Nuclear Theory·nucl-th

Wednesday·October 10, 2018

12 papers—5 primary·7 cross-listed

01
Magnetic Vortex Lattices in Finite Isospin Chiral Perturbation Theory
Prabal Adhikari🇺🇸
We study finite isospin chiral perturbation theory ( $χ$ PT) in a uniform external magnetic field and find the condensation energy of magnetic vortex lattices using the method of successive approximations (originally used by Abrikosov) near the upper critical point beyond which the system is in the normal vacuum phase. The difference between standard Ginzburg-Landau (GL) theory (or equivalently the Abelian Higgs model) and $χ$ PT arises due to the presence of additional momentum-dependent (derivative) interactions in $χ$ PT and the presence of electromagnetically neutral pions that interact with the charged pions via strong interactions but do not couple directly to the external magnetic field. We find that while the vortex lattice structure is hexagonal similar to vortices in GL theory, the condensation energy (relative to the normal vacuum state in a uniform, external magnetic field) is smaller (larger in magnitude) due to the presence of derivative interactions. Furthermore, we establish that neutral pions do not condense in the vortex lattice near the upper critical field.
nucl-thhep-phPLB(2019)·26 citations
02
Deep learning: Extrapolation tool for ab initio nuclear theory
Gianina Alina Negoita · James P. Vary · Glenn R. Luecke · Pieter Maris · Andrey M. Shirokov · Ik Jae Shin · Youngman Kim · Esmond G. Ng · Chao Yang · Matthew Lockner · Gurpur M. Prabhu
Ab initio approaches in nuclear theory, such as the no-core shell model (NCSM), have been developed for approximately solving finite nuclei with realistic strong interactions. The NCSM and other approaches require an extrapolation of the results obtained in a finite basis space to the infinite basis space limit and assessment of the uncertainty of those extrapolations. Each observable requires a separate extrapolation and most observables have no proven extrapolation method. We propose a feed-forward artificial neural network (ANN) method as an extrapolation tool to obtain the ground state energy and the ground state point-proton root-mean-square (rms) radius along with their extrapolation uncertainties. The designed ANNs are sufficient to produce results for these two very different observables in $^{6}$ Li from the ab initio NCSM results in small basis spaces that satisfy the following theoretical physics condition: independence of basis space parameters in the limit of extremely large matrices. Comparisons of the ANN results with other extrapolation methods are also provided.
nucl-thcs.LGPRC(2019)·66 citations
03
Real time description of fission
I. Stetcu🇺🇸 · A. Bulgac🇺🇸 · S. Jin🇺🇸 · K. J. Roche🇺🇸 · N. Schunck🇺🇸
Using the time-dependent superfluid local density approximation, the dynamics of fission is investigated in real time from just beyond the saddle to fully separated fragments. Simulations produced in this fully microscopic framework can help to assess the validity of the current approaches to fission, and to obtain estimate of fission observables. In this contribution, we concentrate on general aspects of fission dynamics.
nucl-thCERN Proc.(2019)·3 citations
04
Analysis of multinucleon transfer reactions involving spherical and statically deformed nuclei using a Langevin-type approach
Vyacheslav Saiko · Alexander Karpov
An increasing interest in multinucleon transfer processes in low-energy deep inelastic (damped) collisions of heavy ions appeared in recent years is due, in part, to by the possibility of using them as a method of production of heavy neutron-enriched nuclei. Possible promising projectile-target combinations include nuclei deformed in the ground state (e.g., actinides). Mutual orientations of such the nuclei in the entrance channel of the reaction may significantly influence the reaction dynamics. Available experimental data on multinucleon transfer reactions with statically deformed as well as spherical heavy nuclei 144Sm + 144Sm, 154Sm + 154Sm, 160Gd + 186W, and 208Pb + 208Pb/238U have been analyzed within the developed model. A good agreement of the calculated quantities with the corresponding experimental data is reached. Special attention in the paper is paid to analysis of production possibility of the neutron-enriched isotopes of heavy and superheavy elements in multinucleon transfer processes in the 238U + 238U/248Cm/254Es collisions.
nucl-thPRC(2019)·85 citations
05
Low-Energy Lepton-Proton Bremsstrahlung via Effective Field Theory
Pulak Talukdar🇮🇳 · Fred Myhrer🇺🇸 · Ghanashyam Meher🇮🇳 · Udit Raha🇮🇳
We present a systematic calculation of the cross section for the lepton-proton bremsstrahlung process l + p --> l' + p + gamma in chiral perturbation theory at next-to-leading order. This process corresponds to an undetected background signal for the proposed MUSE experiment at PSI. MUSE is designed to measure elastic scattering of low-energy electrons and muons off a proton target in order to extract a precise value of the proton's r.m.s. radius. We show that the commonly used peaking approximation, which is used to evaluate the radiative tail for the elastic cross section, is not applicable for muon-proton scattering at the low-energy MUSE kinematics. Furthermore, we point out a certain pathology with the standard chiral power counting scheme associated with electron scattering, whereby the next-to-next-to-leading order contribution from the pion loop diagrams is kinematically enhanced and numerically of the same magnitude as the next-to-leading order corrections. We correct a misprint in a commonly cited review article.
nucl-thhep-phEPJA(2018)·9 citations
06
Inclusive Studies of Short-Range Correlations: Overview and New Results
Zhihong Ye🇺🇸 · John Arrington🇺🇸
We present an overview of Short-Range Correlations (SRC) studies using the inclusive measurement of the electron scattering off nuclei. A brief introduction of the origin of the SRC is given, followed by the survey of the two-nucleon SRC (2N-SRC) study and its interesting connection to the EMC effect. A discussion of the three-nucleon SRC study (3N-SRC) measured by the Jefferson Lab's Hall B and Hall C experiments which showed contradictory results is given and, most importantly, we report a new result from the Hall A E08-014 experiment which was dedicated on studying 3N-SRC. Our high precision 4He/3He cross section ratios at the x > 2 region do not show a 3N-SRC plateau as predicted by the naive SRC model. To further investigate the 3N-SRC as well as the Isospin effect of the SRC, we have designed several approved experiments in Hall A and in Hall C, including the Tritium experiments using the mirror nuclei (3H and 3He) which are currently running in Hall A.
↳ nucl-exhep-phnucl-th9 citations
07
Progress in the Nucleon Electric Dipole Moment Calculations in Lattice QCD
S. Syritsyn🇺🇸 · T. Izubuchi🇺🇸 · H. Ohki🇺🇸
Electric dipole moments (EDMs), which are sought as evidence of CP violation, require lattice calculations to connect constraints from experiments to limits on the strong CP violation within QCD or CP violation in new physics beyond the standard model. Nucleon EDM calculations on a lattice are notoriously hard due to large statistical noise, chiral symmetry violating effects, and potential mixing of the EDM and the anomalous magnetic moment of the nucleon. In this report, details of ongoing lattice calculations of proton and neutron EDMs induced by the QCD $θ$ -term and the quark chromo-EDM, the lowest-dimension effective CP-violating quark-gluon interaction are presented. Our calculation employs chiral-symmetric fermion discretization. An assessment of feasibility of nucleon EDM calculations at the physical point is discussed.
↳ hep-lathep-phnucl-th7 citations
08
Chiral spiral in the presence of chiral imbalance
Michael Thies🇩🇪
The phase diagram of the two-dimensional Nambu-Jona-Lasinio (or chiral Gross-Neveu) model is characterized by an order parameter in the form of a chiral spiral. Its radius vanishes at a critical temperature, its period depends only on the chemical potential. We generalize these findings to chirally imbalanced systems by including a chiral chemical potential $μ_{5}$ . The relationship between the present, static approach and a previous, time dependent one is traced back to a half-local symmetry which the NJL $_{2}$ model shares with massless Dirac fermions, but which has been neglected so far. The structure of chiral spiral matter is further elucidated by computing fermion and antifermion momentum distribution functions, using a Bogoliubov transformation.
↳ hep-thhep-phnucl-thPRD(2018)·12 citations
09
Simulations of Subatomic Many-Body Physics on a Quantum Frequency Processor
Hsuan-Hao Lu🇺🇸 · Natalie Klco🇺🇸 · Joseph M. Lukens🇺🇸 · Titus D. Morris🇺🇸 · Aaina Bansal🇺🇸 · Andreas Ekström🇸🇪 · Gaute Hagen🇺🇸 · Thomas Papenbrock🇺🇸 · Andrew M. Weiner🇺🇸 · Martin J. Savage🇺🇸 · Pavel Lougovski🇺🇸
Simulating complex many-body quantum phenomena is a major scientific impetus behind the development of quantum computing, and a range of technologies are being explored to address such systems. We present the results of the largest photonics-based simulation to date, applied in the context of subatomic physics. Using an all-optical quantum frequency processor, the ground-state energies of light nuclei including the triton ( $^{3}$ H), $^{3}$ He, and the alpha particle ( $^{4}$ He) are computed. Complementing these calculations and utilizing a 68-dimensional Hilbert space, our photonic simulator is used to perform sub-nucleon calculations of the two-body and three-body forces between heavy mesons in the Schwinger model. This work is a first step in simulating subatomic many-body physics on quantum frequency processors---augmenting classical computations that bridge scales from quarks to nuclei.
↳ quant-phhep-lathep-phnucl-th+1PRA(2019)·146 citations
10
Meson cloud effects on kaon quark distribution functions and the SU(3) flavor symmetry
Akira Watanabe🇨🇳 · Takahiro Sawada🇯🇵 · Chung Wen Kao🇹🇼
We present our analysis on the valence quark distribution functions of the $K^{+}$ meson, $v^{K (u)} (x, Q^{2})$ and $v^{K (s ˉ)} (x, Q^{2})$ , taking into account the meson cloud effects in the framework of the chiral constituent quark model. Assuming appropriate bare quark distribution functions at the initial scale, evaluating the Goldstone boson dressing corrections with the model, and performing the QCD evolution, one can obtain the realistic dressed distributions at a certain scale. The phenomenologically satisfactory valence quark distribution of the pion was obtained in the previous study and there are available experimental data of the valence $u$ quark distribution ratio $v^{K (u)} (x, Q^{2}) / v^{π (u)} (x, Q^{2})$ , which enable us to obtain the kaon quark distribution functions. Besides presenting the resulting dressed distributions, we also show how the meson cloud effects affect the bare distributions in detail. A striking result is that the observed size of the SU(3) flavor symmetry breaking is considerably smaller than those seen in the preceding works based on other approaches.
↳ hep-phnucl-thNucl.Part.Phys.Proc.(2018)·3 citations
11
Hyperon-Nucleon Interaction from Lattice QCD at $(m_{π}, m_{K}) \approx (146, 525)$ MeV
Hidekatsu Nemura (for HAL QCD Collaboration)🇯🇵
Comprehensive study of generalized baryon-baryon ( $B B$ ) interaction including strangeness is one of the important subject of nuclear physics. In order to obtain a complete set of isospin-base baryon interactions, we perform a large scale lattice QCD calculation with almost physical quark masses corresponding to $(m_{π}, m_{K}) \approx (146, 525)$ MeV and large volume $(L a)^{4} = (96 a)^{4} \approx$ (8.1 fm) $^{4}$ . A large number of Nambu-Bethe-Salpeter (NBS) correlation functions from nucleon-nucleon ( $N N$ ) to $ΞΞ$ are calculated simultaneously. In this contribution, we focus on the strangeness $S = - 1$ channels of the hyperon interactions by means of HAL QCD method. Three potentials ((i) the $^{1} S_{0}$ central, (ii) the $^{3} S_{1} -^{3} D_{1}$ central, and (iii) $^{3} S_{1} -^{3} D_{1}$ tensor potentials) are presented for four isospin components; (1) the $Σ N - Σ N$ (the isospin $I = 3/2$ ) diagonal, (2) the $Λ N - Λ N$ diagonal, (3) the $Λ N \to Σ N$ transition, and (4) the $Σ N - Σ N$ ( $I = 1/2$ ) diagonal. Scattering phase shifts for $Σ N$ $(I = 3/2)$ system are presented.
↳ hep-latnucl-thAIP Conf.Proc.(2019)·10 citations
12
Productions of $f_{1} (1420)$ in pion and kaon induced reactions
Xiao-Yun Wang🇨🇳 · Jun He🇨🇳 · Quanjin Wang🇨🇳 · Hao Xu🇨🇳
The $f_{1} (1420)$ productions via pion and kaon induced reactions on a proton target are investigated in an effective Lagrangian approach. Two treatments of the $t$ -channel Born term, the Feynman model and the Regge model, are introduced to calculate the total and differential cross sections of the $π^{-} p \to f_{1} (1420) n$ and $K^{-} p \to f_{1} (1420) Λ$ reactions. The numerical results indicate that the experimental data of the total cross section of the $π^{-} p \to f_{1} (1420) n$ reaction can be reproduced in both the Feynman and the Regge models. Based on the parameters determined in the pion induced reaction, the cross sections of the $K^{-} p \to f_{1} (1420) Λ$ reaction, about which there is little data found in the literature, are predicted in the same beam momentum range. It is found that the line shapes of the total cross section obtained in a kaon induced reaction with two treatments are quite different. The cross sections for both reactions are at an order of magnitude of $μ$ b, or larger, at a beam momenta up to 10 GeV/c. The differential cross sections for both pion and kaon induced reactions are also present. It is found that in the Regge model, the $t$ channel provides a sharp increase at extreme forward angles. The results suggest that the experimental study of the $f_{1} (1420)$ in the kaon induced reaction on a proton target is as promising as in the pion induced reaction. Such an experimental measurement is also very helpful to clarify the production mechanism of the $f_{1} (1420)$ .
↳ hep-phnucl-exnucl-thPRD(2019)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE