Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths

We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems, and compute Gamow-Teller transitions in carbon-14, oxygen-22 and oxygen-24 using consistent two-body currents. We compute spectra of the daughter nuclei nitrogen-14, fluorine-22 and fluorine-24 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q^2 ~ 0.84-0.92 of the axial-vector coupling. The half life of carbon-14 depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current

Spectral function for 4^4He using the Chebyshev expansion in coupled-cluster theory

We compute spectral function for $^4$He by combining coupled-cluster theory with an expansion of integral transforms into Chebyshev polynomials. Our method allows to estimate the uncertainty of spectral reconstruction. The properties of the Chebyshev polynomials make the procedure numerically stable and considerably lower in memory usage than the typically employed Lanczos algorithm. We benchmark our predictions with other calculations in the literature and with electron scattering data in the quasi-elastic peak. The spectral function formalism allows one to extend ab-initio lepton-nucleus cross sections into the relativistic regime. This makes it a promising tool for modeling this process at higher energy transfers. The results we present open the door for studies of heavier nuclei, important for the neutrino oscillation programs.Comment: 12 pages, 5 figure

Continuous flow adsorption of phenolic compounds from olive mill wastewater with resin XAD16N: life cycle assessment, cost\u2013benefit analysis and process optimization

BACKGROUND: Olive mill wastewaters (OMWs) represent a major environmental concern due to their high organic load and phytotoxic activity. The selective recovery of phenolic compounds (PCs) from OMW is promising, thanks to the antioxidant and antimicrobial properties of PCs. The goal of this work was to perform a life cycle assessment (LCA) and cost\u2013benefit analysis (CBA) of a full-scale process of PC adsorption/desorption on resin Amberlite XAD16N. The industrial process was designed on the basis of laboratory tests aimed at performing a preliminary process optimization. RESULTS: Adsorption tests were conducted at different velocities in a 1.8-m column packed with XAD16N. The optimal superficial velocity and retention time (2.78 m h \u20131 and 0.56 h) allowed the attainment of satisfactory performances in terms of resin operating capacity (0.46), PC adsorption yield (0.92), PC mass fraction in the sorbed product (0.50 g PC /g VS ) and specific antioxidant activity (3\u20136 g ascorbic acid /g PC ). Six consecutive adsorption/desorption cycles, operated with the same resin load, resulted in stable process performances. The LCA indicated that the environmental impact of the process could be decreased markedly through the addition of an anaerobic digestion step for the production of irrigation-quality water and fertilizers from the dephenolized OMW. The PC market price required for the generation of a positive business case resulted relatively low (\u20ac1.7\u201313.5 kg PC\u20131 ). CONCLUSION: The results indicate that the proposed PC adsorption/desorption technology, if integrated with an anaerobic digestion step, represents a promising solution for the treatment and valorization of OMW, a major agro-industrial waste in Mediterranean countries

The magnetic dipole transition in 48^{48}Ca

The magnetic dipole transition strength $B(M1)$ of $^{48}$Ca is dominated by a single resonant state at an excitation energy of 10.23 MeV. Experiments disagree about $B(M1)$ and this impacts our understanding of spin flips in nuclei. We performed ab initio computations based on chiral effective field theory and found that $B(M1:0^+\rightarrow1^+)$ lies in the range from $7.0$ to $10.2~\mu_N^2$. This is consistent with a $(\gamma,n)$ experiment but larger than results from $(e,e^\prime)$ and $(p,p')$ scattering. Two-body currents yield no quenching of the $B(M1)$ strength and continuum effects reduce it by about 10%. For a validation of our approach, we computed magnetic moments in $^{47,49}$Ca and performed benchmark calculations in light nuclei

Response functions and giant monopole resonances for light to medium-mass nuclei from the \textit{ab initio} symmetry-adapted no-core shell model

Using the \textit{ab initio} symmetry-adapted no-core shell model, we compute sum rules and response functions for light to medium-mass nuclei, starting from interactions that are derived in the chiral effective field theory. We investigate electromagnetic transitions of monopole, dipole and quadrupole nature for symmetric nuclei such as $^4$He, $^{16}$O, $^{20}$Ne and $^{40}$Ca. Furthermore, we study giant monopole resonance, which can provide information on the incompressibility of symmetric nuclear matter

Magnetic dipole operator from chiral effective field theory for many-body expansion methods

Many-body approaches for atomic nuclei generally rely on a basis expansion of the nuclear states, interactions, and current operators. In this work, we derive the representation of the magnetic dipole operator in plane-wave and harmonic-oscillator basis states, as needed for Faddeev calculations of few-body systems or many-body calculations within, e.g., the no-core shell model, the in-medium renormalization group, coupled-cluster theory, or the nuclear shell model. We focus in particular on the next-to-leading-order two-body contributions derived from chiral effective field theory. We provide detailed benchmarks and also comparisons with quantum Monte Carlo results for three-body systems. The derived operator matrix elements represent the basic input for studying magnetic properties of atomic nuclei based on chiral effective field theory.Comment: 17 pages, 7 figure

On the Accuracy of Hyperspherical Harmonics Approaches to Photonuclear Reactions

Using the Lorentz Integral Transform (LIT) method we compare the results for the triton total photodisintegration cross section obtained using the Correlated Hyperspherical Harmonics (CHH) and the Effective Interaction Hyperspherical Harmonics (EIHH) techniques. We show that these two approaches, while rather different both conceptually and computationally, lead to results which coincide within high accuracy. The calculations which include two- and three-body forces are of the same high quality in both cases. We also discuss the comparison of the two approaches in terms of computational efficiency. These results are of major importance in view of applications to the much debated case of the four-nucleon photoabsorption.Comment: 12 pages, 3 figure

First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He

The first direct mass-measurement of $^{6}$He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of $^{8}$He was determined with improved precision over our previous measurement. The obtained masses are $m$($^{6}$He) = 6.018 885 883(57) u and $m$($^{8}$He) = 8.033 934 44(11) u. The $^{6}$He value shows a deviation from the literature of 4$\sigma$. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and 1.959(16) fm for $^{6}$He and $^{8}$He respectively. We present a detailed comparison to nuclear theory for $^6$He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure