arXiv subjects

K. Topolnicki

Publications and source records attributed to K. Topolnicki.

At least 19 recordsLinked to original sources

arXiv2026

Challenging chiral EFT with tritium beta decay

We present a detailed investigation of tritium beta decay up to third order (N2LO) in chiral effective field theory (EFT) using the LENPIC interactions. Unlike existing studies, we use nucleon-deuteron scattering observables to fix the low-energy constant D that governs the strength of the short-range contributions to the exchange axial current operator and three-nucleon forces. Surprisingly, the resulting parameter-free predictions for the tritium Gamow-Teller reduced matrix element are found to considerably overestimate its empirical value. This result remains robust against reasonable variations of the pion-nucleon coupling constants and regularization scheme. A closer look at the size of the parameter-free long-range two-body contributions to the Gamow-Teller matrix element reveals the fine-tuned nature this observable in chiral EFT, which may partially explain the observed deviation. Our results indicate a considerable N2LO truncation uncertainty for tritium beta decay and point towards large higher-order two-body corrections. More definite conclusions await a complete fourth-order analysis of nucleon-deuteron scattering observables and tritium half-life.

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arXiv2026

Field-theoretical description of the deuteron breakup in the clothed particle representation

We present a field-theoretical description of the deuteron electrodisintegration reaction d(e,e'p)n induced by unpolarized and polarized electrons. The approach combines the Lehmann-Symanzik-Zimmermann in(out) formalism with the clothed particle representation in the instant form of relativistic dynamics, providing a fully relativistic and gauge-independent framework based on the Fock-Weyl criterion. Within the method of unitary clothing transformations, one and the same transformation that generates the relativistic nucleon-nucleon interaction (the Kharkiv potential) also induces a fresh family of electromagnetic current operators. As a result, one-body and two-body (meson-exchange) currents emerge on a common footing. We compute differential cross sections and polarization observables with the inclusion of final-state interaction effects and meson-exchange current contributions, and compare the results with Saclay and Jefferson Lab data as well as with earlier theoretical predictions. The role of relativistic ingredients (one- and two-body currents, Fermi-motion effects, etc.) and the interplay between them are analyzed in several kinematic regimes of the experiments at Saclay and Jefferson Lab.

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arXiv2026

Comparison of Relativistic and Non-relativistic Faddeev calculations for Proton-Deuteron Elastic Scattering

This investigation compares non-relativistic and relativistic nucleon-nucleon potentials in the context of proton-deuteron scattering. Conventional NN potentials (e.g., CDBonn, AV18, Nijmegen) rely on the nonrelativistic Schroedinger equation, whereas the Kharkiv potential is intrinsically relativistic. We employ the Coester-Pieper-Serduke (CPS) and Kamada-Gloeckle (KG) conversion methods to construct a phenomenological-relativistic potential (PRP) from a realistic NN potential, preserving the deuteron binding energy and phase shifts. Focusing on relativistic effects and not including Coulomb forces to avoid complexity, the solutions are compared by solving relativistic and nonrelativistic Faddeev equations. Calculations of the differential cross section using the relativistic Faddeev equation show that relativistic effects - particularly the deviation at the backward angle - become pronounced at 135 MeV. The differences in the forward angle were attributed to the characteristics of the Kharkiv potential itself. The reverse transformation of the Kharkiv potential into a pseudo-nonrelativistic potential (PNRP) confirms that the backward-angle relativistic effect increases with energy in the range from 100 MeV to 400 MeV. Comparisons of the polarization observables indicate that relativistic effects, as well as the discrepancy between the CPS and KG transformations, become significant above 300 MeV. However, for polarization observations below 300 MeV, the nonrelativistic results from PNRP do not deviate significantly from relativistic calculations.

