Few-Body Systems最新文献

The growing interest in the physics of unstable nuclei, along with their manifestations in laboratory experiments and astrophysical observations, highlights the existence of features in decay processes within complex quantum systems that are not yet fully understood. This paper considers examples of such phenomena, including two-step decay processes, resonance effects, threshold peculiarities, and the interactions between bound and continuum states, as well as the related dynamics.

An important feature of an effective field theory is its renormalizability, which implies that one can apply a certain power counting to renormalized quantities and perform a systematic expansion of the calculated observables in terms of some small parameter. When nonperturbative effects become relevant, the requirement of renormalizability imposes nontrivial constraints on a choice of the effective interaction and the renormalization scheme. We discuss several instructive examples and counterexamples of renormalizability to illustrate potential issues one has to deal with in realistic calculations such as nuclear chiral effective field theory.

About 3 decades ago, Steven Weinberg came up with an idea of using the effective chiral Lagrangian to describe nuclear interactions, which has had a long-lasting impact on nuclear physics. Here, I will reflect on what has been learned since that time about the role of chiral symmetry in this context and discuss achievements and challenges in advancing chiral EFT into a precision tool for light nuclei.

Approximate solutions of Schrödinger equation are established, for some quasi-exactly solvable central potentials. Each potential is a sum of the generalized Cornell and an exponential potential. The radial equation is turned to the biconfluent Heun equation. The energy values are obtained explicitly. For given values of the parameters Schrödinger equation approximate eigensolutions are established.

We present a theoretical study of resonance lifetimes in a two-component three-body system, specifically examining the decay of three-body resonances into a deep dimer and an unbound particle. Utilising the Gaussian expansion method together with the complex scaling method, we obtain the widths of these resonances from first principles. We focus on mass ratios in the typical range for mixtures of ultracold atoms and reveal an intriguing dependence of the resonance widths on the mass ratio: as the mass ratio increases, the widths exhibit oscillations on top of an overall decreasing trend. In particular, for some mass ratios the resonance width vanishes, implying that the resonance becomes in fact stable. Notably, near the mass ratio for Caesium–Lithium mixtures, we obtain nearly vanishing widths of the resonances which validates to treat them in the bound-state approximation. In addition, we perform our analysis of the resonance widths in both one and three dimensions and find a qualitatively similar dependence on the mass ratio.

The GANIL campaign around the first 4n signal was very peculiar. The beginning and end were both dictated by unexpected events that, unfortunately, do not fit within the streamlined format of standard scientific publications. However, they illustrate many aspects of how basic research should work, or at least does work. Therefore, I take this opportunity to share them with those not involved in the campaign, hoping that they will offer a better perspective of that research in particular and of basic research in general. As a disclaimer, this is only a personal recollection of those events.

The differential cross sections for the (^2)H(p,pp)n reaction have been measured for more than 80 angular configurations of the outgoing protons in the range of polar angles from 13(^circ ) to 33(^circ ) with a proton beam at 108 MeV. Data have been collected at the first experimental run in the Cyclotron Center Bronowice (CCB) at the Institute of Nuclear Physics PAS in Cracow, using the BINA detector setup. Analysis leading to determination of the breakup cross section values is described. Absolute normalization is obtained by normalization to the simultaneously measured (^1)H(d,d)p scattering events. Experimental results are compared to the state-of-the-art theoretical calculations. Global analysis shows significant influence of the Coulomb interaction and small effects of three nucleon force in the studied phase space region.

The squeezing process of a three-dimensional quantum system by use of an external deformed one-body oscillator potential can also be described by the d-method, without external field and where the dimension can take non-integer values. In this work we first generalize both methods to N particles and any transition between dimensions below 3. Once this is done, the use of harmonic oscillator interactions between the particles allows complete analytic solutions of both methods, and a direct comparison between them is possible. Assuming that both methods describe the same process, leading to the same ground state energy and wave function, an analytic equivalence between the methods arises. The equivalence between both methods and the validity of the derived analytic relation between them is first tested for two identical bosons and for squeezing transitions from 3 to 2 and 1 dimensions, as well as from 2 to 1 dimension. We also investigate the symmetric squeezing from 3 to 1 dimensions of a system made of three identical bosons. We have in all the cases found that the derived analytic relations between the two methods work very well. This fact permits to relate both methods also for large squeezing scenarios, where the brute force numerical calculation with the external field is too much demanding from the numerical point of view, especially for systems with more than two particles.

We studied influence of lattice discretization on a HAL QCD two-baryon force. We have carried out 3-flavor lattice QCD numerical calculations at a same quark mass with three different values of lattice spacing. We extracted a potential of interaction in the flavor singlet S-wave two-baryon sector, and drew out binding energy of a bound state in the sector, the H-dibaryon. It turned out that the qualitative nature of the interaction does not change at all, while strength of the interaction change considerably with respect to change of lattice spacing a at a around 0.1 [fm]. Accordingly, binding energy of the H-dibaryon depends to the lattice spacing. This result is consistent to that reported by Mainz lattice QCD group. This issue may indicate a challenging point common to lattice QCD studies of multi-hadron systems.

Because of the absence of indistinguishability constraint, interparticle interactions between nonidentical particles have in general much more variety than those between identical particles. In particular, it is known that there exists a U(2) family of two-body contact interactions between nonidentical particles in one spatial dimension. This paper studies breakdown of continuous scale invariance to discrete scale invariance under this U(2) family of two-body contact interactions in two-body problems of nonidentical particles on the half line. We show that, in contrast to the corresponding identical-particle problem, there exist two distinct channels that admit geometric sequences of two-body bound states.