arXiv subjects

R. Skibinski

Publications and source records attributed to R. Skibinski.

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.

nucl-th↗

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↗

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.

nucl-th↗

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.

nucl-th↗

arXiv2020

A comprehensive analysis of differential cross sections and analyzing powers in the proton-deuteron break-up channel at 135 MeV

A selection of measured cross sections and vector analyzing powers, Ax and Ay, are presented for the pd break-up reaction. The data are taken with a polarized proton beam energy of 135 MeV using the Big Instrument for Nuclear-polarization Analysis (BINA) at KVI, the Netherlands. With this setup, Ax is extracted for the first time for a large range of energies as well as polar and azimuthal angles of the two outgoing protons. For most of the configurations, the results at small and large relative azimuthal angles differ in behavior when comparing experimental data with the theoretical calculations. We also performed a more global comparison of our data with theoretical calculations using a chi-square ($χ^2$) analysis. The cross-section results show huge values of $χ^2$/d.o.f.. The absolute values of $χ^2$/d.o.f. for the components of vector analyzing powers, Ax and Ay, are smaller than the ones for the cross section, partly due to larger uncertainties for these observables. However, also for these observables no satisfactory agreement is found for all angular combinations. This implies that the present models of a three-nucleon force are not able to provide a satisfactory description of experimental data.

nucl-ex↗

arXiv2020

Analyzing powers in $d(\vec{p}, pp)n$ at intermediate and large scattering angles at $190$~MeV

Understanding of the exact nature of three-nucleon forces is the most challenging topic in the field of nuclear physics. Three-nucleon break-up reaction is a good tool to look into the underlying dynamics of the nuclear force, thanks to its rich kinematical phase space which has different levels of sensitivity to three-nucleon force effects. The recent studies on few-nucleon systems have revealed that the current nuclear force models cannot describe nucleon-deuteron scattering data accurately. In the present work, the analyzing powers of the proton-deuteron break-up reaction obtained using a 190 MeV polarized proton beam will be discussed. We present for the first time the vector analyzing powers for the kinematics in which one of the protons scatters to intermediate and large scattering angles at this energy. The results show a fairly good agreement with various theoretical predictions for both intermediate and large scattering angles of the break-up phase space.

nucl-ex↗

arXiv2019

Study of Three-Nucleon Dynamics in the dp breakup collisions using the WASA detector

Differential cross section for the 1H(d,pp)n breakup reaction at deuteron beam energy of 340 MeV has been measured with the use of WASA detector at COSY-Juelich. The set of proton-proton coincidences registered at Forward Detector has been analysed on dense grid of kinematic variables, giving in total around 5600 data points. The cross section data are compared to theoretical predictions based on the state-of-the-art nucleon-nucleon potentials, combined with three-nucleon force, Coulomb interaction or carried out in a relativistic regime.

nucl-ex↗

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)].

nucl-th↗

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.

nucl-ex↗

arXiv2018

Radiative pion capture in 2H, 3He and 3H

The $π^- + {^2{\rm H}} \rightarrow γ+ n + n$, $π^- + {^3{\rm He}} \rightarrow γ+ {^3{\rm H}}$, $π^- + {^3{\rm He}} \rightarrow γ+ n + d$, $π^- + {^3{\rm He}} \rightarrow γ+ n + n + p$ and $π^- + {^3{\rm H}} \rightarrow γ+ n + n + n$ capture reactions are studied with the AV18 two-nucleon potential and the Urbana~IX three-nucleon potential. We provide for the first time realistic predictions for the differential and total capture rates for all these processes, treating consistently the initial and final nuclear states. Our results are based on the single nucleon Kroll-Ruderman-type transition operator and concentrate on the full treatment of the nuclear final state interactions. They are compared with older theoretical predictions and experimental data.

nucl-th↗

arXiv2018

Momentum space treatment of inclusive neutrino scattering off the deuteron and trinucleons

The $\barν_e + {^2{\rm H}} \rightarrow e^+ + n + n$, $ν_e + {^2{\rm H}} \rightarrow e^- + p + p$, $\barν_l + {^2{\rm H}} \rightarrow \barν_l + {^2{\rm H}}$, $ν_l + {^2{\rm H}} \rightarrow ν_l + {^2{\rm H}}$, $\barν_l + {^2{\rm H}} \rightarrow \barν_l + p + n$, $ν_l + {^2{\rm H}} \rightarrow ν_l + p + n$, $\barν_e + {^3{\rm He}} \rightarrow e^+ + {^3{\rm H}}$, $\barν_l + {^3{\rm He}} \rightarrow \barν_l + {^3{\rm He}}$, $ν_l + {^3{\rm He}} \rightarrow ν_l + {^3{\rm He}}$, $\barν_l + {^3{\rm H}} \rightarrow \barν_l + {^3{\rm H}}$, $ν_l + {^3{\rm H}} \rightarrow ν_l + {^3{\rm H}}$, $\barν_e + {^3{\rm He}} \rightarrow e^+ + n + d$, $\barν_e + {^3{\rm He}} \rightarrow e^+ + n + n + p$, $\barν_l + {^3{\rm He}} \rightarrow \barν_l + p + d$, $\barν_l + {^3{\rm He}} \rightarrow \barν_l + p + p +n$, $ν_l + {^3{\rm H}} \rightarrow ν_l + n + d$ and $ν_l + {^3{\rm H}} \rightarrow ν_l + n + n + p$ reactions ($l= e, μ, τ$) are studied consistently in momentum space for (anti)neutrino energies up to 300 MeV. For most of these processes we provide predictions for the total cross sections and in the case of the (anti)neutrino-$^3$He and (anti)neutrino-$^3$H inelastic scattering we compute examples of essential response functions, using the AV18 nucleon-nucleon potential and a single-nucleon weak current operator. For the reactions with the deuteron we study relativistic effects in the final state kinematics and compare two-nucleon scattering states obtained in momentum and coordinate spaces. Our results from momentum space are compared with the theoretical predictions by G.Shen et al., Phys. Rev. C 86, 035503 (2012). The observed disagreement can be attributed to the differences in kinematics and in the weak current operator.

nucl-th↗

arXiv2018

Theoretical uncertainties of the elastic nucleon-deuteron scattering observables

Theoretical uncertainties of various types are discussed for the nucleon-deuteron elastic scattering observables at the incoming nucleon laboratory energies up to 200 MeV. We are especially interested in the statistical errors arising from uncertainties of parameters of a nucleon-nucleon interaction. The obtained uncertainties of the differential cross section and numerous scattering observables are in general small, grow with the reaction energy and amount up to a few percent at 200 MeV. We compare these uncertainties with the other types of theoretical errors like truncation errors, numerical uncertainties and uncertainties arising from using the various models of nuclear interaction. We find the latter ones to be dominant source of uncertainties of modern predictions for the three-nucleon scattering observables. To perform above mentioned studies we use the One-Pion-Exchange Gaussian potential derived by the Granada group, for which the covariance matrix of its parameters is known, and solve the Faddeev equation for the nucleon-deuteron elastic scattering. Thus beside studying theoretical uncertainties we also show a description of the nucleon-deuteron elastic scattering data by the One-Pion-Exchange Gaussian model and compare it with results obtained with other nucleon-nucleon potentials, including chiral N$^4$LO forces from the Bochum-Bonn and Moscow(Idaho)-Salamanca groups. In this way we confirm the usefulness and high quality of the One-Pion-Exchange Gaussian force.

nucl-th↗

arXiv2018

Nucleon-deuteron scattering with the JISP16 potential

The nucleon-nucleon J-matrix Inverse Scattering Potential JISP16 is applied to elastic nucleon-deuteron (Nd) scattering and the deuteron breakup process at the lab. nucleon energies up to 135 MeV. The formalism of the Faddeev equations is used to obtain 3N scattering states. We compare predictions based on the JISP16 force with data and with results based on various NN interactions: the CD Bonn, the AV18, the chiral force with the semi-local regularization at the 5th order of the chiral expansion and with low-momentum interactions obtained from the CD Bonn force as well as with the predictions from the combination of the AV18 NN interaction and the Urbana IX 3N force. JISP16 provides a satisfactory description of some observables at low energies but strong deviations from data as well as from standard and chiral potential predictions with increasing energy. However, there are also polarization observables at low energies for which the JISP16 predictions differ from those based on the other forces by a factor of two. The reason for such a behavior can be traced back to the P-wave components of the JISP16 force. At higher energies the deviations can be enhanced by an interference with higher partial waves and by the properties of the JISP16 deuteron wave function. In addition, we compare the energy and angular dependence of predictions based on the JISP16 force with the results of the low-momentum forces obtained with different values of the momentum cutoff parameter. We found that such low-momentum forces can be employed to interpret the Nd elastic scattering data only below some specific energy which depends on the cutoff parameter. Since JISP16 is defined in a finite oscillator basis, it has properties similar to low momentum interactions and its application to the description of Nd scattering data is limited to a low momentum transfer region.

nucl-th↗

arXiv2017

Workshop on Chiral Forces in Low Energy Nuclear Physics - the LENPIC Meeting

We present mini-proceedings of the international workshop on "Chiral Forces in Low Energy Nuclear Physics - the LENPIC Meeting" held at the Jagiellonian University, Krakow, Poland from February 10 to 11, 2017. The workshop focused on the new generation of chiral forces with the semi-local regularization and their applications to few- and many-nucleon systems. Included short contributions summarize talks given by E.Epelbaum, K.Hebeler, R.Roth, H.Witala, A.Calci, P.Reinert, J.P.Vary, H.Kamada, I.Ciepal, H.Krebs, H.Le, K.Topolnicki, K.Vobig and Yu.Volkotrub.

nucl-th↗

arXiv2016

Testing semi-local chiral two-nucleon interaction in selected electroweak processes

The recently developed semi-local improved chiral nucleon-nucleon interaction is used for the first time to study several electromagnetic and weak processes at energies below the pion production threshold. Cross sections and selected polarization observables for deuteron photodisintegration, nucleon-deuteron radiative capture, three-body $^3$He photodisintegration as well as capture rates for decays of the muonic $^2$H and $^3$He atoms are calculated. The Lippmann-Schwinger and Faddeev equations in momentum space are solved to obtain nuclear states. The electromagnetic current operator is taken as a single nucleon current supplemented by many-body contributions induced via the Siegert theorem. For muon capture processes the nonrelativistic weak current together with the dominant relativistic corrections is used. Our results compare well with experimental data, demonstrating the same quality as is observed for the semi-phenomenological AV18 potential. Compared to the older version of the chiral potential with a nonlocal regularization, a much smaller cut-off dependence is found for the state-of-art chiral local interaction employed in this paper. Finally, estimates of errors due to the truncation of the chiral expansion are given.

nucl-th↗

arXiv2016

Muon capture on 3H

The muon capture on 3H leading to muonic neutrino and three neutrons in the final state is studied under full inclusion of final state interactions. Predictions for the three-body break-up of 3H are calculated with the AV18 potential, augmented by the Urbana IX three-nucleon force. Our results are based on the single nucleon weak current operator comprising the dominant relativistic corrections. This work is a natural extension of our investigations of the muon capture on 3He leading to 3H or n+d or n+n+p and muonic neutrino in the final state, presented in Phys. Rev. C90, 024001 (2014).

nucl-th↗

arXiv2015

Few-nucleon systems with state-of-the-art chiral nucleon-nucleon forces

We apply improved nucleon-nucleon potentials up to fifth order in chiral effective field theory, along with a new analysis of the theoretical truncation errors, to study nucleon-deuteron (Nd) scattering and selected low-energy observables in 3H, 4He, and 6Li. Calculations beyond second order differ from experiment well outside the range of quantified uncertainties, providing truly unambiguous evidence for missing three-nucleon forces within the employed framework. The sizes of the required three-nucleon force contributions agree well with expectations based on Weinberg's power counting. We identify the energy range in elastic Nd scattering best suited to study three-nucleon force effects and estimate the achievable accuracy of theoretical predictions for various observables.

nucl-th↗

arXiv2015

Efficient calculation of chiral three-nucleon forces up to N3LO for ab initio studies

We present a novel framework to decompose three-nucleon forces in a momentum space partial-wave basis. The new approach is computationally much more efficient than previous methods and opens the way to ab initio studies of few-nucleon scattering processes, nuclei and nuclear matter based on higher-order chiral 3N forces. We use the new framework to calculate matrix elements of chiral three-nucleon forces at N2LO and N3LO in large basis spaces and carry out benchmark calculations for neutron matter and symmetric nuclear matter. We also study the size of the individual three-nucleon force contributions for $^3$H. For nonlocal regulators, we find that the sub-leading terms, which have been neglected in most calculations so far, provide important contributions. All matrix elements are calculated and stored in a user-friendly way, such that values of low-energy constants as well as the form of regulator functions can be chosen freely.

nucl-th↗