We present a new high-quality nucleon-nucleon potential with explicit charge dependence and charge asymmetry, which we designate Argonne v 18 . The model has a charge-independent part with fourteen operator components that is an updated version of the Argonne v 14 potential. Three additional chargedependent and one charge-asymmetric operators are added, along with a complete electromagnetic interaction. The potential has been fit directly to the Nijmegen pp and np scattering data base, low-energy nn scattering parameters, and deuteron binding energy. With 40 adjustable parameters it gives a 1 χ 2 per datum of 1.09 for 4301 pp and np data in the range 0-350 MeV.

Quantum Monte Carlo methods have proved very valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states, moments and transitions in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. We review the nuclear interactions and currents, and describe the continuum Quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit, and three-body interactions. We present a variety of results including the low-lying spectra of light nuclei, nuclear form factors, and transition matrix elements. We also describe low-energy scattering techniques, studies of the electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter as found in neutron stars. A coherent picture of nuclear structure and dynamics emerges based upon rather simple but realistic interactions and currents.

We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8 B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.

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Two-nucleon momentum distributions are calculated for the ground states of nuclei with mass number A ≤ 8, using variational Monte Carlo wave functions derived from a realistic Hamiltonian with two-and three-nucleon potentials. The momentum distribution of np pairs is found to be much larger than that of pp pairs for values of the relative momentum in the range (300-600) MeV/c and vanishing total momentum. This order of magnitude difference is seen in all nuclei considered and has a universal character originating from the tensor components present in any realistic nucleonnucleon potential. The correlations induced by the tensor force strongly influence the structure of np pairs, which are predominantly in deuteron-like states, while they are ineffective for pp pairs, which are mostly in 1 S0 states. These features should be easily observable in two-nucleon knock-out processes, such as A(e, e ′ np) and A(e, e ′ pp). The two preeminent features of the nucleon-nucleon (NN ) interaction are its short-range repulsion and intermediate-to long-range tensor character. These induce strong spatial-spin-isospin NN correlations, which leave their imprint on the structure of ground-and excited-state wave functions. Several nuclear properties reflect the presence of these features. For example, the two-nucleon density distributions ρ MS T S (r) in states with pair spin S=1 and isospin T =0 are very small at small inter-nucleon separation r and exhibit strong anisotropies depending on the spin projection M S [1]. Nucleon momentum distributions N (k) [2,3] and spectral functions S(k, E) [4] have large high-momentum and, in the case of S(k, E), high-energy components, which are produced by short-range and tensor correlations. The latter also influence the distribution of strength in response functions R(k, ω), which characterize the response of the nucleus to a spin-isospin disturbance injecting momentum k and energy ω into the system [5,6]. Lastly, calculations of low-energy spectra in light nuclei (up to mass number A=10) have demonstrated that tensor forces play a crucial role in reproducing the observed ordering of the levels and, in particular, the observed absence of stable A = 8 nuclei [7].In the present study we show that tensor correlations also impact strongly the momentum distributions of NN pairs in the ground state of a nucleus and, in particular, that they lead to large differences in the np versus pp distributions at moderate values of the relative momentum in the pair. These differences should be observable in two-nucleon knock-out processes, such as A(e, e ′ np) and A(e, e ′ pp) reactions.The probability of finding two nucleons with relative momentum q and total momentum Q in isospin state T M T in the ground state of a nucleus is proportional to the densitywhere r 12 ≡ r 1 − r 2 , R 12 ≡ (r 1 + r 2 )/2, and similarly for r ′ 12 and R ′ 12 . P T MT (12) is the isospin projection operator, and ψ JMJ denotes the nuclear wave function in spin and spin-projection state JM J . The normalization iswhere N T MT is the ...

A two-nucleon potential and consistent electromagnetic currents are derived in chiral effective field theory (χ EFT) at, respectively, Q 2 (or N 2 LO) and eQ (or N 3 LO), where Q generically denotes the low-momentum scale and e is the electric charge. Dimensional regularization is used to renormalize the pion-loop corrections. A simple expression is derived for the magnetic dipole (M1) operator associated with pion loops, consisting of two terms, one of which is determined, uniquely, by the isospin-dependent part of the two-pion-exchange potential. This decomposition is also carried out for the M1 operator arising from contact currents, in which the unique term is determined by the contact potential. Finally, the low-energy constants entering the N 2 LO potential are fixed by fits to the np Sand P -wave phase shifts up to 100 MeV laboratory energies.

The objectives of the present work are twofold. The first is to address and resolve some of the differences present in independent, chiral-effective-field-theory (χEFT) derivations up to one loop, recently appeared in the literature, of the nuclear charge and current operators. The second objective is to provide a complete set of χEFT predictions for the structure functions and tensor polarization of the deuteron, for the charge and magnetic form factors of 3 He and 3 H, and for the charge and magnetic radii of these few-nucleon systems. The calculations use wave functions derived from high-order chiral two-and three-nucleon potentials and Monte Carlo methods to evaluate the relevant matrix elements. Predictions based on conventional potentials in combination with χEFT charge and current operators are also presented. There is excellent agreement between theory and experiment for all these observables for momentum transfers up to q 2.0-2.5 fm −1 ; for a subset of them, this agreement extends to momentum transfers as high as q ≃ 5-6 fm −1 . A complete analysis of the results is provided.

We report variational Monte Carlo calculations of single-nucleon momentum distributions and nucleon-pair and nucleon-cluster momentum distributions for A ≤ 12 nuclei. The wave functions have been generated for a Hamiltonian containing the Argonne v18 two-nucleon and Urbana X threenucleon potentials. The single-nucleon and nucleon-pair momentum distributions exhibit universal features attributable to the pion-exchange tensor interaction. The single-nucleon distributions are broken down into proton and neutron components and spin-up and spin-down components where appropriate. The nucleon-pair momentum distributions are given either in pair spin and isospin ST projection or for pp, pn, and nn pairs. The nucleon-cluster momentum distributions include dp in 3 He, tp and dd in 4 He, αd in 6 Li, αt in 7 Li, and αα in 8 Be. Detailed tables are provided online for download.