Nuclear Theory·nucl-th

Tuesday·June 16, 2015

15 papers—7 primary·8 cross-listed

01
[Submitted on 14 Jun 2015]
Ultra-relativistic light-heavy nuclear collisions and collectivity
Wojciech Broniowski🇵🇱 · Piotr Bozek🇵🇱 · Maciej Rybczynski🇵🇱 · Enrique Ruiz Arriola🇪🇸
We briefly review highlights for ultra-relativistic light-heavy collisions (p-Pb, d-Au, 3He-Au, 12C-Au) which display collective evolution, with the same very characteristic features as in the A-A systems.
Comments:
Talk presented by WB at Excited QCD 2015, Tatranska Lomnica, Slovakia, 8-14 March 2015, 6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1506.04362 [pdf]
Acta Phys.Polon.Supp.(2015)·3 citations
02
[Submitted on 15 Jun 2015]
Study of weakly-bound odd-A nuclei with quasiparticle blocking
Xueyu Xiong · Junchen Pei · Yinu Zhang · Yi Zhu
The coordinate-space Hartree-Fock-Bogoliubov (HFB) approach with quasiparticle blocking has been applied to study the odd-A weakly bound nuclei $^{17, 19}$ B and $^{37}$ Mg, in which halo structures have been reported in experiments. The Skyrme nuclear forces SLy4 and UNEDF1 have been adopted in our calculations. The results with and without blocking have been compared to demonstrate the emergence of deformed halo structures due to blocking effects. In our calculations, $^{19}$ B and $^{37}$ Mg have remarkable features of deformed halos.
Comments:
7 pages, 4 figures, 1 table
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.04484 [pdf]
CPC(2016)·21 citations
03
[Submitted on 15 Jun 2015]
Pairing phase transition: A Finite-Temperature Relativistic Hartree-Fock-Bogoliubov study
Jia Jie Li🇫🇷 · Jérôme Margueron🇫🇷 · Wen Hui Long🇨🇳 · Nguyen Van Giai🇫🇷
Background: The relativistic Hartree-Fock-Bogoliubov (RHFB) theory has recently been developed and it provides a unified and highly predictive description of both nuclear mean field and pairing correlations. Ground state properties of finite nuclei can accurately be reproduced without neglecting exchange (Fock) contributions. Purpose: Finite-temperature RHFB (FT-RHFB) theory has not yet been developed, leaving yet unknown its predictions for phase transitions and thermal excitations in both stable and weakly bound nuclei. Method: FT-RHFB equations are solved in a Dirac Woods-Saxon (DWS) basis considering two kinds of pairing interactions: finite or zero range. Such a model is appropriate for describing stable as well as loosely bound nuclei since the basis states have correct asymptotic behaviour for large spatial distributions. Results: Systematic FT-RH(F)B calculations are performed for several semi-magic isotopic/isotonic chains comparing the predictions of a large number of Lagrangians, among which are PKA1, PKO1 and DD-ME2. It is found that the critical temperature for a pairing transition generally follows the rule $T_{c} = 0.60Δ (0)$ for a finite-range pairing force and $T_{c} = 0.57Δ (0)$ for a contact pairing force, where $Δ (0)$ is the pairing gap at zero temperature. Two types of pairing persistence are analysed: type I pairing persistence occurs in closed subshell nuclei while type II pairing persistence can occur in loosely bound nuclei strongly coupled to the continuum states. Conclusions: This first FT-RHFB calculation shows very interesting features of the pairing correlations at finite temperature and in finite systems such as pairing re-entrance and pairing persistence.
Comments:
13 pages, 11 figures, accepted version in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.04507 [pdf]
PRC(2015)·33 citations
04
[Submitted on 15 Jun 2015]
Nuclear interaction modeled with a simple piston-gas model
Mario J. Pinheiro
A simple one-dimensional gas-piston kinetic model gives the interaction potential between two colliding heavy ions. In the frame of the classical, thermodynamical approach, the colliding heavy ions are not submitted to friction, but produces an irreversible phenomena with cause at the difference of pressure $p$ "felt" by the nucleon gas when ions collide with the target when compared with the pressure that nuclear matter exert on their boundaries when in thermodynamical equilibrium, and offers a straightforward way to calculate interacting potentials.
Comments:
3 pages, 2 figures, submitted to journal
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.04669 [pdf]
Asian Journal of Physical and Chemical Sc…·0 citations
05
[Submitted on 15 Jun 2015]
The Nuclear Symmetry Energy in Heavy Ion Collisions
Hermann Wolter🇩🇪
In this contribution I discuss the nuclear symmetry energy in the regime of hadronic degrees of freedom. The density dependence of the symmetry energy is important from very low densities in supernova explosions, to the structure of neutron-rich nuclei around saturation density, and to several times saturation density in neutron stars. Heavy ion collisions are the only means to study this density dependence in the laboratory. Numerical simulations of transport theories are used to extract the equation-of-state, and thus also the symmetry energy. I discuss some examples, which relate particularly to the high density symmetry energy, which is of particular interest today. I review the status and point out some open problems in the determination of the symmetry energy in heavy ion collisions.
Comments:
9 pages, 4 figures, report for workshop Compact Stars in the QCD Phase Diagram IV (CSQCD IV), Prerow, Germany, Sept. 26-30, 2014
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1506.04687 [pdf]
0 citations
06
[Submitted on 15 Jun 2015]
Systematics of strength function sum rules
Calvin W. Johnson
Sum rules provide useful insights into transition strength functions and are often expressed as expectation values of an operator. In this letter I demonstrate that non-energy-weighted transition sum rules have strong secular dependences on the energy of the initial state. Such non-trivial systematics have consequences: the simplification suggested by the generalized Brink-Axel hypothesis, for example, does not hold for most cases, though it weakly holds in at least some cases for electric dipole transitions. Furthermore, I show the systematics can be understood through spectral distribution theory, calculated via traces of operators and of products of operators. Seen through this lens, violation of the generalized Brink-Axel hypothesis is unsurprising: one \textit{expects} sum rules to evolve with excitation energy. Furthermore, to lowest order the slope of the secular evolution can be traced to a component of the Hamiltonian being positive (repulsive) or negative (attractive).
Comments:
5 pages, 4 figures; minor revisions; references updated; title revised; matches accepted version
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1506.04700 [pdf]
PLB(2015)·37 citations
07
[Submitted on 15 Jun 2015]
A unified approach to electron and neutrino elastic scattering off nuclei with an application to the study of the axial structure
O. Moreno🇺🇸 · T. W. Donnelly🇺🇸
We show a relationship between elastic electron scattering observables and the elastic neutrino cross section that provides a straightforward determination of the latter from experimental data of the former and relates their uncertainties. An illustration of this procedure is presented using a Hartree-Fock mean field for the nuclear structure of a set of even-even nuclear targets, using the spectra of the neutrinos produced in pion decay at rest. We also analyze the prospects to measure the incoherent axial contribution to the neutrino elastic scattering in odd targets.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1506.04733 [pdf]
PRC(2015)·18 citations
08
[Submitted on 12 Jun 2015] (cross-list from hep-ph)
High-precision determination of the pion-nucleon $σ$ -term from Roy-Steiner equations
Martin Hoferichter🇩🇪 · Jacobo Ruiz de Elvira🇩🇪 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪
We present a determination of the pion-nucleon ( $π N$ ) $σ$ -term $σ_{π N}$ based on the Cheng-Dashen low-energy theorem (LET), taking advantage of the recent high-precision data from pionic atoms to pin down the $π N$ scattering lengths as well as of constraints from analyticity, unitarity, and crossing symmetry in the form of Roy-Steiner equations to perform the extrapolation to the Cheng-Dashen point in a reliable manner. With isospin-violating corrections included both in the scattering lengths and the LET, we obtain $σ_{π N} = (59.1 \pm 1.9 \pm 3.0)$ MeV $= (59.1 \pm 3.5)$ MeV, where the first error refers to uncertainties in the $π N$ amplitude and the second to the LET. Consequences for the scalar nucleon couplings relevant for the direct detection of dark matter are discussed.
Comments:
6 pages, 1 figure; title changed by journal, version to be published in PRL
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1506.04142 [pdf]
PRL(2015)·341 citations
09
[Submitted on 13 Jun 2015] (cross-list from hep-ph)
Electromagnetic $N - Δ (1232)$ transitions within the point-form of relativistic quantum mechanics
Yubing Dong🇨🇳 · Mauro Giannini🇮🇹 · Elena Santopinto🇮🇹 · Andrea Vassallo🇮🇹
The electromagnetic $N - Δ (1232)$ transition amplitudes are calculated using the point-form of relativistic quantum mechanics. The relativistic effects incorporated in the electromagnetic matrix elements give a good description of the transition amplitudes to the $Δ (1232)$ resonance, reproducing well the $Q^{2}$ behaviour of the data, apart from the low $Q^{2}$ one.
Comments:
4 pages, two figures, Conference: C13-09-09 Proceedings
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1506.04203 [pdf]
Few Body Syst.(2014)·5 citations
10
[Submitted on 13 Jun 2015] (cross-list from hep-ph)
Compositeness of the strange, charm and beauty odd parity $Λ$ states
C. Garcia-Recio🇪🇸 · C. Hidalgo-Duque🇪🇸 · J. Nieves🇪🇸 · L.L. Salcedo🇪🇸 · L. Tolos🇪🇸
We study the dependence on the quark mass of the compositeness of the lowest-lying odd parity hyperon states. Thus, we pay attention to $Λ -$ like states in the strange, charm and beauty, sectors which are dynamically generated using a unitarized meson-baryon model. In the strange sector we use an SU(6) extension of the Weinberg-Tomozawa meson-baryon interaction, and we further implement the heavy-quark spin symmetry to construct the meson-baryon interaction when charmed or beauty hadrons are involved. In the three examined flavor sectors, we obtain two $J^{P} = 1/ 2^{-}$ and one $J^{P} = 3/ 2^{-}$ $Λ$ states. We find that the $Λ$ states which are bound states (the three $Λ_{b}$ ) or narrow resonances (one $Λ (1405)$ and one $Λ_{c} (2595)$ ) are well described as molecular states composed of $s$ -wave meson-baryon pairs. The $\frac{1}{2}^{-}$ wide $Λ (1405)$ and $Λ_{c} (2595)$ as well as the $\frac{3}{2}^{-}$ $Λ (1520)$ and $Λ_{c} (2625)$ states display smaller compositeness and so they would require new mechanisms, such as $d$ -wave interactions.
Comments:
14 pages, 2 figures, 5 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1506.04235 [pdf]
PRD(2015)·46 citations
11
[Submitted on 14 Jun 2015] (cross-list from hep-ph)
Relativistic quark-diquark model of baryons. Non strange spectrum and nucleon electromagnetic form factors
M. De Sanctis🇨🇴 · J. Ferretti🇲🇽 · E. Santopinto🇮🇹 · A. Vassallo🇮🇹
We briefly describe our relativistic quark-diquark model, developed within the framework of point form dynamics, which is the relativistic extension of the interacting quark-diquark model. In order to do that we have to show the main properties and quantum numbers of the effective degree of freedom of constituent diquark. Our results for the nonstrange baryon spectrum and for the nucleon electromagnetic form factors are discussed.
Comments:
Talks presented at the conference "Beauty in Physics: Theory and Experiment : Meeting in honor of Francesco Iachello on the occasion of his 70th birthday", 14-18 May 2012. Cocoyoc, Mexico
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1506.04413 [pdf]
AIP Conf.Proc.(2012)·2 citations
12
[Submitted on 15 Jun 2015] (cross-list from nucl-ex)
On the sensitivity of extracting the astrophysical cross section factor of the 12C(a,g) reaction from existing data [Comment on Schuermann et al. Phys. Lett. B711(2012)35]
Moshe Gai (U Connecticut)
We address a conflicting report on the value and uncertainty of the astrophysical cross section factor of the 12C(a,g) reaction extracted from existing data. In sharp contrast to previously reported ambiguities (by up to a factor 8), Schuermann et al. suggest an accuracy of 12%. We demonstrate that the so claimed "rigorous data selection criteria" used by Schuermann et al. relies on the s-factors extracted by Assuncao et al. But these results were shown in a later analysis (by this author) to have large error bars (considerably larger than claimed by Assuncao em et al.) which render these data not appropriate for a rigorous analysis. When their "rigorous data selection" is adjusted to remove the results of Assuncao et al. the astrophysical cross section factor cannot be extracted with 12% accuracy, or even close to it. Such data on the S_E2 values at low energies deviate by up to a factor two from their fit and exhibit a sharper slope rising toward low energies, leading to strong doubt on their extrapolated S_E2(300) value and the quoted small error bar. Contrary to their claim the small value of S_E1(300) ~10 keVb cannot be ruled out by current data including the most modern gamma-ray data. As previously observed by several authors current data reveal ambiguities in the value of S_E1(300) ~10 keVb or ~80 keVb, and the new ambiguity that was recently revealed (by this author) of S_E2(300) ~60 keVb or ~154 keVb, appear to be a more reasonable evaluation the status of current data.
