Photodisintegration Process Research Articles

PANDORA Project for the study of photonuclear reactions below A=60

Photonuclear reactions of light nuclei below a mass of A=60 are planned to be studied experimentally and theoretically with the PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project. Two experimental methods, virtual photon excitation by proton scattering and real photo absorption by a high-brilliance gamma -ray beam produced by laser Compton scattering, will be applied to measure the photoabsorption cross sections and decay branching ratio of each decay channel as a function of the photon energy. Several nuclear models, e.g. anti-symmetrized molecular dynamics, mean-field and beyond-mean-field models, a large-scale shell model, and ab initio models, will be employed to predict the photonuclear reactions. The uncertainty in the model predictions will be evaluated based on the discrepancies between the model predictions and experimental data. The data and predictions will be implemented in the general reaction calculation code, TALYS. The results will be applied to the simulation of the photo-disintegration process of ultra-high-energy cosmic rays in inter-galactic propagation.

Amplitudes of 3H, 3He Two-Particle Photo-Breakup in Non-Local QED Approach

Three-nucleon systems are essential for the investigation of many-body forces in nuclear physics. Well-grounded parametrization of their vertex functions with further application for the calculation of cross-sections in nonlocal QED approach provides the ground for investigation of the variety of multi-particle systems. In present paper we describe the process of parametrization of two-particle photo-breakup amplitudes of three-nucleon systems (3H, 3He). We provide the general description of the wave function construction for three-nucleon systems as well as the parametrization of their vertex functions accounting two- and three-nucleon interactions based on meson exchange current formalism. In our calculations we account first and second order one-pion exchange terms and the term related to the exchange of ω and ρ mesons. The three-nucleon interaction potential is given as a sum of attraction (two-pion exchange) term andappropriate repulsive part. Based on the variational ”Urbana + Model VII” amplitudes we provide the results for energy dependence of differential cross-section of 3He(γ, p)d reaction at proton angle θ = 90◦ from the threshold up to Eγ = 40 MeV and compare theoretical predictions with the available experimental data. The investigation is also provided for angular cross-section distributions at high photon energies (Eγ = 305 ± 5 MeV; 365 ± 5 MeV; 450 ± 10 MeV and 675 ± 50 MeV). Correct description of 3H, 3He photo-disintegration processes in a unified approach based on the gauge nature of the electromagnetic field implies application of this model for other multi-particle systems.

Similarity and distinctions of <sup>58, 60</sup>Ni photodisintegration processes

Reliability of (γ, 1n) and (γ, 2n) reactions cross sections for 58, 60Ni obtained in experiments carried out on the beams of bremsstrahlung and quasimonoenergetic annihilation photons was investigated using objective physical criteria. It was found that data of the first type experiment do not satisfy those criteria and definitely are not reliable. At the same time there are serious doubts in reliability of the data obtained in the second type experiment. New partial photoneutron reaction cross sections on 58, 60Ni satisfying physical criteria of data reliability were used for analysis of characteristics of both isotope photodisintegration processes. It was obtained that for neighboring (differ in two neutrons) isotopes because of various type systematic uncertainties there are significant disagreements between evaluated and experimental cross sections of various reactions which for isotopes 58Ni and 60Ni are of significant different character. It was shown that the reasons are not only the differences in energy thresholds and absolute values of cross sections of the (γ, 1n), (γ, 1n1p) and (γ, 2n) reactions on 58Ni and 60Ni but significant differences in specific features of neighboring isotopes shell structure also.

UHECR echoes from the Council of Giants

ABSTRACT Recent anisotropy studies of UHECR data at energies ≳40 EeV have disclosed a correlation of their angular distribution with the extragalactic local structure, specifically with either local starburst galaxies or AGN. Using Monte Carlo simulations taking into account photodisintegration processes, we further explore a framework in which these UHECRs were accelerated by Centaurus A in a recent powerful outburst before being scattered by magnetic fields associated with local, Council of Giant, extragalactic structure. We find that the observed intermediate-scale anisotropies can be accounted for by the Council of Giant structure imposing a response function on the initial outburst of UHECRs from a single source located at Centaurus A’s position. The presence of these local structures create ‘echoes’ of UHECRs after the initial impulse and focusing effects. The strongest echo wave has a lag of ∼20 Myr, comparable to the age of synchrotron-emitting electrons in the giant Centaurus A lobes. Through consideration of the composition of both the direct and echo wave components, we find that the distribution of the light (1 < ln A < 1.5) component across the sky offers exciting prospects for testing the echo model using future facilities such as Auger prime. Our results demonstrate the potential that UHECR nuclei offer, as ‘composition clocks’, for probing propagation scenarios from local sources.

Measuring the cross section of the N15(α,γ)19F reaction using a single-fluid bubble chamber

$^{15}$N($\alpha$,$\gamma$)$^{19}$F is believed to be the primary means of stellar nucleosynthesis of fluorine. Here we present the use of a single-fluid bubble chamber to measure the cross section of the time-inverse photo-dissociation reaction. The method benefits from a luminosity increase of several orders of magnitude due to the use of a thicker liquid target -- when compared to thin films or gas targets -- and from the reciprocity theorem. We discuss the results of an experiment at the Thomas Jefferson National Accelerator Facility, where the cross section of the photodisintegration process $^{19}$F($\gamma$, $\alpha$)$^{15}$N was measured by bombarding a superheated fluid of C$_3$F$_8$ with bremsstrahlung $\gamma$-rays produced by impinging a 4 - 5.5 MeV electron beam on a Cu radiator. From the photodissociation yield the cross section was extracted by performing a convolution with a Monte Carlo-generated $\gamma$-ray beam spectrum. The measurement produced a cross section that was then time inverted using the reciprocity theorem. The cross section for the $^{15}$N($\alpha$,$\gamma$)$^{19}$F reaction was determined down to a value in the range of hundreds of picobarns. With further improvements of the experimental setup the technique could potentially push cross section measurements down to the single picobarn range.

Studies of photo-nuclear reactions at astrophysical energies with an active-target TPC

An experiment was conducted at the High Intensity γ-ray Source (HIγS) facility at the Triangle Universities Nuclear Laboratory (TUNL) in Durham, NC, USA to measure the cross-section of the key astrophysical thermonuclear reaction 12C(α,γ)16O by means of its inverse photo-disintegration process. A high-intensity monochromatic γ-ray beam interacted with the CO2 gas in the active volume of the Warsaw active target TPC detector. The reaction products were detected and their momenta reconstructed, so to also determine angular correlations. Data were collected at 15 beam energies ranging from 8.51 to 13.9 MeV. Preliminary results are presented.

Light Element Abundances Constrain Primordial Black Holes in the Critical Collapse Model

We study the photodisintegration process triggered by the nonthermal electromagnetic Hawking radiation from primordial black holes (PBHs) in the critical collapse model. The presence of a low-mass tail of critical collapse mass function could enhance energetic photon emissions from Hawking radiation of PBHs. Nuclear photodisintegration rates are calculated with a non-thermal photon spectrum derivedby solving the Boltzmann equation iteratively. Withthenewest observational limitonthe3Heabundancein GalacticHII regions, the updated 3He constraints on PBH mass spectrum in the horizon mass range 1012–1013gare derived. Our results showthat3He constraints on the critical mass function are about one order of magnitude severer than the monochromatic one, although the fraction of PBHs in the low-mass tail region is relatively small.

Impacts of Hawking radiation from primordial black holes in critical collapse model on the light element abundances

We study the photodisintegration process triggered by the nonthermal electromagnetic Hawking radiation from primordial black holes (PBHs) in critical collapse model. We consider the simplest case that all PBHs formed at a single epoch stemming from an inflationary spectrum with a narrow peak, and an extended mass distribution is obtained due to critical phenomena of gravitational collapse. The presence of a low-mass tail of critical collapse mass function could lead to an enhancement of energetic photon emissions from Hawking radiation of PBHs. Nuclear photodisintegration rates are calculated with a nonthermal photon spectrum derived by solving the Boltzmann equation iteratively. The exact spectrum is much different than that based on an often-used analytical bended power-law spectrum and it is found to significantly depend on the adopted PBH mass functions. With the newest observational limit on the 3He abundance in Galactic H II regions, the updated 3He constraints on PBH mass spectrum in the horizon mass range 1012–1013 g are derived. Our results for the first time show that 3He constraints on the critical mass function are about one order of magnitude severer than the monochromatic one although the fraction of PBHs in the low-mass tail region is relatively small. The 6Li elemental abundance is also enhanced significantly for the critical mass function. More precise measurement of 6Li abundance is highly desirable to provide a promising constraint on PBHs in the future. For monochromatic mass function, we provide the analytical bounds for photodisintegration and hadrodissociation from PBH radiation, and we report discrepancies between our updated 3He constraints and the previous results.

Application of a momentum-space semi-locally regularized chiral potential to selected disintegration processes

We apply the chiral potential with the momentum space semi-local regularization to the $^2$H and $^3$He photodisintegration processes and to the (anti)neutrino induced deuteron breakup reactions. Specifically, the differential cross section, the photon analyzing power and the final proton polarization have been calculated for the deuteron photodisintegration at the photon energies 30 MeV and 100 MeV. For the $^3$He photodisintegration predictions for the semi-inclusive and exclusive differential cross sections are presented for the photon energies up to 120 MeV. The total cross section is calculated for the (anti)neutrino disintegrations of the deuteron for the (anti)neutrino energies below 200 MeV. The predictions based on the Argonne V18 potential or on the older chiral force with regularization applied in coordinate space are used for comparison. Using the fifth order chiral nucleon-nucleon potential supplemented with dominant contributions from the sixth order allows us to obtain converged predictions for the regarded reactions and observables. Our results based on the newest semi-local chiral potentials show even smaller cutoff dependence for the considered electroweak observables than the previously reported ones with a coordinate-space regulator. However, some of the studied polarization observables in the deuteron photodisintegration process reveal more sensitivity to the regulator value than the unpolarized cross section. The chiral potential regularized semi-locally in momentum space yields also fast convergence of results with the chiral order. These features make the used potential a high quality tool to study electroweak processes.

An application of chiral forces with the semi-local regularization in momentum space to the deuteron photodisintegration process

A recent paper by P. Reinert et al. [Eur. Phys. J. A54, 86 (2018)] showed a possibility of improving chiral nucleon-nucleon potential models by employing a semi-local regularization in momentum space. The authors derived nucleon-nucleon potentials with this kind of regularization completely up to the fifth order of the chiral expansion and considered additionally some contact interactions which appear at the sixth order. Such a chiral interaction has never been applied to study electromagnetic processes in two- or three-nucleon systems. Here we continue our research of photodisintegration processes, now using the improved chiral force. In particular, we discuss our predictions for the deuteron photodisintegration reaction in the photon energy range up to 100 MeV. The results of our calculations reveal that the new potential yields predictions characterized by a weaker dependence on the regularization parameter and faster convergence with respect to the chiral expansion order compared to the older chiral potentials.

The role of resonances in the capture of 8Li(p, γ)9Be on the reaction rate of the relevant astrophysical synthesis of 9Be

The total cross sections of the radiative proton capture on 8Li at astrophysical energies are considered in the framework of the modified potential cluster model with forbidden states with the classification of the orbital cluster states according to Young diagrams. The data obtained from the 9Be(γ, p0)8Li photodisintegration process according to the detailed balancing principle are used for the experimental data of the 8Li(p, γ)9Be capture. It is possible to reproduce the available data on cross sections at the energies up to 7.0 MeV. Astrophysical S-factors and reaction rates 〈σν〉 are calculated at the temperature range of 0.01 to 10 T9. It is shown that the reaction rate is significantly affected by the resonances in the p8Li scattering channel, and, especially by the first 1/2− resonance at 87 keV. The analytical parametrization is performed for the calculated reaction rate 〈σν〉.

The Application of Chiral Forces to the Deuteron Photodisintegration Process at \(E_\gamma =140\)~MeV

The Application of Chiral Forces to the Deuteron Photodisintegration Process at \(E_\gamma =140\)~MeV

Study of the PeV neutrino, γ-rays, and UHECRs around the lobes of Centaurus A

Pierre Auger observatory reported the distribution of arrival directions of the highest energy cosmic rays. These events were collected in 10 years of operations with declinations between -90$^\circ$ and +45$^\circ$. The IceCube neutrino telescope reported the detection of 82 extraterrestrial neutrinos in the High-Energy Starting Events catalog. The highest-energy neutrino event (IC35) reported in this catalog had an energy of 2004$^{+236}_{-262}$ TeV and its reconstruction was centered at RA=$208.4^\circ$ and DEC=$-55.8^\circ$ (J2000). Being Centaurus A the nearest radio-loud active Galactic nucleus and one of the potential candidates for accelerating cosmic rays up to $\sim\, 10^{20}$ eV, we show that the ultra-high-energy cosmic rays (UHECRs) around the direction of Centaurus A (15$^\circ$ radius) could be accelerated inside the giant lobes. Studying the composition of UHECRs through the photo-disintegration processes, the maximum energy that these can reach in the giant lobes and the average deflecting angles that nuclei undergo due to Galactic and extragalactic magnetic fields, it is shown that the most promise candidates of UHECR composition are light nuclei such as carbon/nitrogen nuclei. Considering the interactions of the relativistic carbon nuclei with photon fields (extragalactic background light and synchrotron) and materials (inside and outside the lobes), we do not find enough evidence to associate the IC35 event with the UHECRs reported by Pierre Auger observatory.

A new method of creating high intensity neutron source

We propose a new scheme of producing an intense neutron beam whose yields may exceed those of the existing facilities by a few to several orders of magnitude in the sub-eV region. This scheme employs a MeV gamma beam extracted from circulating quantum ions, which has been recently proposed. The gamma beam is directed to a deuteron target and the photo-disintegration process generates a neutron beam. The calculated neutron energy spectrum is nearly flat down to the neV range, and thus there exists a possibility to utilize a good quality of neutrons especially in sub-eV energy region without using a moderator.

Particle storage ring enables a role reversal in proton capture

A novel technique for measuring nuclear reaction cross sections may yield long-sought parameters for short-lived isotopes.

A helium gas scintillator active target for photoreaction measurements

A multi-cell He gas scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 g/cm3 at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of N2 to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has a timing resolution of around 1 ns and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in 4He, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response.

Ab initio Calculation of the np→dγ Radiative Capture Process.

Lattice QCD calculations of two-nucleon systems are used to isolate the short-distance two-body electromagnetic contributions to the radiative capture process np→dγ, and the photo-disintegration processes γ^{(*)}d→np. In nuclear potential models, such contributions are described by phenomenological meson-exchange currents, while in the present work, they are determined directly from the quark and gluon interactions of QCD. Calculations of neutron-proton energy levels in multiple background magnetic fields are performed at two values of the quark masses, corresponding to pion masses of m_{π}~450 and 806 MeV, and are combined with pionless nuclear effective field theory to determine the amplitudes for these low-energy inelastic processes. At m_{π}~806 MeV, using only lattice QCD inputs, a cross section σ^{806 MeV}~17 mb is found at an incident neutron speed of v=2,200 m/s. Extrapolating the short-distance contribution to the physical pion mass and combining the result with phenomenological scattering information and one-body couplings, a cross section of σ^{lqcd}(np→dγ)=334.9(+5.2-5.4) mb is obtained at the same incident neutron speed, consistent with the experimental value of σ^{expt}(np→dγ)=334.2(0.5) mb.

Galactic production of 138La: Impact of 138,139La statistical properties

The γ-ray strength functions and nuclear level densities of 138La and 139La have been measured below the neutron separation energies. These new data were used to calculate astrophysical Maxwellian-averaged (n,γ) cross-sections to investigate the production and destruction of the p-nucleus 138La in the photodisintegration process. The results confirm the underproduction of 138La in the p-process with respect to the observed abundances and strongly support the ν-process through νe capture on 138Ba as the main contributor to the synthesis of 138La in Type II supernovae.

Statistical nuclear properties and synthesis of138La

The synthesis of the neutron deficient ^138La nucleus has been a puzzle for a long time. It has not been clear whether it is produced through photodisintegration processes or neutrino induced reactions due to unavailability of experimental data for nuclear level densities and gamma strength functions of ^138,139La nuclei. In the present work these nuclear properties have been measured and are used to investigate the synthesis of ^138La. The results support the neutrino interactions as a dominant production process for ^138La.

Low-Energy 12C States in Three-α Model

Cross sections for three-α photodisintegration process of the12C nucleus are calculated by a Faddeev formalism, from which 0+- and 2+ low-lying resonant 12C states are studied. The triple-alpha reaction rate is evaluated from the calculated cross sections of the disintegration process.