The second J(π)=2+ state of 12C, predicted over 50 years ago as an excitation of the Hoyle state, has been unambiguously identified using the 12C(γ,α0)(8)Be reaction. The alpha particles produced by the photodisintegration of 12C were detected using an optical time projection chamber. Data were collected at beam energies between 9.1 and 10.7 MeV using the intense nearly monoenergetic gamma-ray beams at the HIγS facility. The measured angular distributions determine the cross section and the E1-E2 relative phases as a function of energy leading to an unambiguous identification of the second 2+ state in 12C at 10.03(11) MeV, with a total width of 800(130) keV and a ground state gamma-decay width of 60(10) meV; B(E2:2(2)+→0(1)+)=0.73(13)e(2)  fm(4) [or 0.45(8) W.u.]. The Hoyle state and its rotational 2+ state that are more extended than the ground state of 12C presents a challenge and constraints for models attempting to reveal the nature of three alpha-particle states in 12C. Specifically, it challenges the ab initio lattice effective field theory calculations that predict similar rms radii for the ground state and the Hoyle state.

Neutron elastic-scattering angular distributions were measured at beam energies of 11.9 and 16.9 MeV on 40,48 Ca targets. These data plus other elastic-scattering measurements, total and reaction cross sections measurements, (e, e ′ p) data, and single-particle energies for magic and doubly magic nuclei have been analyzed in the dispersive optical model (DOM) generating nucleon self-energies (optical-model potentials) which can be related, via the many-body Dyson equation, to spectroscopioc factors and occupation probabilities. It is found that for stable nuclei with N ≥ Z, the imaginary surface potential for protons exhibits a strong dependence on the neutron-proton asymmetry. This result leads to a more modest dependence of the spectroscopic factors on asymmetry. The measured data and the DOM analysis of all considered nuclei clearly demonstrates that the neutron imaginary surface potential displays very little dependence on the neutron-proton asymmetry for nuclei near stability (N ≥ Z).

A dispersive-optical-model analysis of p+ 40,42,44,48 Ca and n+ 40 Ca interactions has been carried out. The real and imaginary potentials have been constrained by fitting elastic-scattering data, total and reaction cross sections, and level properties of valence hole states deduced from (e, e p) data. The resulting surface imaginary potential increases with asymmetry for protons, implying that in heavier Ca isotopes, protons experience stronger long-range correlations. Presently, there is not enough data for neutrons to determine their asymmetry dependence. Global optical-model fits usually assume that the neutron asymmetry dependence is equal in magnitude, but opposite in sign, to that for protons. Such a dependence was found to give unphysical results for heavy Ca isotopes. The dispersive optical model is shown to be a useful tool for data-driven extrapolations to the drip lines. Neutron and proton data at larger asymmetries are needed to achieve more reliable extrapolations. The present analysis predicts 60 Ca and 70 Ca to be bound, while the intermediate isotopes are not.

This study examined the effects of group decision rules and decision outcomes on satisfaction with the outcomes, perceived fairness of the rules, and amount of rejection between majority members and deviates. Two hundred and seventy male subjects were led to believe that they belonged to groups, each of which consisted of a four-person majority and a lone deviate. The groups ostensibly made decisions by using a majority, dictatorial, or unanimity rule. Principal findings of the study were as follows: Subjects were more satisfied with decisions with which they agreed than with decisions with which they disagreed. The perceived fairness of the decision rules was primarily a function of the representativeness of the decision. Subjects felt the rule was fairer when it resulted in a decision that was representative of the preferences of most group members than when it resulted in a decision that was unrepresentative. Finally, mutual rejection occurred between majority members and the lone deviate. The strongest rejection, however, was by majority members toward the deviate in instances when, under the dictatorship and unanimity rules, the deviate was able to impose an unrepresentative decision on the majority. Findings are discussed partly in terms of the effects of outcomes on the perceived legitimacy of decision rules and the resulting feelings toward group members held to be responsible for implementation of the rules.

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The photodisintegration of 12 C into three α particles was observed using intense, nearly monoenergetic γ-ray beams available at the HIγS facility. An optical time projection chamber was used to detect the recoiling α particles from the 12 C(γ,α) 8 Be reaction. A J π = 2 + state in 12 C was found at 10.03(11) MeV with a width of 800(130) keV. Recently EFT lattice calculations have been performed in order to understand the structure of the 'Hoyle state' at 7.65 MeV, and extensions of these calculations have identified a 2 + excitation of the Hoyle state. This newly observed 2 + state in 12 C provides an important test for these calculations as well as for other models of light nuclei. Furthermore, a state in 12 C near this energy increases the rate of stellar thermonuclear helium burning at the high temperatures which occur in core-collapse supernovae and other astrophysical scenarios.

Gamma-Beams at the HIγS facility in the USA and anticipated at the ELI-NP facility, now constructed in Romania, present unique new opportunities to advance research in nuclear astrophysics; not the least of which is resolving open questions in oxygen formation during stellar helium burning via a precise measurement of the 12 C(α, γ) reaction. Time projection chamber (TPC) detectors operating with low pressure gas (as an active target) are ideally suited for such studies. We review the progress of the current research program and plans for the future at the HIγS facility with the optical readout TPC (O-TPC) and the development of an electronic readout TPC for the ELI-NP facility (ELITPC).