Comments:
The Physics Letters Journal does not publish comments on previously published articles (even if it contains unfortunate elementary mistakes in for example chi-square analyses). For all its worth I am posting here my criticism of the paper of Schuermann et al. Phys. Lett. B711(2012)35
Subjects:
Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1506.04501 [pdf]
Comment on Schuermann et al. Phys. Lett. …·2 citations
13
[Submitted on 15 Jun 2015] (cross-list from astro-ph.SR)
R-mode constraints from neutron star equation of state
M. C. Papazoglou🇬🇷 · C. C. Moustakidis🇬🇷
The gravitational radiation has been proposed a long time before, as an explanation for the observed relatively low spin frequencies of young neutron stars and of accreting neutron stars in low-mass X-ray binaries as well. In the present work we studied the effects of the neutron star equation of state on the r-mode instability window of rotating neutron stars. Firstly, we employed a set of analytical solution of the Tolman-Oppemheimer-Volkoff equations with special emphasis on the Tolman VII solution. In particular, we tried to clarify the effects of the bulk neutron star properties (mass, radius, density distribution, crust size and elasticity) on the r-mode instability window. We found that the critical angular velocity $Ω_{c}$ depends mainly on the neutron star radius. The effects of the gravitational mass and the mass distribution are almost negligible. Secondly, we studied the effect of the elasticity of the crust, via to the slippage factor $S$ and also the effect of the nuclear equation of state, via the slope parameter $L$ , on the instability window. We found that the crust effects are more pronounced, compared to those originated from the equation of state. Moreover, we proposed simple analytical expressions which relate the macroscopic quantity $Ω_{c}$ to the radius, the parameter $L$ and the factor $S$ . We also investigated the possibility to measure the radius of a neutron star and the factor $S$ with the help of accurate measures of $Ω_{c}$ and the neutron star temperature. Finally, we studied the effects of the mutual friction on the instability window and discussed the results in comparison with previous similar studies.
Comments:
29 pages, 10 figures, 2 tables
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1506.04572 [pdf]
Astrophys.Space Sci.(2016)·16 citations
14
[Submitted on 15 Jun 2015] (cross-list from hep-ph)
Dissipative properties of hot and dense hadronic matter in excluded volume hadron resonance gas model
Guru Prakash Kadam🇮🇳 · Hiranmaya Mishra🇮🇳
We estimate dissipative properties viz: shear and bulk viscosities of hadronic matter using relativistic Boltzmann equation in relaxation time approximation within ambit of excluded volume hadron resonance gas (EHRG) model. We find that at zero baryon chemical potential the shear viscosity to entropy ratio ( $η / s$ ) decreases with temperature while at finite baryon chemical potential this ratio shows same behavior as a function of temperature but reaches close to Kovtun-Son-Starinets (KSS) bound. Further along chemical freezout curve, ratio $η / s$ is almost constant apart from small initial monotonic rise. This observation may have some relevance to the experimental finding that the differential elliptic flow of charged hadrons does not change considerably at lower center of mass energy. We further find that bulk viscosity to entropy density ( $ζ / s$ ) decreases with temperature while this ratio has higher value at finite baryon chemical potential at higher temperature. Along freezout curve $ζ / s$ decreases monotonically at lower center of mass energy and then saturates.
Comments:
Results corrected, 2 new figures, abstract, discussion and conclusion revised, references added, accepted for publication in Physical Review C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1506.04613 [pdf]
PRC(2015)·97 citations
15
[Submitted on 15 Jun 2015] (cross-list from hep-ph)
Strangeness production in heavy-ion collisions
Alessia Palmese🇩🇪 · Giuseppe Pagliara🇮🇹 · Alessandro Drago🇮🇹 · Olena Linnyk🇩🇪 · Wolfgang Cassing🇩🇪
A study of the "horn" in the particle ratio $K^{+} / π^{+}$ for central heavy-ion collisions as a function of the collision energy $s$ is presented. We analyse two different interpretations: the onset of deconfinement and the transition from a baryon- to a meson-dominated hadron gas. We use a realistic equation of state (EOS), which includes both hadron and quark degrees-of-freedom. The Taub-adiabate procedure is followed to determine the system at the early stage. Our results do not support an explanation of the horn as due to the onset of deconfinement. Using only hadronic EOS we reproduced the energy dependence of the $K^{+} / π^{+}$ and $Λ/ π^{-}$ ratios employing an experimental parametrisation of the freeze-out curve. We observe a transition between a baryon- and a meson-dominated regime; however, the reproduction of the $K^{+} / π^{+}$ and $Λ/ π^{-}$ ratios as a function of $s$ is not completely satisfying. We finally propose a new idea for the interpretation of the data, the roll-over scheme, in which the scalar meson field $σ$ has not reached the thermal equilibrium at freeze-out. The rool-over scheme for the equilibration of the $σ$ -field is based on the inflation mechanism. The non-equilibrium evolution of the scalar field influences the particle production, e.g. $K^{+} / π^{+}$ , however, the fixing of the free parameters in this model is still an open issue.
Comments:
10 pages, 7 figures, 9th International Workshop on Critical Point and Onset of Deconfinement, 17-21 November, 2014
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1506.04653 [pdf]
PoS(2015)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE