arXiv subjects

A. Deltuva

Publications and source records attributed to A. Deltuva.

At least 19 recordsLinked to original sources

arXiv2026

Comparison of Pauli projection and supersymetric transformation methods for three-body nuclear structure and reactions

Three-body Faddeev-type equations for bound, resonant, and scattering states in the systems with a nuclear core and two nucleons are solved using the momentum-space framework. Two approaches for eliminating the Pauli-forbidden deeply-bound states are compared: projecting out those states by a nonlocal term in the potential, and by using a supersymmetric transformation of the potential. While the former method is preferred by the experimental data for the deuteron-${}^4${He} scattering, the results for bound and resonant states do not indicate a clear superiority of a single method. Instead, systematic differences between them are found.

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arXiv2026

Second excited state of ${}^4\mathrm{He}$ tetramer

The four-boson universality suggests the existence of the second excited tetramer state in a system of cold ${}^4\mathrm{He}$ atoms. It is not bound but could be seen as a resonance in the atom-trimer scattering. This process is rigorously calculated using the momentum-space transition operator framework with two realistic interatomic potentials. The $S$-wave phase shift and cross section show a resonant behavior below the excited trimer threshold, but there are sizable nonresonant contributions from $P$ and $D$ waves as well. The position and width of the resonant state is determined, and for the latter significant finite-range effects are found.

cond-mat.quant-gas↗

arXiv2025

Three-Nucleon Dynamics in the dp breakup collisions at 190 MeV/nucleon using the WASA detector at COSY-J\"{u}lich

The differential cross section for the $^{1}$H$(d,pp)n$ breakup reaction at deuteron beam energy of 380 MeV has been determined with high precision for 189 angular configurations of outgoing protons in the region of forward laboratory angles. The cross section data were compared to theoretical predictions based on the state-of-the-art nucleon-nucleon potentials, combined with a three-nucleon force, the Coulomb interaction or carried out in a relativistic approach. In the region of the lowest differential cross section, the discrepancy between the data and the theoretical predictions is observed, also in the case of relativistic calculations.

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arXiv2025

Faddeev-type calculation of nonelastic breakup in deuteron-nucleus scattering

The nonelastic breakup (NEB), one of channels in $(d,p)$ inclusive reactions, is studied using the Faddeev-type scattering theory. The NEB differential cross section is obtained in terms of the imaginary part of the neutron-nucleus optical potential sandwiched between the Alt-Grassberger-Sandhas three-body transition operators. The momentum-space calculations including the Coulomb force are extended to higher charge numbers. Well converged numerical results are obtained for the energy distribution of the NEB cross section, being roughly consistent with previous works. The spin-dependent interaction terms do not play a significant role. The optical potential nonlocality effect shows up at higher proton energies, but is comparable to local potential uncertainties.

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arXiv2025

Three-body calculation of deuteron-nucleus scattering using microscopic global optical potential

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.

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arXiv2025

Examination of the multiple-scattering expansion in the four-nucleon system

The elastic neutron-${}^3\mathrm{H}$ scattering at intermediate energies is studied using rigorous integral equations solved in the momentum-space partial-wave basis. The four-particle transition operators are expanded into multiple-scattering series in terms of subsystem transition operators. Various approximations resulting from truncation of the series in different ways are evaluated and their validity is investigated. They fail at lower energies but at higher energies provide a rough reproduction of exact results at small scattering angles. In the large-angle region all approximations fail heavily, indicating that the scattering amplitude results from a delicate interplay of many multiple-scattering terms. The partial-wave analysis reveals that the developed approximations are reliable in higher partial waves, and for practical calculations an efficient ``hybrid'' approach is proposed, combining exact amplitudes in lower partial waves with approximations in higher partial waves. The implications for often used approximation of the first order in two-body transition matrix and development of microscopic optical potentials are discussed.

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arXiv2024

Deuteron-${}^{3}\mathrm{He}$ scattering using nucleon-${}^{3}\mathrm{He}$ optical potentials fitted to four-body amplitudes

Deuteron-${}^{3}\mathrm{He}$ reactions in the 15 to 40 MeV range are studied using a three-body model where the constructed nonlocal optical potentials rely on rigorous nucleon-${}^{3}\mathrm{He}$ scattering calculations. The differential cross section for the elastic scattering and neutron transfer reaction is predicted quite well up to 90 deg scattering angles. The importance of the Pauli term in complex potentials is demonstrated.

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arXiv2024

Nonlocal interaction and collective excitation in deuteron breakup on ${}^{24}$Mg nucleus

Deuteron breakup in collision with a ${}^{24}\mathrm{Mg}$ nucleus is studied using rigorous three-body scattering equations, extended to include also the excitation of the nucleus. Predictions based on local and nonlocal nucleon-nucleus optical potentials with rotational quadrupole deformation enabling the excitation of the ${}^{24}\mathrm{Mg}(2^+)$ state are compared. The nonlocality effect is less pronounced than in the deuteron inelastic scattering ${}^{24}\mathrm{Mg}(d,d')$ at the same energies, and manifests itself quite differently for semi-inclusive differential cross sections of elastic and inelastic breakup.

nucl-th↗

arXiv2024

Quasielastic $\overrightarrow{^{3}\mathrm{He}}(\overrightarrow{e},{e'})$ Asymmetry in the Threshold Region

A measurement of the double-spin asymmetry from electron-$^{3}$He scattering in the threshold region of two- and three-body breakup of $^{3}$He was performed at Jefferson Lab, for Q$^{2}$ values of 0.1 and 0.2 (GeV/$c$)$^{2}$. The results of this measurement serve as a stringent test of our understanding of few-body systems. When compared with calculations from plane wave impulse approximation and Faddeev theory, we found that the Faddeev calculations, which use modern nuclear potentials and prescriptions for meson-exchange currents, demonstrate an overall good agreement with data.

nucl-ex↗

arXiv2024

Interplay of single-particle and collective modes in the $^{12}$C(p,2p) reaction near 100 MeV

The $^{12}$C(p,2p)$^{11}$B reaction at $E_p =98.7$ MeV proton beam energy is analyzed using a rigorous three-particle scattering formalism extended to include the internal excitation of the nuclear core or residual nucleus. The excitation proceeds via the core interaction with any of the external nucleons. We assume the $^{11}$B ground and low-lying excited states [$\frac32^-$ (0.0 MeV), $\frac52^-$ (4.45 MeV), $\frac72^-$ (6.74 MeV)] and the excited states [$\frac12^-$ (2.12 MeV), $\frac32^-$ (5.02 MeV)] to be members of $K=\frac32^-$ and $K=\frac12^-$ rotational bands, respectively. The dynamical core excitation results in a significant cross section for the reaction leading to the $\frac52^-$ (4.45 MeV) excited state of $^{11}$B that cannot be populated through the single-particle excitation mechanism. The detailed agreement between the theoretical calculations and data depends on the used optical model parametrizations and the kinematical configuration of the detected nucleons.

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arXiv2024

Coulomb screening in the momentum-space description of the proton-deuteron elastic scattering: Why the renormalization is needed?

Proton-deuteron elastic scattering is considered in the framework of momentum-space Faddeev equations with the screening method for the Coulomb interaction. It is shown how the interplay of the proton-proton Coulomb potential and the deuteron pole in the neutron-proton transition operator leads to coinciding singularities in the Faddeev equation. As a consequence, the renormalization of the scattering amplitude is needed in the unscreened Coulomb limit. This finding possibly explains why no need for the renormalization was conjectured in a previous work [Witała et al., Eur.~Phys.~J.~A 41, 369 (2009)] missing the coincidence of those singularities.

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arXiv2023

Nonlocal optical potential in the inelastic deuteron scattering off $^{24}$Mg

Nonlocal nucleon-nucleus optical potential with rotational quadrupole deformation enabling the excitation of the ${}^{24}\mathrm{Mg}(2^+)$ state is developed; it fits well the proton-${}^{24}\mathrm{Mg}$ elastic and inelastic differential cross section in the beam energy range from 30 to 45 MeV per nucleon. The inelastic deuteron-${}^{24}\mathrm{Mg}$ scattering leading to the excited ${}^{24}\mathrm{Mg}(2^+)$ state is studied in the same energy regime by solving the three-body Faddeev-type equations for transition operators. Effects of the optical potential nonlocality are evaluated by comparison with local models. Significant effects on the inelastic differential cross section are found at forward angles up to the first peak and at larger angles beyond the second peak. Nonlocal optical potential provides a simultaneous reasonable reproduction of the experimental data for the elastic and inelastic proton-${}^{24}\mathrm{Mg}$ and deuteron-${}^{24}\mathrm{Mg}$ scattering, not achieved using local potentials.

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arXiv2023

Nonlocal optical potential with core excitation in ${}^{10}\mathrm{Be}(d,p){}^{11}\mathrm{Be}$ and ${}^{11}\mathrm{Be}(p,d){}^{10}\mathrm{Be}$ reactions

We propose a new nonlocal form of the nucleon-nucleus optical potential and demonstrate its reliability. We extend the nonlocal potential to include the excitation of the nuclear core and develop energy-independent roton-${}^{10}\mathrm{Be}$ potential reasonably reproducing the experimental data at low energies. We apply the new potential to the study of deuteron stripping and pickup reactions ${}^{10}\mathrm{Be}(d,p){}^{11}\mathrm{Be}$ and ${}^{11}\mathrm{Be}(p,d){}^{10}\mathrm{Be}$ using rigorous three-body Faddeev-type equations for transition operators that are solved in the momentum-space partial-wave framework. The achieved description of the experimental data is considerably more successful as compared to previous studies with local potentials. The values of spectroscopic factors consistent with the data are determined, exhibiting only weak energy dependence. The results possibly indicate an increased predicting power of the proposed calculational scheme.

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arXiv2022

Signatures of the $Δ$ isobar in spin observables of ${}^3\mathrm{He}$ electrodisintegration

The electrodisintegration of ${}^3\mathrm{He}$ is considered focusing on the effects of the $Δ$ isobar excitation which is treated dynamically on the same footing as nucleons. In the region beyond the quasi-elastic peak the predicted transverse response functions $R_{T}$ and $R_{T'}$ are visibly affected. This leads to sizable $Δ$ isobar effects for inclusive and exclusive electron polarization asymmetries in particular kinematic regions. A measurement performed in the proposed regime could provide judgment for models of nuclear forces and currents.

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arXiv2022

Three-nucleon system: Irreducible and reducible contributions of the three-nucleon force

The three-nucleon bound and scattering equations are solved in momentum space for a coupled-channel Hamiltonian. The Hamiltonian couples the purely nucleonic sector of Hilbert space with a sector in which one nucleon is excited to a $Δ$ isobar. The interaction consists of irreducible two-baryon and irreducible three-baryon potentials. The calculation keeps only the purely nucleonic one among the irreducible three-baryon potentials. The coupled-channel two-baryon potential yields additional reducible contributions to the three-nucleon force. The Coulomb interaction between the two protons is included using the method of screening and renormalization. Three-nucleon force effects on the bound-state energies and on observables of elastic nucleon-deuteron scattering and breakup are studied.

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arXiv2022

Four-body system of ${}^4\mathrm{He}$ atoms: Dimer-dimer scattering

The strong short-range repulsion, characteristic to realistic interatomic potentials, complicates the description of weakly-bound few-body systems such as those of \He atoms. The present work proposes an approach for solving this problem and applies it to a realistic system of four ${}^4\mathrm{He}$ atoms. The potential is gradually softened such that rigorous four-body equations for bound and scattering tates can be accurately solved in the momentum-space framework, and the results are extrapolated back to the limit of the original potential. Linear correlations between three- and four body quantities are observed, and the accuracy of the procedure is improved by extrapolating in one of the three-body quantities. Results for the ${}^4\mathrm{He}$ tetramer ground and excited state binding energies and atom-trimer scattering agree well with at least some of earlier determinations and shed light on the existing disagreements. An additional case of the Phillips correlation line is established for the dimer-dimer scattering length. The trimer production rate via the ultracold two-dimer collisions is estimated, it exhibits significant finite-range effects despite the weak binding of the dimer.

physics.atom-ph↗

arXiv2021

Recombination in the universal four-fermion system

In the systems of spin $\frac12$ fermions with resonant $S$-wave interactions supporting only weakly bound dimers the antisymmetry forbids recombination of three (or more) fermions at zero energy. However, the fermion-fermion-dimer recombination is only partially suppressed. It is studied in the framework of momentum-space integral equations for the four-particle transition operators. In the vicinity of the unitary limit the fermion-fermion-dimer recombination rate, rescaled to build dimensionless quantity, is found to be linear in the effective range parameter, enabling a simple and accurate parametrization as well as evaluation of finite-range effects for any potential model. This feature makes the present results very useful in benchmarking different methods for three-cluster breakup and recombination calculations in four-particle systems. The interplay of the three-fermion and fermion-fermion-dimer recombination processes and their consequences for ultracold mixtures of fermions and dimers is discussed.

cond-mat.quant-gas↗

arXiv2021

Efimov resonances above four-boson threshold

Four-boson Efimov physics is well known in the negative energy regime but far less above the four-body breakup threshold. The part of this region with negative two-boson scattering length is studied solving rigorous four-particle scattering equations for transition operators in the momentum space. Moving away from the unitary limit the Efimov tetramers evolve from unstable bound states into resonances. Their energies and widths are studied as functions of the two-boson scattering length; a universal behavior is established and given in a dimensionless representation. The Efimov tetramers have finite width in the whole regime; they broaden rapidly in the resonance regime but remain narrower than the associated trimer. The resonant behavior is most clearly seen in the four-particle recombination rate.

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