Nuclear Theory·nucl-th

Wednesday·June 21, 2017

15 papers—10 primary·5 cross-listed

01
Correlation Energy of Proton-Neutron Subsystem in Valence Orbit
Tomohiro Oishi🇮🇹 · Lorenzo Fortunato🇮🇹
Deuteron correlation energy (DCE) of the valence proton-neutron subsystem is evaluated by utilizing a simple three-body model. We focus on the $^{6}$ Li and $^{18}$ F nuclei assuming the doubly-closed core and the valence proton and neutron. Two interaction models, schematic density-dependent contact (SDDC) and Minnesota potentials, are utilized to describe the proton-neutron interaction. Evaluating DCE, we conclude that the proton-neutron binding in $^{6}$ Li can be stronger than its counterpart of a deuteron in vacuum. On the other hand, in $^{18}$ F, the energetic correlation is remarkably weak, and does not favor the bound, deuteron-like configuration. This significant difference between two systems can be understood from a competition between the proton-neutron kinetic and pairing energies, which are sensitive to the spatial extension of the wave function. This result indicates a remarkable dependence of the deuteron correlation to its environment and the valence orbits.
nucl-thnucl-exphysics.atm-clus0 citations
02
Three-body Unitarity with Isobars Revisited
M. Mai🇺🇸 · B. Hu🇺🇸 · M. Doring🇺🇸 · A. Pilloni🇺🇸 · A. Szczepaniak🇺🇸
The particle exchange model of hadron interactions can be used to describe three-body scattering under the isobar assumption. In this study we start from the 3->3 scattering amplitude for spinless particles, which contains an isobar-spectator scattering amplitude. Using a Bethe-Salpeter Ansatz for the latter, we derive a relativistic three-dimensional scattering equation that manifestly fulfills three-body unitarity and two-body unitarity for the sub-amplitudes. This property holds for energies above breakup and also in the presence of resonances in the sub-amplitudes.
nucl-thhep-phEPJA(2017)·108 citations
03
Multiple Chirality in Nuclear Rotation: A Microscopic View
P. W. Zhao🇺🇸
Covariant density functional theory and three-dimensional tilted axis cranking are used to investigate multiple chirality in nuclear rotation for the first time in a fully self-consistent and microscopic way. Two distinct sets of chiral solutions with negative and positive parities, respectively, are found in the nucleus 106Rh. The negative-parity solutions reproduce well the corresponding experimental spectrum as well as the B(M1)/B(E2) ratios of the transition strengths. This indicates that a predicted positive-parity chiral band should also exist. Therefore, it provides a further strong hint that multiple chirality is realized in nuclei.
nucl-thnucl-exPLB(2017)·91 citations
04
Four-body continuum effects in 11Be+d scattering
Pierre Descouvemont🇧🇪
We present a new reaction model, which permits the description of reactions where both colliding nuclei present a low threshold to breakup. The method corresponds to a four-body extension of the Continuum Discretized Coupled Channel (CDCC) model. We first discuss the theoretical formalism, and then apply the method to 11Be+d scattering at Ecm = 45.5 MeV. The 11Be nucleus and the deuteron are described by 10Be+n and p + n structures, respectively. The model involves very large bases, but we show that an accurate description of elastic-scattering data may be achieved only when continuum states of 11Be and of the deuteron are introduced simultaneously. We also discuss breakup calculations, and show that the cross section is larger for 11Be than for the deuteron. The present theory provides reliable wave functions that may be used in the analysis of (d,p) or (d,n) experiments involving radioactive beams.
nucl-thPLB(2017)·20 citations
05
Improved version of simplified method for including tensor effect in cluster models
N. Itagaki🇯🇵 · A Tohsaki🇯🇵
The tensor contribution can be directly incorporated in the cluster model in a simplified way. In conventional $α$ cluster models, the contribution of the non-central interactions exactly cancels because of the antisymmetrization effect and spatial symmetry of $α$ clusters. The mixing of breaking components of $α$ clusters to take into account the spin-orbit and tensor effects is needed. Previously we proposed a simplified method to include the spin-orbit effect, and also for the tensor part, a simplified model to directly take into account the contribution of the tensor interaction (called SMT) was introduced; however the contribution of the tensor interaction was quite limited. Here we improve SMT, which is called $i$ SMT. Using newly proposed $i$ SMT, the contribution of the tensor interaction in $^{4}$ He is more than $- 40$ MeV, four times larger than the previous version. The method is applied to four- $α$ cluster structure of $^{16}$ O. In $^{16}$ O, the tensor contribution is also large, and this is coming from the finite size effect for the distances among $α$ clusters with a tetrahedral configuration.
nucl-thPRC(2018)·24 citations
06
Two-nucleon emission in neutrino and electron scattering from nuclei: the modified convolution approximation
I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · T.W. Donnelly🇺🇸
The theoretical formalism of inclusive lepton-nucleus scattering in the two-nucleon emission channel is discussed in the context of a simplified approach, the modified convolution approximation. This allows one to write the 2p2h responses of the relativistic Fermi gas as a folding integral of two 1p1h responses with the energies and momenta transferred to each nucleon. The idea behind this method is to introduce different average momenta for the two initial nucleons in the matrix elements of the two-body current, with the innovation that they depend on the transferred energies and momenta. This method treats exactly the two-body phase space kinematics, and reduces the formulae of the response functions from seven-dimensional integrals over momenta to much simpler three-dimensional ones. The applicability of the method is checked by comparing with the full results within a model of electroweak meson-exchange currents. The predictions are accurate enough, especially in the low-energy threshold region where the average momentum approximation works the best.
nucl-thhep-phAnnals Phys.(2018)·14 citations
07
Onset of $η$ -meson binding in the He isotopes
N. Barnea🇮🇱 · E. Friedman🇺🇸 · A. Gal🇮🇱
The onset of binding $η$ (548) mesons in nuclei is studied in the He isotopes by doing precise $η N N N$ and $η N N N N$ few-body stochastic variational method calculations for two semi-realistic $N N$ potentials and two energy dependent $η N$ potentials derived from coupled-channel models of the $N^{*} (1535)$ nucleon resonance. The energy dependence of the $η N$ subthreshold input is treated self consistently. It is found that a minimal value of the real part of the $η N$ scattering length $a_{η N}$ close to 1 fm is required to bind $η$ mesons in $^{3}$ He, yielding then a few MeV $η$ binding in $^{4}$ He. The onset of $η$ -meson binding in $^{4}$ He requires that Re $a_{η N}$ exceeds 0.7 fm approximately. These results compare well with results of recent $η N N N$ and $η N N N N$ pionless effective field theory calculations. Related optical-model calculations are also discussed.
nucl-thhep-phnucl-exNPA(2017)·34 citations
08
Sampling General N-Body Interactions with Auxiliary Fields
Christopher Körber🇩🇪 · Evan Berkowitz🇩🇪 · Thomas Luu🇩🇪
We present a general auxiliary field transformation which generates effective interactions containing all possible N-body contact terms. The strength of the induced terms can analytically be described in terms of general coefficients associated with the transformation and thus are controllable. This transformation provides a novel way for sampling 3- and 4-body (and higher) contact interactions non-perturbatively in lattice quantum monte-carlo simulations. We show that our method reproduces the exact solution for a two-site quantum mechanical problem.
nucl-thcond-mat.str-elhep-latEPL(2017)·9 citations
09
New cluster approach on properties of 8-11Be isotopes with isospin-dependent spin-orbit potential
Mengjiao Lyu🇨🇳 · Zhongzhou Ren🇨🇳 · Hisashi Horiuchi🇯🇵 · Bo Zhou🇯🇵 · Yasuro Funaki🇨🇳 · Gerd Röpke🇩🇪 · Peter Schuck🇫🇷 · Akihiro Tohsaki🇯🇵 · Chang Xu🇨🇳 · Taiichi Yamada🇯🇵
The nonlocalized clustering approach is generalized to 8-11Be isotopes with isospin dependent spin-orbit potential. A new form of the Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function is introduced to provide a correct description for the {\sigma}-binding neutron in 11Be. Systematic calculations for 8-11Be isotopes are performed and results fit well with experimental values. The low energy spectrum of 11Be is also obtained, especially the correct spin-parity 1/2+ is reproduced for the intruder ground state. The exotic neutron halo structure of 11Be is studied by calculations of root-mean-square radii and density distribution. We obtain a large spatial distribution for the last valence neutron of 11Be, which fits the phenomenological extracted value from experimental data. The spectroscopic factor is also calculated and discussed for the 1/2+ ground state of 11Be.
nucl-th6 citations
10
Extending pairing energy density functional using pairing rotational moments of inertia
Nobuo Hinohara🇯🇵
The pairing energy density functionals (EDFs) that include the spatial derivative and kinetic terms of the pair densities are discussed. The coupling constants of the pairing EDF are adjusted to reproduce the experimental pairing rotational moment of inertia, and the pair-density derivative terms are shown to systematically improve the values of the pairing rotational moments of inertia in Sn and Pb isotopes. It is pointed out that the conventional average pairing gaps overestimate the experimental odd-even mass staggering in the presence of the pair-density derivative terms.
nucl-thJ.Phys.G(2018)·5 citations
11
Scattering processes and resonances from lattice QCD
Raul A. Briceno🇺🇸 · Jozef J. Dudek🇺🇸 · Ross D. Young🇦🇺
The vast majority of hadrons observed in nature are not stable under the strong interaction, rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy non-perturbative region, and in addition, many probes of the limits of the electroweak sector of the Standard Model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required non-perturbative evaluation of hadron observables. In this article, we review progress in the study of few-hadron reactions in which resonances and bound-states appear using lattice QCD techniques. We describe the leading approach which takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. We explain how from explicit lattice QCD calculations, one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.
