# Presentation: 416924

## Study of the 12N(p,)13O reaction in relation to 

**Study of the ****12****N(p,********)****13****O reaction in relation to **
**Population III star evolution**

**A. Banu****1****, T. Al.-Abdullah****1****, V. Burjan****2****, C. Fu****1****, C.A. Gagliardi****1****, Y. Li****1****, M. McCleskey****1****, A.M. Mukhamedzhanov****1****, G. Tabacaru****1****, L. Trache****1****, R.E. Tribble****1****, and Y. Zhai****1**
*1**Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA*
*2**Institute of Nuclear Physics, Czech Academy of Sciences, Prague-**Řež, Czech Republic*

**Motivation:**

- In 1986, Fuller, Woosley, and Weaver [1] addressed the classic problem of supermassive star evolution:
***given that a nonrotating supermassive star has formed and contracted to its instability point, does the rapid nuclear burning in the subsequent collapse generate enough thermal energy to stabilize the collapse and  trigger an explosion?***
- It was found that high-mass, low-metallicity stars (Population III) with M  5105 M○ and Z<< 0.005 will collapse to black holes while stars of higher metallicity will explode. For the failed explosions, it is reasoned that in the short time scales of the collapse insufficient amounts of 12C and other heavier isotopes are produced by the 3 process *but* alternative paths from the slow 3 process to produce CNO seed nuclei could change their fate.

- In 1989, Wiescher, Buchmann, and Thielemann [2] reinvestigated the reaction rates for nuclei up to oxygen and suggested several reaction sequences – *hot pp-IV, pp-V and rap-process chains - *  that would allow supermassive stars of very low-metallicity to bypass the 3 process. They also determined the required temperature and density conditions where proton or  capture reactions on short lived nuclei were of equal strength with competing  decays or inverse photodisintegration **(see Figure and Table on the left).**
- The 12N(p,)13O reaction is an important branch point in one of such alternative paths. With a very low  Q-value, Q = 1.516 MeV,  the reaction rate will be determined by the direct capture to the ground state in 13O, J = 3/2-, and a resonant capture to the first excited in 13O at Ex = 2.75 MeV, J =1/2+. Wiescher *et al*. [2] have made the first estimate of the reaction rate for 12N(p,)13O radiative capture assuming the  width of resonance of the first excited state to be of 24 meV. They concluded that the non-resonant contribution dominates in the whole temperature range and will therefore, in competition with the -decay, determine the depletion of the 12N via 12N(p,)13O reaction.

**Method:**

**ANC**** **(***A****symptotic ****N****ormalization ****C****oefficient* determination)

***The one-nucleon ANC determines the magnitude of the large distance behavior of the overlap integral between the bound state wave functions of nuclei with A and A-1 nucleons. Such overlaps enter the amplitude for non-resonant nucleon capture reactions. If the capture occurs outside the nuclear interior, as often happens at very low stellar energies, then the overall normalization of its cross section as well as of the astrophysical S-factor, is determined by the ***_***squared ANC***_***.***
***Since the same ANCs play a crucial role in other peripheral nuclear processes such as nucleon transfer reactions, they can be measured in laboratory and used to predict non-resonant capture processes at low stellar energies (for details see [3]).***

- 

**Transfer amplitude:**

**Forward angle cross section:**

**and**

- Integrate over  :

**Experimental setup:**

**Position measurement for scattering angle reconstruction :**

**Reaction channel identification :**

**Peripheral proton transfer transfer *****b + B ************ A + a***** :**

**Radiative proton capture *****p + B ************ A + ************  *****:**

**Direct radiative capture  amplitude:**

- where **, ***,** *

- , ***i**+**, I**A**Bp *

- are the wave function, the internal

- coordinates for the proton bound state, the electromagnetic
- operator, the distorted wave in the initial channel *p + B, *and the
- overlap function for *A **** p + B*.

**and**

**Results:**

***OMP – double folding [4] w/ JLM eff. inter. [5] & DWBA calc. w/ PTOLEMY code [6]***

***References: ***[1] G.M. Fuller et al., Ap.J **307**, 675 (1986)  [2] M. Wiescher et al., Ap.J. **343**, 352 (1989)  [3] H.M. Xu et al., PRL **15**, 2027 (1994)  [4] L. Trache et al., PRC **61**, 024612 (2000)  [5] J.P. Jeukenne et al., PRC **16**, 80 (1977)  [6] M. Rhoades-Brown et al., PRC **21**, 2417 (1980)

- Astrophysical S-factor at zero energy
- for the 12N(p,)13O reaction only non-
- resonant component:
**S****1-12****(0) = 418 (67) eVb**

- Stable primary beam

- K500 superconducting
- Cyclotron at TAMU

- We present here preliminary results on the asymptotic normalization coefficient (ANC) for the system 13O  12N + p, and calculate from it the direct radiative capture component of the astrophysical S-factor. Our result along with information on resonant capture into first excited state of 13O will determine the real astrophysical S-factor of the 12N(p,)13O reaction. This reaction was proposed by M. Wiescher et al [2] as one of the rap-process chains that can lead to the production of sufficient amounts of CNO material before the 3 reaction becomes effective. This may also result in an explosion of supermassive stars with lower metallicity than proposed by Fuller et al. [1]. To test this scenario, hydrodynamical calculations of the collapse including the full nuclear reaction network are necessary.