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تسجيل مستخدم جديدIn-beam spectroscopic studies of $^{44}$S nucleus
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L. Caceres
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The structure of the $^{44}$S nucleus has been studied at GANIL through the one proton knock-out reaction from a $^{45}$Cl secondary beam at 42 A$cdot$MeV. The $gamma$ rays following the de-excitation of $^{44}$S were detected in flight using the 70 BaF${_2}$ detectors of the Ch^{a}teau de Cristal array. An exhaustive $gammagamma$-coincidence analysis allowed an unambiguous construction of the level scheme up to an excitation energy of 3301 keV. The existence of the spherical 2$^+_2$ state is confirmed and three new $gamma$-ray transitions connecting the prolate deformed 2$^+_1$ level were observed. Comparison of the experimental results to shell model calculations further supports a prolate and spherical shape coexistence with a large mixing of states built on the ground state band in $^{44}$S.
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The structure of $^{44}$S has been studied using delayed $gamma$ and electron spectroscopy at textsc{ganil}. The decay rates of the 0$^+_2$ isomeric state to the 2$^+_1$ and 0$^+_1$ states have been measured for the first time, leading to a reduced t
ransition probability B(E2~:~2$^{+}_1$$rightarrow$0$^{+}_2)$= 8.4(26)~e$^2$fm$^4$ and a monopole strength $rho^2$(E0~:~0$^{+}_2$$rightarrow$0$^{+}_1)$ =~8.7(7)$times$10$^{-3}$. Comparisons to shell model calculations point towards prolate-spherical shape coexistence and a phenomenological two level mixing model is used to extract a weak mixing between the two configurations.
Differential production cross sections of K$^-$ and K$^+$ mesons have been measured as function of the polar emission angle in Ni+Ni collisions at a beam energy of 1.93 AGeV. In near-central collisions, the spectral shapes and the widths of the rapid
ity distributions of K$^-$ and K$^+$ mesons are in agreement with the assumption of isotropic emission. In non-central collisions, the K$^-$ and K$^+$ rapidity distributions are broader than expected for a single thermal source. In this case, the polar angle distributions are strongly forward-backward peaked and the nonisotropic contribution to the total yield is about one third both for K$^+$ and K$^-$ mesons. The K$^-$/K$^+$ ratio is found to be about 0.03 independent of the centrality of the reaction. This value is significantly larger than predicted by microscopic transport calculations if in-medium modifications of K mesons are neglected.
We renew our intent to submit a proposal to perform a search for a non-zero value of the unmeasured hadronic double helicity flip structure function $Delta(x,Q^2)$, predicted to be sensitive to gluons in the nucleus. This would be performed with an u
npolarized electron beam and transversely polarized, spin-1, nuclear target. This structure function was first identified by Jaffe and Manohar in 1989 as a clear signature for exotic gluonic components in the target, and a recent lattice QCD result by our collaborators has prompted renewed interest in the topic. An inclusive search with deep inelastic scattering, below $x$ of 0.3, via single spin tensor asymmetries may be feasible using the CEBAF 12 GeV electron beam and JLab/UVa solid polarized target, and would represent the first experimental exploration of this quantity.
High-spin states in the odd-odd nucleus $^{168}$Ta have been populated in the $^{120}$Sn($^{51}$V,3n) reaction. Two multi-quasiparticle structures have been extended significantly from spin $sim{20hbar}$ to above ${40hbar}$. As a result, the first ro
tational alignment has been fully delineated and a second band crossing has been observed for the first time in this nucleus. Configurations for these strongly-coupled rotational bands are proposed based on signature splitting, $B(M1)/B(E2)$ ratio information, and observed rotation-alignment behavior. Properties of the observed bands in $^{168}$Ta are compared to related structures in the neighboring odd-$Z$, odd-$N$, and odd-odd nuclei and are discussed within the framework of the cranked shell model.
Preliminary results from an experiment aiming at Dy-170. Submitted to the LNL Annual Report 2008.
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