↳ hep-lathep-phnucl-thRMP(2018)·416 citations
12
Parton model description of multiparticle azimuthal correlations in $p A$ collisions
Kevin Dusling🇺🇸 · Mark Mace🇺🇸 · Raju Venugopalan🇺🇸
In arXiv:1705.00745, an initial state "parton model" of quarks scattering off a dense nuclear target was shown to qualitatively reproduce the systematics of multiparticle azimuthal anisotropy cumulants measured in proton/deuteron-nucleus ( $p A$ ) collisions at RHIC and the LHC. The systematics included i) the behavior of the four-particle cumulant $c_{2} {4}$ , which generates a real four-particle second Fourier harmonic $v_{2} {4}$ , ii) the ordering $v_{2} {2} > v_{2} {4} \approx v_{2} {6} \approx v_{2} {8}$ for two-, four-, six-, and eight-particle Fourier harmonics, iii) the behavior of so-called symmetric cumulants $SC (2, 3)$ and $SC (2, 4)$ . These features of azimuthal multiparticle cumulants were previously interpreted as a signature of hydrodynamic flow; our results challenge this interpretation. We expand here upon our previous study and present further details and novel results on the saturation scale and transverse momentum ( $p_{⊥}$ ) dependence of multiparticle azimuthal correlations. We find that the dependence of $v_{2} {2}$ and $v_{2} {4}$ on the number of color domains in the target varies with the $p_{⊥}$ window explored. We extend our prior discussion of symmetric cumulants and compute as yet unmeasured symmetric cumulants. We investigate the $N_{c}$ dependence of $v_{2} {2}$ and $v_{2} {4}$ . We contrast our results, which include multiple scatterings of each quark off the target, to the Glasma graph approximation, where each quark suffers at most two gluon exchanges with the target. We find that coherent multiple scattering is essential to obtain a positive definite $v_{2} {4}$ . We provide an algorithm to compute expectation values of arbitrary products of the "dipole" lightlike Wilson line correlators.
↳ hep-phnucl-exnucl-thPRD(2018)·79 citations
13
Beyond integrability: Baryon-baryon backward scattering in the massive Gross-Neveu model
Michael Thies🇩🇪
Due to integrability, baryon-baryon scattering in the massless Gross-Neveu model at large N features only forward elastic scattering. A bare mass term breaks integrability and is therefore expected to induce backward elastic scattering as well as inelastic reactions. We confirm these expectations by a study of baryon-baryon scattering in the massive Gross-Neveu model near the non-relativistic limit. This restriction enables us to solve the time-dependent Hartree-Fock equations with controlled approximations, using a combination of analytical methods from an effective field theory and the numerical solution of partial differential equations.
↳ hep-thhep-phnlin.SInucl-thPRD(2017)·5 citations
14
Baryon-Baryon Interactions and Spin-Flavor Symmetry from Lattice Quantum Chromodynamics
Michael L. Wagman🇺🇸 · Frank Winter🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸 · Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸
Lattice quantum chromodynamics is used to constrain the interactions of two octet baryons at the SU(3) flavor-symmetric point, with quark masses that are heavier than those in nature (equal to that of the physical strange quark mass and corresponding to a pion mass of $\approx 806 MeV$ ). Specifically, the S-wave scattering phase shifts of two-baryon systems at low energies are obtained with the application of Lüscher's formalism, mapping the energy eigenvalues of two interacting baryons in a finite volume to the two-particle scattering amplitudes below the relevant inelastic thresholds. The values of the leading-order low-energy scattering parameters in the irreducible representations of SU(3) are consistent with an approximate SU(6) spin-flavor symmetry in the nuclear and hypernuclear forces that is predicted in the large- $N_{c}$ limit of QCD. The two distinct SU(6)-invariant interactions between two baryons are constrained at this value of the quark masses, and their values indicate an approximate accidental SU(16) symmetry. The SU(3) irreducible representations containing the $N N (^{1} S_{0})$ , $N N (^{3} S_{1})$ and $\frac{1}{2} (Ξ^{0} n + Ξ^{-} p) (^{3} S_{1})$ channels unambiguously exhibit a single bound state, while the irreducible representation containing the $Σ^{+} p (^{3} S_{1})$ channel exhibits a state that is consistent with either a bound state or a scattering state close to threshold. These results are in agreement with the previous conclusions of the NPLQCD collaboration regarding the existence of two-nucleon bound states at this value of the quark masses.
↳ hep-lathep-phnucl-thPRD(2017)·125 citations
15
Constructing probability density function of net-proton multiplicity distributions using Pearson curve method
Nirbhay Kumar Behera🇰🇷 · Min Jung Kweon🇰🇷
The probability density functions of proton, anti-proton, and net-proton multiplicity distributions are constructed from the Beam Energy Scan results of the STAR experiment using the Pearson curve method. The constructed distributions of proton and anti-proton are compared with Poisson and Binomial distributions. The net-proton probability distributions are compared with Skellam distributions to study the O(4) criticality near the chiral crossover transition. The $C_{6} / C_{2}$ results estimated from the obtained PDFs are compared with Skellam and Binomial baselines for the Beam Energy Scan data. The current study shows some signatures of O(4) criticality, which can be further investigated by precision measurements of the cumulants and understanding the contribution of non-critical fluctuations to them. This study also provides a baseline for the higher-order cumulant measurement in the upcoming RHIC BES II program and future LHC run.
↳ nucl-exhep-exhep-phnucl-thEPJA(2022)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE