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Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles 60◦ , 120◦ and 150◦ . Analysis of these data using a Chiral Effective Field Theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of αs = [12.1 ± 0.8(stat) ± 0.2(BSR) ± 0.8(th)] × 10−4 fm3 and βs = [2.4 ± 0.8(stat) ± 0.2(BSR) ± 0.8(th)] × 10−4 fm3 are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections., Physics

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical A(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as αn = [11.55+1.25(stat)+0.2(BSR)+ 0.8(th)] x 10-4 fm3 and βn = [3.65≠ 1.25(stat) +0.2(BSR) ≠ 0.8(th)] x 10-4 fm3, with X2 = 45.2 for 44 degrees of freedom. [ABSTRACT FROM AUTHOR]

The second Jπ=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)8Be 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(E2:22+→01+)=0.73(13)e2 fm4 [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. [ABSTRACT FROM AUTHOR]

The photodisintegration cross section of 4He into a neutron and helion was measured at incident photon energies of 27.0, 27.5, and 28.0 MeV. A high-pressure 4He-Xe gas scintillator served as target and detector while a pure Xe gas scintillator was used for background measurements. A Nal detector in combination with the standard HI&ggr;S scintillator paddle system was employed for absolute photon-flux determination. Our data are in good agreement with the theoretical prediction of the Trento group and the recent data of Nilsson et al. [Phys. Rev. C 75, 014007 (2007)] but deviate considerably from the high-precision data of Shima et al. [ABSTRACT FROM AUTHOR]

The article presents a measurement of two-body photodisintegration cross section of 4) He into a proton and triton with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. Pure Xe gas scintillators were used for background studies while a NaI detector and a plastic scintillator paddle was employed for determining the incident photon flux. Though lower in magnitude by about 5%, the data set follows the trend of the theoretical calculations of the Trento group.

The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together with a plastic scintillator paddle was employed for determining the incident photon flux. Our comprehensive data set follows the trend of the theoretical calculations of the Trento group very well, although our data are consistently lower in magnitude by about 5%. However, they differ significantly from the majority of the previous data, especially from the recent data of Shima et al. The latter data had put into question the validity of theoretical approaches used to calculate core-collapse supernova explosions and big-bang nucleosynthesis abundances of certain light nuclei.