arXiv : Testing ab initio nuclear structure in neutron-rich nuclei: lifetime measurements of second 2$^+$ states in $^{16}$C and $^{20}$O

Ciemala, M.; Jacquot, B.; Birkenbach, B.; Judson, D.S.; de France, G.; Michelagnoli, C.; Leoni, S.; Schwenk, A.; Menendez, J.; Matejska-Minda, M.; Erturk, S.; Lewitowicz, M.; Kmiecik, M.; Benzoni, G.; Dudouet, J.; Labiche, M.; Salsac, M.D.; Rejmund, M.; Valiente-Dobon, J.J.; Kicinska-Habior, M.; Recchia, F.; Bottoni, S.; Zieblinski, M.; Coelli, S.; Reiter, P.; Million, B.; Atac, A.; Perez-Vidal, R.M.; Camera, F.; Simonis, J.; Karpov, A.; Boston, A.J.; Matea, I.; Maj, A.; Harakeh, M.N.; Bednarczyk, P.; Mazurek, K.; Boiano, C.; Kim, Y.; Beckers, M.; Lemasson, A.; Li, H.; Stezowski, O.; Braunroth, T.; Napoli, D.R.; Dorvaux, O.; Bracco, A.; Crespi, F.C.L.; Iskra, L.W.; Brambilla, S.; Podolyak, Zs.; Zielinska, M.; Cieplicka-Orynczak, N.; Saillant, F.; Hess, H.; Holt, J.D.; Ziliani, S.; Nanal, V.; Goupil, J.; Lefevre, A.; Napiorkowski, P.; Wasilewska, B.; Lenzi, S.M.; Sanchis, E.; Barrientos, D.; Theisen, Ch.; Pullia, A.; Palit, R.; Domingo-Pardo, C.; Desesquelles, P.; Goldkuhle, A.; Gonzalez, V.; Eberth, J.; Jungclaus, A.; Fransen, C.; Muller-Gatermann, C.; Vardaci, E.; Schmitt, Ch.; Stefan, I.; Stanoiu, M.; Grebosz, J.; Harkness-Brennan, L.J.; Collado, J.; Charles, L.; Mengoni, D.; Nyberg, J.; Korten, W.; Cullen, D.M.; Bast, M.; Wieland, O.; Fornal, B.; Cederwall, B.; Menegazzo, R.; Clément, E.

doi:10.1103/PhysRevC.101.021303

Article
Report number	arXiv:2002.04814
Title	Testing ab initio nuclear structure in neutron-rich nuclei: lifetime measurements of second 2$^+$ states in $^{16}$C and $^{20}$O
Related title	Testing ab initio nuclear structure in neutron-rich nuclei: Lifetime measurements of second 2+ state in C16 and O20
Author(s)	Ciemala, M. (Cracow, INP) ; Ziliani, S. (Milan U. ; INFN, Milan) ; Crespi, F.C.L. (Milan U. ; INFN, Milan) ; Leoni, S. (Milan U. ; INFN, Milan) ; Fornal, B. (Cracow, INP) ; Maj, A. (Cracow, INP) ; Bednarczyk, P. (Cracow, INP) ; Benzoni, G. (INFN, Milan) ; Bracco, A. (Milan U. ; INFN, Milan) ; Boiano, C. (INFN, Milan) ; Bottoni, S. (Milan U. ; INFN, Milan) ; Brambilla, S. (INFN, Milan) ; Bast, M. (Cologne U.) ; Beckers, M. (Cologne U.) ; Braunroth, T. (Cologne U.) ; Camera, F. (Milan U. ; INFN, Milan) ; Cieplicka-Orynczak, N. (Cracow, INP) ; Clément, E. (GANIL) ; Coelli, S. (INFN, Milan) ; Dorvaux, O. (Strasbourg, IPHC) ; Erturk, S. (Nigde U.) ; de France, G. (GANIL) ; Fransen, C. (Cologne U.) ; Goldkuhle, A. (Cologne U.) ; Grebosz, J. (Cracow, INP) ; Harakeh, M.N. (Groningen, KVI) ; Iskra, L.W. (Cracow, INP ; INFN, Milan) ; Jacquot, B. (GANIL) ; Karpov, A. (Dubna, JINR) ; Kicinska-Habior, M. (Warsaw U.) ; Kim, Y. (GANIL) ; Kmiecik, M. (Cracow, INP) ; Lemasson, A. (GANIL) ; Lenzi, S.M. (INFN, Padua ; Padua U.) ; Lewitowicz, M. (GANIL) ; Li, H. (GANIL) ; Matea, I. (Orsay, IPN) ; Mazurek, K. (Cracow, INP) ; Michelagnoli, C. (Laue-Langevin Inst.) ; Matejska-Minda, M. (Warsaw U., Heavy Ion Lab ; Cracow, INP) ; Million, B. (INFN, Milan) ; Muller-Gatermann, C. (Cologne U.) ; Nanal, V. (Tata Inst.) ; Napiorkowski, P. (Warsaw U., Heavy Ion Lab) ; Napoli, D.R. (INFN, Legnaro) ; Palit, R. (Tata Inst.) ; Rejmund, M. (GANIL) ; Schmitt, Ch. (Strasbourg, IPHC) ; Stanoiu, M. (Bucharest, IFIN-HH) ; Stefan, I. (Orsay, IPN) ; Vardaci, E. (Naples U. ; INFN, Naples) ; Wasilewska, B. (Cracow, INP) ; Wieland, O. (INFN, Milan) ; Zieblinski, M. (Cracow, INP) ; Zielinska, M. (IRFU, Saclay) ; Atac, A. (Royal Inst. Tech., Stockholm) ; Barrientos, D. (CERN) ; Birkenbach, B. (Cologne U.) ; Boston, A.J. (Royal Inst. Tech., Stockholm) ; Cederwall, B. (Royal Inst. Tech., Stockholm) ; Charles, L. (Strasbourg, IPHC) ; Collado, J. (Valencia U., Dept. Ing. Electronica) ; Cullen, D.M. (U. Manchester (main)) ; Desesquelles, P. (CSNSM, Orsay) ; Domingo-Pardo, C. (Valencia U., IFIC) ; Dudouet, J. (Lyon, IPN) ; Eberth, J. (Cologne U.) ; Gonzalez, V. (Valencia U., Dept. Ing. Electronica) ; Goupil, J. (GANIL) ; Harkness-Brennan, L.J. (Liverpool U.) ; Hess, H. (Cologne U.) ; Judson, D.S. (Liverpool U.) ; Jungclaus, A. (Madrid, Inst. Estructura Materia) ; Korten, W. (IRFU, Saclay) ; Labiche, M. (Daresbury) ; Lefevre, A. (GANIL) ; Menegazzo, R. (Laue-Langevin Inst.) ; Mengoni, D. (INFN, Padua ; Padua U.) ; Nyberg, J. (Uppsala U.) ; Perez-Vidal, R.M. (Valencia U., IFIC) ; Podolyak, Zs. (Surrey U.) ; Pullia, A. (Milan U. ; INFN, Milan) ; Recchia, F. (INFN, Padua ; Padua U.) ; Reiter, P. (Cologne U.) ; Saillant, F. (GANIL) ; Salsac, M.D. (IRFU, Saclay) ; Sanchis, E. (Valencia U., Dept. Ing. Electronica) ; Stezowski, O. (Lyon, IPN) ; Theisen, Ch. (IRFU, Saclay) ; Valiente-Dobon, J.J. (INFN, Legnaro) ; Holt, J.D. (TRIUMF) ; Menendez, J. (Tokyo U., CNS ; Barcelona U.) ; Schwenk, A. (Darmstadt, Tech. Hochsch. ; Darmstadt, EMMI ; Heidelberg, Max Planck Inst.) ; Simonis, J. (Mainz U., Inst. Kernphys. ; U. Mainz, PRISMA)
Publication	2020-02-28
Imprint	2020-02-12
Number of pages	7
In:	Phys. Rev. C 101 (2020) 021303
DOI	10.1103/PhysRevC.101.021303
Subject category	nucl-ex ; Nuclear Physics - Experiment ; nucl-th ; Nuclear Physics - Theory
Abstract	To test the predictive power of ab initio nuclear structure theory, the lifetime of the second 2+ state in neutron-rich 20O, tau(2+_2 ) = 150(+80-30) fs, and an estimate for the lifetime of the second 2+ state in 16C have been obtained, for the first time. The results were achieved via a novel Monte Carlo technique that allowed us to measure nuclear state lifetimes in the tens-to-hundreds femtoseconds range, by analyzing the Doppler-shifted gamma-transition line shapes of products of low-energy transfer and deep-inelastic processes in the reaction 18O (7.0 MeV/u) + 181Ta. The requested sensitivity could only be reached owing to the excellent performances of the AGATA gamma-tracking array, coupled to the PARIS scintillator array and to the VAMOS++ magnetic spectrometer. The experimental lifetimes agree with predictions of ab initio calculations using two- and three-nucleon interactions, obtained with the valence-space in-medium similarity renormalization group for 20O, and with the no-core shell model for 16C. The present measurement shows the power of electromagnetic observables, determined with high-precision gamma spectroscopy, to assess the quality of first-principles nuclear structure calculations, complementing common benchmarks based on nuclear energies. The proposed experimental approach will be essential for short lifetimes measurements in unexplored regions of the nuclear chart, including r-process nuclei, when intense ISOL-type beams become available.
Copyright/License	preprint: (License: CC-BY-4.0) publication: © 2020-2024 authors (License: CC-BY-4.0)

$\textit{Left}: Identification plots, charge Q versus A/Q, for O (a) and C (b) ions, as measured by VAMOS++. \textit{Right}: velocity distributions measured at the VAMOS++ focal plane (black histograms), in coincidence with $2^+_2\rightarrow2^+_1$ transitions of $^{20}$O (c) and $^{16}$C (d), detected in AGATA. Solid red lines are simulated final velocity distributions - quasi-elastic (deep-inelastic) components are given by red (green) shaded areas. Insets: reconstructed initial (dashed blue) and final (solid red lines) product velocities.$ $\textit{Left}: $\gamma$-ray spectra of $^{19}$O (a), $^{20}$O (b) and $^{16}$C (c), as measured by AGATA. \textit{Right}: Corresponding level schemes of $^{19}$O (d), $^{20}$O (e) and $^{16}$C (f). In a), blue stars mark weak transitions of $^{19}$O not shown in d).$ $\textit{Panels (a)-(c), (d)-(f) and (g)-(i)}: 2371-, 2779- and 2396-keV $\gamma$ rays from the long-lived ($\tau>$3.5 ps) 9/2$^+$ state in $^{19}$O, and the 7/2$^+$ and the 2$^+_2$ states in $^{19}$O and $^{20}$O, respectively, as measured by AGATA (precision $<$4 mm) in the angular ranges \ang{130}$\pm$\ang{10}, \ang{150}$\pm$\ang{10} and \ang{170}$\pm$\ang{10}. In (d)-(f) and (g)-(i) simulated spectra (shaded bands) are calculated on basis of the global $\chi^2$ lifetime-energy surface (see corresponding insets), with 1$\sigma$ uncertainty (white contour line) around the optimum $\gamma$-energy ($E_{\gamma}$) and lifetime ($\tau$) values (white cross). Black crosses and dashed lines indicate the $\chi^2$ minimum and 1$\sigma$ uncertainty for $\gamma$-detection angles defined by the AGATA front segment centers (precision $\sim$20 mm). In (a)-(c), simulated spectra for $\tau$ = 100 and 1000 fs (blue and red lines, respectively) are shown to demonstrate the absence of broadening and tails for decays from long-lived states. \textit{Panel j)}: $\chi^2$ surface for the $^{16}$C 2$^+_2\rightarrow2^+_1$ transition. \textit{Panel k)}: $^{16}$C 2$^+_2\rightarrow2^+_1$ transition measured over the full AGATA angular range (histogram), compared with simulated spectra relative to the minimum of the $\chi^2$ map, for $E_{\gamma}$ = 2215 keV ($\tau$=230 fs) and $E_{\gamma}$ = 2217 keV ($\tau$=50 fs).$ Show more plots

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