Nuclear Theory·nucl-th

Tuesday·July 19, 2016

15 papers—6 primary·9 cross-listed

07
Matter Neutrino Resonance Transitions above a Neutron Star Merger Remnant
Yong-Lin Zhu🇺🇸 · Albino Perego🇩🇪 · Gail C. McLaughlin🇺🇸
The Matter-Neutrino Resonance (MNR) phenomenon has the potential to significantly alter the flavor content of neutrinos emitted from compact object mergers. We present the first calculations of MNR transitions using neutrino self interaction potentials and matter potentials generated selfconsistently from a dynamical model of a three-dimensional neutron star merger. In the context of the single angle approximation, we find that Symmetric and Standard MNR transitions occur in both normal and inverted hierarchy scenarios. We examine the spatial regions above the merger remnant where propagating neutrinos will encounter the matter neutrino resonance and find that a significant fraction of the neutrinos are likely to undergo MNR transitions.
↳ hep-phastro-ph.HEnucl-thPRD(2016)·86 citations
08
Spectrum and electromagnetic transitions of bottomonium
Wei-Jun Deng🇨🇳 · Hui Liu🇨🇳 · Long-Cheng Gui🇨🇳 · Xian-Hui Zhong🇨🇳
Stimulated by the exciting progress in the observation of new bottomonium states, we study the bottomonium spectrum. To calculate the mass spectrum, we adopt a nonrelativistic screened potential model. The radial Schrödinger equation is solved with the three-point difference central method, where the spin-dependent potentials are dealt with non-perturbatively. With this treatment, the corrections of the spin-dependent potentials to the wave functions can be included successfully. Furthermore, we calculate the electromagnetic transitions of the $n S$ ( $n \leq 4$ ), $n P$ ( $n \leq 3$ ), and $n D$ ( $n \leq 2$ ) bottomonium states with a nonrelativistic electromagnetic transition operator widely applied to meson photoproduction reactions. Our predicted masses, hyperfine and fine splittings, electromagnetic transition widths and branching ratios of the bottomonium states are in good agreement with the available experimental data. Especially, the EM transitions of $Υ (3 S) \to χ_{b 1, 2} (1 P) γ$ , which were not well understood in previous studies, can be reasonably explained by considering the corrections of the spin-dependent interactions to the wave functions. We also discuss the observations of the missing bottomonium states by using radiative transitions. Some important radiative decay chains involving the missing bottomonium states are suggested to be observed. We hope our study can provide some useful references to observe and measure the properties of bottomonium mesons in forthcoming experiments.
↳ hep-phhep-exnucl-thPRD(2017)·89 citations
09
Properties of strongly magnetized ultradense matter and their imprints on magnetar pulsations
C. Vásquez Flores🇧🇷 · L. B. Castro🇧🇷 · G. Lugones🇧🇷
We investigate the effect of strong magnetic fields on the adiabatic radial oscillations of hadronic stars. We describe magnetized hadronic matter within the framework of the relativistic nonlinear Walecka model and integrate the equations of relativistic radial oscillations to determine the fundamental pulsation mode. We consider that the magnetic field increases, in a density dependent way, from the surface, where it has a typical magnetar value of $1 0^{15}$ G, to the interior of the star where it can be as large as $3 \times 1 0^{18}$ G. We show that magnetic fields of the order of $1 0^{18}$ G at the stellar core produce a significant change in the frequency of neutron star pulsations with respect to unmagnetized objects. If radial pulsations are excited in magnetar flares, they can leave an imprint in the flare lightcurves and open a new window for the study of highly magnetized ultradense matter.
↳ astro-ph.HEhep-phnucl-thPRC(2016)·7 citations
10
Forward Hadron Productions in Proton-Proton Collisions in Small- $x$ Formalism
Kazuhiro Watanabe🇨🇳 · Bo-Wen Xiao🇨🇳
Employing the so-called hybrid formalism, we calculate the cross section of inclusive hadron production in proton-proton collisions at forward rapidity in small- $x$ formalism at one-loop order. For the case of hadron production at forward rapidity, we can uses collinear parton distributions for projectile proton and $k_{⊥}$ dependent gluon distribution for target proton. We show that collinear divergences associated with initial and final state parton radiations are renormalized into parton distributions and fragmentation functions in terms of the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equation, respectively. Furthermore, rapidity divergence can be absorbed into the wave function of target proton which gives rise to the well-known Balitsky-Fadin-Kuraev-Lipatov equation. These divergences are completely separated from the short distance partonic hard parts, which is now finite at the next-to-leading order accuracy. The result presented in this paper can be reckoned as a baseline calculation without any non-linear QCD effects in small- $x$ formalism. As a consistency check, we compare our results with the previous calculation for non-linear proton-nucleus collisions in the small- $x$ formalism and find complete agreement in the dilute and large $N_{c}$ limit. In phenomenology, the direct comparison of the above two separate calculations can reveal the role and strength of the non-linear dynamics in high energy QCD, and thus help us reliably study the onset of gluon saturation when genuine non-linear interactions become important.
↳ hep-phnucl-thPRD(2016)·4 citations
11
Phases of kinky holographic nuclear matter
Matthew Elliot-Ripley🇬🇧 · Paul Sutcliffe🇬🇧 · Marija Zamaklar🇬🇧
Holographic QCD at finite baryon number density and zero temperature is studied within the five-dimensional Sakai-Sugimoto model. We introduce a new approximation that models a smeared crystal of solitonic baryons by assuming spatial homogeneity to obtain an effective kink theory in the holographic direction. The kink theory correctly reproduces a first order phase transition to lightly bound nuclear matter. As the density is further increased the kink splits into a pair of half-kink constituents, providing a concrete realization of the previously suggested dyonic salt phase, where the bulk soliton splits into constituents at high density. The kink model also captures the phenomenon of baryonic popcorn, in which a first order phase transition generates an additional soliton layer in the holographic direction. We find that this popcorn transition takes place at a density below the dyonic salt phase, making the latter energetically unfavourable. However, the kink model predicts only one pop, rather than the sequence of pops suggested by previous approximations. In the kink model the two layers produced by the single pop form the surface of a soliton bag that increases in size as the baryon chemical potential is increased. The interior of the bag is filled with abelian electric potential and the instanton charge density is localized on the surface of the bag. The soliton bag may provide a holographic description of a quarkyonic phase.
↳ hep-thhep-phnucl-thJHEP(2016)·35 citations
12
Single-inclusive jet production in electron-nucleon collisions through next-to-next-to-leading order in perturbative QCD
Gabriel Abelof🇺🇸 · Radja Boughezal🇺🇸 · Xiaohui Liu🇺🇸 · Frank Petriello🇺🇸
We compute the $O (α^{2} α_{s}^{2})$ perturbative corrections to inclusive jet production in electron-nucleon collisions. This process is of particular interest to the physics program of a future Electron Ion Collider (EIC). We include all relevant partonic processes, including deep-inelastic scattering contributions, photon-initiated corrections, and parton-parton scattering terms that first appear at this order. Upon integration over the final-state hadronic phase space we validate our results for the deep-inelastic corrections against the known next-to-next-to-leading order (NNLO) structure functions. Our calculation uses the $N$ -jettiness subtraction scheme for performing higher-order computations, and allows for a completely differential description of the deep-inelastic scattering process. We describe the application of this method to inclusive jet production in detail, and present phenomenological results for the proposed EIC. The NNLO corrections have a non-trivial dependence on the jet kinematics and arise from an intricate interplay between all contributing partonic channels.
↳ hep-phnucl-thPLB(2016)·50 citations
13
Lattice Prediction for Deeply Bound Doubly Heavy Tetraquarks
Anthony Francis🇨🇦 · Renwick J. Hudspith🇨🇦 · Randy Lewis🇨🇦 · Kim Maltman🇦🇺
We investigate the possibility of $q q^{'} b ˉ b ˉ$ tetraquark bound states using $n_{f} = 2 + 1$ lattice QCD ensembles with pion masses $≃ 164$ , $299$ , and $415$ MeV. Motivated by observations from heavy baryon phenomenology, we consider two lattice interpolating operators both of which are expected to couple efficiently to tetraquark states: one with diquark-antidiquark and one with a meson-meson structure. Using nonrelativistic QCD to simulate the bottom quarks, we study the $u d b ˉ b ˉ$ , $ℓ s b ˉ b ˉ$ channels with $ℓ = u, d$ , and find unambiguous signals for strong-interaction-stable $J^{P} = 1^{+}$ tetraquarks. These states are found to lie $189 (10)$ and $98 (7)$ MeV below the corresponding free two-meson thresholds.
↳ hep-lathep-exhep-phnucl-thPRL(2017)·244 citations
14
Nonlinear dynamics from the relativistic Boltzmann equation in the Friedmann-Lemaître-Robertson-Walker spacetime
D. Bazow🇺🇸 · G. S. Denicol🇧🇷 · U. Heinz🇺🇸 · M. Martinez🇺🇸 · J. Noronha🇧🇷
The dissipative dynamics of an expanding massless gas with constant cross section in a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe is studied. The mathematical problem of solving the full nonlinear relativistic Boltzmann equation is recast into an infinite set of nonlinear ordinary differential equations for the moments of the one-particle distribution function. Momentum-space resolution is determined by the number of non-hydrodynamic modes included in the moment hierarchy, i.e., by the truncation order. We show that in the FLRW spacetime the non-hydrodynamic modes decouple completely from the hydrodynamic degrees of freedom. This results in the system flowing as an ideal fluid while at the same time producing entropy. The solutions to the nonlinear Boltzmann equation exhibit transient tails of the distribution function with nontrivial momentum dependence. The evolution of this tail is not correctly captured by the relaxation time approximation nor by the linearized Boltzmann equation. However, the latter probes additional high-momentum details unresolved by the relaxation time approximation. While the expansion of the FLRW spacetime is slow enough for the system to move towards (and not away from) local thermal equilibrium, it is not sufficiently slow for the system to actually ever reach complete local equilibrium. Equilibration is fastest in the relaxation time approximation, followed, in turn, by kinetic evolution with a linearized and a fully nonlinear Boltzmann collision term.
↳ hep-phcond-mat.stat-mechgr-qchep-th+1PRD(2016)·57 citations
15
Ag diffusion in SiC high-energy grain boundaries: kinetic Monte Carlo study with first-principle calculations
Hyunseok Ko · Jie Deng · Izabela Szlufarska · Dane Morgan
The diffusion of silver (Ag) impurities in high energy grain boundaries (HEGBs) of cubic (3C) silicon carbide (SiC) is studied using an ab initio based kinetic Monte Carlo (kMC) model. This study assesses the hypothesis that the HEGB diffusion is responsible for Ag release in Tristructural-Isotropic fuel particles, and provides a specific example to increase understanding of impurity diffusion in highly disordered grain boundaries. The HEGB environment was modeled by an amorphous SiC. The structure and stability of Ag defects were calculated using density functional theory code. The defect energetics suggested that the fastest diffusion takes place via an interstitial mechanism in a-SiC. The formation energy of Ag interstitials and the kinetic resolved activation energies between them were well approximated with Gaussian distributions that were then sampled in the kMC. The diffusion of Ag was simulated with the effective medium model using kMC. At 1200-1600C, Ag in a HEGB is predicted to exhibit an Arrhenius type diffusion and with a diffusion prefactor and effective activation energy of (2.73+-1.09)*10-10 m2s-1 and 2.79+-0.18 eV, respectively. The comparison between HEGB results to other theoretical studies suggested not only that GB diffusion is predominant over bulk diffusion, but also that the HEGB is one of fastest grain boundary paths for Ag diffusion in SiC. The Ag diffusion coefficient in the HEGB shows a good agreement with ion-implantation measurements, but is 2-3 orders of magnitude lower than the diffusion coefficients extracted from integral release measurements. The discrepancy between GB diffusion and integral release measurements suggests that other contributions are responsible for the fast release of Ag in some experiments and we propose that these contributions may arise from radiation enhanced diffusion.
↳ cond-mat.mtrl-scinucl-thComput.Mater.Sci.(2016)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE