Open Access

Guillermo Ribeiro Jimenez, Enrique Nácher González, Olof Tengblad, Paloma Díaz Fernández, Yuliya Aksyutina, Héctor Alvarez-Pol, Leyla Atar, Thomas Aumann, Vladimir Avdeichikov, Saul Beceiro-Novo, Daniel Bemmerer, Jose Fernando Benlliure Anaya, Carlos A. Bertulani, Juan Manuel Boillos Betete, Konstanze Boretzky, Maria José Garcia Borge, Manuel Caamano, Christoph Caesar, Enrique Casarejos Ruiz, Wilton N. Catford, Joakim Cederkäll, Marielle Chartier, Leonid V. Chulkov, Dolores Cortina Gil, Edgar Cravo, Raquel Crespo, Ushasi Datta Pramanik, Iris Dillmann, Zoltán Elekes, Joachim Enders, Olga Ershova, Alfredo Estradé Vaz, Fabio Farinon, Luis Mario Fraile Prieto, Martin Freer, Hans Otto Uldall Fynbo, Daniel Galaviz Redondo, Hans Geissel, Roman Gernhäuser, Pavel Golubev, Kathrin Göbel, Julius Hagdahl, Tanja Heftrich, Michael Heil, Marcel Heine, Andreas Heinz, Ana Henriques, Matthias Holl, A. Hufnagel, Alexander Ignatov, Håkan T. Johansson, Björn Jonson, Nasser Kalantar-Nayestanaki, Rituparna Kanungo, Aleksandra Kelic-Heil, Nikolaus Kurz, Thorsten Kröll, Marc Labiche, Christoph Langer, Tudi Le Bleis, Roy Crawford Lemmon, Simon Lindberg, Jorge Machado, Justyna Marganiec, Alina Movsesyan, Thomas Nilsson, Chiara Nociforo, Valerii Panin, Stefanos Paschalis, Angel Perea Martinez, Marina Petri, Stephane Pietri, Ralf Plag, René Reifarth, Catherine Rigollet, Karsten Riisager, Dominic M. Rossi, Marko Röder, Deniz Savran, Heiko Scheit, Haik Simon, Olivier Sorlin, Ina Syndikus, Jonathan Thomas Taylor, Ronja Thies, Paulo Velho, Andreas Wagner, Felix Wamers, Marine Vandebrouck, Helmut Weick, Carl Wheldon, Gemma Louise Wilson, Christine Wimmer, John S. Winfield, Philip John Woods, Mikhail V. Zhukov, Andreas Zilges, Kai Zuber

• The neutron-unbound isotope 13Be has been studied in several experiments using different reactions, different projectile energies, and different experimental setups. There is, however, no real consensus in the interpretation of the data, in particular concerning the structure of the low-lying excited states. Gathering new experimental information, which may reveal the 13Be structure, is a challenge, particularly in light of its bridging role between 12Be, where the N = 8 neutron shell breaks down, and the Borromean halo nucleus 14Be. The purpose of the present study is to investigate the role of bound excited states in the reaction product 12Be after proton knockout from 14B, by measuring coincidences between 12Be, neutrons, and γ rays originating from de-excitation of states fed by neutron decay of 13Be. The 13Be isotopes were produced in proton knockout from a 400 MeV/nucleon 14B beam impinging on a CH2 target. The 12 Be-n relative-energy spectrum d σ /d Ef n was obtained from coincidences between 12Be(g.s.) and a neutron, and also as threefold coincidences by adding γ rays, from the de-excitation of excited states in 12Be. Neutron decay from the first 5/2+ state in 13Be to the 2+ state in 12Be at 2.11 MeV is confirmed. An energy independence of the proton-knockout mechanism is found from a comparison with data taken with a 35 MeV/nucleon 14B beam. A low-lying p-wave resonance in 13Be(1/2−) is confirmed by comparing proton- and neutron-knockout data from 14B and 14Be.