On the origin of the reactor antineutrino anomalies in light of a new summation model with parameterized β−\beta^{-} transitions

We investigate the possible origins of the norm and shape reactor antineutrino anomalies in the framework of a summation model (SM) where $\beta^{-}$ transitions are simulated by a phenomenological Gamow-Teller $\beta$-decay strength model. The general trends of the discrepancies to the Huber-Mueller model on the antineutrino side can be reproduced both in norm and shape. From the exact electron-antineutrino correspondence of the SM model, we predict similar distortions in the electron spectra, suggesting that biases on the reference fission-electron spectra could be at the origin of the anomalies

Structure of unbound neutron-rich 9^{9}He studied using single-neutron transfer

The 8He(d,p) reaction was studied in inverse kinematics at 15.4A MeV using the MUST2 Si-CsI array in order to shed light on the level structure of 9He. The well known 16O(d,p)17O reaction, performed here in reverse kinematics, was used as a test to validate the experimental methods. The 9He missing mass spectrum was deduced from the kinetic energies and emission angles of the recoiling protons. Several structures were observed above the neutron-emission threshold and the angular distributions were used to deduce the multipolarity of the transitions. This work confirms that the ground state of 9He is located very close to the neutron threshold of 8He and supports the occurrence of parity inversion in 9He.Comment: Exp\'erience GANIL/SPIRAL1/MUST

Nuclear structure and reaction studies at SPIRAL

The SPIRAL facility at GANIL, operational since 2001, is described briefly. The diverse physics program using the re-accelerated (1.2 to 25 MeV/u) beams ranging from He to Kr and the instrumentation specially developed for their exploitation are presented. Results of these studies, using both direct and compound processes, addressing various questions related to the existence of exotic states of nuclear matter, evolution of new "magic numbers", tunnelling of exotic nuclei, neutron correlations, exotic pathways in astrophysical sites and characterization of the continuum are discussed. The future prospects for the facility and the path towards SPIRAL2, a next generation ISOL facility, are also briefly presented.Comment: 48 pages, 27 figures. Accepted for publication in Journal of Physics

Shell Gap Reduction In Exotic N = 17 Nuclei

An experimental spectroscopic investigation of some neutron rich Mg and Al isotopes around the shell closure N=20 has been performed. The delayed neutron and $\gamma$ spectra, following the $\beta$-decay of $^{33}$Mg and $^{35}$Al have been measured using the delayed neutron detector array TONNERRE coupled with high efficiency EXOGAM clover detectors, a LEPS detector and eight low-energy neutron detectors. A detailed analysis of such spectra allows one to construct the level schemes of their daughters, ^{32,33)Al and $^{34,35}$Si. The resulting spectroscopic information will provide stringent tests of large scale shell model calculations including np - nh excitations aimed at the understanding of the structural effects occurring in this region

γ\gamma spectroscopy of 25,27^{25,27}Ne and 26,27{26,27}Na

Expérience GANILThe $\gamma$ spectroscopy of $^{25,27}$Ne and $^{26,27}$Na was studied from the reaction of $^{26}$Ne with a deuterium target in inverse kinematics at 9.7 MeV/nucleon. The selectivity of the (d,p),(d,t), and (d,n) transfer reactions provides new spectroscopic information on low-lying states. The validity of the sd shell-model space for these nuclei is discussed

Breakdown of the Z = 8 Shell Closure in Unbound 12^{12}O and its Mirror Symmetry

Expérience GANIL, SISSI, MUST2/E537International audienceAn excited state in the proton-rich unbound nucleus 12O was identified at 1.8(4) MeV via missing-mass spectroscopy with the 14Oðp; tÞ reaction at 51 AMeV. The spin-parity of the state was determined to be 0þ or 2þ by comparing the measured differential cross sections with distorted-wave calculations. The lowered location of the excited state in 12O indicates the breakdown of the major shell closure at Z ¼ 8 near the proton drip line. This demonstrates the persistence of mirror symmetry in the disappearance of the magic number 8 between 12O and its mirror partner 12Be

Resonances of 6He via the 8He(p,t)6He reaction

We investigated the low-lying spectroscopy of 6He via the 2-neutron transfer reaction induced by the 8He SPIRAL beam at 15.4 A.MeV on a proton-rich target. The light charged recoil particles produced by the direct reactions were measured using theMUST2 Si-strip telescope array. Two new resonances were observed above the known 2+ state in 6He, and the angular momentum transfer was deduced through the analysis of the angular distributions. Results are discussed in comparison with the recent calculations of various nuclear structure theories which include the coupling to the continuum technique and to the ones which give an understanding of the cluster correlations in the light weakly-bound nuclei

Resonances of 6He via the 8He(p,t)6He reaction

CERN-Proceedings-2010-001 available at http://www.fluka.org/Varenna2009/procmat.htmInternational audienceWe investigated the low-lying spectroscopy of 6He via the 2-neutron transfer reaction induced by the 8He SPIRAL beam at 15.4 A.MeV on a proton-rich target. The light charged recoil particles produced by the direct reactions were measured using theMUST2 Si-strip telescope array. Two new resonances were observed above the known 2+ state in 6He, and the angular momentum transfer was deduced through the analysis of the angular distributions. Results are discussed in comparison with the recent calculations of various nuclear structure theories which include the coupling to the continuum technique and to the ones which give an understanding of the cluster correlations in the light weakly-bound nuclei