Nuclear Theory·nucl-th

Thursday·October 1, 2015

20 papers—11 primary·9 cross-listed

01
Running Masses in the Nucleon and its Resonances
Craig D. Roberts🇺🇸
An overarching scientific challenge for the coming decade is to discover the meaning of confinement, its relationship to dynamical chiral symmetry breaking (DCSB) - the origin of visible mass - and the connection between them. In progressing toward meeting this challenge, significant progress has been made using continuum methods in QCD. For example, a novel understanding of gluon and quark confinement and its consequences has begun to emerge from quantum field theory; a clear picture is being drawn of how hadron masses emerge dynamically in a universe with light quarks; and ground-state hadron wave functions with a direct connection to QCD are becoming available, which reveal that quark-quark correlations are crucial in hadron structure. There is growing experimental support for this body of predictions in both elastic and nucleon-to-resonance-transition form factors.
nucl-thhep-lathep-phnucl-exJPS Conf.Proc.(2016)·5 citations
02
Ab initio calculations of reactions with light nuclei
S. Quaglioni (1)🇺🇸 · G. Hupin (2,1)🇫🇷 · A. Calci (3)🇨🇦 · P. Navratil (3)🇨🇦 · R. Roth (4) ((1) LLNL, (2) IN2P3/CNRS, (3) TRIUMF, (4) TU Darmstadt)🇩🇪
An {\em ab initio} (i.e., from first principles) theoretical framework capable of providing a unified description of the structure and low-energy reaction properties of light nuclei is desirable to further our understanding of the fundamental interactions among nucleons, and provide accurate predictions of crucial reaction rates for nuclear astrophysics, fusion-energy research, and other applications. In this contribution we review {\em ab initio} calculations for nucleon and deuterium scattering on light nuclei starting from chiral two- and three-body Hamiltonians, obtained within the framework of the {\em ab initio} no-core shell model with continuum. This is a unified approach to nuclear bound and scattering states, in which square-integrable energy eigenstates of the $A$ -nucleon system are coupled to $(A - a) + a$ target-plus-projectile wave functions in the spirit of the resonating group method to obtain an efficient description of the many-body nuclear dynamics both at short and medium distances and at long ranges.
nucl-thEPJ Web Conf.(2016)·7 citations
03
Nucleon Resonances Near 2 GeV
Jun He🇨🇳
The nucleon resonances near 2 GeV are investigated through the $Σ$ (1385) and $Λ (1520)$ photoproductions within a Regge-plus-resonance approach based on the new experimental data released by the CLAS Collaboration. The $Δ (2000)$ and the $N (2120)$ are found essential to reproduce the experimental data and should be assigned as second $[Δ5/ 2^{+}]$ and third $[N 3/ 2^{-}]$ in the constituent quark model, respectively. A calculation of the binding energy and decay pattern supports that the $N (1875)$ , which is listed in the PDG as the third $N 3/ 2^{-}$ nucleon resonance instead of the $N (2120)$ , is from the $Σ (1385) K$ interaction rather than a three quark state.
nucl-thnucl-exJPS Conf.Proc.(2016)·1 citation
04
On Distributions of Emission Sources and Speed of Sound in Proton-proton (Proton-antiproton) Collisions
Li-Na Gao🇨🇳 · Fu-Hu Liu🇨🇳
The revised (three-source) Landau hydrodynamic model is used in this paper to study the (pseudo)rapidity distributions of charged particles produced in proton-proton and proton-antiproton collisions at high energies. The central source is assumed to contribute with a Gaussian function which covers the rapidity distribution region as wide as possible. The target and projectile sources are assumed to emit isotropically particles in their respective rest frames. The model calculations obtained with a Monte Carlo method are fitted to the experimental data over an energy range from 0.2 to 13 TeV. The values of the squared speed-of-sound parameter in different collisions are then extracted from the width of the rapidity distributions.
nucl-thhep-exhep-phnucl-exAdv.High Energy Phys.(2015)·8 citations
05
Nuclear Reactions at Intermediate Energies
Radhey Shyam🇮🇳
In the domain of Nuclear reactions at intermediate energies, the QCD coupling constant $α_{s}$ is large enough ( $\sim$ 0.3 - 0.5) to render the perturbative calculational techniques inapplicable. In this regime the quarks are confined into colorless hadrons and it is expected that effective field theories of hadron interactions via exchange of hadrons, provide useful tools to describe such reactions. In this contribution we discuss applications of one such theory, the effective Lagrangian model, in describing the hadronic reactions at intermediate energies whose measurements are the focus of a vast international experimental program.
nucl-thhep-phnucl-exEPJ Web Conf.(2016)·0 citations
06
Testing two-nucleon transfer reaction mechanism with elementary modes of excitation in exotic nuclei
R.A. Broglia🇮🇹 · G.Potel🇺🇸 · A. Idini🇫🇮 · F. Barranco🇪🇸 · E. Vigezzi🇮🇹
Nuclear Field Theory of structure and reactions is confronted with observations made on neutron halo dripline nuclei, resulting in the prediction of a novel (symbiotic) mode of nuclear excitation, and on the observation of the virtual effect of the halo phenomenon in the apparently non-halo nucleus $^{7}$ Li. This effect is forced to become real by intervening the virtual process with an external (t,p) field which, combined with accurate predictive abilities concerning the absolute differential cross section, reveals an increase of a factor 2 in the cross section due to the presence of halo ground state correlations, and is essential to reproduce the value of the observed $d σ (^{7}$ Li(t,p) $^{9}$ Li)/d $Ω$ .
nucl-th0 citations
07
Alpha decay in electron environments of increasing density: from the bare nucleus to compressed matter
Fabio Belloni
The influence of the electron environment on the alpha decay is elucidated. Within the frame of a simple model based on the generalized Thomas-Fermi theory of the atom, it is shown that the increase of the electron density around the parent nucleus drives a mechanism which shortens the lifetime. Numerical results are provided for 144Nd, 154Yb and 210Po. Depending on the nuclide, fractional lifetime reduction relative to the bare nucleus is of the order of 0.1-1% in free ions, neutral atoms and ordinary matter, but may reach up to 10% at matter densities as high as 10^4 g/cm3, in a high-Z matrix. The effect induced by means of state-of-the-art compression techniques, although much smaller than previously found, would however be measurable. The extent of the effect in ultra-high-density stellar environments might become significant and would deserve further investigation.
nucl-thastro-ph.SREPJA(2016)·7 citations
08
Projectile deformation effects in the breakup of $^{37}$ Mg
Shubhchintak (TAMU-Commerce) · R. Chatterjee (IIT-R) · R. Shyam (Saha Inst.)
We study the breakup of $^{37}$ Mg on Pb at 244MeV/u with the recently developed extended theory of Coulomb breakup within the post-form finite range distorted wave Born approximation that includes deformation of the projectile. Comparing our calculated cross section with the available Coulomb breakup data we determine the possible ground state configuration of $^{37}$ Mg.
nucl-thnucl-exEPJ Web Conf.(2016)·1 citation
09
Collectivity in small and large amplitude microscopic mean-field dynamic
Denis Lacroix🇫🇷 · Yusuke Tanimura🇫🇷 · Guillaume Scamps🇯🇵
The time-dependent energy density functional with pairing allows to describe a large variety of phenomena from small to large amplitude collective motion. Here, we briefly summarize the recent progresses made in the field using the TD-BCS approach. A focus is made on the mapping of the microscopic mean-field dynamic to the macroscopic dynamic in collective space. A method is developed to extract the collective mass parameter from TD-EDF. Illustration is made on the fission of $^{258}$ Fm. The collective mass and collective momentum associated to quadrupole deformation including non-adiabatic effects is estimated along the TD-EDF path. With these information, the onset of dissipation during fission is discussed.
nucl-thnucl-exActa Phys.Polon.Supp.(2015)·1 citation
10
Compton Scattering and Nucleon Polarisabilities in Chiral EFT: Update and Future
Harald W. Griesshammer (George Washington U.)🇺🇸 · Judith A. McGovern (U. of Manchester)🇬🇧 · Daniel R. Phillips (Ohio U.)🇺🇸
We review theoretical progress and prospects for determining the nucleon's static dipole polarisabilities from Compton scattering on few-nucleon targets, including new values; see Refs. [1-5] for details and a more thorough bibliography.
nucl-thhep-lathep-phnucl-exAIP Conf.Proc.(2016)·3 citations
11
Symmetry energy of cold nucleonic matter within a relativistic mean field model encapsulating effects of high momentum nucleons induced by short-range correlations
Bao-Jun Cai · Bao-An Li
Significant progress has been made recently in constraining the isospin-dependent parameters characterizing the SRC (short-range correlation)-modified single-nucleon momentum distribution in neutron-rich nucleonic matter using both experimental data and microscopic model calculations. Using the constrained single-nucleon momentum distribution in a nonlinear relativistic mean field (RMF) model, we study the equation of state (EOS) of asymmetric nucleonic matter (ANM), especially the density dependence of nuclear symmetry energy $E_{sym} (ρ)$ . Firstly, as a test of the model, the average nucleon kinetic energy extracted recently from electron-nucleus scattering experiments using a neutron-proton dominance model is well reproduced by the RMF model incorporating effects of the SRC-induced high momentum nucleons, while it is significantly under predicted by the RMF model using a step function for the single-nucleon momentum distribution as in free Fermi gas (FFG) models. Secondly, the kinetic symmetry energy of quasi-nucleons is found to be $E_{sym}^{kin} (ρ_{0}) = - 16.94 \pm 13.66 MeV$ which is dramatically different from the prediction of $E_{sym}^{kin} (ρ_{0}) \approx 12.5$ MeV by FFG models at nuclear matter saturation density $ρ_{0} = 0.16 fm^{- 3}$ . Thirdly, comparing the RMF calculations with and without the high momentum nucleons using two sets of model parameters both reproducing identically all empirically constraints on the EOS of symmetric nuclear matter (SNM) and the symmetry energy of ANM at $ρ_{0}$ , the SRC-modified single-nucleon momentum distribution is found to make the $E_{sym} (ρ)$ more concave around $ρ_{0}$ by softening it significantly at both sub-saturation and supra-saturation densities, leading to an isospin-dependent incompressibility of ANM in better agreement with existing experimental data.
nucl-thastro-ph.SRnucl-exPRC(2016)·78 citations
12
SU(N) Multi-Skyrmions at Finite Volume
Fabrizio Canfora🇨🇱 · Marco Di Mauro🇮🇹 · Maxim A. Kurkov🇮🇹 · Adele Naddeo🇮🇹
We study multi-soliton solutions of the four-dimensional SU(N) Skyrme model by combining the hedgehog ansatz for SU(N) based on the harmonic maps of $S^{2}$ into $C P^{N - 1}$ and a geometrical trick which allows to analyze explicitly finite-volume effects without breaking the relevant symmetries of the ansatz. The geometric setup allows to introduce a parameter which is related to the 't Hooft coupling of a suitable large $N$ limit, in which $N \to \infty$ and the curvature of the background metric approaches zero, in such a way that their product is constant. The relevance of such a parameter to the physics of the system is pointed out. In particular, we discuss how the discrete symmetries of the configurations depend on it.
↳ hep-thhep-phmath-phmath.MP+1EPJC(2015)·29 citations
13
A study of transverse momentum distributions of jets produced in p-p, p-\bar p, d-Au, Au-Au, and Pb-Pb collisions at high energies
Hua-Rong Wei🇨🇳 · Fu-Hu Liu🇨🇳
The transverse momentum distributions of jets produced in p-p, p-\bar p, d-Au, Au-Au, and Pb-Pb collisions at high energies with different selected conditions are analyzed by using a multi-source thermal model. The multi-component (mostly two-component) Erlang distribution used in our description is in good agreement with the experimental data measured by the STAR, D0, CDF II, ALICE, ATLAS, and CMS Collaborations. Related parameters are extracted from the transverse momentum distributions and some information on different interacting systems are obtained. In the two-component Erlang distribution, the first component has usually two or more sources which are contributed by strong scattering interactions between two quarks or more quarks and gluons, while the second component has mostly two sources which are contributed by harder head-on scattering between two quarks.
↳ nucl-exhep-exhep-phnucl-thAdv.High Energy Phys.(2015)·1 citation
14
Physics of neutrino flavor transformation through matter-neutrino resonances
Meng-Ru Wu🇩🇪 · Huaiyu Duan🇺🇸 · Yong-Zhong Qian🇺🇸
In astrophysical environments such as core-collapse supernovae and neutron star-neutron star or neutron star-black hole mergers where dense neutrino media are present, matter-neutrino resonances (MNRs) can occur when the neutrino propagation potentials due to neutrino-electron and neutrino-neutrino forward scattering nearly cancel each other. We show that neutrino flavor transformation through MNRs can be explained by multiple adiabatic solutions similar to the Mikheyev-Smirnov-Wolfenstein mechanism. We find that for the normal neutrino mass hierarchy, neutrino flavor evolution through MNRs can be sensitive to the shape of neutrino spectra and the adiabaticity of the system, but such sensitivity is absent for the inverted hierarchy.
↳ hep-phastro-ph.HEnucl-thPLB(2016)·61 citations
15
New Topological Structures of Skyrme Theory: Baryon Number and Monopole Number
Y.M. Cho🇨🇳 · Kyoungtae Kimm🇰🇷 · J. H. Yoon🇰🇷 · Pengming Zhang🇨🇳
Based on the observation that the skyrmion in Skyrme theory can be viewed as a dressed monopole, we show that the skyrmions have two independent topology, the baryon topology $π_{3} (S^{3})$ and the monopole topology $π_{2} (S^{2})$ . With this we propose to classify the skyrmions by two topological numbers $(m, n)$ , the monopole number $m$ and the shell (radial) number $n$ . In this scheme the popular (non spherically symmetric) skyrmions are classified as the $(m, 1)$ skyrmions but the spherically symmetric skyrmions are classified as the $(1, n)$ skyrmions, and the baryon number $B$ is given by $B = mn$ . Moreover, we show that the vacuum of the Skyrme theory has the structure of the vacuum of the Sine-Gordon theory and QCD combined together, which can also be classified by two topological numbers $(p, q)$ . This puts the Skyrme theory in a totally new perspective.
↳ hep-thnucl-thEPJC(2017)·6 citations
16
Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions
Hua-Rong Wei🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸
In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavour particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead ( $p$ -Pb), and proton-proton ( $p$ - $p$ ) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of "thermometers" or "thermometric scales" and "speedometers". A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature ( $T$ ) curve as a function of particle's rest mass ( $m_{0}$ ) when plotting $T$ versus $m_{0}$ , and the mean transverse flow velocity from the slope of the mean transverse momentum ( $⟨ p_{T} ⟩$ ) curve as a function of mean moving mass ( $m$ ) when plotting $⟨ p_{T} ⟩$ versus $m$ .
↳ nucl-exhep-exhep-phnucl-thJ.Phys.G(2016)·42 citations
17
Radiative lifetime and energy of the low-energy isomeric level in $^{229}$ Th
E. V. Tkalya · Christian Schneider · Justin Jeet · Eric R. Hudson
We estimate the range of the radiative lifetime and energy of the anomalous, low-energy $3/ 2^{+} (7.8 \pm 0.5$ eV) state in the $^{229}$ Th nucleus. Our phenomenological calculations are based on the available experimental data for the intensities of $M 1$ and $E 2$ transitions between excited levels of the $^{229}$ Th nucleus in the $K^{π} [N n_{Z} Λ] = 5/ 2^{+} [633]$ and $3/ 2^{+} [631]$ rotational bands. We also discuss the influence of certain branching coefficients, which affect the currently accepted measured energy of the isomeric state. From this work, we establish a favored region where the transition lifetime and energy should lie at roughly the 90% confidence level. We also suggest new nuclear physics measurements, which would significantly reduce the ambiguity in the present data.
↳ physics.atom-phnucl-thPRC(2015)·89 citations
18
Study of the $f_{2} (1270)$ and $a_{2} (1320)$ resonances in $γ^{*} (Q^{2}) γ$ collisions
N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺 · G.N. Shestakov🇷🇺
We discuss studies of the $Q^{2}$ dependence of the $f_{2} (1270)$ and $a_{2} (1320)$ production cross sections in $γ^{*} (Q^{2}) γ$ collisions at current and coming into operation colliders with a high luminosity. Changing the dominant helicity amplitude occurs in the reactions $γ^{*} (Q^{2}) γ \to f_{2} (1270)$ and $γ^{*} (Q^{2}) γ \to a_{2} (1320)$ with increasing $Q^{2}$ . This is caused by the coming of the QCD asymptotics. It is shown that the transition to the asymptotic behavior of QCD in the amplitudes $γ^{*} (Q^{2}) γ \to f_{2} (1270), a_{2} (1320)$ is provided by the compensation of the contributions of ground vector states $ρ$ and $ω$ in $Q^{2}$ -channel with the contributions of their radial excitations.
↳ hep-phhep-exnucl-thJETP Lett.(2015)·7 citations
19
Efficient magnetic-field amplification due to the Kelvin-Helmholtz instability in binary neutron star mergers
Kenta Kiuchi · Pablo Cerdá-Durán · Koutarou Kyutoku · Yuichiro Sekiguchi · Masaru Shibata
We explore magnetic-field amplification due to the Kelvin-Helmholtz instability during binary neutron star mergers. By performing high-resolution general relativistic magnetohydrodynamics simulations with a resolution of $17.5$ m for $4$ -- $5$ ms after the onset of the merger on the Japanese supercomputer "K", we find that an initial magnetic field of moderate maximum strength $1 0^{13}$ G is amplified at least by a factor of $\approx 1 0^{3}$ . We also explore the saturation of the magnetic-field energy and our result shows that it is likely to be $≳ 4 \times 1 0^{50}$ erg, which is $≳ 0.1%$ of the bulk kinetic energy of the merging binary neutron stars.
↳ astro-ph.HEastro-ph.COastro-ph.SRgr-qc+1PRD(2015)·278 citations
20
Low Energy Effective Theory of QCD at High Isospin Chemical Potential
Thomas D. Cohen🇺🇸 · Srimoyee Sen🇺🇸
The goal of this paper is to arrive at a low energy effective theory of QCD with two massless flavors of quarks at very high isospin density and zero baryon density. In a seminal paper by Son and Stephanov in the year 2001, it was conjectured that the low energy dynamics of QCD with two light flavors at asymptotically high isospin density was described by that of a pure Yang-Mills effective Lagrangian. Since the existence of a first order deconfinement phase transition with increasing temperature is a feature of every pure SU(N) Yang-Mills theory with N greater than or equal to 3, the regime considered in this paper is also expected to exhibit a first order deconfinement phase transition with increasing temperature. However, the low energy constants(LEC) of this pure Yang-Mills theory have not been calculated till date. We calculate the LEC s for this effective theory which in turn enables us to calculate the critical temperature of the deconfinement transition as a function of the isospin chemical potential $μ_{I}$ .The scaling of the critical temperature as a function of the isospin chemical potential that we find in this paper can be compared with future lattice calculations at finite isospin density.
↳ hep-phnucl-th1 citation

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