Few-Body Systems最新文献

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

We provide an overview of experiments exploring resonances in the collision of ultracold clouds of atoms. Using a laser-based accelerator that capitalises on the energy resolution provided by the ultracold atomic setting, we unveil resonance phenomena such as Feshbach and shape resonances in their quintessential form by literally photographing the halo of outgoing scattered atoms. We exploit the tunability of magnetic Feshbach resonances to instigate an interplay between scattering resonances. By experimentally recording the scattering in a parameter space spanned by collision energy and magnetic field, we capture the imprint of the S-matrix pole flow in the complex energy plane. After revisiting experiments that place a Feshbach resonance in the proximity of a shape resonance and an anti-bound state, respectively, we discuss the possibility of using S-matrix pole interplay between two Feshbach resonances to create a bound-state-in-the-continuum.

Despite its role in the continuing evolution of the Universe, only a small fraction of the mass of visible material can be attributed to the Higgs boson alone. The overwhelmingly dominant share may/should arise from the strong interactions that act in the heart of nuclear matter; namely, those described by quantum chromodynamics. This contribution describes how studying and explaining the attributes of pseudoscalar mesons can open an insightful window onto understanding the origin of mass in the Standard Model and how these insights inform our knowledge of hadron structure. The survey ranges over distribution amplitudes and functions, electromagnetic and gravitational form factors, light-front wave functions, and generalized parton distributions. Advances made using continuum Schwinger function methods and their relevance for experimental efforts are highlighted.

Recently we formulated covariant equations describing the tetraquark in terms of an admixture of two-body states (D{bar{D}}) (diquark-antidiquark), MM (meson-meson), and three-body-like states where two of the quarks are spectators while the other two are interacting (Phys Rev D 107:094014, 2023). A feature of these equations is that they unify descriptions of seemingly unrelated models of the tetraquark, like, for example, the (D{bar{D}}) model of the Moscow group (Faustov et al. in Universe 7:94, 2021) and the coupled channel (D {bar{D}}-MM) model of the Giessen group (Heupel et al. in Phys Lett B718:545, 2012). Here we extend these equations to the exact case where (qbar{q}) annihilation is incorporated explicitly, and all previously neglected terms (three-body forces, non-pole contributions to two-quark t matrices, etc.) are taken into account through the inclusion of a single (qbar{q}) potential (Delta ).

Starting from a complete set of relativistic nucleon–nucleon contact operators up to order (O(p^4)) of the expansion in the soft (relative or nucleon) momentum p, we show that non-relativistic expansions of relativistic operators involve twenty-six independent combinations, two starting at (O(p^0)), seven at order (O(p^2)) and seventeen at order (O(p^4)). This demonstrates the existence of two low-energy free constants that parameterize interactions dependent on the total momentum of the pair of nucleons P. The latter, through the use of a unitary transformation, can be removed in the two-nucleon fourth-order contact interaction of the Chiral Effective Field Theory, generating a three-nucleon interaction at the same order. Within a hybrid approach in which this interaction is considered together with the phenomenological potential AV18, we show that the LECs involved can be used to fit very accurate data on the polarization observables of the low-energy (p-d) scattering, in particular the (A_y) asymmetry.

We summarize the main properties of the so called “abnormal solutions” of the Wick–Cutkosky model, i.e. two massive scalar particles interacting via massless scalar exchange (“photons”), within the Bethe–Salpeter equation. These solutions do not exist in the non-relativistic limit, in spite of having very small binding energies. They present a genuine many-body character dominated by photons, with a norm of the valence constituent wave function (two-body norm) that vanishes in the limit of zero binding energy. We present new results concerning the massive-exchange case, in particular determine under which conditions is it possible to obtain such peculiar solutions without spoiling the model by tachyonic states ((M^2<0)).