Nuclear Theory·nucl-th

Tuesday·November 6, 2018

19 papers—13 primary·6 cross-listed

01
Effective density functionals beyond mean field
Marcella Grasso🇫🇷
I present a review on non relativistic effective energy--density functionals (EDFs). An introductory part is dedicated to traditional phenomenological functionals employed for mean--field--type applications and to several extensions and implementations that have been suggested over the years to generalize such functionals, up to the most recent ideas. The heart of this review is then focused on density functionals designed for beyond--mean--field models. Examples of these studies are discussed. Starting from these investigations, some illustrations of {\it{ab--initio}}--based or {\it{ab--initio}}--inspired functionals are provided. Constructing functionals by building bridges with {\it{ab--initio}} models represents an extremely challenging and timely objective. This will eventually reduce/eliminate the empirical character of EDFs and link them with the underlying theory of QCD. Conclusions are presented in the last part of the review.
nucl-thPPNP(2019)·39 citations
02
Magic numbers for shape coexistence
I. E. Assimakis · D. Bonatsos · A. Martinou · S. Sarantopoulou · S. Peroulis · T. Mertzimekis · N. Minkov
The increasing deformation in atomic nuclei leads to the change of the classical magic numbers (2,8,20,28,50,82..) which dictate the arrangement of nucleons in complete shells. The magic numbers of the three-dimensional harmonic oscillator (2,8,20,40,70...) emerge at deformations around epsilon=0.6. At lower deformations the two sets of magic numbers antagonize, leading to shape coexistence. A quantitative investigation is performed using the usual Nilsson model wave functions and the recently introduced proxy-SU(3) scheme.
nucl-thAdv.Nucl.Phys.(2018)·3 citations
03
Inclusive breakup reaction of a two-cluster projectile on a two-fragment target: A genuine four-body problem
M. S. Hussein · C. A. Bertulani · B. V. Carlson · T. Frederico
We develop a four-body model for the inclusive breakup of two-fragment halo projectiles colliding with two-fragment targets. In the case of a short lived projectiles, such as halo nuclei, on a deuteron target, the model allows the extraction of the neutron capture cross section of such projectiles. We supply examples.
nucl-thSpringer Proc.Phys.(2020)·2 citations
04
First calculation of $q^$ on a quenched SU(3) plasma
Amit Kumar🇺🇸 · Abhijit Majumder🇺🇸 · Chiho Nonaka🇯🇵
The jet transport coefficient $q^$ is the leading transport coefficient that controls the modification of hard jets produced in heavy-ion collisions. This coefficient is inherently non-perturbative, and hence, is challenging to compute from first principles. In this report, we present a perturbative quantum chromodynamics (pQCD) and lattice gauge theory based formulation to study $q^$ . We formulate $q^$ within a 4-dimensional (4D) quenched SU(3) lattice. We consider a leading order diagram for a hard parton passing through the quark-gluon plasma. The non-perturbative part is expressed in terms of a non-local (two-point) Field-Strength-Field-Strength (FF) operator product which can be Taylor expanded after analytic continuation to the Euclidean region. Such an expansion allows us to write $q^$ in terms of the expectation of local operators. Finally, we present our results for $q^$ in a pure gluon plasma.
nucl-thhep-latnucl-exPoS(2018)·9 citations
05
Theory of two-pion photo- and electroproduction off the nucleon
Helmut Haberzettl🇺🇸 · Kanzo Nakayama🇺🇸 · Yongseok Oh🇰🇷
A theory of two-pion photo- and electroproduction off the nucleon is derived considering all explicit three-body mechanisms of the interacting $π π N$ system. The full three-body dynamics of the interacting $π π N$ system is accounted for by the Faddeev-type ordering structure of the Alt-Grassberger-Sandhas equations. The formulation is valid for hadronic two-point and three-point functions dressed by arbitrary internal mechanisms provided all associated electromagnetic currents are constructed to satisfy their respective (generalized) Ward-Takahashi identities. It is shown that coupling the photon to the Faddeev structure of the underlying hadronic two-pion production mechanisms results in a natural expansion of the full two-pion photoproduction current $M_{π π}^{μ}$ in terms of multiple dressed loops involving two-body subsystem scattering amplitudes of the $π π N$ system that preserves gauge invariance as a matter of course order by order in the number of (dressed) loops. A closed-form expression is presented for the entire gauge-invariant current $M_{π π}^{μ}$ with complete three-body dynamics. Individually gauge-invariant truncations of the full dynamics most relevant for practical applications at the no-loop, one-loop, and two-loop levels are discussed in detail. An approximation scheme to the full two-pion amplitude for calculational purposes is also presented. It approximates, systematically, the full amplitude to any desired order of expansion in the underlying hadronic two-body amplitude. Moreover, it allows for the approximate incorporation of all neglected higher-order mechanisms in terms of a phenomenological remainder current. The effect and phenomenological usefulness of this remainder current is assessed in a tree-level calculation of the $γ N \to K K Ξ$ reaction.
