Nuclear Theory·nucl-th

Tuesday·May 2, 2017

14 papers—8 primary·6 cross-listed

01
[Submitted on 28 Apr 2017]
The production of primordial $J / ψ$ in p+p and relativistic heavy-ion collisions
Taesoo Song🇩🇪 · Joerg Aichelin🇩🇪 · Elena Bratkovskaya🇩🇪
$J / ψ$ observables of p+p collisions at $s =$ 200 GeV and 2.76 TeV are calculated using the PYTHIA event generator for the production of $c$ and $c ˉ$ and the Wigner density formalism. The charm quark momentum from PYTHIA is tuned in such a way that the transverse momentum and rapidity distribution correspond to the Fixed-Order Next-to-Leading Logarithm (FONLL) calculations and hence to the experimental data for open charm mesons. Using the Wigner density of the charmonium wave function we calculate for each charm quark pair the probability to form a charmonium. As a result, the experimental data on the total $J / ψ$ yield, its rapidity and transverse momentum distribution as well as the fractions of feed-down from excited states of charmonium are reproduced. Applying the same approach to relativistic heavy-ion collisions, we find, if quark gluon plasma (QGP) effects are ignored, a considerable enhancement of the primordial $J / ψ$ 's.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1705.00046 [pdf]
PRC(2017)·30 citations
02
[Submitted on 28 Apr 2017]
Multistage Monte-Carlo simulation of jet modification in a static medium
JETSCAPE Collaboration: Shanshan Cao🇺🇸 · Chanwook Park🇨🇦 · R. Alex Barbieri🇺🇸 · Steffen A. Bass🇺🇸 · Dennis Bazow🇺🇸 · Jonah Bernhard🇺🇸 · Jacob Coleman🇺🇸 · Rainer Fries🇺🇸 · Charles Gale🇨🇦 · Yayun He🇨🇳 · Ulrich Heinz🇺🇸 · Barbara V. Jacak🇺🇸 and 21 other authors
The modification of hard jets in an extended static medium held at a fixed temperature is studied using three different Monte-Carlo event generators (LBT, MATTER, MARTINI). Each event generator contains a different set of assumptions regarding the energy and virtuality of the partons within a jet versus the energy scale of the medium, and hence, applies to a different epoch in the space-time history of the jet evolution. For the first time, modeling is developed where a jet may sequentially transition from one generator to the next, on a parton-by-parton level, providing a detailed simulation of the space-time evolution of medium modified jets over a much broader dynamic range than has been attempted previously in a single calculation. Comparisons are carried out for different observables sensitive to jet quenching, including the parton fragmentation function and the azimuthal distribution of jet energy around the jet axis. The effect of varying the boundary between different generators is studied and a theoretically motivated criterion for the location of this boundary is proposed. The importance of such an approach with coupled generators to the modeling of jet quenching is discussed.
Comments:
10 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1705.00050 [pdf]
PRC(2017)·110 citations
03
[Submitted on 28 Apr 2017]
Nuclear Fission: from more phenomenology and adjusted parameters to more fundamental theory and increased predictive power
A. Bulgac · S. Jin · P. Magierski · K. Roche · N. Schunck · I. Stetcu
Two major recent developments in theory and computational resources created the favorable conditions for achieving a microscopic description of nuclear fission almost eighty years after its discovery in 1939 by Hahn and Strassmann (1930). The first major development was in theory, the extension of the Time-Dependent Density Functional Theory (TDDFT) to superfluid fermion systems. The second development was in computing, the emergence of powerful enough supercomputers capable of solving the complex systems of equations describing the time evolution in three dimensions without any restrictions of hundreds of strongly interacting nucleons. Even though the available nuclear energy density functionals (NEDFs) are phenomenological still, their accuracy is improving steadily and the prospects of being able to perform calculations of the nuclear fission dynamics and to predict many properties of the fission fragments, otherwise not possible to extract from experiments, are within reach, all without making recourse anymore to uncontrollable assumptions and simplified phenomenological models.
Comments:
6 pages, account of invited talk given at FUSION17, Hobart, Tasmania, February 20-24, 2017
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1705.00052 [pdf]
EPJ Web Conf.(2017)·3 citations
04
[Submitted on 30 Apr 2017]
Charge asymmetry in elastic scattering of massive leptons on protons
O. Koshchii🇺🇸 · A. Afanasev🇺🇸
The charge asymmetry due to higher-order QED corrections in elastic lepton-proton scattering is estimated without employing the ultrarelativistic approximation. Our calculation is performed by generalizing the soft-photon approximation approach suggested by Tsai. Corresponding loop integrals that take a form of Passarino-Veltman scalar three-point functions are calculated analytically without neglecting the mass of the lepton. Our results provide model-independent charge asymmetry predictions for scattering of unpolarized and massive leptons on proton targets. These predictions can be used in corresponding experiments to determine the contribution coming from model-dependent hard two-photon exchange processes.
Comments:
10 pages, 4 figures; minor changes, published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1705.00338 [pdf]
PRD(2017)·31 citations
05
[Submitted on 1 May 2017]
Alpha Cluster Formation and Decay in Quartetting Wave Function Approach
Chang Xu🇨🇳 · G. Ropke🇩🇪 · P. Schuck🇫🇷 · Zhongzhou Ren🇨🇳 · Y. Funaki🇯🇵 · H. Horiuchi🇯🇵 · A. Tohsaki🇯🇵 · T. Yamada · Bo Zhou🇯🇵
We present a microscopic calculation of alpha-cluster formation in heavy nuclei by using the quartetting wave function approach. The interaction of the quartet with the core nucleus is taken in local density approximation. The alpha-cluster formation is found to be particularly sensitive to the interplay of the mean field felt by the alpha-cluster and the Pauli blocking as a consequence of antisymmetrization. The striking feature of alpha-cluster formation probability across the major shell closures of 82 protons and 126 neutrons is reproduced. The shell (or subshell) effects on the alpha-cluster formation in superheavy nuclei are also analyzed.
Comments:
11 pages, 6 figures, 1 table, discussion added, accepted for publication in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1705.00391 [pdf]
PRC(2017)·75 citations
06
[Submitted on 1 May 2017]
Nucleon-anti-nucleon intruder state of Dirac equation for nucleon in deep scalar potential well
T.T.S. Kuo · T.K. Kuo · E. Osnes · S. Shu
We solve the Dirac radial equation for a nucleon in a scalar Woods-Saxon potential well of depth $V_{0}$ and radius $r_{0}$ . A sequence of values for the depth and radius are considered. For shallow potentials with $- 1000 M e V ≲ V_{0} < 0$ the wave functions for the positive-energy states $Ψ_{+} (r)$ are dominated by their nucleon component $g (r)$ . But for deeper potentials with $V_{0} ≲ - 1500 M e V$ the $Ψ_{+} (r)$ s begin to have dominant anti-nucleon component $f (r)$ . In particular, a special intruder state enters with wave function $Ψ_{1/2} (r)$ and energy $E_{1/2}$ . We have considered several $r_{0}$ values between 2 and 8 fm. For $V_{0} ≲ - 2000 M e V$ and the above $r_{0}$ values, $Ψ_{1/2}$ is the only bound positive-energy state and has its $g (r)$ closely equal to $- f (r)$ , both having a narrow wave-packet shape centered around $r_{0}$ . The $E_{1/2}$ of this state is practically independent of $V_{0}$ for the above $V_{0}$ range and obeys closely the relation $E_{1/2} = \frac{ℏ c}{r _{0}}$ .
Comments:
20 pages, 15 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1705.00489 [pdf]
IJMPE(2017)·0 citations
07
[Submitted on 1 May 2017]
Low density nuclear matter with light clusters in a generalized nonlinear relativistic mean-field model
Zhao-Wen Zhang · Lie-Wen Chen
We systematically investigate the thermodynamic properties of homogeneous nuclear matter with light clusters at low densities and finite temperatures using a generalized nonlinear relativistic mean-field (gNL-RMF) model, in which light clusters up to $α$ ( $1 \leq A \leq 4$ ) are included as explicit degrees of freedom and treated as point-like particles with their interactions described by meson exchanges and the medium effects on the cluster binding energies are described by density- and temperature-dependent energy shifts with the parameters obtained by fitting the experimental cluster Mott densities. We find that the composition of low density nuclear matter with light clusters is essentially determined by the density- and temperature-dependence of the cluster binding energy shifts. Compared with the values of the conventional (second-order) symmetry energy, symmetry free energy and symmetry entropy, their fourth-order values are found to be significant at low densities ( $ρ \sim 1 0^{- 3}$ fm $^{- 3}$ ) and low temperatures ( $T ≲ 3$ MeV), indicating the invalidity of the empirical parabolic law for the isospin asymmetry dependence of these nuclear matter properties. Our results indicate that in the density region of $ρ ≳ 0.02$ fm $^{- 3}$ , the clustering effects become insignificant and the nuclear matter is dominated by nucleon degree of freedom. In addition, we compare the gNL-RMF model predictions with the corresponding experimental data on the symmetry energy and symmetry free energy at low densities and finite temperatures extracted from heavy-ion collisions, and reasonable agreement is found.
Comments:
13 pages, 12 figures, 2 tables. Discussions added. Accepted version to appear in PRC
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1705.00555 [pdf]
PRC(2017)·18 citations
08
[Submitted on 27 Apr 2017]
Relativistic fluid dynamics with spin
Wojciech Florkowski🇵🇱 · Bengt Friman🇩🇪 · Amaresh Jaiswal🇩🇪 · Enrico Speranza🇩🇪
Using the conservation laws for charge, energy, momentum, and angular momentum, we derive hydrodynamic equations for the charge density, local temperature, and fluid velocity, as well as for the spin tensor, starting from local equilibrium distribution functions for particles and antiparticles with spin 1/2. The resulting set of differential equations extend the standard picture of perfect-fluid hydrodynamics with a conserved entropy current in a minimal way. This framework can be used in space-time analyzes of the evolution of spin and polarization in various physical systems including high-energy nuclear collisions. We demonstrate that a stationary vortex, which exhibits vorticity-spin alignment, corresponds to a special solution of the spin-hydrodynamical equations.
Comments:
PRC version, corrected signs in Sec. 6
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1705.00587 [pdf]
PRC(2018)·321 citations

Affiliations

first authorsco-authorsvia INSPIRE