Nuclear Theory·nucl-th

Tuesday·July 12, 2016

12 papers—8 primary·4 cross-listed

01
[Submitted on 7 Jul 2016]
Production of Energetic Light Fragments in CEM, LAQGSM, and MCNP6
Stepan G. Mashnik · Leslie M. Kerby · Konstantin K. Gudima · Arnold J. Sierk · Jeffrey S. Bull · Michael R. James
We extend the cascade-exciton model (CEM), and the Los Alamos version of the quark-gluon string model (LAQGSM), event generators of the Monte-Carlo N-particle transport code version 6 (MCNP6), to describe production of energetic light fragments (LF) heavier than 4He from various nuclear reactions induced by particles and nuclei at energies up to about 1 TeV/nucleon. In these models, energetic LF can be produced via Fermi break-up, preequilibrium emission, and coalescence of cascade particles. Initially, we study several variations of the Fermi break-up model and choose the best option for these models. Then, we extend the modified exciton model (MEM) used by these codes to account for a possibility of multiple emission of up to 66 types of particles and LF (up to 28Mg) at the preequilibrium stage of reactions. Then, we expand the coalescence model to allow coalescence of LF from nucleons emitted at the intranuclear cascade stage of reactions and from lighter clusters, up to fragments with mass numbers A < 8, in the case of CEM, and A < 13, in the case of LAQGSM. Next, we modify MCNP6 to allow calculating and outputting spectra of LF and heavier products with arbitrary mass and charge numbers. The improved version of CEM is implemented into MCNP6. Finally, we test the improved versions of CEM, LAQGSM, and MCNP6 on a variety of measured nuclear reactions. The modified codes give an improved description of energetic LF from particle- and nucleus-induced reactions; showing a good agreement with a variety of available experimental data. They have an improved predictive power compared to the previous versions and can be used as reliable tools in simulating applications involving such types of reactions.
Comments:
24 pages, 24 figures, 2 tables, to be submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1607.02506 [pdf]
PRC(2017)·13 citations
02
[Submitted on 10 Jul 2016]
Charmonium dissociation in collision with phi meson in hadronic matter
Shi-Tao Ji🇨🇳 · Xiao-Ming Xu🇨🇳
The phi-charmonium dissociation reactions in hadronic matter are studied. Unpolarised cross sections for 12 reactions are calculated in the Born approximation, in the quark-interchange mechanism and with a temperature-dependent quark potential. The potential leads to remarkable temperature dependence of the cross sections. With the cross sections and the phi distribution function we calculate the dissociation rates of the charmonia in the interactions with the phi meson in hadronic matter. The dependence of the rates on temperature and charmonium momentum is meaningful to the influence of phi mesons on charmonium suppression.
Comments:
21 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1607.02691 [pdf]
CPC(2017)·0 citations
03
[Submitted on 10 Jul 2016]
Remarks on the Woods-Saxon Potential
M Capak · B Gonul
More recently, comprehensive application results of approximate analytical solutions of the Woods-Saxon potential in closed form for the 5-dimensional Bohr Hamiltonian have been appeared [14] and its comparison to the data for many different nuclei has clearly revealed the domains for the sucsess and failure in case of using such potential forms to analyse the data concerning with the nuclear structure of deformed nuclei within the frame of the collective model. Gaining confidence from this work, exact solvability of the Woods-Saxon type potentials in lower dimensions for the bound states having zero angular momentum is carefully reviewed to finalize an ongoing discussion in the related literature and clearly shown that such kind of potentials have no analytical solutions even for l=0 case.
Comments:
8 pages, Mod.Phys.Lett.A (2016)
Subjects:
Nuclear Theory (nucl-th); Mathematical Physics (math-ph); math.MP (math.MP); Quantum Physics (quant-ph)
arXiv:
1607.02742 [pdf]
Mod.Phys.Lett.A(2016)·10 citations
04
[Submitted on 10 Jul 2016]
Large-scale shell-model calculations on the spectroscopy of $N < 126$ Pb isotopes
Chong Qi🇸🇪 · L.Y. Jia🇨🇳 · G.J. Fu🇨🇳
Large-scale shell-model calculations are carried out in the model space including neutron-hole orbitals $2 p_{1/2}$ , $1 f_{5/2}$ , $2 p_{3/2}$ , $0 i_{13/2}$ , $1 f_{7/2}$ and $0 h_{9/2}$ to study the structure and electromagnetic properties of neutron deficient Pb isotopes. An optimized effective interaction is used. Good agreement between full shell-model calculations and experimental data is obtained for the spherical states in isotopes $^{194 - 206}$ Pb. The lighter isotopes are calculated with an importance-truncation approach constructed based on the monopole Hamiltonian. The full shell-model results also agree well with our generalized seniority and nucleon-pair-approximation truncation calculations. The deviations between theory and experiment concerning the excitation energies and electromagnetic properties of low-lying $0^{+}$ and $2^{+}$ excited states and isomeric states may provide a constraint on our understanding of nuclear deformation and intruder configuration in this region.
Comments:
11 pages, to appear in PRC, supplementary materials available upon request
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1607.02771 [pdf]
PRC(2016)·25 citations
05
[Submitted on 10 Jul 2016]
Large-scale configuration interaction description of the structure of nuclei around $^{100}$ Sn and $^{208}$ Pb
Chong Qi
In this contribution I would like to discuss briefly the recent developments of the nuclear configuration interaction shell model approach. As examples, we apply the model to calculate the structure and decay properties of low-lying states in neutron-deficient nuclei around $^{100}$ Sn and $^{208}$ Pb that are of great experimental and theoretical interests.
Comments:
5 pages, proceedings for the FAIRNESS workshop 2016
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1607.02772 [pdf]
J.Phys.Conf.Ser.(2016)·4 citations
06
[Submitted on 10 Jul 2016]
The anomalous quadrupole collectivity in Te isotopes
Chong Qi
We present systematic calculations on the spectroscopy and transition properties of even-even Te isotopes by using the large-scale configuration interaction shell model approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behavior, which cannot be reproduced by collective models. Our calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behavior of the $B (E 2)$ values in $^{114}$ Te. The calculated $B (E 2)$ values for neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The $B (E 2)$ of light isotopes can exhibit a nearly constant bevavior upto high spins. We show that this is related to the enhanced neutron-proton correlation when approaching $N = 50$ .
Comments:
7 pages, 4 figures, submitted to PRC
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1607.02775 [pdf]
PRC(2016)·33 citations
07
[Submitted on 11 Jul 2016]
Monopole excitation of the Hoyle state and linear-chain state in 12C
Yasuro Funaki
Background: Two new $J^{π} = 0^{+}$ states are recently observed around a few MeV above the Hoyle state (the second $0^{+}$ state in 12C). The characters of them are only poorly discussed in theory and are still mysterious. Purpose: I give for the first time a comprehensive understanding of the structures of the $0^{+}$ states by analyzing their wave functions, and discuss relationship with the Hoyle state, similarities, and differences between the states. Method: I extend a microscopic $α$ -cluster model called Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function so as to incorporate $2 α + α$ asymmetric configuration explicitly. The so-called $r^{2}$ -constraint method to effectively eliminate spurious continuum components is also used. Results: The $0_{3}^{+}$ state is shown to have a very large squared overlap with a single configuration of the extended THSR wave function in an orthogonal space to the Hoyle state as well as to the ground state. The $0_{4}^{+}$ state has a maximal squared overlap with a single extended THSR wave function with an extremely prolately-deformed shape. Conclusions: The $0_{3}^{+}$ state appears as a family of the Hoyle state to have a higher nodal structure in the internal motions of the $3 α$ clusters, due to the orthogonalization to the Hoyle state. The $0_{4}^{+}$ state dominantly has a linear-chain structure, where the $3 α$ clusters move freely in a non-localized way, like a one-dimensional gas of the $3 α$ clusters.
Comments:
8 pages, 8 figures, 1 table, and the title is slightly changed. To be published in PRC
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1607.02832 [pdf]
PRC(2016)·29 citations
08
[Submitted on 11 Jul 2016]
Effects of an induced electric field on \pi^{-}/\pi^{+} ratio in heavy-ion collisions
Gao-Feng Wei🇨🇳 · Shi-Hai Dong🇲🇽 · Xin-Wei Cao🇨🇳 · Yun-Liang Zhang🇨🇳
Using an isospin- and momentum-dependent transport model, we examine the effects of an electric field induced by a variable magnetic field on the \pi^{-}/\pi^{+} ratio in central to peripheral heavy-ion collisions at beam energies of 400 and 1500MeV/nucleon. It is shown that while the induced electric field does not affect the total multiplicities of both $π^{-}$ and $π^{+}$ mesons at both the lower beam energy of 400MeV/nucleon and the higher beam energy of 1500MeV/nucleon, it reduces (enhances) the emission of $π^{-}$ ( $π^{+}$ ) mesons in midrapidity, but enhances (reduces) the emission of $π^{-}$ ( $π^{+}$ ) mesons in forward and backward rapidities especially for the more peripheral collisions at the lower beam energy because of the rapidly transient variable magnetic field at more peripheral collisions and longer reaction duration time at the lower beam energy. These findings indicate that the total \pi^{-}/\pi^{+} ratio is still a precisely reliable probe of symmetry energy at both the lower and higher beam energies, but one should consider the induced electric field when using the differential \pi^{-}/\pi^{+} ratio to probe the symmetry energy especially for the lower beam energy and more peripheral collisions. Finally, the relative suppression factor based on the ratio of \pi^{-}/\pi^{+} in different rapidities is proposed to be an effective probe of the induced electric field generated in heavy-ion collisions due to its maximizing effects of induced electric fields on the differential \pi^{-}/\pi^{+} ratio but minimizing effects of some uncertainty factors in heavy-ion collisions.
Comments:
7 pages, 15 figures, Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1607.02891 [pdf]
PRC(2016)·4 citations
09
[Submitted on 8 Jul 2016] (cross-list from hep-ex)
Parton Fragmentation Functions
Andreas Metz🇺🇸 · Anselm Vossen🇺🇸
The field of fragmentation functions of light quarks and gluons is reviewed. In addition to integrated fragmentation functions, attention is paid to the dependence of fragmentation functions on transverse momenta and on polarization degrees of freedom. Higher-twist and di-hadron fragmentation functions are considered as well. Moreover, the review covers both theoretical and experimental developments in single-inclusive hadron production in electron-positron annihilation, deep-inelastic lepton-nucleon scattering, and proton-proton collisions.
Comments:
103 pages, 31 figures, discussion and references added, accepted for publication in Progress in Particle and Nuclear Physics
Subjects:
High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1607.02521 [pdf]
PPNP(2016)·298 citations
10
[Submitted on 8 Jul 2016] (cross-list from hep-ph)
Kaon fluctuations from lattice QCD
Jacquelyn Noronha-Hostler🇺🇸 · Rene Bellwied🇺🇸 · Jana Gunther🇩🇪 · Paolo Parotto🇺🇸 · Attila Pasztor🇩🇪 · Israel Portillo Vazquez🇺🇸 · Claudia Ratti🇺🇸
We show that it is possible to isolate a set of kaon fluctuations in lattice QCD. By means of the Hadron Resonance Gas (HRG) model, we calculate the actual kaon second-to-first fluctuation ratio, which receives contribution from primordial kaons and resonance decays, and show that it is very close to the one obtained for primordial kaons in the Boltzmann approximation. The latter only involves the strangeness and electric charge chemical potentials, which are functions of $T$ and $μ_{B}$ due to the experimental constraint on strangeness and electric charge, and can therefore be calculated on the lattice. This provides an unambiguous method to extract the kaon freeze-out temperature, by comparing the lattice results to the experimental values for the corresponding fluctuations.
Comments:
5 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1607.02527 [pdf]
47 citations
11
[Submitted on 8 Jul 2016] (cross-list from nucl-ex)
A Search for $0^{+}$ States in $^{50}$ Cr: Implications for the Superallowed $β$ -decay of $^{50}$ Mn
K.G. Leach · P.E. Garrett · G.C. Ball · P.C. Bender · V. Bildstein · B.A. Brown · C. Burbadge · T. Faestermann · B. Hadinia · J.D. Holt · A.T. Laffoley · D.S. Jamieson and 7 other authors
A $^{52}$ Cr $(p, t)$ $^{50}$ Cr two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in $^{50}$ Cr were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited $0^{+}$ state was found. As a result, the $0_{2}^{+}$ state is reassigned at an excitation energy of $E_{x} = 3895.0 (5)$ keV in $^{50}$ Cr. This reassignment directly impacts direct searches for a non-analogue Fermi $β^{+}$ decay branch in $^{50}$ Mn. These results also show better systematic agreement with the theoretical predictions for the $0^{+}$ state spectrum in $^{50}$ Cr using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to $ab$ - $ini t i o$ shell-model predictions using the IM-SRG formalism based on $N N$ and $3 N$ forces from chiral-EFT in the $p f$ -shell for the first time.
Comments:
Accepted for Publication in Physical Review C as a Rapid Communication
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1607.02540 [pdf]
PRC(2016)·10 citations
12
[Submitted on 11 Jul 2016] (cross-list from hep-ph)
Short Range Correlations and the EMC Effect in Effective Field Theory
Jiunn-Wei Chen🇹🇼 · William Detmold🇺🇸 · Joel E. Lynn🇩🇪 · Achim Schwenk🇩🇪
We show that the empirical linear relation between the magnitude of the EMC effect in deep inelastic scattering on nuclei and the short range correlation scaling factor $a_{2}$ extracted from high-energy quasi-elastic scattering at $x \geq 1$ is a natural consequence of scale separation and derive the relationship using effective field theory. While the scaling factor $a_{2}$ is a ratio of nuclear matrix elements that individually depend on the calculational scheme, we show that the ratio is independent of this choice. We perform Green's function Monte Carlo calculations with both chiral and Argonne-Urbana potentials to verify this and determine the scaling factors for light nuclei. The resulting values for $^{3}$ He and $^{4}$ He are in good agreement with experimental values. We also present results for $^{9}$ Be and $^{12}$ C extracted from variational Monte Carlo calculations.
Comments:
8 pages, 4 figures, including the Supplemental Material, PRL version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1607.03065 [pdf]
PRL(2017)·75 citations

Affiliations

first authorsco-authorsvia INSPIRE