Nuclear Theory·nucl-th

Friday·February 26, 2016

15 papers—7 primary·8 cross-listed

01
[Submitted on 24 Feb 2016]
From Bethe-Salpeter Wave Functions to Generalised Parton Distributions
C. Mezrag🇺🇸 · H. Moutarde🇫🇷 · J. Rodriguez-Quintero🇪🇸
We review recent works on the modelling of Generalised Parton Distributions within the Dyson-Schwinger formalism. We highlight how covariant computations, using the impulse approximation, allows one to fulfil most of the theoretical constraints of the GPDs. Specific attention is brought to chiral properties and especially the so-called soft pion theorem, and its link with the Axial-Vector Ward-Takahashi identity. The limitation of the impulse approximation are also explained. Beyond impulse approximation computations are reviewed in the forward case. Finally, we stress the advantages of the overlap of lightcone wave functions, and possible ways to construct covariant GPD models within this framework, in a two-body approximation.
Comments:
Review paper, 52 pages, 20 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1602.07722 [pdf]
Few Body Syst.(2016)·68 citations
02
[Submitted on 25 Feb 2016]
Investigating multi-channel quantum tunneling in heavy-ion fusion reactions with Bayesian spectral deconvolution
K. Hagino
Excitations of colliding nuclei during a nuclear reaction considerably affect fusion cross sections at energies around the Coulomb barrier. It has been demonstrated that such channel coupling effects can be represented in terms of a distribution of multiple fusion barriers. We here apply a Bayesian approach to analyze the so called fusion barrier distributions. This method determines simultaneously the barrier parameters and the number of barriers. We particularly investigate the $^{16}$ O+ $^{144}$ Sm and $^{16}$ O+ $^{154}$ Sm systems in order to demonstrate the effectiveness of the method. The present analysis indicates that the fusion barrier distribution for the former system is most consistent with three fusion barriers, even though the experimental data show only two distinct peaks.
Comments:
6 pages, 4 eps figures. The version to appear in Phys. Rev. C (rapid communications)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
1602.07801 [pdf]
PRC(2016)·8 citations
03
[Submitted on 25 Feb 2016]
Large-scale shell-model analysis of the neutrinoless $β β$ decay of $^{48}$ Ca
Y. Iwata🇯🇵 · N. Shimizu🇯🇵 · T. Otsuka🇯🇵 · Y. Utsuno🇯🇵 · J. Menendez🇯🇵 · M. Honma🇯🇵 · T. Abe🇯🇵
We present the nuclear matrix element for the neutrinoless double-beta decay of $^{48}$ Ca based on large-scale shell-model calculations including two harmonic oscillator shells ( $s d$ and $p f$ shells). The excitation spectra of $^{48}$ Ca and $^{48}$ Ti, and the two-neutrino double-beta decay of $^{48}$ Ca are reproduced in good agreement to experiment. We find that the neutrinoless double-beta decay nuclear matrix element is enhanced by about 30\% compared to $p f$ -shell calculations. This reduces the decay lifetime by almost a factor of two. The matrix-element increase is mostly due to pairing correlations associated with cross-shell $s d$ - $p f$ excitations. We also investigate possible implications for heavier neutrinoless double-beta decay candidates.
Comments:
Phys. Rev. Lett., accepted
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1602.07822 [pdf]
PRL(2016)·108 citations
04
[Submitted on 25 Feb 2016]
Thermal QRPA with Skyrme interactions and supernova neutral-current neutrino-nucleus reactions
Alan A. Dzhioev · A. I. Vdovin · G. Martínez-Pinedo · J. Wambach · Ch. Stoyanov
The Thermal Quasiparticle Random-Phase Approximation is combined with the Skyrme energy density functional method (Skyrme-TQRPA) to study the response of a hot nucleus to an external perturbation. For the sample nuclei, $^{56}$ Fe and $^{82}$ Ge, the Skyrme-TQRPA is applied to analyze thermal effects on the strength function of charge-neutral Gamow-Teller transitions which dominate neutrino-nucleus reactions at $E_{ν} ≲ 20$ ~MeV. For the relevant supernova temperatures we calculate the cross sections for inelastic neutrino scattering. We also apply the method to examine the rate of neutrino-antineutrino pair emission by hot nuclei. The cross sections and rates are compared with those obtained earlier from the TQRPA calculations based on the phenomenological Quasiparticle-Phonon Model Hamiltonian. For inelastic neutrino scattering on $^{56}$ Fe we also compare the Skyrme-TQRPA results to those obtained earlier from a hybrid approach that combines shell-model and RPA calculations.
Comments:
Minor revisions according to referee's recomendations
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.07869 [pdf]
PRC(2016)·24 citations
05
[Submitted on 25 Feb 2016]
The Skyrme-TQRPA calculations of electron capture on hot nuclei in pre-supernova environment
Alan A. Dzhioev · A. I. Vdovin · Ch. Stoyanov
We combine the thermal QRPA approach with the Skyrme energy density functional theory (Skyrme-TQRPA) for modelling the process of electron capture on nuclei in supernova environment. For a sample nucleus, $^{56}$ Fe, the Skyrme-TQRPA approach is applied to analyze thermal effects on the strength function of GT $_{+}$ transitions which dominate electron capture at $E_{e} \leq 30$ ~MeV. Several Skyrme interactions are used in order to verify the sensitivity of the obtained results to the Skyrme force parameters. Finite-temperature cross sections are calculated and the results are compared with those of the other model calculations.
Comments:
4 figures. arXiv admin note: text overlap with arXiv:1602.07869
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.07875 [pdf]
Phys.Atom.Nucl.(2016)·7 citations
06
[Submitted on 25 Feb 2016]
Regulator Artifacts in Uniform Matter for Chiral Interactions
A. Dyhdalo🇺🇸 · R.J. Furnstahl🇺🇸 · K. Hebeler🇩🇪 · I. Tews🇩🇪
Regulator functions applied to two- and three-nucleon forces are a necessary ingredient in many-body calculations based on chiral effective field theory interactions. These interactions have been developed recently with a variety of different cutoff forms, including regulating both the momentum transfer (local) and the relative momentum (nonlocal). While in principle any regulator that suppresses high momentum modes can be employed, in practice artifacts are inevitable in current power counting schemes. Artifacts from particular regulators may cause significant distortions of the physics or may affect many-body convergence rates, so understanding their nature is important. Here we characterize the differences between cutoff effects using uniform matter at Hartree-Fock and second-order in the interaction as a testbed. This provides a clean laboratory to isolate phase-space effects of various regulators on both two- and three-nucleon interactions. We test the normal-ordering approximation for three-nucleon forces in nuclear matter and find that the relative size of the residual 3N contributions is sensitive to the employed regularization scheme.
Comments:
29 pages, 27 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.08038 [pdf]
PRC(2016)·65 citations
07
[Submitted on 25 Feb 2016]
Towards Quantum Transport for Central Nuclear Reactions
Pawel Danielewicz (MSU NSCL) · Arnau Rios (U Surrey) · Brent Barker (Roosevelt U)
Nonequilibrium Green's functions represent a promising tool for describing central nuclear reactions. Even at the single-particle level, though, the Green's functions contain more information that computers may handle in the foreseeable future. In this study, we explore slab collisions in one dimension, first in the mean field approximation and demonstrate that only function elements close to the diagonal in arguments are relevant, in practice, for the reaction calculations. This bodes well for the application of the Green's functions to the reactions. Moreover we demonstrate that an initial state for a reaction calculation may be generated through adiabatic transformation of interactions. Finally, we report on our progress in incorporating correlations into the dynamic calculations.
Comments:
Contribution to Proc Workshop on Progress in Nonequilibrium Green's Functions VI, Lund U, Sweden, Aug 17-21, 2015, ed. C. Verdozzi; 13 pages, 13 figures. arXiv admin note: text overlap with arXiv:0906.4841
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.08047 [pdf]
J.Phys.Conf.Ser.(2016)·0 citations
08
[Submitted on 24 Feb 2016] (cross-list from hep-lat)
Remarks on the pion-nucleon sigma-term
Martin Hoferichter🇺🇸 · Jacobo Ruiz de Elvira🇩🇪 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪
The pion-nucleon $σ$ -term can be stringently constrained by the combination of analyticity, unitarity, and crossing symmetry with phenomenological information on the pion-nucleon scattering lengths. Recently, lattice calculations at the physical point have been reported that find lower values by about $3 σ$ with respect to the phenomenological determination. We point out that a lattice measurement of the pion-nucleon scattering lengths could help resolve the situation by testing the values extracted from spectroscopy measurements in pionic atoms.
Comments:
5 pages, 2 figures; version published in PLB
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07688 [pdf]
PLB(2016)·77 citations
09
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Elements of QED-NRQED Effective Field Theory: I. NLO scattering at leading power
Steven P. Dye🇺🇸 · Matthew Gonderinger🇺🇸 · Gil Paz🇺🇸
The proton radius puzzle, i.e. the large discrepancy in the extraction of the proton charge radius between regular and muonic hydrogen, challenges our understanding of the structure of the proton. It can also be an indication of a new force that couples to muons, but not to electrons. An effective field theory analysis using Non Relativistic Quantum Electrodynamics (NRQED) indicates that the muonic hydrogen result can be interpreted as a large, compared to some model estimates, muon-proton spin-independent contact interaction. The muonic hydrogen result can be tested by a muon-proton scattering experiment, MUSE, that is planned at the Paul Scherrer Institute in Switzerland. The typical momenta of the muons in this experiment are of the order of the muon mass. In this energy regime the muons are relativistic but the protons are still non-relativistic. The interaction between the muons and protons can be described by a hybrid QED-NRQED effective field theory. We present some elements of this effective field theory. In particular we consider $O (Z α)$ scattering up to power $m^{2} / M^{2}$ , where $m$ ( $M$ ) is the muon (proton) mass and $Z = 1$ for a proton, and $O (Z^{2} α^{2})$ scattering at leading power. We show how the former reproduces Rosenbluth scattering up to power $m^{2} / M^{2}$ and the latter the relativistic scattering off a static potential. Proton structure corrections at $O (Z^{2} α^{2})$ will be considered in a subsequent paper.
Comments:
15 pages, 3 figures. v2: text and references added, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07770 [pdf]
PRD(2016)·16 citations
10
[Submitted on 25 Feb 2016] (cross-list from hep-lat)
$Λ_{c} - N$ interaction from lattice QCD
Takaya Miyamoto · for HAL QCD Collaboration
We investigate the s-wave $Λ_{c} - N$ interaction for spin singlet systems( $^{1} S_{0}$ ) using the HAL QCD method. In our lattice QCD simulations, we employ gauge configurations generated by the PACS-CS Collaboration at $a = 0.0907 (13)$ fm on a $3 2^{3} \times 64$ lattice ( $L a = 2.902 (42)$ fm). We employ two ensembles, one at $m_{π} = 700 (1)$ MeV and the other at $m_{π} = 570 (1)$ MeV to study the quark mass dependence of the $Λ_{c} - N$ interactions. We calculate a $^{1} S_{0}$ central potential not only for the $Λ_{c} - N$ system but also for $Λ - N$ system to understand the role of heavy charm quarks in $Λ_{c} - N$ system. We find repulsion at short distance and attraction at mid-range for both the $Λ_{c} - N$ and the $Λ - N$ potentials. The short range repulsion of the $Λ_{c} - N$ potential is smaller than that of the $Λ - N$ potential, and the attraction of the $Λ_{c} - N$ potential is small compared with the $Λ - N$ potential. The phase shift and scattering length calculated with these potentials show that there exist no bound state for both the $Λ_{c} - N$ and $Λ - N$ systems for $m_{π} > 570$ MeV.
Comments:
7 pages, 3 figures, and 3 tables, Proceedings for the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe, Japan
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07797 [pdf]
PoS(2016)·15 citations
11
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Coherent Pion Production in Neutrino Nucleus Scattering
Kapil Saraswat🇮🇳 · Prashant Shukla🇮🇳 · Vineet Kumar🇮🇳 · Venktesh Singh🇮🇳
In this article, we study the coherent pion production in neutrino-nucleus interaction in the resonance region using the formalism based on partially conserved axial current (PCAC) theorem which relates the neutrino-nucleus cross section to the pion-nucleus elastic cross section. The pion nucleus elastic cross section is calculated using the Glauber model in terms of pion-nucleon cross sections obtained by parameterizing the experimental data. We calculate the differential and integrated cross sections for charged current coherent pion production in neutrino carbon scattering. The results of integrated cross section calculations are compared with the measured data. Predictions for the differential and integrated cross sections for coherent pion productions in neutrino iron scattering using above formalism are also made.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07820 [pdf]
PRC(2016)·10 citations
12
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Decay $B_{s} \to ϕ ℓ^{+} ℓ^{-}$ in covariant quark model
Stanislav Dubnička🇸🇰 · Anna Z. Dubničková🇸🇰 · Aidos Issadykov🇷🇺 · Mikhail A. Ivanov🇷🇺 · Andrej Liptaj🇸🇰 · Sayabek K. Sakhiyev🇰🇿
Our article is devoted to the study of the rare $B_{s} \to ϕ ℓ^{+} ℓ^{-}$ decay where $ℓ = μ, τ$ . We compute the relevant form factors in the framework of the covariant quark model with infrared confinement in the full kinematical momentum transfer region. The calculated form factors are used to evaluate branching fractions and polarization observables in the cascade decay $B \to ϕ (\to K^{+} K^{-}) ℓ^{+} ℓ^{-}$ . We compare the obtained results with available experimental data and the results from other theoretical approaches.
