electrolytes containing water was found to promote the formation of LiOOH·H
2
O, LiOH·H
2
O and LiOH at the expense of Li
2
O
2
. At low H
2
O : LiI ratios (lower than 5), LiOH instead of Li
2
O
2
was formed, which was accompanied by the oxidation of iodide to triodide while at high H
2
O : LiI ratios (12, 24, 134), a mixture of Li
2
O
2
, LiOOH·H
2
O and LiOH·H
2
O was observed and no triiodide was detected. The reaction between peroxide Li
2
O
2
and/or superoxide LiO
2
with H
2
O to form LiOH is facilitated by increased water acidity by strong I
−
-H
2
O interactions as revealed by
1
H NMR and FT-IR measurements. This mechanism of LiOH formation in the presence of LiI and H
2
O was also found upon Li-O
2
cell discharge, which is critical to consider when developing LiI as a redox mediator for Li-O
2
batteries.
Iodide ions promote deprotonation of water; in consequence LiOH/LiOH·H
2
O is formed as a final discharge product.
PDF
