Few-Body Systems最新文献

By developing the mean-field theory valid for large N, we investigate the problem of two light fermions interacting via a zero-range potential with N heavy fermions in two dimensions. We obtain numerical evidence that this system is never fully bound. It always splits into droplets containing a single light atom. This is in contrast to the one-dimensional case where any number of heavy and light fermions can be bound together.

We use a combination of effective field theory and the renormalization group to determine the impact of radiative corrections on the nucleon–nucleon potential and the binding energy of the deuteron. In order to do so, we present a modified version of pionless effective field theory inspired by earlier work in nonrelativistic quantum electrodynamics. The renormalization group improvement of the deuteron binding energy leads to a shift on the order of a few percent and is consistent with the experimental value. This work serves as a starting point for a dedicated study of radiative corrections in few-body systems relevant for precision tests of the Standard Model in an effective field theory framework.

We present the findings of a study based on a new inelastic electron-scattering experiment on the ({}^{12})C nucleus focusing on the kinematic region of (Q^2=0.8,textrm{GeV}^2/{c}^2). The measured cross section is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10(%).

We address the question of the reliability of the Born-Oppenheimer (BO) approximation for a mass-imbalanced resonant three-body system embedded in noninteger dimensions. We address this question within the problem of a system of currently experimental interest, namely (^7)Li(-^{87})Rb(_2). We compare the Efimov scale parameter as well as the wave functions obtained using the BO approximation with those obtained using the Bethe-Peierls boundary condition.

We study the nonrelativistic effects of the Lorentz symmetry violation determined by the coupling between the fixed vector field (f^{mu }gamma ^{5}) and the derivative of the fermionic field on the squared cotangent potential and a periodic potential in (left( 1+1right) )-dimensions. Our analysis focusses on how the energy eigenvalues can be influenced by the Lorentz symmetry violation background. From the energy eigenvalues, we extend our discussion to the revival time.

We consider a specific form of explicitly correlated Gaussians—with tensor pre-factors—which appear naturally when dealing with certain few-body systems in nuclear and particle physics. We derive analytic matrix elements with these Gaussians—overlap, kinetic energy, and Coulomb potential—to be used in variational calculations of those systems. We also perform a quick test of the derived formulae by applying them to p- and d-waves of the hydrogen atom.

The ({{}^4textrm{He}}) monopole form factor is studied by computing the transition matrix element of the electromagnetic charge operator between the ({{}^4textrm{He}}) ground-state and the (p+{{}^3textrm{H}}) and (n+{{}^3textrm{He}}) scattering states. The nuclear wave functions are calculated using the hyperspherical harmonic method, by starting from Hamiltonians including two- and three-body forces derived in chiral effective field theory. The electromagnetic charge operator retains, beyond the leading order (impulse approximation) term, also higher order contributions, as relativistic corrections and meson-exchange currents. The results for the monopole form factor are in fair agreement with recent MAMI data. Comparison with other theoretical calculations are also provided.

The aim of this work is to explain how, starting from the orthogonality expression of two polynomials, we deduce the Schrödinger equation and the solution of the N-body problem including two-body correlations as well as the existence of shells. Generated by the behaviour of kinetic energy for a two-body interaction. The quantification of matters is obtained by the application of the weight function algorithm to the statement that two states are independents when their product integrated over the whole space is null leading to a two variables second order differential equation. The Nuclear Shell Model is a consequence of the kinetic energy behaviour for increasing number of nucleons in ground state. It leaves the mean field theory useless.

Efimov physics in the vicinity of two overlapping narrow Feshbach resonances can be explored within a framework of a three-channel model where a non-interacting open channel is coupled to two closed molecular channels. Here, we determine how it compares to the extended two-channel model, which includes an open channel with finite background scattering and a single molecular channel. We identify the parameter range in which the three-channel model surpasses the extended two-channel model. Furthermore, the three-channel model is extended to include background scattering, and then both models are applied to the experimentally relevant system of bosonic lithium atoms polarized on two different energy levels, with an isolated and two overlapping narrow Feshbach resonances, respectively. We confirm, in agreement with previous studies, that being small, the background scattering length in lithium has a negligible effect on the Efimov features in the case of isolated resonance. However, in the case of overlapping Feshbach resonances, the inclusion of background scattering improves the performance of the theory with respect to the experimentally measured position of the Efimov resonance.

A discussion is presented of the estimates of the energy and width of resonances in constituent models, with focus on the tetraquark states containing heavy quarks.