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arXiv2025

Observability of modified threshold behavior near unitarity

A number of recent references have pointed out that an N-particle system having short-range interactions at S-wave and/or P-wave unitarity can exhibit modified threshold behavior for various reactive processes. But the question of how close to unitarity one must get in order to observe such modifications has not been addressed. The present study quantities this question by treating cases involving 3- or 4-neutrons, at the physical value of the neutron-neutron singlet scattering length a and at artificially altered values. One major conclusion is that the neutron-neutron scattering length is not yet sufficiently large for the 3n or 4n systems to demonstrate the unitarity threshold exponent.

hep-ph↗

arXiv2024

Estimating theoretical uncertainties of the two-nucleon observables by using backpropagation

We present a novel approach to calculating theoretical uncertainties in few-nucleon calculations, making use of automatic differentiation via backpropagation, which is particularly efficient when there are many input variables but only a few outputs. The methods described in this paper constitute tools that can be used to investigate the properties of scalar functions used to define nuclear potentials and quantify their contribution to the uncertainty of few nucleon calculations. We demonstrate these methods in deuteron bound state and nucleon - nucleon scattering calculations. Backpropagation, implemented in the Python pytorch library, is used to calculate the gradients with respect to model parameters and propagate errors from these parameters to the deuteron binding energy and selected phase-shift parameters. The uncertainty values obtained using this approach are validated by directly sampling from the potential parameters. We find very good agreement between two ways of estimating that uncertainty.

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arXiv2022

Pion absorption from the lowest atomic orbital in 2H, 3H and 3He

The pi- + 2H -> n + n, pi- + 3H -> n + n + n, pi- + 3He -> n + d and pi- + 3He -> p + n + n capture reactions from the lowest atomic orbitals are studied under full inclusion of final state interactions. Our results are obtained with the single-nucleon and two-nucleon transition operators derived at leading order in chiral effective field theory. The initial and final three-nucleon states are calculated with the chiral nucleon-nucleon SMS potential up to N4LO+ augmented by the consistently regularized chiral N2LO three-nucleon potential. We found that absorption rates depend strongly on the nuclear pion absorption operator used, and its two-body parts change the rates by a few orders of magnitude. The final state interactions between nucleons generated by the two-nucleon forces are also important, while the three-nucleon interaction plays a visible role only in the pi- + 3He -> n + d reaction. Our absorption rate for the pi- + 2H -> n + n process is in good agreement with the experimental data from the hadronic ground-state broadening in pionic deuterium. The capture rates on 3He are also generally consistent with the spectroscopic data within error bars, though our central values are found to be systematically below the data. We show that for the three-body breakup processes the dominant contributions to the absorption rates arise from the quasi-free scattering and final-state interaction kinematical configurations.

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arXiv2022

Approximate method for helical particle trajectory reconstruction in high energy physics experiments

High energy physics experiments, in particular experiments at the LHC, require the reconstruction of charged particle trajectories. Methods of reconstructing such trajectories have been known for decades, yet the applications at High Luminosity LHC require this reconstruction to be fast enough to be suitable for online event filtering. A particle traversing the detector volume leaves signals in active detector elements from which the trajectory is reconstructed. If the detector is submerged in a uniform magnetic field that trajectory is approximately helical. Since a collision event results in the production of many particles, especially at high luminosities, the first phase of trajectory reconstruction is the formation of candidate trajectories composed of a small subset of detector measurements that are then subject of resource intensive precise track parameters estimation. In this paper, we suggest a new approach that could be used to perform this classification. The proposed procedure utilizes the $z$ coordinate in the longitudinal direction in addition to the $x, y$ coordinates in the plane perpendicular to the direction of the magnetic field. The suggested algorithm works equally well for helical trajectories with different proximities to the beamline which is beneficial when searching for products of particles with longer lifetimes.

physics.ins-det↗

arXiv2021

Perturbative treatment of three-nucleon force contact terms in three-nucleon Faddeev equations

We present a perturbative approach to solving the three-nucleon continuum Faddeev equation. This approach is particularly well suited to dealing with variable strengths of contact terms in a chiral three-nucleon force. We use examples of observables in the elastic nucleon-deuteron scattering as well as in the deuteron breakup reaction to demonstrate high precision of the proposed procedure and its capability to reproduce exact results. A significant reduction of computer time achieved by the perturbative approach in comparison to exact treatment makes this approach valuable for fine-tuning of the three-nucleon Hamiltonian parameters.

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arXiv2021

Comprehensive investigation of the symmetric space-star configuration in the nucleon-deuteron breakup

We examine a description of available cross section data for symmetric space star (SST) configurations in the neutron-deuteron (nd) and proton-deuteron (pd) breakup reaction using numerically exact solutions of the three-nucleon (3N) Faddeev equation based on two- and three-nucleon (semi)phenomenological and chiral forces. The predicted SST cross sections are very stable with respect to the underlying dynamics for incoming nucleon laboratory energies below $\approx 25$ MeV. We discuss possible origins of the surprising discrepancies between theory and data found in low-energy nd and pd SST breakup measurements.

