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From galaxies far far away!

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In a paper to be published in Science on 22 September, the Pierre Auger Collaboration reports observational evidence demonstrating that cosmic rays with energies a million times greater than that of the protons accelerated in the Large Hadron (...)

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Marie Curie, les femmes et la science, d’hier à aujourd’hui

Dans le cadre de la conférence grand public qui s’est déroulée au CERN le 29 juin dernier, retrouvez les présentations et interviews d’Hélène Langevin. A voir également : Le jour où j’ai rencontré la petite-fille de Marie Curie Photo: © graine de genie graine de citoyen 2017 Vidéo: © 2017 CERN

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Scientific news

Competing Shapes in Neutron Rich Krypton Isotopes

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An international team led by scientists from IPN Orsay (CNRS/Université Paris-Sud), CEA, and RIKEN (Japan) has performed the first spectroscopy of the extremely neutron-rich isotopes 98,100Kr. This experiment showed that there are two coexisting, competing quantum shapes at low energy in 98Kr, (...)

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An innovative technique to measure the isotope distributions from fission of 238U

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Measurements of the mass and charge distributions of isotopes, produced when a heavy nucleus fissions into two lighter fragments, are important for several reasons. These include understanding the complex phenomenon of fission itself, the (...)

J.N. Wilson, M. Lebois, L. Qi, et al.

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Publications

Narrow exotic tetraquark mesons in large-N_c QCD

Discussing four-point Green functions of bilinear quark currents in large-N_c QCD, we formulate rigorous criteria for selecting diagrams appropriate for the analysis of potential tetraquark poles. We find that both flavor-exotic and cryptoexotic (i.e., flavor-nonexotic) tetraquarks, if such poles exist, have a width of order O(1/N_c^2), so they are parametrically narrower compared to the ordinary mesons, which have a width of order O(1/N_c). Moreover, for flavor-exotic states, the (...)

Hagop Sazdjian

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Delta(1232) Dalitz decay in proton-proton collisions at T=1.25 GeV measured with HADES at GSI

We report on the investigation of Δ(1232) production and decay in proton-proton collisions at a kinetic energy of 1.25 GeV measured with HADES. Exclusive dilepton decay channels ppe+e− and ppe+e−γ have been studied and compared with the partial-wave analysis of the hadronic ppπ0 channel. They allow to access both Δ+→pπ0(e+e−γ) and Δ+→pe+e− Dalitz decay channels. The perfect reconstruction of the well-known π0 Dalitz decay serves as a proof of the consistency of the analysis. The Δ Dalitz decay is (...)

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Lee-Yang–inspired functional with a density-dependent neutron-neutron scattering length

Inspired by the low-density Lee-Yang expansion for the energy of a dilute Fermi gas of density ρ and momentum kF, we introduce here a Skyrme-type functional that contains only s-wave terms and provides, at the mean-field level, (i) a satisfactory equation of state for neutron matter from extremely low densities up to densities close to the equilibrium point, and (ii) a good-quality equation of state for symmetric matter at density scales around (...)

M. Grasso, D. Lacroix, and C. J. Yang

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Renormalizability of the nuclear many-body problem with the Skyrme interaction beyond mean field

Phenomenological effective interactions like Skyrme forces are currently used in mean-field calculations in nuclear physics. Mean-field models have strong analogies with the first order of the perturbative many-body problem and the currently used effective interactions are adjusted at the mean-field level. In this work, we analyze the renormalizability of the nuclear many-body problem in the case where the effective Skyrme interaction is employed in (...)

C. J. Yang, M. Grasso, K. Moghrabi, and U. van Kolck

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Power counting in peripheral partial waves: The singlet channels

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 (...)

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

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

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 (...)

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

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

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 (...)

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

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IPN

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

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