The $n+{}^3$H, $p+{}^3$He, $p+{}^3$H, and $n+{}^3$He elastic and charge exchange reactions at low energies are studied by means of the hyperspherical harmonic method. The considered nuclear Hamiltonians include modern two- and three-nucleon interactions, in particular results are reported in case of chiral two-nucleon potentials, with and without the inclusion of chiral three-nucleon (3N) interactions. A detailed study of the convergence and numerical stability of the method is presented. We have found that the effect the 3N force is in general tiny except for $p+{}^3$H scattering below the opening of the $n+{}^3$He channel. In such a case, the effect of 3N forces is appreciable and a clear dependence on the cutoff used to regularize the high-momentum tail of the interactions is observed. Such a dependence is related to the presence of the poorly known sharp $0^+$ resonance, considered to be the first excited state of ${}^4$He.
To obtain an understanding of the structure and reactions of nuclear systems from first principles has been a long-standing goal of nuclear physics. In this respect, few- and many-body systems provide a unique laboratory for studying nuclear interactions. During the past decades, the development of accurate representations of the nuclear force has undergone substantial progress. Particular emphasis has been devoted to chiral effective field theory (EFT), a low-energy effective representation of quantum chromodynamics (QCD). Within chiral EFT, many studies have been carried out dealing with the…
We investigate single-particle properties in infinite nuclear matter using a variety of interactions. One of the focal points is to study the impact of chiral three-nucleon forces on the nucleon self-energy and related quantities, such as spectral function and momentum distribution. We also present results for pairing correlations in nuclear matter. We find characteristic and systematic differences between the predictions obtained with the (softer) chiral interactions and those based on one-boson-exchange or phenomenology.
We investigate the importance of the three-nucleon (3N) force contact terms in elastic nucleon-deuteron (Nd) scattering by applying the N$^4$LO$^+$ chiral semi-local momentum space (SMS) regularized nucleon-nucleon (NN) chiral potential supplemented by N$^2$LO and all subleading N$^4$LO three-nucleon force (3NF) contact terms. Strength parameters of the contact terms were obtained by least squares fitting of theoretical predictions to cross section and analyzing powers data at three energies of the impinging nucleon. Although the N$^3$LO contributions to the 3N force were completely neglected,…
We calculate the complete $T$ matrices of the elastic nucleon-nucleon scattering up to third order in SU(3) heavy baryon chiral perturbation theory. The phase shifts with orbital angular momentum $L\geq 2$ and the mixing angles with $J\geq 2$ are evaluated by using low-energy constants that were extracted from the meson-baryon analysis. It turns out that our prediction is consistent with the empirical phase shifts and mixing angles data, and also the results from SU(2) heavy baryon chiral perturbation theory. The errors from the low-energy constants are analyzed in detail. Our calculation prov…
We demonstrate a computational scheme which drastically decreases the required time to get theoretical predictions based on chiral two- and three-nucleon forces for observables in three-nucleon continuum. For a three-nucleon force containing N short-range terms all workload is reduced to solving N+1 Faddeev-type integral equations. That done, computation of observables for any combination of strengths of the contact terms is done in a flash. We demonstrate on example of the elastic nucleon-deuteron scattering observables the high precision of the proposed emulator and its capability to reprodu…
Nucleon-nucleon scattering in a chiral constituent quark model
本文利用共振群方法研究了手征组分夸克模型中的核子-核子相互作用。计算的3S 1和1 S 0通道的相移表明，由于夸克交换和有效夸克-夸克相互作用的自旋-味结构的综合效应，存在一个强排斥核。这种对称结构源于夸克之间的赝标介子交换，是手征对称性自发破缺的结果。我们进行单通道和耦合通道的计算，并显示耦合的$ΔΔ$和隐藏的颜色CC通道上的相移的行为的作用。
We study perturbativeness of chiral nuclear forces in the $^3P_0$ channel. In previous works, the focus has been on one-pion exchange, and the applicable window of perturbative pion exchanges has been shown to span from threshold to the center-of-mass momentum $k \simeq$ 180 MeV. We will examine, instead, whether cancellation of short and long-range parts can sufficiently soften the $^3P_0$ chiral force to make it more amenable to perturbation theory. The result is encouraging, as the combined $^3P_0$ force is shown to be perturbative up to $k \simeq$ 280 MeV, covering many nuclear-structure c…
The truncation errors in equations of state (EOSs) of nuclear matter derived from the chiral nucleon-nucleon ($NN$) potentials at different expansion orders are analyzed by a Bayesian model. These EOSs are expanded as functions of a dimensionless parameter, $Q$, which is determined by Fermi momentum, $k_F$ and breakdown scale, $Λ_b$. The degree-of-belief (DoB) intervals predicted by the chiral effective field theory are calculated within the corresponding expansion coefficients and the specific prior probability distribution functions in terms of Bayes theorem. The truncation errors of EOSs, g…
Improved chiral nucleon-nucleon potential up to next-to-next-to-next-to-leading order
我们提出了改进的手征有效场论导出的核子-核子势，达到了次次次领头阶。我们认为，非定域动量空间调节器中采用的双核子势的参考。[E. Epelbaum，W. Gloeckle，U.- G. Meißner，Nucl.Phys.A747（2005）362]，[D.R.恩特姆河，巴西-地Machleidt，Phys.Rev.C68（2003）041001]不是最有效的选择，特别是因为它影响相互作用的长程部分。我们能够通过在坐标空间中使用适当的正则化来显着减少有限截止伪影，该正则化保持幅度的分析结构。新势不需要在参考文献[E. Epelbaum，W. Gloeckle，U.- G. Meißner，Nucl.Phys.A747（2005）362]，以切断两π介子交换的短程分量，并利用由π介子-核子散射确定的低能常数c_i和d_i，而无需任何微调。我们详细讨论了新势的构造和双核子观测量手征展开的收敛性。我们还介绍了一个新的程序估计的理论不确定性的手征展开，取代以前的依赖截止变差的截断。
