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First Nb94(n,γ) Measurement: Constraining the Nucleosynthetic Origin of Mo94 in Presolar Grains

J. Balibrea-Correa1,†, J. Lerendegui-Marco1, C. Domingo-Pardo1, V. Babiano-Suarez1, I. Ladarescu1, M. Krtička2, G. Cescutti3,4, S. Cristallo5,6, D. Vescovi7,6 et al. (n_TOF Collaboration*)

D. Vescovi7,6, N. Liu8, E. A. Maugeri9, U. Köster10, I. Mönch20, A. Casanovas11, V. Alcayne12, D. Cano-Ott12, E. Mendoza12, O. Aberle13, J. Andrzejewski14, S. Altieri15,16, S. Amaducci17, M. Bacak13, C. Beltrami15, S. Bennett18, A. P. Bernardes13, E. Berthoumieux19, R. Beyer20, M. Boromiza21, D. Bosnar22, M. Caamaño23, F. Calviño11, M. Calviani13, D. M. Castelluccio24,25, F. Cerutti13, S. Chasapoglou26, E. Chiaveri13,18, P. Colombetti27,28, N. Colonna29, P. Console Camprini25,24, G. Cortés11, M. A. Cortés-Giraldo30, L. Cosentino17, S. F. Dellmann7, M. Diakaki26, M. Di Castro13, M. Dietz31, S. Di Maria32, R. Dressler9, E. Dupont19, I. Durán23, Z. Eleme33, S. Fargier13, B. Fernández30, B. Fernández-Domínguez23, P. Finocchiaro17, S. Fiore24, V. Furman34, F. García-Infantes35,13, A. Gawlik-Ramięga14, G. Gervino27,28, S. Gilardoni13, E. González-Romero12, C. Guerrero30, F. Gunsing19, C. Gustavino36, J. Heyse37, W. Hillman18, D. G. Jenkins38, E. Jericha39, A. Junghans20, Y. Kadi13, K. Kaperoni26, G. Kaur19, A. Kimura40, I. Knapová2, M. Kokkoris26, Y. Kopatch34, N. Kyritsis26, C. Lederer-Woods41, G. Lerner13, A. Manna25,42, T. Martínez12, A. Masi13, C. Massimi25,42, P. Mastinu43, M. Mastromarco29,44, A. Mazzone29,45, A. Mengoni24,25, V. Michalopoulou26, P. M. Milazzo3, R. Mucciola5,46, F. Murtas47, E. Musacchio González43, A. Musumarra48,49, A. Negret21, N. Patronis33,13, J. A. Pavón30,13, M. G. Pellegriti48, P. Pérez-Maroto30, A. Pérez de Rada Fiol12, J. Perkowski14, C. Petrone21, E. Pirovano31, J. Plaza del Olmo12, S. Pomp50, I. Porras35, J. Praena35, J. M. Quesada30, R. Reifarth7, D. Rochman9, Y. Romanets32, C. Rubbia13, A. Sánchez-Caballero12, M. Sabaté-Gilarte13, P. Schillebeeckx37, D. Schumann9, A. Sekhar18, A. G. Smith18, N. V. Sosnin41, M. E. Stamati33,13, A. Sturniolo27, G. Tagliente29, A. Tarifeño-Saldivia11, D. Tarrío50, P. Torres-Sánchez35, S. Urlass20,13, E. Vagena33, S. Valenta2, V. Variale29, P. Vaz32, G. Vecchio17, V. Vlachoudis13, R. Vlastou26, A. Wallner20, P. J. Woods41, T. Wright18, R. Zarrella25,42, and P. Žugec22 (n_TOF Collaboration*)

  • 1Instituto de Física Corpuscular, CSIC - Universidad de Valencia, Valencia, Spain
  • 2Charles University, Prague, Czech Republic
  • 3Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Italy
  • 4Department of Physics, University of Trieste, Trieste, Italy
  • 5Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Italy
  • 6Istituto Nazionale di Astrofisica - Osservatorio Astronomico d’Abruzzo, L’Aquila, Italy
  • 7Goethe University Frankfurt, Frankfurt, Germany
  • 8Institute for Astrophysical Research, Boston University, Boston, USA
  • 9Paul Scherrer Institut (PSI), Villigen, Switzerland
  • 10Institut Laue-Langevin (ILL), Grenoble, France
  • 11Universitat Politècnica de Catalunya, Barcelona, Spain
  • 12Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
  • 13European Organization for Nuclear Research (CERN), Geneva, Switzerland
  • 14University of Lodz, Lodz, Poland
  • 15Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Italy
  • 16Department of Physics, University of Pavia, Pavia, Italy
  • 17INFN Laboratori Nazionali del Sud, Catania, Italy
  • 18University of Manchester, Manchester, United Kingdom
  • 19CEA Irfu, Université Paris-Saclay, Gif-sur-Yvette, France
  • 20Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
  • 21Horia Hulubei National Institute of Physics and Nuclear Engineering, Măgurele, Romania
  • 22Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia
  • 23University of Santiago de Compostela, Santiago de Compostela, Spain
  • 24Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Rome, Italy
  • 25Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Italy
  • 26National Technical University of Athens, Athens, Greece
  • 27Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Italy
  • 28Department of Physics, University of Torino, Torino, Italy
  • 29Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Italy
  • 30Universidad de Sevilla, Sevilla, Spain
  • 31Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, Braunschweig, Germany
  • 32Instituto Superior Técnico, Lisbon, Portugal
  • 33University of Ioannina, Ioannina, Greece
  • 34Affiliated with an institute covered by a cooperation agreement with CERN
  • 35University of Granada, Granada, Spain
  • 36Istituto Nazionale di Fisica Nucleare, Sezione di Roma1, Roma, Italy
  • 37European Commission, Joint Research Centre (JRC), Geel, Belgium
  • 38University of York, New York, United Kingdom
  • 39TU Wien, Atominstitut, Stadionallee 2, Wien, Austria
  • 40Japan Atomic Energy Agency (JAEA), Tokai-Mura, Japan
  • 41School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
  • 42Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna, Italy
  • 43INFN Laboratori Nazionali di Legnaro, Legnaro, Italy
  • 44Dipartimento Interateneo di Fisica, Università degli Studi di Bari, Bari, Italy
  • 45Consiglio Nazionale delle Ricerche, Bari, Italy
  • 46Dipartimento di Fisica e Geologia, Università di Perugia, Bari, Italy
  • 47INFN Laboratori Nazionali di Frascati, Rome, Italy
  • 48Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Italy
  • 49Department of Physics and Astronomy, University of Catania, Catania, Italy
  • 50Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala, Sweden

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Phys. Rev. Lett. 137, 082701 – Published 18 August, 2026

DOI: https://doi.org/10.1103/538w-rhqb

Abstract

Isotopic measurements of presolar silicon carbide grains from dying stars have revealed a puzzling overabundance of Mo94 that stellar nucleosynthesis models have failed to reproduce for two decades. This discrepancy challenged our understanding of the slow neutron-capture process (s-process) that forges approximately half of the elements heavier than iron. The key uncertainty lies at Nb94, a radioactive branching point where competition between neutron capture and beta decay governs the Mo94 production, yet the neutron-capture cross section had never been measured. Here, we report the first experimental determination of the Nb94(n,γ)Nb95 cross section important for Mo isotopic abundances. The measurement was enabled by a coordinated effort involving high-purity target preparation at Institute of Solid State and Materials Research Dresden, radioactive sample production at the Institut Laue-Langevin Grenoble, radiochemical characterization at Paul Scherrer Institut Villigen, and the time-of-flight CERN n_TOF facility using for the first time segmented total-energy detectors. Incorporation of the resulting Maxwellian-averaged cross section into fully coupled nucleosynthesis models of low-mass asymptotic giant-branch stars brings them into agreement with the presolar grain data. These results remove a major nuclear-physics input uncertainty at the Nb94 branching point and provide a firmer foundation for understanding the origin of Mo94 in the Solar System.

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Phys. Rev. Lett. 137, 082701– Published 18 August, 2026
  • Received 4 March 2026
  • Revised 11 May 2026
  • Accepted 22 June 2026
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