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arXiv2020

Light nuclei with semilocal momentum-space regularized chiral interactions up to third order

We present a systematic investigation of few-nucleon systems and light nuclei using the current LENPIC interactions comprising semilocal momentum-space regularized two- and three-nucleon forces up to third chiral order (N$^2$LO). Following our earlier study utilizing the coordinate-space regularized interactions, the two low-energy constants entering the three-body force are determined from the triton binding energy and the differential cross section minimum in elastic nucleon-deuteron scattering. Predictions are made for selected observables in elastic nucleon-deuteron scattering and in the deuteron breakup reactions, for properties of the $A=3$ and $A=4$ nuclei, and for spectra of $p$-shell nuclei up to $A = 16$. A comprehensive error analysis is performed including an estimation of correlated truncation uncertainties for nuclear spectra. The obtained predictions are generally found to agree with experimental data within errors. Similar to the coordinate-space regularized chiral interactions at the same order, a systematic overbinding of heavier nuclei is observed, which sets in for $A \sim 10$ and increases with $A$.

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arXiv2020

Applications of the chiral potential with the semi-local regularization in momentum space to the disintegration processes

We apply the chiral potential with the momentum space semi-local regularization to the $^2$H and $^3$He photodisintegration processes and to the (anti)neutrino induced deuteron breakup reactions. Specifically, the differential cross section, the photon analyzing power and the final proton polarization have been calculated for the deuteron photodisintegration at the photon energies 30 MeV and 100 MeV. For the $^3$He photodisintegration predictions for the semi-inclusive and exclusive differential cross sections are presented for the photon energies up to 120 MeV. The total cross section is calculated for the (anti)neutrino disintegrations of the deuteron for the (anti)neutrino energies below 200 MeV. The predictions based on the Argonne V18 potential or on the older chiral force with regularization applied in coordinate space are used for comparison. Using the fifth order chiral nucleon-nucleon potential supplemented with dominant contributions from the sixth order allows us to obtain converged predictions for the regarded reactions and observables. Our results based on the newest semi-local chiral potentials show even smaller cutoff dependence for the considered electroweak observables than the previously reported ones with a coordinate-space regulator. However, some of the studied polarization observables in the deuteron photodisintegration process reveal more sensitivity to the regulator value than the unpolarized cross section. The chiral potential regularized semi-locally in momentum space yields also fast convergence of results with the chiral order. These features make the used potential a high quality tool to study electroweak processes.

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arXiv2020

Uncertainty of three-nucleon continuum observables arising from uncertainties of two-nucleon potential parameters

Propagation of uncertainties from two-nucleon potential parameters to three-nucleon observables, that is statistical errors for the neutron-deuteron elastic scattering and the deuteron breakup reaction at neutron laboratory energies up to 200 MeV is investigated. To that end we use the chiral nucleon-nucleon interaction with the semi-local momentum-space regularization at various orders of the chiral expansion, exploiting knowledge of the covariance matrix of its parameters. For both reactions we compare statistical uncertainties for chiral predictions with the uncertainties obtained in the same way but for the semi-phenomenological One-Pion-Exchange two-nucleon force. In addition for the elastic scattering we show also the truncation errors arising from restriction to a given order of chiral predictions, estimated among others within the Bayesian method, and the cutoff dependence of chiral predictions. We find that the resulting statistical uncertainty is smaller than the truncation errors for the chiral force at lower orders of the chiral expansion. At the higher orders of the chiral expansion and at low energies the statistical errors exceed the truncation ones but at intermediate and higher energies truncation errors are more important. Overall, magnitudes of the theoretical uncertainties are small and amount up to 0.5\%-4\%, depending on the observable and energy. We also find that the magnitudes of statistical uncertainties for the chiral and semi-phenomenological potentials are similar and that the dependence of predictions on the regularization parameter values is important at all investigated energies.

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arXiv2020

Three-nucleon force effects in inclusive spectra of the neutron-deuteron breakup reaction

We investigate the sensitivity of the non-exclusive nucleon induced deuteron breakup reaction to the three-nucleon interaction and distributions of three-nucleon force effects in inclusive spectra. To this end we solve the three-nucleon Faddeev equation at a number of incoming nucleon laboratory energies using the CD Bonn nucleon-nucleon interaction alone or combined with the 2{\pi}-exchange Tucson-Melbourne three-nucleon force. Based on these solutions energy spectra of an outgoing nucleon, at a specified detection angle as well as spectra integrated over that angle, are calculated. By integrating the spectra at a given angle over the energy of the outgoing nucleon the angular distributions of three-nucleon force effects in the breakup process are additionally obtained. Contrary to elastic nucleon-deuteron scattering, where at higher energies significant three-nucleon force effects were encountered for scattering angles around the minimum of the cross section, for the breakup process only moderate effects are found and they are restricted to forward angles. Results of the present investigation show that the large three-nucleon force effects found for some specific complete breakup configurations are reduced substantially in the incomplete spectra when averaging over contributing complete geometries is performed.

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arXiv2019

Investigation of interaction of circularly and linearly polarized photon beams with polarized 3He target

Photodisintegration of polarized 3He by linearly or circularily polarized photons offers a rich choice of observables which can be calculated with high precision using a rigorous scheme of three-nucleon Faddeev equations. Using the (semi)phenomenological AV18 nucleon-nucleon potential combined with the Urbana IX three-nucleon force we investigate sensitivity of 3He photodisintegration observables to underlying currents taken in the form of a single-nucleon current supplemented by two-body contributions for $\pi$- and $\rho$-meson exchanges or incorporated by the Siegert theorem. Promising observables to be measured for two- and three-body fragmentation of 3He are identified. These observables form a challenging test ground for consistent forces and currents being under derivation within the framework of chiral perturbation theory. For thre-body 3He photodisintegration several kinematicaly complete configurations, including SST and FSI, are also discussed.

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arXiv2019

From response functions to cross sections in neutrino scattering off the deuteron and trinucleons

Response functions, differential cross sections and total cross sections for several (anti)neutrino induced reactions on 2H, 3He and 3H are calculated in momentum space for (anti)neutrino energies up to 160 MeV, using the AV18 nucleon-nucleon potential and a single-nucleon weak current operator. This work is a continuation of our investigations presented in J. Golak et al. [Phys. Rev. C 98, 015501 (2018)].

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arXiv2019

Towards high-order calculations of three-nucleon scattering in chiral effective field theory

We discuss the current status of chiral effective field theory in the three-nucleon sector and present selected results for nucleon-deuteron scattering observables based on semilocal momentum-space-regularized chiral two-nucleon potentials together with consistently regularized three-nucleon forces up to third chiral order. Using a Bayesian model for estimating truncation errors, the obtained results are found to provide a good description of the experimental data. We confirm our earlier findings that a high-precision description of nucleon-deuteron scattering data below pion production threshold will require the theory to be pushed to fifth chiral order. This conclusion is substantiated by an exploratory study of selected short-range contributions to the three-nucleon force at that order, which, as expected, are found to have significant effects on polarization observables at intermediate and high energies. We also outline the challenges that will need to be addressed in order to push the chiral expansion of three-nucleon scattering observables to higher orders.

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arXiv2018

Dominance of tensor correlations in high-momentum nucleon pairs studied by (p,pd) reaction

The isospin character of p-n pairs at large relative momentum has been observed for the first time in the 16O ground state. A strong population of the J,T=1,0 state and a very weak population of the J,T=0,1 state were observed in neutron pick up domain of 16O(p,pd) at 392 MeV. This strong isospin dependence at large momentum transfer is not reproduced by the distorted-wave impulse approximation calculations with known spectroscopic amplitudes. The results indicate the presence of high-momentum protons and neutrons induced by the tensor interactions in ground state of 16O.

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arXiv2018

3H and 3He calculations without angular momentum decomposition

Results for the three nucleon (3N) bound state carried out using the "three dimensional" (3D) formalism are presented. In this approach calculations are performed without the use of angular momentum decomposition and instead rely directly on the 3D degrees of freedom of the nucleons. In this paper, for the first time, 3D results for $^{3}$He bound state with the inclusion of the screened Coulomb potential are compared to $^{3}$H calculations. Additionally, using these results, matrix elements of simple current operators related to the description of beta decay of the triton are given. All computations are carried out using the first generation of NNLO two nucleon (2N) and 3N forces from the Bochum - Bonn group.

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