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News & Highlighted Publications

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Comprendre le processus de quasi-fission : Une étape essentielle pour la synthèse de nouveaux éléments super-lourds

Au cours d’une expérience réalisée auprès de l’accélérateur cryogénique de l’Australian National University (Canberra, Australie), une collaboration franco-australienne1 a pour la première fois identifié simultanément en masse et en numéro atomique Z jusqu’au plutonium, les fragments créés dans des réactions de quasi-fission. La quasi-fission est le mécanisme dominant dans les collisions très dissipatives entre noyaux très lourds. Elle est en compétition avec le mécanisme de fusion utilisé pour synthétiser de (...)

PHYS. REV. LETT. 119, 222502 (2017)

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GROUND-STATE PROPERTIES OF UNITARY BOSONS: FROM CLUSTERS TO MATTER [1]

"One of the most important properties of nuclei is saturation : although nuclear interactions are attractive overall, the growth in binding energy tapers off as the number of nucleons in the nucleus increases. As a consequence, heavy nuclei have some properties of a liquid drop. The simplest nucleus --- the deuteron --- has a small binding energy, which has led to a recent suggestion by Bira van Kolck and collaborators that nuclei can be described in a systematic expansion around the (...)

PHYS. REV. LETT. 119, 223002 (2017)

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IPN Orsay involved in the first Spectroscopy of 79Cu held with success at Riken

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The 78Ni nucleus, with 28 protons and 50 neutrons, is a cornerstone for nuclear structure as it is one of the most exotic nuclei with two magic numbers. The study of its proton-neighbour 79Cu allows to understand the movement of a single proton around 78Ni and it is therefore a powerful tool (...)

Phys. Rev. Lett. 119, 192501 (2017

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Le Central Neutron Detector (CND) a été installé en septembre dans le Hall-B du Jefferson Laboratory (USA).

Ce détecteur a été conçu pour aider les physiciens dans la compréhension de la structure du neutron en termes de quarks. Conçu et construit entièrement à l’IPN sur plusieurs années, il a été financé par l’IN2P3 et des fonds européens. Au cours d’une semaine de travail très intense et efficace à JLab, une équipe de l’IPN composée de cinq collègues techniciens et ingénieurs, d’un doctorant et d’une chercheuse du groupe PHEN, a mené l’installation du CND en mettant notamment en place la mécanique et (...)

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Comment l’état de Hoyle décroît

Dans le cadre d’une collaboration entre l’IPNO, l’Université de Naples et l’INFN, les réactions 14N(d, alpha)12C à 10.5 MeV ont été étudiées au Tandem du LNS de Catane pour analyser la décroissance de l’état de Hoyle dans le Carbone-12. La réaction est montrée schématiquement dans la figure annexe : elle induit le transfert d’une paire neutron-proton vers le faisceau, produisant comme ça une particule alpha et un noyau de Carbone-12 excité. La particule alpha émise, observée à une énergie cinétique donnée, a (...)

Phys. Rev. Lett. 119, 132501 – (2017)

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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 (...)

Science 357, 1266 (2017)

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Publications

Violent fluctuations in fluids of neutrons and protons explain how atomic nuclei disintegrate

Perturbing fluids of neutrons and protons (nuclear matter) may lead, as the most catastrophic effect, to the rearrangement of the fluid into clusters of nucleons. A similar process may occur in a single atomic nucleus undergoing a violent perturbation, like in heavy-ion collisions tracked in particle accelerators at around 30 to 50 MeV per nucleon : in this conditions, after the initial collision shock, the nucleus expands and then clusterizes into several smaller nuclear fragments. (...)

P. Napolitani and M. Colonna

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Unexpected high-energy γ emission from decaying exotic nuclei

The N = 52 83Ga β decay was studied at ALTO. The radioactive 83Ga beam was produced through the ISOL photofission technique and collected on a movable tape for the measurement of γ -ray emission following β decay. While β-delayed neutron emission has been measured to be 56–85% of the decay path, in this experiment an unexpected high-energy 5–9 MeV γ -ray yield of 16(4)% was observed, coming from states several MeVs above the (...)

A. Gottardo, D. Verney, I. Deloncle, S. Péru, C. Delafosse, S. Roccia, I. Matea, C. Sotty, C. Andreoiu, C. Costache, M.-C. Delattre, A. Etilé, S. Franchoo, C. Gaulard, J. Guillot, F. Ibrahim, M. Lebois, M. MacCormick, N. Marginean, R. Marginean, M. Martini, C. Mihai, I. Mitu, L. Olivier, C. Portail, L. Qi, B. Roussière, L. Stan, D. Testov, J. Wilson, D.T. Yordanov

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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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Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
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