Nuclear Theory·nucl-th

Monday·December 19, 2016

19 papers—13 primary·6 cross-listed

01
Event-By-Event Initial Conditions for Heavy Ion Collisions
Steven Rose🇺🇸 · Rainer J. Fries🇺🇸
The early time dynamics of heavy ion collisions can be described by classical fields in an approximation of Quantum ChromoDynamics (QCD) called Color Glass Condensate (CGC). Monte-Carlo sampling of the color charge for the incoming nuclei are used to calculate their classical gluon fields. Following the recent work by Chen et al. we calculate the energy momentum tensor of those fields at early times in the collision event-by-event. This can then be used for subsequent hydrodynamic evolution of the single events.
nucl-thJ.Phys.Conf.Ser.(2017)·1 citation
02
Solution of the Skyrme-Hartree-Fock-Bogolyubov equations in the Cartesian deformed harmonic-oscillator basis. (VIII) hfodd (v2.73y): a new version of the program
N. Schunck🇺🇸 · J. Dobaczewski🇬🇧 · W. Satuła🇵🇱 · P. Bączyk🇵🇱 · J. Dudek🇫🇷 · Y. Gao🇫🇮 · M. Konieczka🇵🇱 · K. Sato🇯🇵 · Y. Shi🇫🇮 · X.B. Wang🇫🇮 · T.R. Werner🇵🇱
We describe the new version (v2.73y) of the code HFODD which solves the nuclear Skyrme Hartree-Fock or Skyrme Hartree-Fock-Bogolyubov problem by using the Cartesian deformed harmonic-oscillator basis. In the new version, we have implemented the following new features: (i) full proton-neutron mixing in the particle-hole channel for Skyrme functionals, (ii) the Gogny force in both particle-hole and particle-particle channels, (iii) linear multi-constraint method at finite temperature, (iv) fission toolkit including the constraint on the number of particles in the neck between two fragments, calculation of the interaction energy between fragments, and calculation of the nuclear and Coulomb energy of each fragment, (v) the new version 200d of the code HFBTHO, together with an enhanced interface between HFBTHO and HFODD, (vi) parallel capabilities, significantly extended by adding several restart options for large-scale jobs, (vii) the Lipkin translational energy correction method with pairing, (viii) higher-order Lipkin particle-number corrections, (ix) interface to a program plotting single-particle energies or Routhians, (x) strong-force isospin-symmetry-breaking terms, and (xi) the Augmented Lagrangian Method for calculations with 3D constraints on angular momentum and isospin. Finally, an important bug related to the calculation of the entropy at finite temperature and several other little significant errors of the previous published version were corrected.
nucl-thComput.Phys.Commun.(2017)·77 citations
03
From local correlations to regional systematics
Z. Z. Q · M. Bao · Y. Lei
Local correlations of $2_{1}^{+}$ excitation energies and B(E2, $2_{1}^{+} \to g.s.$ ) values require linear $N_{p} N_{n}$ systematics in a logarithmic scale, as confirmed by an experiment survey. Based on local correlations of $α$ -decay energies, neutron separation energies, and proton separation energies, one can decouple them into their proton and neutron contributions separately. These contributions exhibit smooth regional systematics beyond the $N_{p} N_{n}$ scheme.
nucl-thPRC(2017)·1 citation
04
Simultaneous microscopic description of nuclear level density and radiative strength function
N. Quang Hung · N. Dinh Dang · L. T. Quynh Huong
Nuclear level density (NLD) and radiative strength function (RSF) are described simultaneously within a microscopic approach, which takes into account the thermal effects of the exact pairing as well as the giant resonances within the phonon-damping model. The good agreement between the results of calculations and experimental data extracted by the Oslo group for $^{170, 171, 172}$ Yb isotopes shows the importance of exact thermal pairing in the description of NLD at low and intermediate excitation energies and invalidates the assumption based on the Brink-Axel hypothesis in the description of the RSF.
nucl-thPRL(2017)·56 citations
05
First estimation of the fission dynamics of the spectator created in heavy-ion collisions
K. Mazurek🇵🇱 · A. Szczurek🇵🇱 · P.N. Nadtochy🇷🇺
In peripheral high-energy heavy-ion collisions only parts of colliding nuclei interact leading to the production of a fireball. The remnants of such nuclei are called spectators. We estimated the excitation energy as a function of impact parameter. Their excitation energy is of the order of 100 MeV. The dynamical evolution of hot nuclei is described by solving a set of Langevin equations in four-dimensional collective coordinate space. The range of nuclear masses and excitation energies suits very well to ability of our model. Thus for the first time we investigate dynamically the fission and evaporation channels in de-excitation of the spectators produced in heavy-ions collision.
