Nuclear Theory·nucl-th

Monday·April 16, 2018

14 papers—8 primary·6 cross-listed

01
Nuclear applications of ANL-Osaka amplitudes: pion photo-productions on deuteron
S.X. Nakamura (Univ. Cruzeiro do Sul)🇧🇷 · H. Kamano (RCNP)🇯🇵 · T.-S. H. Lee (Argonne Nat'l Lab)🇺🇸 · T. Sato (RCNP, J-PARC)🇯🇵
The Argonne National Laboratory-Osaka University (ANL-Osaka) amplitudes (http://www.phy.anl.gov/theory/research/anl-osaka-pwa/) are applied to study pion photo-production reactions on the deuteron target. Within the multiple scattering formulation, we predict the cross sections of $d (γ, π) N N$ in the nucleon resonance region. The calculations include the impulse term and the final-state interaction (FSI) terms due to pion-exchange and nucleon-exchange. We show that the off-shell effects, calculated from the meson-exchange mechanisms, on the propagations of the exchanged nucleon and pion are significant in determining the reaction amplitudes. The FSI effects on the predicted cross sections are found to be important at energies near the $Δ$ (1232) resonance, and are still significant at higher energies. The results are in good agreement with most of the available data of $d (γ, π^{0}) n p$ and $d (γ, π^{-}) pp$ reactions.
nucl-thhep-phnucl-ex15 citations
02
Hydrodynamic attractor and the fate of perturbative expansions in Gubser flow
Gabriel Denicol🇧🇷 · Jorge Noronha🇧🇷
Perturbative expansions, such as the well-known gradient series and the recently proposed slow-roll expansion, have been recently used to investigate the emergence of hydrodynamic behavior in systems undergoing Bjorken flow. In this paper we determine for the first time the large order behavior of these perturbative expansions in relativistic hydrodynamics in the case of Gubser flow. While both series diverge, the slow-roll series can provide a much better overall description of the system's dynamics than the gradient expansion when both series are truncated at low orders. The truncated slow-roll series can also describe the attractor solution of Gubser flow as long as the system is sufficiently close to equilibrium near the origin (i.e., $ρ = 0$ ) in $d S_{3} \otimes R$ . Differently than the case of Bjorken flow, here we show that the Gubser flow attractor solution is not solely a function of the effective Knudsen number $τ_{R} σ_{μν} σ^{μν} \sim τ_{R} tanh ρ$ . Our results give further support to the idea that new \emph{resummed} constitutiv relations between dissipative currents and the gradients of conserved quantities can emerge in systems far from equilibrium that are beyond the regime of validity of the usual gradient expansion.
nucl-thhep-phhep-thPRD(2019)·73 citations
03
On the spin-isospin decomposition of nuclear symmetry energy
Wenmei Guo · M. Colonna · V. Greco · U. Lombardo · H. J. Schulze
The decomposition of nuclear symmetry energy into spin and isospin components is discussed to elucidate the underlying properties of the NN bare interaction. This investigation was carried out in the framework of the Brueckner-Hartree-Fock theory of asymmetric nuclear matter with consistent two and three body forces. It is shown the interplay among the various two body channels in terms of isospin singlet and triplet components as well as spin singlet and triplet ones. The broad range of baryon densities enables to study the effects of three body force moving from low to high densities.
nucl-thCPC(2020)·2 citations
04
Three-level mixing model for nuclear chiral rotation: Role of planar component
Q. B. Chen · K. Starosta · T. Koike
Three- and two-level mixing models are proposed to understand the doubling of states at the same spin and parity in triaxially-deformed atomic nuclei with odd numbers of protons and neutrons. The Particle-Rotor Model for such nuclei is solved using the newly proposed basis which couples angular momenta of two valence nucleons and the rotating triaxial mean-field into left-handed $∣ L ⟩$ , right-handed $∣ R ⟩$ , and planar $∣ P ⟩$ configurations. The presence and the impact of the planar component is investigated as a function of the total spin for mass A $\approx$ 130 nuclei with the valence h $_{11/2}$ proton particle, valence h $_{11/2}$ neutron hole and the maximum difference between principle axes allowed by the quadrupole deformation of the mean field. It is concluded that at each spin value the higher-energy member of a doublet of states is built on the anti-symmetric combination of $∣ L ⟩$ and $∣ R ⟩$ and is free of the $∣ P ⟩$ component, indicating that it is of pure chiral geometry. For the lower-energy member of the doublet, the contribution of the $∣ P ⟩$ component to the eigenfunction first decreases and then increases as a function of the total spin. This trend as well as the energy splitting between the doublet states are both determined by the Hamiltonian matrix elements between the planar ( $∣ P ⟩$ ) and non-planar ( $∣ L ⟩$ and $∣ R ⟩$ ) subspaces of the full Hilbert space.
nucl-thnucl-exPRC(2018)·18 citations
05
Interplay of drag by hot matter and electromagnetic force on the directed flow of heavy quarks
Sandeep Chatterjee🇵🇱 · Piotr Bozek🇵🇱
Rapidity-odd directed flow in heavy ion collisions can originate from two very distinct sources in the collision dynamics i. an initial tilt of the fireball in the reaction plane that generates directed flow of the constituents independent of their charges, and ii. the Lorentz force due to the strong primordial electromagnetic field that drives the flow in opposite directions for constituents carrying unlike sign charges. We study the directed flow of open charm mesons $D^{0}$ and $D^{0}$ in the presence of both these sources of directed flow. The drag from the tilted matter dominates over the Lorentz force resulting in same sign flow for both $D^{0}$ and $D^{0}$ , albeit of different magnitudes. Their average directed flow is about ten times larger than their difference. This charge splitting in the directed flow is a sensitive probe of the electrical conductivity of the produced medium. We further study their beam energy dependence; while the average directed flow shows a decreasing trend, the charge splitting remains flat from $s_{N N} = 60$ GeV to $5$ TeV.
nucl-thhep-phnucl-exPLB(2019)·75 citations
06
Radial flow in a multi phase transport model at FAIR energies
Soumya Sarkar🇮🇳 · Provash Mali🇮🇳 · Somnath Ghosh🇮🇳 · Amitabha Mukhopadhyay🇮🇳
Azimuthal distributions of radial velocities of charged hadrons produced in nucleus-nucleus $(A B)$ collisions are compared with the corresponding azimuthal distribution of charged hadron multiplicity in the framework of a multiphase transport (AMPT) model at two different collision energies. The mean radial velocity seems to be a good probe for studying radial expansion. While the anisotropic part of the distributions indicates a kind of collective nature of radial expansion, the isotropic part characterizes a thermal motion. The present investigation is carried out keeping the upcoming Compressed Baryonic Matter (CBM) experiment to be held at the Facility for Anti-proton Ion Research (FAIR) in mind. As far as high-energy heavy-ion interactions are concerned, CBM will supplement the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) experiments. In this context our simulation results at high baryochemical potential would be interesting, when scrutinized from the perspective of almost a baryon free environment achieved at RHIC and LHC.
nucl-thhep-phAdv.High Energy Phys.(2018)·1 citation
07
Shell-model interactions from chiral effective field theory
Lukas Huth · Victoria Durant · Johannes Simonis · Achim Schwenk
We construct valence-space Hamiltonians for use in shell-model calculations, where the residual two-body interaction is based on symmetry principles and the low-momentum expansion from chiral effective field theory. In addition to the usual free-space contact interactions, we also include novel center-of-mass--dependent operators that arise due to the Galilean invariance breaking by in-medium effects. We fitted the low-energy constants to 441 ground- and excited-state energies in the sd shell and obtained a root-mean-square derivation of 1.8 MeV at leading order and of 0.5 MeV at next-to-leading order, with natural low-energy constants in all cases. The developed chiral shell-model interactions enable order-by-order uncertainty estimates and show promising predictions for neutron-rich isotopes beyond the fitted data set.
nucl-thnucl-exPRC(2018)·26 citations
08
Charge symmetry violation in the doubly charmed cascade masses
K. K. Cushman🇦🇺 · A. W. Thomas🇦🇺 · R. D. Young🇦🇺
We investigate the electromagnetic contribution to the charge symmetry breaking in the $Ξ_{cc}$ baryon masses using a subtracted dispersion relation based on the Cottingham formula, following the formalism developed in an analysis of the octet baryon mass differences. In the absence of experimental information on the structure of charmed baryons, we use parameters for the electromagnetic structure of the $Ξ_{cc}$ and the difference in its charge states obtained from lattice QCD and estimates of SU(4) symmetry breaking. We report a conservative estimate for the mass splitting of the doubly charmed cascades to be 8 $\pm$ 9 MeV. While a smaller isospin splitting is compatible with this result, surprisingly it does not preclude the large splitting reported by the SELEX Collaboration. We identify those quantities which could be determined from lattice QCD and which would reduce the quoted theoretical uncertainty.
nucl-thhep-ph2 citations
09
Partonic quasidistributions in two-dimensional QCD
Yu Jia🇨🇳 · Shuangran Liang🇨🇳 · Xiaonu Xiong🇩🇪 · Rui Yu🇨🇳
As a sequel of our preceding work [1] we carry out a comprehensive comparative study between the quasi parton distribution functions (PDFs), distribution amplitudes (DAs) and their light-cone counterparts for various flavor-neutral mesons, in the context of the 't Hooft model, that is, the two-dimensional QCD in the large $N$ limit. In contrast to the original derivation via diagrammatic techniques exemplified by Dyson-Schwinger and Bethe-Salpeter equations, here we employ the Hamiltonian operator approach to reconstruct the celebrated 't Hooft equation in light-front quantization, and Bars-Green equations in equal-time quantization. The novelty of our derivation is to employ the soft momentum cutoff as the IR regulator. As a virtue of this operator approach, the functional form of the quasi distributions can be transparently built out of the Bars-Green wave functions and the Bogoliubov angle with the aid of bosonization technique. Equipped with various bound-state wave functions numerically inferred in [1], we then investigate how rapidly the quasi distributions approach their light-cone counterparts with the increasing meson momentum. We observe that, light mesons' quasi distributions approach the light-cone distributions in a slower pace than the heavy quarkonia. Curiously, lattice simulations of quasi distributions in four-dimensional QCD also discover this feature. Furthermore, we also compute the partonic light-cone PDF and quasi-PDF to one-loop order in perturbation theory, again employing the momentum cutoff as the IR regulator. We explicitly verify one of the backbones underlying the large momentum effective field theory (LaMET), namely, both quasi-PDFs and light-cone PDFs in $QCD_{2}$ indeed possess the same IR behavior at leading order in $1/ P^{z}$
↳ hep-thhep-lathep-phnucl-thPRD(2018)·44 citations
10
First Subleading Power Resummation for Event Shapes
Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Gherardo Vita🇺🇸 · Hua Xing Zhu🇨🇳
We derive and analytically solve renormalization group (RG) equations of gauge invariant non-local Wilson line operators which resum logarithms for event shape observables $τ$ at subleading power in the $τ ≪ 1$ expansion. These equations involve a class of universal jet and soft functions arising through operator mixing, which we call $θ$ -jet and $θ$ -soft functions. An illustrative example involving these operators is introduced which captures the generic features of subleading power resummation, allowing us to derive the structure of the RG to all orders in $α_{s}$ , and provide field theory definitions of all ingredients. As a simple application, we use this to obtain an analytic leading logarithmic result for the subleading power resummed thrust spectrum for $H \to g g$ in pure glue QCD. This resummation determines the nature of the double logarithmic series at subleading power, which we find is still governed by the cusp anomalous dimension. We check our result by performing an analytic calculation up to $O (α_{s}^{3})$ . Consistency of the subleading power RG relates subleading power anomalous dimensions, constrains the form of the $θ$ -soft and $θ$ -jet functions, and implies an exponentiation of higher order loop corrections in the subleading power collinear limit. Our results provide a path for carrying out systematic resummation at subleading power for collider observables.
↳ hep-phhep-thnucl-thJHEP(2018)·120 citations
11
Analysis of $Λ_{c} (2595)$ , $Λ_{c} (2625)$ , $Λ_{b} (5912)$ , $Λ_{b} (5920)$ based on a chiral partner structure
Yohei Kawakami🇯🇵 · Masayasu Harada🇯🇵
We construct an effective hadronic model including $Λ_{c} (2595)$ , $Λ_{c} (2625)$ , $Λ_{b} (5912)$ and $Λ_{b} (5920)$ regarding them as chiral partners to $Σ_{c} (2455)$ , $Σ_{c} (2520)$ , $Σ_{b}$ and $Σ_{b}^{*}$ , respectively, with respecting the chiral symmetry and heavy-quark spin-flavor symmetry. We determine the model parameters from the experimental data for relevant masses and decay widths of $Σ_{c}^{(*)}$ and $Λ_{c} (2595)$ . Then, we study the decay widths of $Λ_{c} (2625)$ , $Λ_{b} (5912)$ and $Λ_{b} (5920)$ . We find that, although the decay of $Λ_{c} (2595)$ is dominated by the resonant contribution through $Σ_{c} (2455)$ , non-resonant contributions are important for $Λ_{c} (2625)$ , $Λ_{b} (5912)$ and $Λ_{b} (5920)$ , which reflects the chiral partner structure. We also study the radiative decays of the baryons, and show that each of their widths is determined from the radiative decay width of their chiral partners.
↳ hep-phnucl-thPRD(2018)·32 citations
12
Crust breaking and the limiting rotational frequency of neutron stars
F. J. Fattoyev · C. J. Horowitz · Hao Lu
The limiting rotational frequency of neutron stars may be determined by the strength of their crusts. As a star spins up from accretion, centrifugal forces will cause the crust to fail. If the crust breaks unevenly, a rotating mass quadrupole moment will radiate gravitational waves (GW). This radiation can prevent further spin up and may be a promising source for continuous GW searches. We calculate that for a breaking strain (strength) of neutron star crust that is consistent with molecular dynamics simulations, the crust may fail at rotational frequencies in agreement with observations.
↳ astro-ph.HEgr-qcnucl-th26 citations
13
TMD gluon distributions at small x in the CGC theory
Elena Petreska🇳🇱
We review recent progress in the description of unpolarized transverse-momentum-dependent (TMD) gluon distributions at small $x$ in the color glass condensate (CGC) effective theory. We discuss the origin of the non-universality of TMD gluon distributions in the TMD factorization framework and in the CGC theory and the equivalence of the two approaches in their overlapping domain of validity. We show some applications of this equivalence, including recent results on the behavior of TMD gluon distributions at small $x$ , and on the study of gluon saturation. We discuss recent advances in the unification of the TMD evolution and the non-linear small- $x$ evolution of gluon distributions.
↳ hep-phnucl-thIJMPE(2018)·47 citations
14
Deconfinement Transition Effects on Cosmological Parameters and Primordial Gravitational Wave Spectrum
P. Castorina🇮🇹 · D. Lanteri🇮🇹 · S. Mancani🇮🇹
The cosmological evolution can be described in terms of directly measurable cosmological scalar parameters (deceleration $q$ , jerk $j$ , snap $s$ , etc...) constructed out of high order derivatives of the scale factor. Their behavior at the critical temperature of the Quantum Chromodynamics (QCD) phase transition in early universe could be a specific tool to study the transition, analogously to the fluctuations of conserved charges in QCD. We analyze the effect of the crossover transition from quarks and gluons to hadrons in early universe on the cosmological scalars and on the gravitational wave spectrum, by using the recent lattice QCD equation of state and including the electroweak degrees of freedom and different models of dark matter. Near the transition the cosmological parameters follow the behavior of QCD trace anomaly and of the speed of sound of the entire system. The effects of deconfinement turn out to be more relevant for the modification of the primordial spectrum of gravitational waves and our complete analysis, based on lattice QCD simulations and on the hadron resonance gas below the critical temperature, refines previous results.
↳ hep-phastro-ph.HEnucl-thPRD(2018)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE