Few-Body Systems最新文献

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.

Strongly interacting systems appear in several areas of physics and are characterized by attractive interactions that can almost, or just barely, loosely bind two particles. Although this definition is made at the two-body level, this gives rise to fascinating effects in larger systems, including the so-called Efimov physics. In this context, the zero-range theory aims to describe low-energy properties based only on the scattering length. However, for a broad range of physical applications, the finite range of the interactions plays an important role. In this work, I discuss some aspects of finite-range effects in strongly interacting systems. I present the zero-range and shapeless universalities in two-body systems with applications in atomic and nuclear physics. I derived an analytical expression for the s-wave bound-state spectrum of the modified Pöschl–Teller potential for two particles in three dimensions, which is compared with the approximations to illustrate their usefulness. Concerning three identical bosons, I presented a trimer energy scaling function that explicitly includes the effective range. The implications for larger systems are briefly discussed.

Low-energy theorems (LETs) for effective-range parameters in nucleon-nucleon scattering encode properties of the long-range part of the nuclear force. We compute LETs for S-wave neutron–proton scattering using chiral effective field theory with a modified version of Weinberg power counting. Corrections to the leading order amplitude are included in distorted-wave perturbation theory and we incorporate contributions up to the third order in the power counting. We find that LETs in the (^1S_0) and (^3S_1) partial waves agree well with empirical effective-range parameters. At the same time, phase shifts up to laboratory scattering energies of about 100 MeV can be reproduced. We show that it is important to consider the pion mass splitting in the one-pion exchange potential in the (^1S_0) partial wave while the effect is negligible in the (^3S_1) partial wave. We conclude that pion exchanges, as treated in this power counting, accurately describe the long-range part of the S-wave nuclear interaction.

We test microscopic global optical potential in three-body calculations of deuteron–nucleus scattering. We solve Faddeev-type equations for three-body transition operators. We calculate differential cross section and analyzing power for the deuteron elastic scattering and breakup in collisions with ({}^{12})C, ({}^{16})O and ({}^{24})Mg nuclei, and find a reasonable agreement with available experimental data. Comparison with respective predictions using phenomenological optical potentials reveals systematic deviations in particular kinematic regimes.

Chiral effective field theory ((chi )EFT) is a powerful tool for studying electroweak processes in nuclei. I discuss (chi )EFT calculations of three key nuclear electroweak processes: primordial deuterium production, proton–proton fusion, and magnetic dipole excitations of (^{48}textrm{Ca}). This article showcases (chi )EFT’s ability to quantify theory uncertainties at the appropriate level of rigor for addressing the different precision demands of these three processes.

The doubly excited states (DES) of beryllium-like ions (BLI) embedded in dense quantum plasma (QP) have been investigated by applying the stabilization method. Ions having atomic number Z lying between 4 to 10 are considered and treated as an effective three-body system by means of the ‘method of model potential’. Exponential cosine screened Coulomb potential is used to describe the screened interactions among the charged particles in QP. Using an extensive wavefunction, it has been possible to detect the existence of one, four and five DESs lying above the (1s^22p) threshold in the ions having (Z = 4), (Z = 5) and (Z = 6)–10 respectively. The energies and widths of these states for the plasma-free case agree nicely with the reliable results available in the literature. A detailed study has been made to explore the changes in the energies and widths of these states subject to the varying screening effect of the background quantum plasma environment. Furthermore, Z-dependence of the changes induced by the plasma has also been investigated in detail.

We investigate the exotic hadrons consisting of two light quarks and two heavy antiquarks, ((qbar{Q}))-((qbar{Q})). The spin-dependent term between quarks is known to give an attraction to the ud spin-0 component in the isospin-0 (ubar{c} dbar{c}) system, (T_{cc}). However, the said component also gets a repulsion from the partial Pauli-blocking. By the dynamical calculation with a simplified quark model, we discuss that the competition of the two effects leads to a shallow bound state for (T_{cc}), which is preferred from the experiment, and a deep bound state for (T_{bb}).

The resonance mass spectra have been studied through a non-relativistic hypercentral Constituent Quark Model using a linear potential. Also, the effects of higher order correction terms (({mathcal {O}}(frac{1}{m})), ({mathcal {O}}(frac{1}{m^{2}}))) have been studied for improvisation of the results. Other baryonic properties such as Regge trajectories, magnetic moment and decay widths have been considered. A detailed comparison with other approaches are discussed in the present review