Nuclear Theory·nucl-th

Tuesday·June 14, 2016

11 papers—6 primary·5 cross-listed

01
[Submitted on 12 Jun 2016]
Investigation of constraints on few-neutron forces in neutron matter by empirical information on the neutron skin of 48Ca and 208Pb
Francesca Sammarruca🇺🇸
The neutron matter equation of state is calculated from two-neutron forces up to fifth order of the chiral expansion and the order-by-order convergence of the predictions is investigated. Based on these equations of state, the binding energies and the neutron and proton density distributions in 208Pb and 48Ca are derived, with particular attention to the neutron skins, the focal point of this paper. Anticipating future experiments which will provide reliable information on the weak charge density in nuclei, the theoretical uncertainties and the possibility of constraining the size of few-neutron forces in neutron matter are discussed.
Comments:
Revised version accepted for publication in Physical Review C; 9 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.03648 [pdf]
PRC(2016)·11 citations
02
[Submitted on 13 Jun 2016]
Consistency between SU(3) and SU(2) chiral perturbation theory for the nucleon mass
Xiu-Lei Ren (Beihang U. & Peking U., SKLNPT)🇨🇳 · L. Alvarez-Ruso (Valencia U., IFIC)🇪🇸 · Li-Sheng Geng (Beihang U.)🇨🇳 · T. Ledwig (Valencia U., IFIC)🇪🇸 · Jie Meng (Beihang U. & Peking U., SKLNPT & Stellenbosch U.)🇨🇳 · M.J. Vicente Vacas (Valencia U. & Valencia U., IFIC)🇪🇸
Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the $19$ low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order~\cite{Ren:2014vea} is supported by comparing the effective parameters (the combinations of the $19$ couplings) with the corresponding low-energy constants in the SU(2) sector~\cite{Alvarez-Ruso:2013fza}. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus providing support to the assumption made in Ref.~\cite{Alvarez-Ruso:2013fza}.
Comments:
11 pages, 1 table, 6, added reference, a few points clarified, matches the version accepted for publication
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1606.03820 [pdf]
PLB(2017)·16 citations
03
[Submitted on 13 Jun 2016]
Thermal blurring of event-by-event fluctuations provoked by rapidity conversion
Yutaro Ohnishi🇯🇵 · Masakiyo Kitazawa🇯🇵 · Masayuki Asakawa🇯🇵
We study the effect of thermal blurring caused by the use of (momentum-space) rapidity as a proxy of coordinate-space rapidity in experimental measurements of conserved charge fluctuations in relativistic heavy ion collisions. In theoretical studies assuming statistical mechanics, calculated fluctuations are those in a spatial volume. Experiments, on the other hand, can measure fluctuations only in a momentum-space in the final state. In a standard argument to compare experimental results for a momentum space with theoretical studies for a coordinate space, rapidities of particles are implicitly regarded as equivalent to their coordinate-space rapidity. We show that the relation of two fluctuations is significantly altered by the existence of the thermal motion, i.e. thermal blurring. We discuss that the thermal blurring can be regarded as a part of the diffusion process, and the effect can be understood by studying the rapidity window dependences of fluctuations. Centrality dependence of the thermal blurring effect is also discussed.
Comments:
9 pages, 7 figures; version accepted for publication in Phys. Rev. C, minor changes
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1606.03827 [pdf]
PRC(2016)·32 citations
04
[Submitted on 13 Jun 2016]
Perspective on the origin of hadron masses
Craig D. Roberts🇺🇸
The energy-momentum tensor in chiral QCD, $T_{μν}$ , exhibits an anomaly, viz. $Θ_{0} := T_{μμ} \neq = 0$ . Measured in the proton, this anomaly yields $m_{p}^{2}$ , where $m_{p}$ is the proton's mass; but, at the same time, when computed in the pion, the answer is $m_{π}^{2} = 0$ . Any attempt to understand the origin and nature of mass, and identify observable expressions thereof, must explain and unify these two apparently contradictory results, which are fundamental to the nature of our Universe. Given the importance of Poincaré-invariance in modern physics, the utility of a frame-dependent approach to this problem seems limited. That is especially true of any approach tied to a rest-frame decomposition of $T_{μν}$ because a massless particle does not possess a rest-frame. On the other hand, the dynamical chiral symmetry breaking (DCSB) paradigm, connected with a Poincaré-covariant treatment of the continuum bound-state problem, provides a straightforward, simultaneous explanation of both these identities, and also a diverse array of predictions, testable at existing and proposed facilities. From this perspective, $⟨ π ∣ Θ_{0} ∣ π ⟩ = 0$ owing to exact, symmetry-driven cancellations which occur between one-body dressing effects and two-body-irreducible binding interactions in any well-defined computation of the forward scattering amplitude that defines this expectation value in the pseudoscalar meson. The cancellation is incomplete in any other hadronic bound state, with a remainder whose scale is set by the size of one-body dressing effects.
Comments:
12 pages, 2 figures. Contribution to a Topical Issue of Few Body Systems, celebrating the journal's 30th birthday
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1606.03909 [pdf]
Few Body Syst.(2017)·97 citations
05
[Submitted on 13 Jun 2016]
From superdeformation to extreme deformation and clusterization in the N~Z nuclei of the A~40 mass region
D. Ray · A. V. Afanasjev
A systematic search for extremely deformed structures in the N~Z nuclei of the A~40 mass region has been performed for the first time in the framework of covariant density functional theory. At spin zero such structures are located at high excitation energies which prevents their experimental observation. The rotation acts as a tool to bring these exotic shapes to the yrast line or its vicinity so that their observation could become possible with future generation of $γ -$ tracking (or similar) detectors such as GRETA and AGATA. The major physical observables of such structures (such as transition quadrupole moments as well as kinematic and dynamic moments of inertia), the underlying single-particle structure and the spins at which they become yrast or near yrast are defined. The search for the fingerprints of clusterization and molecular structures is performed and the configurations with such features are discussed. The best candidates for observation of extremely deformed structures are identified. For several nuclei in this study (such as $^{36}$ Ar), the addition of several spin units above currently measured maximum spin of $16ℏ$ will inevitably trigger the transition to hyper- and megadeformed nuclear shapes.
Comments:
27 pages, 35 figures, submitted to Physical Review C, supplemental material is provided in file supplement.pdf
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.04019 [pdf]
PRC(2016)·25 citations
06
[Submitted on 13 Jun 2016]
Factorization Breaking of $A_{d}^{T}$ for polarized deuteron targets in a relativistic framework
Sabine Jeschonnek🇺🇸 · J. W. Van Orden🇺🇸
We discuss the possible factorization of the tensor asymmetry $A_{d}^{T}$ measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if p-waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the d-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the d-wave probability of the various wave functions.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1606.04072 [pdf]
PRC(2017)·5 citations
07
[Submitted on 12 Jun 2016] (cross-list from astro-ph.HE)
Astromaterial Science and Nuclear Pasta
M. E. Caplan · C. J. Horowitz
We define `astromaterial science' as the study of materials in astronomical objects that are qualitatively denser than materials on earth. Astromaterials can have unique properties related to their large density, though they may be organized in ways similar to more conventional materials. By analogy to terrestrial materials, we divide our study of astromaterials into hard and soft and discuss one example of each. The hard astromaterial discussed here is a crystalline lattice, such as the Coulomb crystals in the interior of cold white dwarfs and in the crust of neutron stars, while the soft astromaterial is nuclear pasta found in the inner crusts of neutron stars. In particular, we discuss how molecular dynamics simulations have been used to calculate the properties of astromaterials to interpret observations of white dwarfs and neutron stars. Coulomb crystals are studied to understand how compact stars freeze. Their incredible strength may make crust "mountains" on rotating neutron stars a source for gravitational waves that the Laser Interferometer Gravitational-Wave Observatory (LIGO) may detect. Nuclear pasta is expected near the base of the neutron star crust at densities of $1 0^{14}$ g/cm $^{3}$ . Competition between nuclear attraction and Coulomb repulsion rearranges neutrons and protons into complex non-spherical shapes such as sheets (lasagna) or tubes (spaghetti). Semi-classical molecular dynamics simulations of nuclear pasta have been used to study these phases and calculate their transport properties such as neutrino opacity, thermal conductivity, and electrical conductivity. Observations of neutron stars may be sensitive to these properties, and can be be used to interpret observations of supernova neutrinos, magnetic field decay, and crust cooling of accreting neutron stars. We end by comparing nuclear pasta shapes with some similar shapes seen in biological systems.
Comments:
16 pages, 7 figures, added references and revised for clarity, Reviews of Modern Physics in press
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); cond-mat.mtrl-sci (cond-mat.mtrl-sci); cond-mat.soft (cond-mat.soft); Nuclear Theory (nucl-th)
arXiv:
1606.03646 [pdf]
RMP(2017)·110 citations
08
[Submitted on 12 Jun 2016] (cross-list from hep-ph)
$η_{c}$ Elastic and Transition Form Factors: Contact Interaction and Algebraic Model
Marco A. Bedolla🇲🇽 · Khépani Raya🇲🇽 · J.J. Cobos-Martínez🇲🇽 · Adnan Bashir🇲🇽
For the flavor-singlet heavy quark system of charmonia in the pseudoscalar ( $η_{c} (1 S)$ ) channel, we calculate the elastic (EFF) and transition form factors (TFF) ( $η_{c} (1 S) \to γ γ^{*}$ ) for a wide range of photon momentum transfer squared ( $Q^{2}$ ). The framework for this analysis is provided by a symmetry-preserving Schwinger-Dyson equation (SDE) and Bethe-Salpeter equation (BSE) treatment of a vector $\times$ vector contact interaction (CI). We also employ an algebraic model (AM), developed earlier to describe the light quark systems. It correctly correlates infrared and ultraviolet dynamics of quantum chromodynamics (QCD). The CI results agree with the lattice data for low $Q^{2}$ . For $Q^{2} ⩾ Q_{0}^{2}$ , the results start deviating from the lattice results by more than $20%$ . $Q_{0}^{2} \approx 2.5 GeV^{2}$ for the EFF and $\approx 25 GeV^{2}$ for the TFF. We also present the results for the EFF, TFF as well as $η_{c} (1 S)$ parton distribution amplitude for the AM. Wherever the comparison is possible, these results are in excellent agreement with the lattice, perturbative QCD, the results obtained through an SDE-BSE study, employing refined truncations, as well as the experimental findings of the BABAR experiment.
Comments:
10 pages, 5 figures, 4 tables. arXiv admin note: text overlap with arXiv:1601.05639
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.03760 [pdf]
PRD(2016)·49 citations
09
[Submitted on 13 Jun 2016] (cross-list from hep-ph)
Pairing Phase Transitions of Matter under Rotation
Yin Jiang🇺🇸 · Jinfeng Liao🇺🇸
The phases and properties of matter under global rotation have attracted much interest recently. In this paper we investigate the pairing phenomena in a system of fermions under the presence of rotation. We find that there is a generic suppression effect on pairing states with zero angular momentum. We demonstrate this effect with the chiral condensation and the color superconductivity in hot dense QCD matter as explicit examples. In the case of chiral condensation, a new phase diagram in the temperature-rotation parameter space is found, with a nontrivial critical point.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1606.03808 [pdf]
PRL(2016)·190 citations
10
[Submitted on 13 Jun 2016] (cross-list from nucl-ex)
Cumulants of Net-Proton, Net-Kaon and Net-Charge Multiplicity Distributions in Au+Au Collisions at RHIC BES Energies from UrQMD Model
Ji Xu🇨🇳 · Shili Yu🇨🇳 · Feng Liu🇨🇳 · Xiaofeng Luo🇨🇳
Fluctuations of conserved quantities are sensitive observables to probe the signature of QCD phase transition and critical point in heavy-ion collisions. With the UrQMD model, we have studied the centrality and energy dependence of various order cumulants and cumulant ratios (up to fourth order) of net-proton,net-charge and net-kaon multiplicity distributions in Au+Au collisions at $s_{N N}$ = 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV. The model results show that the production mechanism of the particles and anti-particles have significant impacts on the cumulants of net-particles multiplicity distributions and show strong energy dependence. We also made comparisons between model calculations and experimental data measured in the first phase of the beam energy scan (BES) program by the STAR experiment at RHIC. The comparisons indicate that the baryon conservation effect strongly suppress the cumulants of net-proton distributions at low energies and the non-monotonic energy dependence for the net-proton {\KV} at the most central Au+Au collisions measured by the STAR experiment can not be described by the UrQMD model. Since there has no physics of QCD phase transition and QCD critical point implemented in the UrQMD, the model results provide us baselines and qualitative estimates about the non-critical background contributions to the fluctuations observables in heavy-ion collisions.
Comments:
9 pages, 10 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.03900 [pdf]
PRC(2016)·47 citations
11
[Submitted on 13 Jun 2016] (cross-list from nucl-ex)
Change of nuclear configurations in the neutrinoless double- $β$ decay of $^{130}$ Te $\to$ $^{130}$ Xe and $^{136}$ Xe $\to$ $^{136}$ Ba
J. P. Entwisle🇬🇧 · B. P. Kay🇺🇸 · A. Tamii🇯🇵 · S. Adachi🇯🇵 · N. Aoi🇯🇵 · J. A. Clark🇺🇸 · S. J. Freeman🇬🇧 · H. Fujita🇯🇵 · Y. Fujita🇯🇵 · T. Furuno🇯🇵 · T. Hashimoto🇰🇷 · C. R. Hoffman🇺🇸 and 15 other authors
The change in the configuration of valence protons between the initial and final states in the neutrinoless double- $β$ decay of $^{130}$ Te $\to$ $^{130}$ Xe and of $^{136}$ Xe $\to$ $^{136}$ Ba has been determined by measuring the cross sections of the ( $d$ , $^{3}$ He) reaction with 101-MeV deuterons. Together with our recent determination of the relevant neutron configurations involved in the process, a quantitative comparison with the latest shell-model and interacting-boson-model calculations reveals significant discrepancies. These are the same calculations used to determine the nuclear matrix elements governing the rate of neutrinoless double- $β$ decay in these systems.
Comments:
10 pages, 4 figures, 9 tables
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1606.04028 [pdf]
PRC(2016)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE