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Power counting in peripheral partial waves : The singlet channels

M. Pavón Valderrama, M. Sánchez Sánchez, C.-J. Yang, Bingwei Long, J. Carbonell, and U. van Kolck

We analyze the power counting of the peripheral singlet partial waves in nucleon-nucleon scattering. In agreement with conventional wisdom, we find that pion exchanges are perturbative in the peripheral singlets. We quantify from the effective field theory perspective the well-known suppression induced by the centrifugal barrier in the pion-exchange interactions. By exploring perturbation theory up to fourth order, we find that the one-pion-exchange (...)

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From bare interactions, low-energy constants, and unitary gas to nuclear density functionals without free parameters : Application to neutron matter

Denis Lacroix, Antoine Boulet, Marcella Grasso, and C.-J. Yang

We further progress along the line of Ref. [D. Lacroix, Phys. Rev. A 94, 043614 (2016)] where a functional for Fermi systems with anomalously large s-wave scattering length as was proposed that has no free parameters. The functional is designed to correctly reproduce the unitary limit in Fermi gases together with the leading-order contributions in the s- and p-wave channels at low density. The functional is shown to be predictive up (...)

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Pygmy Gamow-Teller resonance in the N=50 region : New evidence from staggering of β-delayed neutron-emission probabilities

D. Verney, D. Testov, F. Ibrahim, B. Roussière, S. Franchoo, R. Li, I. Matea, I. Stefan, and D. Suzuki

Abstract We report on the β-delayed neutron emission probability (P1n) measurements of the 82,83,84Ga (N=51,52,53) precursors performed in one single experiment using the 3He neutron-counter TETRA at the ALTO facility in Orsay. Altogether our results for the three A=82,83, and 84 Ga precursors point towards a sizable P1n staggering in the N=50 region, similar to the one already observed just after the N=28 shell closure in the K isotopes chain, hinting at a similar mechanism. We will (...)

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96Kr–Low-Z Boundary of the Island of Deformation at N=60

C. Delafosse, A. Gottardo, D. Verney

Abstract Prompt γ-ray spectroscopy of the neutron-rich 96Kr, produced in transfer- and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS++ spectrometer. A second excited state, assigned to Jπ=4+, is observed for the first time, and a previously reported level energy of the first 2+ excited state is confirmed. The measured energy ratio R4/2=E(4+)/E(2+)=2.12(1) indicates that this nucleus does not show a (...)

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Ultrafast-timing lifetime measurements in 94Ru and 96Pd : Breakdown of the seniority scheme in N=50 isotones

I. Matea, D. Verney

Abstract The advanced time-delayed γγ(t) method has been applied to determine half-lives of low-lying states in the N=50 isotones 94Ru and 96Pd. The inferred experimental E2 strengths for the 4+→2+ transitions in the two nuclei show a dramatic deviation with respect to the shell model predictions in the (f5/2,p,g9/2) proton hole space in 100Sn. The anomalous behavior can be ascribed to a breakdown of the seniority quantum number in the πgn9/2 configuration due to particle-hole excitations (...)

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Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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