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Register a new userExperimental study of the two-body spin-orbit force
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G. Burgunder
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Energies and spectroscopic factors of the first $7/2^-$, $3/2^-$, $1/2^-$ and $5/2^-$ states in the $^{35}$Si$_{21}$ nucleus were determined by means of the (d,p) transfer reaction in inverse kinematics at GANIL using the MUST2 and EXOGAM detectors. By comparing the spectroscopic information on the $^{35}$Si and $^{37}$S isotones, a reduction of the $p_{3/2} - p_{1/2}$ spin-orbit splitting by about 25% is proposed, while the $f_{7/2} -f_{5/2}$ spin-orbit splitting seems to remain constant. These features, derived after having unfolded nuclear correlations using shell model calculations, have been attributed to the properties of the 2-body spin-orbit interaction, the amplitude of which is derived for the first time in an atomic nucleus. The present results, remarkably well reproduced by using several realistic nucleon-nucleon forces, provide a unique touchstone for the modeling of the spin-orbit interaction in atomic nuclei.
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The contribution of a chiral three-nucleon force to the strength of an effective spin-orbit coupling is estimated. We first construct a reduced two-body interaction by folding one-nucleon degrees of freedom of the three-nucleon force in nuclear matter. The spin-orbit strength is evaluated by a Scheerbaum factor obtained by the $G$-matrix calculation in nuclear matter with the two-nucleon interaction plus the reduced two-nucleon interaction. The problem of the insufficiency of modern realistic two-nucleon interactions to account for the empirical spin-orbit strength is resolved. It is also indicated that the spin-orbit coupling is weaker in the neutron-rich environment. Because the spin-orbit component from the three-nucleon force is determined by the low-energy constants fixed in the two-nucleon sector, there is little uncertainty in the present estimation.
We present the Bjorken integral extracted from Jefferson Lab experiment EG1b for $0.05<Q^{2}<2.92$ GeV$^2$. The integral is fit to extract the twist-4 element $f_{2}^{p-n}$ which appears to be relatively large and negative. Systematic studies of this higher twist analysis establish its legitimacy at $Q^{2}$ around 1 GeV$^{2}$. We also performed an isospin decomposition of the generalized forward spin polarizability $gamma_{0}$. Although its isovector part provides a reliable test of the calculation techniques of Chiral Perturbation Theory, our data disagree with the calculations.
The Non-Mesonic (NM) decay of $^4_Lambda{mathrm{He}}$ and $^5_Lambda{mathrm{He}}$ in two-body channels has been studied by the FINUDA Collaboration. Two-body NM decays of hypernuclei are rare and the existing observations and theoretical calculations are scarce. The $^4_Lambda{mathrm{He}}rightarrow d+d,; p+t$ decay channels simultaneously observed by FINUDA on several nuclei are compared: the $pt$ channel is the dominant one. The decay yields for the two decay channels are assessed for the first time: they are $(1.37pm 0.37)times 10^{-5}/K^-_{stop}$ and $(8.3pm 1.0)times 10^{-5}/K^-_{stop}$, respectively. Due to the capability of FINUDA of identifying $^5_Lambda{mathrm{He}}$ hypernuclei, a few $^5_Lambda{mathrm{He}}rightarrow d+t$ decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: $(3.0pm 2.3)times 10^{-3}$.
We reported a systematic study of spin-orbit torque biased magnetic sensors based on NiFe/Pt bilayers through both macro-spin modeling and experiments. The simulation results show that it is possible to achieve a linear sensor with a dynamic range of 0.1 - 10 Oe, power consumption of 1uW - 1 mW, and sensitivity of 0.1-0.5 Ohm/Oe. These characteristics can be controlled by varying the sensor dimension and current density in the Pt layer. The latter is in the range of 1 x 10^5 - 10^7 A/cm^2. Experimental results of fabricated sensors with selected sizes agree well with the simulation results. For a Wheatstone bridge sensor comprising of four sensing elements, a sensitivity up to 0.548 Ohm/Oe, linearity error below 6%, and detectivity of about 2.8 nT/Sqrt(Hz) were obtained. The simple structure and ultrathin thickness greatly facilitate the integration of these sensors for on-chip applications. As a proof-of-concept experiment, we demonstrate its application in detection of current flowing in an on-chip Cu wire.
We have measured cross sections for the gamma+3He->p+d reaction at photon energies of 0.4 - 1.4 GeV and a center-of-mass angle of 90 deg. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.
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