Comments:
16 pages, 13 figures. arXiv admin note: text overlap with arXiv:1511.04887
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.07864 [pdf]
PRD(2016)·27 citations
13
[Submitted on 25 Feb 2016] (cross-list from nucl-ex)
Unexpectedly large charge radii of neutron-rich calcium isotopes
R.F. Garcia Ruiz🇧🇪 · M. L. Bissell🇧🇪 · K. Blaum🇩🇪 · A. Ekstrom🇺🇸 · N. Frommgen🇩🇪 · G. Hagen🇺🇸 · M. Hammen🇩🇪 · K. Hebeler🇩🇪 · J.D. Holt🇨🇦 · G.R. Jansen🇺🇸 · M. Kowalska🇨🇭 · K. Kreim🇩🇪 and 10 other authors
Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain "magic" numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly-magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known Ca isotopes have been successfully described by nuclear theory, it is still a challenge to predict their charge radii evolution. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly-magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-rich atomic nuclei.
Comments:
Submitted version. See original publication (doi:10.1038/nphys3645) for final version
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1602.07906 [pdf]
Nat.Phys.(2016)·365 citations
14
[Submitted on 25 Feb 2016] (cross-list from quant-ph)
How to quantify coherence: Distinguishing speakable and unspeakable notions
Iman Marvian · Robert W. Spekkens
Quantum coherence is a critical resource for many operational tasks. Understanding how to quantify and manipulate it also promises to have applications for a diverse set of problems in theoretical physics. For certain applications, however, one requires coherence between the eigenspaces of specific physical observables, such as energy, angular momentum, or photon number, and it makes a difference which eigenspaces appear in the superposition. For others, there is a preferred set of subspaces relative to which coherence is deemed a resource, but it is irrelevant which of the subspaces appear in the superposition. We term these two types of coherence unspeakable and speakable respectively. We argue that a useful approach to quantifying and characterizing unspeakable coherence is provided by the resource theory of asymmetry when the symmetry group is a group of translations, and we translate a number of prior results on asymmetry into the language of coherence. We also highlight some of the applications of this approach, for instance, in the context of quantum metrology, quantum speed limits, quantum thermodynamics, and NMR. The question of how best to treat speakable coherence as a resource is also considered. We review a popular approach in terms of operations that preserve the set of incoherent states, propose an alternative approach in terms of operations that are covariant under dephasing, and we outline the challenge of providing a physical justification for either approach. Finally, we note some mathematical connections that hold among the different approaches to quantifying coherence.
Comments:
A non-technical summary of the results and applications is provided in the first section. V5 close to the published version. Typos corrected
Subjects:
Quantum Physics (quant-ph); cond-mat.dis-nn (cond-mat.dis-nn); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)
arXiv:
1602.08049 [pdf]
PRA(2016)·335 citations
15
[Submitted on 25 Feb 2016] (cross-list from hep-ph)
Measuring light-by-light scattering at the LHC and FCC
David d'Enterria🇨🇭 · Gustavo G. da Silveira🇧🇷
Elastic light-by-light scattering, $γ γ \to γ γ$ , can be measured in electromagnetic interactions of lead (Pb) ions at the Large Hadron Collider (LHC) and Future Circular Collider (FCC), using the large (quasi)real photon fluxes available in ultraperipheral collisions. The $γ γ \to γ γ$ cross sections for diphoton masses m $_{γ γ} >$ 5 GeV in pp, pPb, and PbPb collisions at LHC ( $s_{_{NN}}$ = 5.5, 8.8, 14 TeV) and FCC ( $s_{_{NN}}$ = 39, 63, 100 TeV) center-of-mass energies are presented. The measurement has controllable backgrounds in PbPb collisions, and one expects about 70 and 2500 signal events per year at the LHC and FCC respectively, after typical detector acceptance and reconstruction efficiency selections.
Comments:
7 pages, 3 figures. Proceedings EDS'15 Blois conference, July 2015, Corse
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1602.08088 [pdf]
6 citations

Affiliations

first authorsco-authorsvia INSPIRE