20 β-delayed neutron emission probabilities across the Z=50 and N=82 shell closure: Implication on the formation of the second r-process peak
RIKEN Nishina Center
On Behalf of the BRIKEN collaboration
Outstanding problems on the formation of the second (A~130) r-process abundance peak: from astrophysical observations to nucleosynthesis models
β-delayed neutrons emission probabilities \(P_{n}\) as important inputs for r-process calculations.
New experimental \(P_{n}\) values their impacts on:
Benchmarking the theoretical \(\beta\)-decay models
Odd-even pattern of the second r-process peak
Vi H. Phong | AwRI conference | June 15\(^{th}\) 2022
robust pattern
star-to-star scatter
C. Sneeden et al. 2008
I. Roederer et al. 2022
Deficient: Te and Sb
Metal-poor stars observation: r-process "universality"
S. Shibagaki el al. 2016, N. Nishimura et al. 2015
Magneto-hydrodynamic jet (MHDJ) model
S. Lemaître et al. 2020 and E. Eicher et al. 2015
Neutron star merger model
$$P_{xn} = T_{1/2} \int^{Q_{\beta}}_{S_{xn}} S_{\beta}(E_{x}) f(Z,A,Q_{\beta}-E_{x})$$
$$T_{1/2} = \int^{Q_{\beta}}_{0} S_{\beta}(E_{x}) f(Z,A,Q_{\beta}-E_{x})$$
A. Arcones & G. Martinez-Pinedo 2011
Odd-even pattern
Final nucleous
Precursor
However...
A. Arcones & G. Martinez-Pinedo 2011
\(Q_{\beta 1n} \)
\(Q_{\beta 2n} \)
Emitter
K. Farouqi et. al. 2011
BRIKEN: \(\beta\)-delayed neutron emission probability measurements at RIKEN
RI seperation
RI identification
BRIKEN aims for:
\(P_{xn}\) measurements of neutron-rich nuclei across the Z=50 and N=82 shell closures
r-process path [S. Shibagaki el al. 2016]
N=84
Z=49 \(\rightarrow\) 50
Crucial benchmarks for the theoretical models for predicting \(P_{xn}\)
P. Moller et. al. 2019
F. Minato et. al. 2021
I. Borzov et. al. 2020
With HF
Skynet + Nucnet codes [J. Lippuner 2015, B. S. Mayer 2007]
Baseline simulation: Y\(_{e}\) = 0.06, S = 12 \(k_{b}\)/b and \(\tau\) = 66 ms
Freezout flows and final abundances:
\(^{135}\)In
\(^{134}\)Sn
\(^{136}\)Sn
\(^{131}\)Ag
Robust odd-even pattern for low Ye
Improvement of Ba isotopic abundances using the current experimental results.
\(f_{odd,Ba}\) = \((Y_{135Ba}+Y_{137Ba})/Y_{Ba}\)
Metal poor stars \(f_{odd,Ba}\)
C. Wenyuan et al. 2015
FRDM+QRPA+HF
Exp.
•Sorting the data produced from 3 independent DAQ
•Merging the data from 3 DAQs based on time-stamp
•Time and position correlation → β decay curves: Tβ − Timplant
\(\beta\)-implant
\(\beta\)1n-implant
\(\beta\)2n-implant