nucl-thhep-phnucl-exPRD(2019)·9 citations
06
Beyond mean-field approach for pear-shaped hypernuclei
H. J. Xia🇨🇳 · X. Y. Wu🇨🇳 · H. Mei🇺🇸 · J. M. Yao🇺🇸
We develop both relativistic mean field and beyond approaches for hypernuclei with possible quadrupole-octupole deformation or pear-like shapes based on relativistic point-coupling energy density functionals. The symmetries broken in the mean-field states are recovered with parity, particle-number, and angular momentum projections. We take $_{Λ}^{21}$ Ne as an example to illustrate the method, where the $Λ$ hyperon is put on one of the two lowest-energy orbits (labeled as $Λ_{s}, Λ_{p}$ ), respectively. We find that the $Λ$ hyperon in both cases disfavors the formation of a reflection-asymmetric molecular-like $^{16}$ O $+ α$ structure in $^{20}$ Ne, which is consistent with the Nilsson diagram for the hyperon in $(β_{2}, β_{3})$ deformation plane. In particular, we show that the negative-parity states with the configuration $^{20}$ Ne( $K^{π} = 0^{-}) \otimes Λ_{s}$ are close in energy to those with the configuration $^{20}$ Ne( $K^{π} = 0^{+}) \otimes Λ_{p}$ , even though they have very different structures. The $Λ_{s}$ ( $Λ_{p}$ ) becomes more and more concentrated around the bottom (top) of the "pear" with the increase of octupole deformation.
nucl-thSCPMA(2019)·14 citations
07
In-medium properties of SU(3) baryons
Ki-Hoon Hong🇰🇷 · Ulugbek Yakhshiev🇰🇷 · Hyun-Chul Kim🇰🇷
Changes of baryon properties in nuclear matter are investigated within the framework of an in-medium modified SU(3) Skyrme model. Introducing the medium functionals in the SU(2) sector and considering the alteration of kaon properties in nuclear medium, we are able to examine the medium modification of the nucleon and hyperons. The functionals introduced in the SU(2) sector are related to ordinary nuclear matter properties near the saturation point. The results indicate that the changes of the baryon properties in the strange sector are strongly correlated with the in-medium properties of kaons.
nucl-thhep-phSpringer Proc.Phys.(2020)·0 citations
08
Neutron width statistics using a realistic description of the neutron channel
P. Fanto🇺🇸 · G. F. Bertsch🇺🇸 · Y. Alhassid🇺🇸
A basic prediction of the statistical model of compound nucleus reactions is that the partial widths for decay into any open channel channel fluctuate according to the Porter-Thomas distribution (PTD). A recent experiment on $s$ - and $p$ -wave neutron scattering from platinum isotopes found that the experimental $s$ -wave partial neutron width distributions deviated substantially from the PTD. Several explanations for this finding have been proposed within the statistical model, but none has resolved this issue. Here, we review the application of a realistic resonance-reaction model to $s$ -wave neutron scattering from $^{194}$ Pt. Our main conclusion is that the PTD provides an excellent description of the partial neutron width distribution, provided that the secular energy dependence of the average neutron width is correctly described. Within a realistic range of model parameters, there can be a near-threshold bound or virtual state of the neutron channel that changes this secular dependence from the usual $E$ dependence, as proposed by Weidenmüller [1]. In this case, the use of the $E$ dependence to analyze the data will lead to apparent deviations from the PTD. We discuss the limited parameter range where such a near threshold state can have a significant effect.
nucl-thCERN Proc.(2019)·0 citations
09
Heavy quarkonia production at LHC and EIC using Basis Light-Front Quantization wavefunctions
Guangyao Chen🇺🇸 · Yang Li🇺🇸 · Kirill Tuchin🇺🇸 · James Vary🇺🇸
We study exclusive charmonium and bottomonium production in ultra-peripheral heavy-ion collisions and electron-ion collisions within the dipole picture. We employ heavy quarkonium light-front wavefunctions obtained within the basis light-front quantization framework, which has some features of the light-front holographic QCD. We focus on comparison with measurements of exclusive charmonium and bottomonium production in ultraperipheral $pp$ , $p$ Pb and PbPb collisions at LHC and find reasonable agreement with the cross sections. We also discuss the coherent production cross-section ratios of excited states to the ground state for charmonium and bottomonium, which exhibit insensitivity to the dipole model parameters. We show that electron-ion collisions provide an opportunity for a quantitative study of heavy quarkonium structure.
nucl-thnucl-exPRC(2019)·18 citations
10
A description of transverse momentum distributions in p+p collisions at RHIC and LHC energies
Jiaqi Hui🇨🇳 · Zhijin Jiang🇨🇳
It has long been debated whether the hydrodynamics is suitable for the smaller colliding systems such as p+p collisions. In this paper, by assuming the existence of longitudinal collective motion and long-range interactions in the hot and dense matter created in p+p collisions, the relativistic hydrodynamics incorporating with the nonextensive statistics is used to analyze the transverse momentum distributions of the particles. The investigations of present paper show that the hybrid model can give a good description of the currently available experimental data obtained in p+p collisions at RHIC and LHC energies, except for p and p^bar produced in the range of p_T> 3.0 GeV/c at sqrt(s)=200 GeV.
nucl-thAdv.High Energy Phys.(2019)·0 citations
11
Approximate sum rule for the electric dipole moment of light nuclei
Nodoka Yamanaka🇫🇷
The measurement of the electric dipole moment (EDM) is an excellent test of the standard model of particle physics, and the detection of a finite value is signal of a new source of CP violation beyond it. Among systems for which the EDM can be measured, light nuclei are particularly interesting due to their high sensitivity to new physics. In this proceedings contribution, we examine the sensitivity of the EDM of several light nuclei to the CP-odd one pion-exchange nucleon-nucleon interaction within the cluster model. We suggest an approximate sum rule for the nuclear EDM.
nucl-thhep-exhep-phnucl-exSpringer Proc.Phys.(2020)·0 citations
12
Quantum Monte Carlo calculations of dark matter scattering off light nuclei
Lorenzo Andreoli🇺🇸 · Vincenzo Cirigliano🇺🇸 · Stefano Gandolfi🇺🇸 · Francesco Pederiva🇮🇹
We compute the matrix elements for elastic scattering of dark matter (DM) particles off light nuclei ( $^{2}$ H, $^{3}$ H, $^{3}$ He, $^{4}$ He and $^{6}$ Li) using quantum Monte Carlo methods. We focus on scalar-mediated DM-nucleus interactions and use scalar currents obtained to next-to-leading order in chiral effective theory. The nuclear ground states are obtained from a phenomenological nuclear Hamiltonian that includes the Argonne $v_{18}$ two-body interaction and the three-body Urbana IX interaction. Within this approach, we study the impact of one- and two-body currents and discuss the size of nuclear uncertainties, including for the first time two-body effects in $A = 4$ and $A = 6$ systems. Our results provide the nuclear structure input needed to assess the sensitivity of future experimental searches of (light) dark matter using light nuclei, such as $^{3}$ He and $^{4}$ He.
nucl-thhep-phPRC(2019)·25 citations
13
Fluid dynamics of heavy ion collisions with Mode expansion (FluiduM)
Stefan Floerchinger🇩🇪 · Eduardo Grossi🇩🇪 · Jorrit Lion🇩🇪
The fluid dynamics of a relativistic fireball with longitudinal and transverse expansion is described using a background-fluctuation splitting. Symmetry representations of azimuthal rotations and longitudinal boosts are used for a classification of initial state configurations and their fluid dynamic propagation in terms of a mode expansion. We develop an accurate and efficient numerical scheme based on the pseudo-spectral method to solve the resulting hyperbolic partial differential equations. Comparison to the analytically known Gubser solution underlines the high accuracy of this technique. We also present first applications of FluiduM to central heavy ion collisions at the LHC energies featuring a realistic thermodynamic equations of state as well as shear and bulk viscous dissipation.
nucl-thhep-phPRC(2019)·36 citations
14
The Entropy of a Jet
Duff Neill🇺🇸 · Wouter J. Waalewijn🇳🇱
Scattering processes often inevitably include the production of infrared states, which are highly correlated with the hard scattering event, and decohere the hard states. This can be described using the entropy of the hard reduced density matrix, which is obtained from tracing over infrared states. We determine this entropy for an asymptotically-free gauge theory by separating the Hilbert space into hard and infrared states, and calculate it in a leading-logarithmic approximation for jets. We find that the entropy increases when the resolution scales defining the hard radiation are lowered, that this entropy is related to the subjet multiplicity, and explore connections to using jet images for machine learning, and the forward-scattering density matrix of partons in a nucleon probed in deep-inelastic scattering.
↳ hep-phhep-thnucl-thPRL(2019)·47 citations
15
Determining $α_{s}$ from hadronic $τ$ decay: the pitfalls of truncating the OPE
D. Boito🇧🇷 · M. Golterman🇺🇸 · K. Maltman🇨🇦 · S. Peris🇪🇸
We discuss sum-rule determinations of $α_{s}$ from non-strange hadronic $τ$ -decay data. We investigate, in particular, the reliability of the assumptions underlying the "truncated OPE strategy," which specifies a certain treatment of non-perturbative contributions, and which was employed in Refs. [1-3]. Here, we test this strategy by applying the strategy to the $R$ -ratio obtained from $e^{+} e^{-}$ data, which extend beyond the $τ$ mass, and, based on the outcome of these tests, we demonstrate the failure of this strategy.We then present a brief overview of new results on the form of duality-violating non-perturbative contributions, which are conspicuously present in the experimentally determined spectral functions. As we show, with the current precision claimed for the extraction of $α_{s}$ , including a representation of duality violations is unavoidable if one wishes to avoid uncontrolled theoretical errors.
↳ hep-phhep-latnucl-thSciPost Phys.Proc.(2019)·6 citations
16
Temporal Correlators in the Continuous Time Formulation of Strong Coupling Lattice QCD
Marc Klegrewe🇩🇪 · Wolfgang Unger🇩🇪
We present results for lattice QCD in the limit of infinite gauge coupling on a discrete spatial but continuous Euclidean time lattice. A worm type Monte Carlo algorithm is applied in order to sample two-point functions which gives access to the measurement of mesonic temporal correlators. The continuous time limit, based on sending $N_{τ} \to \infty$ and the bare anistotropy to infinity while fixing the temperature in a non-perturbative setup, has various advantages: the algorithm is sign problem free, fast, and accumulates high statistics for correlation functions. Even though the measurement of temporal correlators requires the introduction of a binning in time direction, this discretization can be chosen to be by orders finer compared to discrete computations. For different spatial volumes, temporal correlators are measured at zero spatial momentum for a variety of mesonic operators. They are fitted to extract the pole masses and corresponding particles as a function of the temperature. We conclude discussing the possibility to extract transport coefficients from these correlators.
↳ hep-latnucl-thPoS(2018)·5 citations
17
Temperature dependence of $η / s$ : uncertainties from the equation of state
Jussi Auvinen🇷🇸 · Kari J. Eskola🇫🇮 · Pasi Huovinen🇵🇱 · Harri Niemi🇫🇮 · Risto Paatelainen🇨🇭 · Peter Petreczky🇺🇸
We perform a global model-to-data comparison on Au+Au collisions at $s_{N N} = 200$ GeV and Pb+Pb collisions at $2.76$ TeV and $5.02$ TeV, using a 2+1D hydrodynamics model with the EKRT initial state and a shear viscosity over entropy density ratio $(η / s) (T)$ with a linear $T$ dependence. To quantify the amount of uncertainty due to the choice of the equation of state (EoS), we compare analysis results based on four different EoSs: the well known $s 95 p$ parametrisation, an updated parametrisation based on the same list of particles in hadron resonance gas, but using recent lattice results for the partonic part of the EoS, and two new parametrisations based on the Particle Data Group 2016 particle list and the recent lattice results. We find that the choice of the EoS does affect the favoured minimum value of $η / s$ , although within the confidence limits of the analysis. On the other hand, our analysis hardly constrains the temperature dependence of $η / s$ , no matter the EoS.
↳ hep-phnucl-thPoS(2018)·4 citations
18
Measurement of Nuclear Transparency Ratios for Protons and Neutrons
M. Duer · O. Hen · E. Piasetzky · L.B. Weinstein · A. Schmidt · I. Korover · E. O. Cohen · H. Hakobyan · the CLAS Collaboration
This paper presents, for the first time, measurements of neutron transparency ratios for nuclei relative to C measured using the (e,e'n) reaction, spanning measured neutron momenta of 1.4 to 2.4 GeV/c. The transparency ratios were extracted in two kinematical regions, corresponding to knockout of mean-field nucleons and to the breakup of Short-Range Correlated nucleon pairs. The extracted neutron transparency ratios are consistent with each other for the two measured kinematical regions and agree with the proton transparencies extracted from new and previous (e,e'p) measurements, including those from neutron-rich nuclei such as lead. The data also agree with and confirm the Glauber approximation that is commonly used to interpret experimental data. The nuclear-mass-dependence of the extracted transparencies scales as A^{\alpha} with {\alpha} = -0.289 {\pm} 0.007, which is consistent with nuclear-surface dominance of the reactions.
↳ nucl-exnucl-thPLB(2019)·27 citations
19
Anisotropic hydrodynamics for Au-Au collisions at 200 GeV
Mubarak Alqahtani🇸🇦 · Dekrayat Almaalol🇺🇸 · Michael Strickland🇺🇸
In this proceedings, we review the basics of quasiparticle anisotropic hydrodynamics (aHydroQP). Thenwe present phenomenological comparisons between 3+1d quasiparticle anisotropic hydrodynamics and experimental data from RHIC experiments at 200 GeV Au-Au collisions. We show that 3+1d aHydroQP model is able to describe the experimental results quite well for the spectra, multiplicity, and elliptic flow for charged particles in different centrality classes.
↳ hep-phnucl-thMDPI Proc.(2019)·2 citations

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