This work embraces the measurement of angular distributions and excitation functions for proton radiative capture to the ground and excited states of 13N, in energy steps from E p = 40 to E p = 52MeV. Legendre polynomial fits to the angular distributions are made and the energy variation of Legendre coefficients is established for several (p, 7 ) transitions involving states up to an excitation energy of 15 MeV. The polynomial coefficients are explained by large dipole-quadrupole interference effects, particularly interesting at excitation energies corresponding to twice (£„ ~ 46 MeV) the centroid value of the ground state based Giant Dipole Excitation. Broad resonances are found in the (p,7o) &nd the (p, 72+3) channels, which involve final states that are members of the same rotational band and therefore should present very similar internal structures as the almost equivalent Legendre coefficients substantiate. For other excited states similar trends have been found although within limits imposed by larger experimental errors. The 2hw -+ Ihuj transition is found largely superimposed on inelastic proton scattering channels, contrary to what was established in previous experiments. Upper limits for the excitation functions are extracted and only for the highest measured energy point are the two contributions clearly separated. This reasearch program is based on a newly-developed anti-coincidence large-volume scintillation spectrometer designed by means of a Monte Carlo simulation code. Sp jcific tests performed with Tandem accelerator beams, and routine application at higher energies, demonstrate the excellent correspondence of the design expectations with the performance as measured, for this spectrometer.

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Thesis (Ph. D.)--University of Chicago, Dept. of Physics. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph.D.)--Ohio University, November, 2006. / Title from PDF t.p. Includes bibliographical references.

Effective field theory (EFT) provides a framework to exploit separation of scales in the physical system in order to perform systematic model-independent calculations. There has been significant interest in applying the methods of EFT to halo nuclei. Using halo effective field theory, I provide a model-independent calculation of the radiative neutron capture on lithium-7 over an energy range where the contribution from the 3+ resonance becomes important. This reaction initiate the sequence in the carbon-nitrogen-oxygen (CNO) cycle in the inhomogeneous BBN models, and determine the amount of heavy element production from its reaction rate. One finds that a satisfactory description of the capture reaction, in the present single-particle approximation, suggests the use of a resonance width about three times larger than the experimental value. Power counting arguments that establish a hierarchy for the electromagnetic one- and two-body currents is also presented. The neutron capture of Lithium7 calculation has direct impact on the proton capture on beryllium7 which plays an important role in the neutrino experiments studying physics beyond the Standard Model of particle physics. As a further study of halo nuclei interactions, the cross section of radiative capture of a neutron by carbon-14 is calculated by considering the dominant contribution from electric dipole transition. This is also a part of the CNO cycle and as the slowest reaction in the chain it limits the flow of the production of heavier nuclei A > 14. The cross section is expressed in terms of the elastic scattering parameters of an effective range expansion. Contributions from both the resonant and non-resonant interactions are calculated. Significant interferences between these leads to a capture contribution that deviates from a simple Breit-Wigner resonance form. Using EFT, I present electromagnetic form factors of several halo nuclei. The magnetic dipole moment and the charge radii of carbon-15, beryllium-11, and carbon-19 halo systems are considered. Prediction is made for the magnetic moment in the leading order. I can only provide some estimates for the form factors in next-to-leading order where two-body currents appear. The estimates are based on power counting unless the effective range and the magnetic moment are known. Charge radii for three systems have also been estimated at LO and NLO.

In this work, the radiative capture reactions 7Li(n, γ)8Li, 7Be(p, γ)8B, 3He(α, γ)7Be, and 3H(α, γ)7Li are studied using halo effective field theory (EFT). These capture reac- tions are some of the key nuclear reactions for the solar neutrino production and heavy element production in stellar and primordial nucleosyntheses. At low energy, halo EFT provides a model independent framework to describe physical observable as an expansion of a low momentum scale over a high momentum scale with well-defined error estimates. In this dissertation, electric dipole (E1) capture cross section of 7Li(n, γ)8Li reaction is calculated as a coupled channel using EFT with excited 7Li⋆ core and is compared with EFT without the excited 7Li⋆ core. Then we extend our coupled channel treatment to 7Be(p, γ)8B reaction which is the iso-spin mirror of 7Li(n, γ)8Li by adding the Coulomb force in the calculation. Similar to 7Li(n,γ)8Li calculation, we calculate the astrophys- ical Sactor for 7Be(p,γ)8B reaction using the two halo EFTs, one halo EFT without excited 7Be⋆ core and the other halo EFT with the excited 7Be⋆ core as an explicit degree of freedom. We present a formalism to compare different EFT power countings using Bayesian analysis. This is useful when the EFT couplings are poorly known, and one has competing power counting proposals. The Sactor for 3He(α,γ)7Be reaction was calculated for two competing power countings in halo EFT approach. The two power countings defer in the contribution of the two body currents. In one power counting, the two body currents contribute at the leading order and in the other power counting, the two body currents contribute at higher orders. Bayesian inference is drawn to estimate EFT parameters and calculate the posterior odds in order to do the model comparison. The posterior odds is used to propose the best power counting. We extend our calculation to the iso-spin mirror 3H(α,γ)7Li reaction using the same expressions by making the appropriate changes in masses, charges, and binding momenta. We estimate the EFT parameters and calculate the posterior odds using Bayesian analysis. The best power counting is proposed using the posterior odds.