Recent Developments in the Nuclear Many-Body Problem

The convergence of the effective field theory (EFT) approach of Furnstahl, Serot and Tang to the nuclear many-body problem is studied by applying it to selected doubly-magic nuclei far from stability. An independently developed code, which can incorporate various levels of approximation of the chiral effective lagrangian, is used to solve the self-consistent relativistic Hartree equations. Results are obtained for ground-state properties such as binding energies, single-particle level structure, and densities of the selected spherical, doubly-magic nuclei 132,100 Sn and 48,78 Ni. Calculated spectra of neighboring nuclei differing by one particle or one hole show agreement with the most recent experimental data. Predictions for nucleon densities are presented.

Section: Introductionmentioning

confidence: 99%

Effective Lagrangian approach to structure of selected nuclei far from stability

Huertas

2002

“…In Refs. [1,2], we introduced the ∆ resonance as a manifest degrees of freedom to the effective field theory (EFT), known as quantum hadrodynamics or QHD [3][4][5][6][7][8][9][10]. (The motivation for this EFT and some calculated results are discussed in Refs.…”

Section: Introductionmentioning

confidence: 99%

Incoherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei

Zhang

Serot

2012

We study the incoherent neutrinoproduction of photons and pions with neutrino energy E ν 0.5 GeV. These processes are relevant to the background analysis in neutrino-oscillation experi- Rev. Lett. 100, 032301 (2008)]. The calculations are carried out using a Lorentz-covariant effective field theory (EFT) which contains nucleons, pions, the Delta (1232) (∆s), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and has SU(2) L ⊗ SU(2) R chiral symmetry realized nonlinearly. The contributions of one-body currents are studied in the local fermi gas approximation. The current form factors are generated by meson dominance in the EFT Lagrangian. The conservation of the vector current and the partial conservation of the axial current are satisfied automatically, which is crucial for photon production. The ∆ dynamics in nuclei, as a key component in the study, are explored. Introduced ∆-meson couplings explain the ∆ spin-orbit (S-L) coupling in nuclei, and this leads to interesting constraints on the theory. Meanwhile a phenomenological approach is applied to parametrize the ∆ width. To benchmark our approximations, we calculate the differential cross sections for quasi-elastic scattering and incoherent electroproduction of pions without a final state interaction (FSI). The FSI can be ignored for photon production.

“…Another important factor related to the ∆ is the distorted pion wave function in the pion production, which is included here by using the Eikonal approximation. Such an 1 The EFT was originally motivated by the nuclear many-body problem [12][13][14][15][16][17][18][19], and is often called quantum hadrodynamics or QHD. 2 Ref.…”

mentioning

confidence: 99%

Coherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei

Zhang

Serot

2012

Purpose: Study coherent productions with Eν 0.5 GeV. Also address the contributions of two contact terms in Neutral Current (NC) photon production that are partially related to the proposed anomalous ω(ρ), Z boson and photon interactions. Methods: We work in the framework of a Lorentz-covariant effective field theory (EFT), which contains nucleons, pions, the Delta (1232) (∆s), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and incorporates a nonlinear realization of (approximate) SU(2) L ⊗ SU(2) R chiral symmetry. A revised version of the so-called "optimal approximation" is applied, where one-nucleon interaction amplitude is factorized out and the medium-modifications and pion wave function distortion are included. The calculation is tested against the coherent pion photoproduction data. Results: The computation shows an agreement with the pion photoproduction data, although precisely determining the ∆ modification is entangled with one mentioned contact term. The uncertainty in the ∆ modification leads to uncertainties in both pion and photon neutrinoproductions. In addition, the contact term plays a significant role in NC photon production. Conclusions: First, the contact term increases NC photon production by ∼ 10% assuming a resonable range of the contact coupling, which however seems not significant enough to explain the MiniBooNE excess. A high energy computation is needed to gain a firm conclusion and will be presented elsewhere. Second, the behavior of coherent neutrinoproductions computed here is significantly different from the expectation at high energy by ignoring the vector current contribution.