The anapole form factor of the nucleon

The anapole form factor of the nucleon is calculated in chiral perturbation theory in leading order. To this order, the form factor originates from the pion cloud, and is proportional to the non-derivative parity-violating pion-nucleon coupling. The momentum dependence of the form factor - and in particular, its radius - is completely determined by the pion mass.Comment: 9 pages, 2 eps figures included by epsf.sty, minor changes in note adde

Compton Scattering on the Deuteron in Baryon Chiral Perturbation Theory

Compton scattering on the deuteron is studied in the framework of baryon chiral perturbation theory to third order in small momenta, for photon energies of order the pion mass. The scattering amplitude is a sum of one- and two-nucleon mechanisms with no undetermined parameters. Our results are in good agreement with existing experimental data, and a prediction is made for higher-energy data being analyzed at SAL.Comment: 39 pages LaTeX, 19 figures (uses epsf

Renormalizability of the nuclear many-body problem with the Skyrme interaction beyond mean field

Phenomenological effective interactions like Skyrme forces are currently used in mean--field calculations in nuclear physics. Mean--field models have strong analogies with the first order of the perturbative many--body problem and the currently used effective interactions are adjusted at the mean--field level. In this work, we analyze the renormalizability of the nuclear many--body problem in the case where the effective Skyrme interaction is employed in its standard form and the perturbative problem is solved up to second order. We focus on symmetric nuclear matter and its equation of state, which can be calculated analytically at this order. It is shown that only by applying specific density dependence and constraints to the interaction parameters could renormalizability be guaranteed in principle. This indicates that the standard Skyrme interaction does not in general lead to a renormalizable theory. For achieving renormalizability, other terms should be added to the interaction and employed perturbatively only at first order.Comment: Revised versio

The Two-Nucleon 1S0 Amplitude Zero in Chiral Effective Field Theory

We present a new rearrangement of short-range interactions in the $^1S_0$ nucleon-nucleon channel within Chiral Effective Field Theory. This is intended to reproduce the amplitude zero (scattering momentum $\simeq$ 340 MeV) at leading order, and it includes subleading corrections perturbatively in a way that is consistent with renormalization-group invariance. Systematic improvement is shown at next-to-leading order, and we obtain results that fit empirical phase shifts remarkably well all the way up to the pion-production threshold. An approach in which pions have been integrated out is included, which allows us to derive analytic results that also fit phenomenology surprisingly well.Comment: 34 pages, 7 figure

Nuclear Matter on a Lattice

We investigate nuclear matter on a cubic lattice. An exact thermal formalism is applied to nucleons with a Hamiltonian that accommodates on-site and next-neighbor parts of the central, spin- and isospin-exchange interactions. We describe the nuclear matter Monte Carlo methods which contain elements from shell model Monte Carlo methods and from numerical simulations of the Hubbard model. We show that energy and basic saturation properties of nuclear matter can be reproduced. Evidence of a first-order phase transition from an uncorrelated Fermi gas to a clustered system is observed by computing mechanical and thermodynamical quantities such as compressibility, heat capacity, entropy and grand potential. We compare symmetry energy and first sound velocities with literature and find reasonable agreement.Comment: 23 pages, 8 figures (some in color), to be submitted to Phys. Rev.

Pion Interactions in the X(3872)

We consider pion interactions in an effective field theory of the narrow resonance X(3872), assuming it is a weakly bound molecule of the charm mesons D^{0} \bar D^{*0} and D^{*0} \bar D^{0}. Since the hyperfine splitting of the D^{0} and D^{*0} is only 7 MeV greater than the neutral pion mass, pions can be produced near threshold and are non-relativistic. We show that pion exchange can be treated in perturbation theory and calculate the next-to-leading-order correction to the partial decay width \Gamma[X \to D^0 \bar D^{0} \pi^0].Comment: 26 pages, 11 figures, revtex4, to appear in Phys. Rev.

Effective interactions for light nuclei: an effective (field theory) approach

One of the central open problems in nuclear physics is the construction of effective interactions suitable for many-body calculations. We discuss a recently developed approach to this problem, where one starts with an effective field theory containing only fermion fields and formulated directly in a no-core shell-model space. We present applications to light nuclei and to systems of a few atoms in a harmonic-oscillator trap. Future applications and extensions, as well as challenges, are also considered

Charge-Independence Breaking in the Two-Pion-Exchange Nucleon-Nucleon Force

Charge-independence breaking due to the pion-mass difference in the (chiral) two-pion-exchange nucleon-nucleon force is investigated. A general argument based on symmetries is presented that relates the charge-symmetric part of that force to the proton-proton case. The static potential linear in that mass difference is worked out as an explicit example by means of Feynman diagrams, and this confirms the general argument.Comment: 10 pages, latex, 1 figure -- epsfig.sty required -- To appear in Phys. Rev.