APS123-QED Deep underground laboratory measurement of13Cn16O in the Gamow windows of the s- and i-processes

2025-04-27 1 0 697.48KB 17 页 10玖币

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APS/123-QED

Deep underground laboratory measurement of 13C(α,n)16O in the

Gamow windows of the s- and i-processes

B. Gao,1, 2, 3 T.Y. Jiao,2, 3 Y.T. Li,2, 3 H. Chen,2, 3 W.P. Lin,4Z. An,4L.H. Ru,2

Z.C. Zhang,2, 3 X.D. Tang,1, 2, 3, ∗X.Y. Wang,2, 3 N.T. Zhang,2, 3 X. Fang,5D.H. Xie,4

Y.H. Fan,2, 6 L. Ma,4X. Zhang,4F. Bai,4P. Wang,4Y.X. Fan,4G. Liu,4H.X. Huang,7

Q. Wu,8Y.B. Zhu,8J.L. Chai,8J. Q. Li,8L. T. Sun,8S. Wang,9J.W. Cai,2, 3 Y.Z. Li,2, 3

J. Su,7, 10 H. Zhang,7Z. H. Li,3, 7 Y. J. Li,7E. T. Li,11 C. Chen,7Y. P. Shen,7G. Lian,7

B. Guo,7X. Y. Li,10 L. Y. Zhang,10 J. J. He,10 Y. D. Sheng,10 Y. J. Chen,10 L. H. Wang,10

L. Zhang,7F. Q. Cao,7W. Nan,7W. K. Nan,7G. X. Li,7N. Song,7B. Q. Cui,7L. H. Chen,7

R. G. Ma,7Z. C. Zhang,11 S. Q. Yan,7J. H. Liao,7Y. B. Wang,7S. Zeng,7D. Nan,7

Q. W. Fan,7N. C. Qi,12 W. L. Sun,12 X. Y. Guo,12 P. Zhang,12 Y. H. Chen,12 Y. Zhou,12

J. F. Zhou,12 J. R. He,12 C. S. Shang,12 M. C. Li,12 S. Kubono,13, 14 and W. P. Liu7, †

(JUNA Collaboration)

R.J. deBoer,15 M. Wiescher,15, 16 and M. Pignatari17, 18, 19, 20

1Joint department for nuclear physics,

Lanzhou University and Institute of Modern Physics,

Chinese Academy of Sciences, Lanzhou 730000, China

2CAS Key Laboratory of High Precision Nuclear Spectroscopy,

Institute of Modern Physics, Chinese Academy of Sciences,

Lanzhou 73000, People’s Republic of China

3School of Nuclear Science and Technology,

University of Chinese Academy of Sciences,

Beijing 100049, People’s Republic of China

4Key Laboratory of Radiation Physics and Technology of the Ministry of Education,

Institute of Nuclear Science and Technology,

Sichuan University, Chengdu 610064, China

5Sino-French Institute of Nuclear Engineering and Technology,

Sun Yat-sen University, Zhuhai, Guangdong 519082, People’s Republic of China

6School of Nuclear Science and Technology,

arXiv:2210.03222v1 [nucl-ex] 6 Oct 2022

Lanzhou University, Lanzhou 730000, China

7China Institute of Atomic Energy,

Beijing 102413, People’s Republic of China

8Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China

9Shandong Provincial Key Laboratory of Optical Astronomy and

Solar-Terrestrial Environment, Institute of Space Sciences,

Shandong University, Weihai 264209, China

10Key Laboratory of Beam Technology and Material Modiﬁcation of Ministry of Education,

College of Nuclear Science and Technology,

Beijing Normal University, Beijing 100875, China

11College of Physics and Optoelectronic Engineering,

Shenzhen University, Shenzhen 518060, China

12Yalong River Hydropower Development Company, Chengdu 610051, China

13RIKEN Nishina Center, Wako, Saitama 351-0198, Japan

14Center for Nuclear Study, University of Tokyo, Wako, Saitama 351-0198, Japan

15Department of Physics and the Joint Institute for Nuclear Astrophysics,

University of Notre Dame, Notre Dame, IN 46556, USA

16Wolfson Fellow of Royal Society, School of Physics and Astronomy,

University of Edinburgh, King’s Buildings,

Edinburgh EH9 3FD, United Kingdom

17Konkoly Observatory, Research Centre for Astronomy and Earth Sciences (CSFK),

E¨otv¨os Lor´and Research Network (ELKH),

Konkoly Thege Mikl´os ´ut 15-17, H-1121 Budapest, Hungary

18CSFK, MTA Centre of Excellence, Budapest,

Konkoly Thege Mikl´os ´ut 15-17, H-1121, Hungary

19E. A. Milne Centre for Astrophysics,

Department of Physics and Mathematics,

University of Hull, HU6 7RX, United Kingdom

20NuGrid Collaboration, http: // nugridstars. org

(Dated: October 10, 2022)

Abstract

The 13C(α,n)16O reaction is the main neutron source for the slow-neutron-capture (s-) process

in Asymptotic Giant Branch stars and for the intermediate (i-) process. Direct measurements

at astrophysical energies in above-ground laboratories are hindered by the extremely small cross

sections and vast cosmic-ray induced background. We performed the ﬁrst consistent direct mea-

surement in the range of Ec.m.=0.24 MeV to 1.9 MeV using the accelerators at the China Jinping

Underground Laboratory (CJPL) and Sichuan University. Our measurement covers almost the en-

tire i-process Gamow window in which the large uncertainty of the previous experiments has been

reduced from 60% down to 15%, eliminates the large systematic uncertainty in the extrapolation

arising from the inconsistency of existing data sets, and provides a more reliable reaction rate for

the studies of the s- and i-processes along with the ﬁrst direct determination of the alpha strength

for the near-threshold state.

∗xtang@impcas.ac.cn

†wpliu@ciae.ac.cn

Low-mass Asymptotic Giant Branch (AGB) stars are the primary sources of elements

above iron in the Galaxy via the activation of the slow-neutron-capture process (s-process) [1].

In these stars, the bulk of the s-process abundances is created by neutrons from the the

13C(α,n)16O reaction at temperatures around T9=0.1 in the radiative 13C-pocket, located

in the helium-rich layers, just below the stellar envelope [2, 3]. Here T9is deﬁned as a

temperature divided by 109Kelvin. The subsequent neutron capture and β-decay processes

transmute lighter elements into heavier ones, with a major production eﬃciency between

Sr and Pb depending on the initial metallicity of the star [4]. In some AGB simulations,

it was also found that part of the 13C is still alive in the 13C-pocket at the onset of the

convective thermal pulse: the remaining 13C is mixed at the bottom of the He intershell

region activating 13C(α,n)16O at He burning temperatures of approximately T9=0.2-0.25

[5, 6]. This scenario tends to be favored by a low 13C(α,n)16O rate [7], and the anomalous

activation of the 13C(α,n)16O reaction together with the 22Ne(α,n)25Mg reaction at the

bottom of the convective thermal pulse. This may aﬀect the s-process isotopic pattern near

the active s-process branching points [6, 7].

The 13C(α,n)16O reaction is also the main neutron source of the intermediate process (i-

process ) [8], which matches the puzzling abundances observed in some post AGB stars [9], of

a subset of carbon-enhanced metal poor (CEMP) stars [10], of presolar grains [11] and stars

in young open clusters [12]. The i-process can be activated in diﬀerent stellar environments,

including among other low-mass AGB stars [10, 13], super AGB stars [14] and post AGB stars

[9], massive stars [15, 16] and rapidly-accreting WDs [17]. In those models, a small amount

of hydrogen is ingested into the convective helium-burning zone underneath the envelope.

Hydrogen reacts with the primary product of He-burning 12C, making 13N that will decay to

13C. The i-process is generated by the 13C(α,n)16O activated at He-burning temperatures of

around T9=0.2 or above [9]. This results in a neutron density of around 1014 ∼1016 cm−3,

which is signiﬁcantly higher than typical values of the s-process (106∼1010 cm−3). At least

for one-dimensional models of metal-poor low-mass AGB models, Cristallo et al. [6] showed

that after the hydrogen ingestion, the 13C(α,n)16O reaction also becomes a relevant energy

source in the He shell: in their calculations even a factor of two variation of the 13C(α,n)16O

rate changes the i-process production by orders of magnitude. Such an impact will need to

be conﬁrmed for diﬀerent types of stars by multi-dimensional hydrodynamics simulations,

providing guidance for how one-dimensional models should behave once hydrogen has been

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APS/123-QEDDeepundergroundlaboratorymeasurementof13C(,n)16OintheGamowwindowsofthes-andi-processesB.Gao,1,2,3T.Y.Jiao,2,3Y.T.Li,2,3H.Chen,2,3W.P.Lin,4Z.An,4L.H.Ru,2Z.C.Zhang,2,3X.D.Tang,1,2,3,X.Y.Wang,2,3N.T.Zhang,2,3X.Fang,5D.H.Xie,4Y.H.Fan,2,6L.Ma,4X.Zhang,4F.Bai,4P.Wang,4Y.X.Fan,4G.Liu,4H.X.Huan...

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APS123-QED Deep underground laboratory measurement of13Cn16O in the Gamow windows of the s- and i-processes

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