nucl-thhep-phActa Phys.Polon.Supp.(2017)·1 citation
06
Determination of S-factors with the LIT method
Winfried Leidemann · Sergio Deflorian · Victor D. Efros
The precise determination of astrophysical S-factors is essential for a detailed understanding of the nucleosynthesis in its various facets. It is discussed how the Lorentz integral transform (LIT) method can be applied for such a determination. The astrophysical S-factor for the proton-deuteron radiative capture is considered as test case. The importance of a specific many-body basis used for the LIT equation solution is pointed out. The excellent results of the test are discussed.
nucl-thFew Body Syst.(2017)·1 citation
07
Nuclear matter properties with nucleon-nucleon forces up to fifth order in the chiral expansion
Jinniu Hu🇨🇳 · Ying Zhang🇨🇳 · Evgeny Epelbaum🇩🇪 · Ulf-G. Meißner🇩🇪 · Jie Meng🇨🇳
The properties of nuclear matter are studied using state-of-the-art nucleon-nucleon forces up to fifth order in chiral effective field theory. The equations of state of symmetric nuclear matter and pure neutron matter are calculated in the framework of the Brueckner-Hartree-Fock theory. We discuss in detail the convergence pattern of the chiral expansion and the regulator dependence of the calculated equations of state and provide an estimation of the truncation uncertainty. For all employed values of the regulator, the fifth-order chiral two-nucleon potential is found to generate nuclear saturation properties similar to the available phenomenological high precision potentials. We also extract the symmetry energy of nuclear matter, which is shown to be quite robust with respect to the chiral order and the value of the regulator.
nucl-thPRC(2017)·48 citations
08
Effect of the Coulomb interaction on the liquid-gas phase transition of nuclear matter
Rana Nandi · Stefan Schramm
We investigate the role of the Coulomb interaction on the liquid-gas phase transition of nuclear matter with three different values of proton fraction ( $Y_{p}$ =0.5,0.3 and 0.1), relevant for heavy-ion physics as well as various astrophysical scenarios, within the framework of quantum molecular dynamics. We perform simulations for a wide range of density and temperature with and without the Coulomb interaction and calculate the two-point correlation functions of nucleon density fluctuations for all the configurations to determine the phase transition region. We also determine the critical end point of the liquid-gas phase transition for all three values of proton fraction considered. We observe that the Coulomb interaction reduces the transition temperature by about 2 MeV for nuclear matter with $Y_{p}$ =0.5 and 0.3 and by about 1 MeV for nuclear matter with $Y_{p}$ =0.1. However, the critical density is found to be more or less insensitive to the Coulomb interaction.
nucl-thPRC(2017)·8 citations
09
Electromagnetic radiation and collectivity in small quark-gluon droplets
Chun Shen🇺🇸 · Jean-Francois Paquet🇺🇸 · Gabriel S. Denicol🇧🇷 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
We study the multiplicity and rapidity dependence of thermal and prompt photon production in p+Pb collisions at 5.02 TeV, using a (3+1)D viscous hydrodynamic framework. Direct photon anisotropic flow coefficients $v_{2, 3}^{γ}$ and nuclear modification factor $R_{pPb}^{γ} (p_{T})$ are presented in both the p-going (backward) and the Pb-going (forward) directions. The interplay between initial state cold nuclear effect and final state thermal enhancement at different rapidity regions is discussed. The proposed rapidity dependent thermal photon enhancement and direct photon anisotropic flow observables can elucidate non-trivial longitudinal dynamics of hot quark-gluon plasma droplets created in small collision systems.
nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2017)·5 citations
10
Electroweak single-pion production off the nucleon: from threshold to high invariant masses
R. González-Jiménez🇧🇪 · N. Jachowicz🇧🇪 · K. Niewczas🇧🇪 · J. Nys🇧🇪 · V. Pandey🇺🇸 · T. Van Cuyck🇧🇪 · N. Van Dessel🇧🇪
[Background] Neutrino-induced single-pion production (SPP) provides an important contribution to neutrino-nucleus interactions, ranging from intermediate to high energies. There exists a good number of low-energy models in the literature to describe the neutrinoproduction of pions in the region around the Delta resonance. Those models consider only lowest-order interaction terms and, therefore, fail in the high-energy region (pion-nucleon invariant masses, $W$ >2 GeV). [Purpose] Our goal is to develop a model for electroweak SPP off the nucleon, which is applicable to the entire energy range of interest for present and future neutrino-oscillation experiments. [Method] We start with the low-energy model of [Phys.Rev.D76,033005(2007)], which includes resonant contributions and background terms derived from the pion-nucleon Lagrangian of chiral-perturbation theory. Then, from the background contributions, we build a high-energy model using a Regge approach. The low- and high-energy models are combined, in a phenomenological way, into a hybrid model. [Results] The Hybrid model is identical to the low-energy model in the low-W region, but, for W>2 GeV, it implements the desired high-energy behavior dictated by Regge theory. We have tested the high-energy model by comparing with one-pion production data from electron and neutrino reactions. The Hybrid model is compared with electron-proton scattering data, with neutrino SPP data and with the predictions of the NuWro Monte Carlo event generator. [Conclusions] Our model is able to provide satisfactory predictions of the electroweak one-pion production cross section from pion threshold to high $W$ . Further investigation and more data are needed to better understand the mechanisms playing a role in the electroweak SPP process in the high-W region, in particular, those involving the axial current contributions.
nucl-thhep-phPRD(2017)·52 citations
11
Bulk viscous corrections to photon production in the quark-gluon plasma
Sigtryggur Hauksson🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Photons radiated in heavy-ion collisions are a penetrating probe, and as such can play an important role in the determination of the quark-gluon plasma (QGP) transport coefficients. In this work we calculate the bulk viscous correction to photon production in two-to-two scattering reactions. Phase-space integrals describing the bulk viscous correction are evaluated explicitly in order to avoid the forward scattering approximation which is shown to be poor for photons at lower energies. We furthermore present hydrodynamical simulations of AA collisions focusing on the effect of this calculation on photonic observables. Bulk corrections are shown to reduce the elliptic flow of photons at higher $p_{T}$ .
nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2017)·7 citations
12
Collective excitations of a quantized vortex in $^{3} P_{2}$ superfluids in neutron stars
Chandrasekhar Chatterjee · Mareike Haberichter · Muneto Nitta
We discuss collective excitations (both fundamental and solitonic excitations) of quantized superfluid vortices in neutron $^{3} P_{2}$ superfluids, which likely exist in high density neutron matter such as neutron stars. Besides the well-known Kelvin modes (translational zero modes), we find a gapfull mode whose low-energy description takes the simple form of a double sine-Gordon model. The associated kink solution and its effects on spontaneous magnetization inside the vortex core are analyzed in detail.
nucl-thastro-ph.HEPRC(2017)·20 citations
13
A Blast Wave Model With Viscous Corrections
Zhidong Yang🇺🇸 · Rainer J. Fries🇺🇸
Hadronic observables in the final stage of heavy ion collision can be described well by fluid dynamics or blast wave parameterizations. We improve existing blast wave models by adding shear viscous corrections to the particle distributions in the Navier-Stokes approximation. The specific shear viscosity $η / s$ of a hadron gas at the freeze-out temperature is a new parameter in this model. We extract the blast wave parameters with viscous corrections from experimental data which leads to constraints on the specific shear viscosity at kinetic freeze-out. Preliminary results show $η / s$ is rather small.
nucl-thJ.Phys.Conf.Ser.(2017)·11 citations
14
Muon bundles as a sign of strangelets from the Universe
P. Kankiewicz🇵🇱 · M. Rybczynski🇵🇱 · Z. Wlodarczyk🇵🇱 · G. Wilk🇵🇱
Recently the CERN ALICE experiment, in its dedicated cosmic ray run, observed muon bundles of very high multiplicities, thereby confirming similar findings from the LEP era at CERN (in the CosmoLEP project). Originally it was argued that they apparently stem from the primary cosmic rays with a heavy masses. We propose an alternative possibility arguing that muonic bundles of highest multiplicity are produced by strangelets, hypothetical stable lumps of strange quark matter infiltrating our Universe. We also address the possibility of additionally deducing their directionality which could be of astrophysical interest. Significant evidence for anisotropy of arrival directions of the observed high multiplicity muonic bundles is found. Estimated directionality suggests their possible extragalactic provenance.
↳ hep-phastro-ph.HEnucl-thApJ(2017)·20 citations
15
Modeling Charmonium- $η$ Decays of $J^{P C} = 1^{--}$ Higher Charmonia
Muhammad Naeem Anwar🇨🇳 · Yu Lu🇨🇳 · Bing-Song Zou🇨🇳
We propose a new model to create a light meson in the heavy quarkonium transition, which is inspired by the Nambu $-$ Jona-Lasinio (NJL) model. Hadronic transitions of $J^{P C} = 1^{--}$ higher charmonia with the emission of an $η$ meson are studied in the framework of the proposed model. The model shows its potential to reproduce the observed decay widths and make predictions for the unobserved channels. We present our predictions for the decay width of $Ψ \to J / ψ η$ and $Ψ \to h_{c} (1 P) η$ , where $Ψ$ are higher $S$ and $D$ wave vector charmonia, which provide useful references to search for higher charmonia and determine their properties in forthcoming experiments. The predicted branching fraction $B (ψ (4415) \to h_{c} (1 P) η) = 4.62 \times 1 0^{- 4}$ is one order of magnitude smaller than the $J / ψ η$ channel. Estimates of partial decay width $Γ (Y \to J / ψ η)$ are given for $Y (4360)$ , $Y (4390)$ and $Y (4660)$ by assuming them as $c c ˉ$ bound states with quantum numbers $3^{3} D_{1}$ , $3^{3} D_{1}$ and $5^{3} S_{1}$ , respectively. Our results are in favor of these assignments for $Y (4360)$ and $Y (4660)$ . The corresponding experimental data for these $Y$ states has large statistical errors which do not provide any constraint on the mixing angle if we introduce $S - D$ mixing. To identify $Y (4390)$ , precise measurements on its hadronic branching fraction are required which are eagerly awaited from BESIII.
↳ hep-phhep-exnucl-thPRD(2017)·30 citations
16
$η$ - $η^{'}$ Mixing in Large- $N_{c}$ Chiral Perturbation Theory
P. Bickert🇩🇪 · P. Masjuan🇪🇸 · S. Scherer🇩🇪
We present a calculation of the $η$ - $η^{'}$ mixing in the framework of large- $N_{c}$ chiral perturbation theory. A general expression for the $η$ - $η^{'}$ mixing at next-to-next-to-leading order (NNLO) is derived, including higher-derivative terms up to fourth order in the four momentum, kinetic and mass terms. In addition, the axial-vector decay constants of the $η$ - $η^{'}$ system are determined at NNLO. The numerical analysis of the results is performed successively at LO, NLO, and NNLO. We investigate the influence of one-loop corrections, OZI-rule-violating parameters, and $O (N_{c} p^{6})$ contact terms.
↳ hep-phhep-latnucl-thPRD(2017)·37 citations
17
Event-by-event picture for the medium-induced jet evolution
Miguel A. Escobedo🇫🇮 · Edmond Iancu🇫🇷
We discuss the evolution of an energetic jet which propagates through a dense quark-gluon plasma and radiates gluons due to its interactions with the medium. Within perturbative QCD, this evolution can be described as a stochastic branching process, that we have managed to solve exactly. We present exact, analytic, results for the gluon spectrum (the average gluon distribution) and for the higher n-point functions, which describe correlations and fluctuations. Using these results, we construct the event-by-event picture of the gluon distribution produced via medium-induced gluon branching. In contrast to what happens in a usual QCD cascade in vacuum, the medium-induced branchings are quasi-democratic, with offspring gluons carrying sizable fractions of the energy of their parent parton. We find large fluctuations in the energy loss and in the multiplicity of soft gluons. The multiplicity distribution is predicted to exhibit KNO (Koba-Nielsen-Olesen) scaling. These predictions can be tested in Pb+Pb collisions at the LHC, via event-by-event measurements of the di-jet asymmetry. Based on JHEP 1605 (2016) 008 and arXiv:1609.06104
↳ hep-phnucl-thEPJ Web Conf.(2017)·0 citations
18
Triple parton scatterings in high-energy proton-proton collisions
David d'Enterria🇨🇭 · Alexander M. Snigirev🇷🇺
A generic expression to compute triple parton scattering (TPS) cross sections in high-energy proton-proton (pp) collisions is presented as a function of the corresponding single-parton cross sections and the transverse parton distribution in the proton encoded in an effective parameter $σ_{eff, TPS}$ . The value of $σ_{eff, TPS}$ is closely related to the similar effective cross section that characterizes double-parton scatterings, and amounts to $σ_{eff, TPS} = 12.5 \pm 4.5$ mb. Estimates for triple charm ( $c c$ ) and bottom ( $b b$ ) production in pp collisions at LHC and FCC energies are presented based on next-to-next-to-leading order perturbative calculations for single $c c, b b$ cross sections. At $s \approx$ 100 TeV, about 15% of the pp collisions produce three $c c$ pairs from three different parton-parton scatterings.
↳ hep-phhep-exnucl-exnucl-thPRL(2017)·78 citations
19
Studies of three-particle correlations and reaction-plane correlators from STAR
Prithwish Tribedy (for the STAR Collaboration)🇺🇸
We present STAR measurements of various harmonics of three-particle correlations in $s_{N N} = 200$ GeV Au+Au collisions at RHIC. The quantity $⟨ cos (m ϕ_{1} + n ϕ_{2} - (m + n) ϕ_{3})⟩$ is measured for inclusive charged particles for different harmonics $m$ and $n$ as a function of collision centrality, transverse momentum $p_{T}$ and relative pseudorapidity $Δ η$ . These observables provide detailed information on global event properties like correlations between event planes of different harmonics and are particularly sensitive to the expansion dynamics of the matter produced in the collisions. We compare our measurements to different viscous hydrodynamic models. We argue that these measurements probe the three-dimensional structure of the initial state and provide unique ways to constrain the transport parameters involved in hydrodynamic modeling of heavy-ion collisions.
↳ nucl-exhep-phnucl-thEPJ Web Conf.(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE