Nuclear Theory·nucl-th

Monday·July 6, 2020

8 papers—5 primary·3 cross-listed

01
Pion-mass dependence of the nucleon-nucleon interaction
Qian-Qian Bai🇨🇳 · Chun-Xuan Wang🇨🇳 · Yang Xiao🇨🇳 · Li-Sheng Geng🇨🇳
Nucleon-nucleon interactions, both bare and effective, play an important role in our understanding of the non-perturbative strong interaction, as well as nuclear structure and reactions. In recent years, tremendous efforts have been seen in the lattice QCD community to derive nucleon-nucleon interactions from first principles. Because of the daunting computing resources needed, most of such simulations were still performed with larger than physical light quark masses. In the present work, employing the recently proposed covariant chiral effective field theory (ChEFT), we study the light quark mass dependence of the nucleon-nucleon interaction extracted by the HALQCD group. It is shown that the pion-full version of the ChEFT can describe the lattice QCD data with $m_{π} = 469$ MeV and their experimental counterpart reasonably well, while the pion-less version can describe the lattice QCD data with $m_{π} = 672, 837, 1015, 1171$ MeV, for both the $^{1} S_{0}$ and $^{3} S_{1}$ - $^{3} D_{1}$ channels. The slightly better description of the single channel than the triplet channel indicates that higher order studies are necessary for the latter. Our results confirmed previous studies that the nucleon-nucleon interaction becomes more attractive for both the singlet and triplet channels as the pion mass decreases towards its physical value. It is shown that the virtual bound state in the $^{1} S_{0}$ channel remains virtual down to the chiral limit, while the deuteron only appears for a pion mass smaller than about 400 MeV. It seems that proper chiral extrapolations of nucleon-nucleon interaction are possible for pion masses smaller than 500 MeV, similar to the mesonic and one-baryon sectors.
nucl-thhep-lathep-phPLB(2020)·19 citations
02
ADG: Automated generation and evaluation of many-body diagrams II. Particle-number projected Bogoliubov many-body perturbation theory
P. Arthuis🇬🇧 · A. Tichai🇩🇪 · J. Ripoche🇫🇷 · T. Duguet🇫🇷
We describe the second version (v2.0.0) of the code ADG that automatically (1) generates all valid off-diagonal Bogoliubov many-body perturbation theory diagrams at play in particle-number projected Bogoliubov many-body perturbation theory (PNP-BMBPT) and (2) evaluates their algebraic expression to be implemented for numerical applications. This is achieved at any perturbative order $p$ for a Hamiltonian containing both two-body (four-legs) and three-body (six-legs) interactions (vertices). All valid off-diagonal BMBPT diagrams of order $p$ are systematically generated from the set of diagonal, i.e., unprojected, BMBPT diagrams. The production of the latter were described at length in https://doi.org/10.1016/j.cpc.2018.11.023 dealing with the first version of ADG. The automated evaluation of off-diagonal BMBPT diagrams relies both on the application of algebraic Feynman's rules and on the identification of a powerful diagrammatic rule providing the result of the remaining $p$ -tuple time integral. The new diagrammatic rule generalizes the one already identified in https://doi.org/10.1016/j.cpc.2018.11.023 to evaluate diagonal BMBPT diagrams independently of their perturbative order and topology. The code ADG is written in Python3 and uses the graph manipulation package NetworkX. The code is kept flexible enough to be further expanded throughout the years to tackle the diagrammatics at play in various many-body formalisms that already exist or are yet to be formulated.
nucl-thcond-mat.str-elphysics.atom-phphysics.chem-phComput.Phys.Commun.(2021)·15 citations
03
Properties of nuclear matter in relativistic Brueckner-Hartree-Fock model with high-precision charge-dependent potentials
Chencan Wang🇨🇳 · Jinniu Hu🇨🇳 · Ying Zhang · Hong Shen🇨🇳
Properties of nuclear matter are investigated in the framework of relativistic Brueckner-Hartree-Fock model with the latest high-precision charge-dependent Bonn (pvCD-Bonn) potentials, where the coupling between pion and nucleon is adopted as pseudovector form. These realistic pvCD-Bonn potentials are renormalized to effective nucleon-nucleon ( $N N$ ) interactions, $G$ matrices. They are obtained by solving the Blankenbecler-Sugar (BbS) equation in nuclear medium. Then, the saturation properties of symmetric nuclear matter are calculated with pvCD-Bonn A, B, C potentials. The energies per nucleon are around $- 10.72$ MeV to $- 16.83$ MeV at saturation densities, $0.139$ fm $^{- 3}$ to $0.192$ fm $^{- 3}$ with these three potentials, respectively. It clearly demonstrates that the pseudovector coupling between pion and nucleon can generate reasonable saturation properties comparing with pseudoscalar coupling. Furthermore, these saturation properties have strong correlations with the tensor components of $N N$ potentials, i.e., the $D$ -state probabilities of deuteron, $P_{D}$ to form a relativistic Coester band. In addition, the charge symmetry breaking (CSB) and charge independence breaking (CIB) effects are also discussed in nuclear matter from the partial wave contributions with these high-precision charge-dependent potentials. In general, the magnitudes of CSB from the differences between $nn$ and $pp$ potentials are about $0.05$ MeV, while those of CIB are around $0.35$ MeV from the differences between $n p$ and $pp$ potentials. Finally, the equations of state of asymmetric nuclear matter are also calculated with different asymmetry parameters. It is found that the effective neutron mass is larger than the proton one in neutron-rich matter.
nucl-thJ.Phys.G(2020)·14 citations
04
On coalescence as the origin of nuclei in hadronic collisions
Francesca Bellini🇨🇭 · Kfir Blum🇮🇱 · Alexander Phillip Kalweit🇨🇭 · Maximiliano Puccio🇨🇭
The origin of weakly-bound nuclear clusters in hadronic collisions is a key question to be addressed by heavy-ion collision (HIC) experiments. The measured yields of clusters are approximately consistent with expectations from phenomenological statistical hadronisation models (SHMs), but a theoretical understanding of the dynamics of cluster formation prior to kinetic freeze out is lacking. The competing model is nuclear coalescence, which attributes cluster formation to the effect of final state interactions (FSI) during the propagation of the nuclei from kinetic freeze out to the observer. This phenomenon is closely related to the effect of FSI in imprinting femtoscopic correlations between continuum pairs of particles at small relative momentum difference. We give a concise theoretical derivation of the coalescence--correlation relation, predicting nuclear cluster spectra from femtoscopic measurements. We review the fact that coalescence derives from a relativistic Bethe-Salpeter equation, and recall how effective quantum mechanics controls the dynamics of cluster particles that are nonrelativistic in the cluster centre of mass frame. We demonstrate that the coalescence--correlation relation is roughly consistent with the observed cluster spectra in systems ranging from PbPb to pPb and pp collisions. Paying special attention to nuclear wave functions, we derive the coalescence prediction for hypertriton and show that it, too, is roughly consistent with the data. Our work motivates a combined experimental programme addressing femtoscopy and cluster production under a unified framework. Upcoming pp, pPb and peripheral PbPb data analysed within such a programme could stringently test coalescence as the origin of clusters.
nucl-thhep-exhep-phPRC(2021)·69 citations
05
Extraction of baryonia from the lightest anti-protonic atoms
B. Loiseau🇫🇷 · S. Wycech🇵🇱
Anti-protonic hydrogen and helium atoms are analyzed. Level shifts and width are expressed in terms of $p ˉ$ -nucleon sub-threshold scattering lengths and volumes. Experimental data are compared to results obtained from the 2009 version of the Paris $N N ˉ$ interaction potential. Comparison with 1999 version is also made. Effects of $N N ˉ$ quasi-bound states are discussed. Atomic 2P hyperfine structure is calculated for antiprotonic deuterium and the significance of new measurements is indicated.
nucl-thhep-phnucl-exPRC(2020)·8 citations
06
An attractive spin-orbit potential from the Skyrme model
Chris Halcrow🇬🇧 · Derek Harland🇬🇧
We derive the nucleon-nucleon isoscalar spin-orbit potential from the Skyrme model and find good agreement with the Paris potential. This solves a problem that has been open for more than thirty years and gives a new geometric understanding of the spin-orbit force. Our calculation is based on the dipole approximation to skyrmion dynamics and higher order perturbation theory.
↳ hep-thnucl-thPRL(2020)·15 citations
07
Color Glass Condensate at next-to-leading order meets HERA data
G. Beuf🇫🇮 · H. Hänninen🇫🇮 · T. Lappi🇫🇮 · H. Mäntysaari🇫🇮
We perform the first dipole picture fit to HERA inclusive cross section data using the full next-to-leading order (NLO) impact factor combined with an improved Balitsky-Kovchegov evolution including the dominant effects beyond leading logarithmic accuracy at low $x$ . We find that three different formulations of the evolution equation that have been proposed in the recent literature result in a very similar description of HERA data, and robust predictions for future deep inelastic scattering experiments. We find evidence pointing towards a significant nonperturbative contribution to the structure function for light quarks, which stresses the need to extend the NLO impact factor calculation to massive quarks.
↳ hep-phnucl-thPRD(2020)·111 citations
08
Experimental constraints on shallow heating in accreting neutron-star crusts
Nicolas Chamel🇧🇪 · Anthea Francesca Fantina🇫🇷 · Julian-Leszek Zdunik🇵🇱 · Pawel Haensel🇵🇱
The observed thermal relaxation of transiently accreting neutron stars during quiescence periods in low-mass X-ray binaries suggests the existence of unknown heat sources in the shallow layers of neutron-star crust. Making use of existing experimental nuclear data, we estimate the maximum possible amount of heat that can be deposited in the outer crust of an accreting neutron star due to electron captures and pycnonuclear fusion reactions triggered by the burial of X-ray burst ashes.
↳ astro-ph.HEnucl-thPRC(2020)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE