Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA Cautionary Tale: The Coulomb Modified ANC for the $mathbf{1/2^+_2}$ State in $^mathbf{17}$O
51
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We discuss the impact of the uncertainty ($pm 8$ keV) in the excitation energy of the astrophysically important 6.356 MeV $1/2^+_2$ state of $^{17}$O on the precision with which the Coulomb reduced ANC ($widetilde{C}$) for the $left<^{17}mathrm{O}(1/2^+_2) mid protect{^{13}mathrm{C}} + alpha right>$ overlap can be extracted from direct reaction data. We find a linear dependence of $widetilde{C}^2$ on the binding energy, the value extracted varying by a factor of 4 over the range $E_{mathrm{ex}} = 6.356$ -- $6.348$ MeV. This represents an intrinsic limit on the precision with which $widetilde{C}^2$ can be determined which cannot be improved unless or until the uncertainty in $E_{mathrm{ex}}$ is reduced.
rate research
Read More
We report on the measurement of the beam asymmetry $Sigma$ for the reactions $vec{gamma}prightarrow peta$ and $vec{gamma}p rightarrow peta^{prime}$ from the GlueX experiment, using an 8.2--8.8 GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Lab. These measurements are made as a function of momentum transfer $-t$, with significantly higher statistical precision than our earlier $eta$ measurements, and are the first measurements of $eta^{prime}$ in this energy range. We compare the results to theoretical predictions based on $t$--channel quasi-particle exchange. We also compare the ratio of $Sigma_{eta}$ to $Sigma_{eta^{prime}}$ to these models, as this ratio is predicted to be sensitive to the amount of $sbar{s}$ exchange in the production. We find that photoproduction of both $eta$ and $eta^{prime}$ is dominated by natural parity exchange with little dependence on $-t$.
We present high-statistic data on charged pion emission from Au+Au collisions at $sqrt{s_{rm{NN}}}$ = 2.4 GeV (corresponding to $E_{beam}$ = 1.23 A GeV) in four centrality classes in the range 0 - 40$%$ of the most central collisions. The data are analyzed as a function of transverse momentum, transverse mass, rapidity, and polar angle. Pion multiplicity per participating nucleon decreases moderately with increasing centrality. The polar angular distributions are found to be non-isotropic even for the most central event class. Our results on pion multiplicity fit well into the general trend of the world data, but undershoot by $2.5 sigma$ data from the FOPI experiment measured at slightly lower beam energy. We compare our data to state-of-the-art transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find substantial differences between the measurement and the results of these calculations.
Precise measurements of the proton electromagnetic form factor ratio $R = mu_p G_E^p/G_M^p$ using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of $R$ with momentum transfer $Q^2$ for $Q^2 gtrsim 1$ GeV$^2$, in strong disagreement with previous extractions of $R$ from cross section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Labs Hall A measured $R$ at four $Q^2$ values in the range 3.5 GeV$^2 le Q^2 le 5.6$ GeV$^2$. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher $Q^2$ motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for $R$, improving the consistency of the polarization transfer data in the high-$Q^2$ region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis.
The $beta$ decay of the odd-odd nucleus $^{70}$Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The $T=0$ ($J^{pi}=9^+$) and $T=1$ ($J^{pi}=0^+$) isomers have both been produced in in-flight fragmentation of $^{78}$Kr with ratios of 41.6(8)% and 58.4(8)%, respectively. A half-life of $t_{1/2}=2157^{+53}_{-49}$ ms has been measured for the $J^{pi}=9^+$ isomer from $gamma$-ray time decay analysis. Based on this result, we provide a new value of the half-life for the $J^{pi}=0^+$ ground state of $^{70}$Br, $t_{1/2}=78.42pm0.51$ ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the $2^+_1$ state in the daughter nucleus $^{70}$Se, $R(2^+_1)=1.3pm1.1%$. We also report four new low-intensity $gamma$-ray transitions at 661, 1103, 1561, and 1749 keV following the $beta$ decay of the $J^{pi}=9^+$ isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in $^{70}$Se with most probable spins and parities of $J^{pi}=(6^+)$ and $(8^+)$, respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.
The determination of the magnon diffusion length (MDL) is important for increasing the efficiency of spin Seebeck effect (SSE) based devices utilising non-metallic magnets. We extract the MDL at $50$ and $300,rm{K}$ in an $rm{Fe}_{3}rm{O}_{4}$ single crystal from the magnon dispersion obtained using inelastic neutron scattering (INS) and find them to be equal within error. We then measure the heat flux normalised SSE responses and in-plane magnetization of $rm{Fe}_{3}rm{O}_{4}$ thin films and normalise by the static magnetization contribution to the SSE before determining the MDLs from a fit of the thickness dependence. We find that the MDLs determined in this way are smaller than that measured from INS which maybe due to differences in magnon propagation between bulk and thin film $rm{Fe}_{3}rm{O}_{4}$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
