Nuclear Theory·nucl-th

Friday·February 13, 2015

13 papers—5 primary·8 cross-listed

01
[Submitted on 11 Feb 2015]
Ab-initio calculation of the photonuclear cross section of $^{10}$ B
M.K.G. Kruse🇺🇸 · W.E. Ormand🇺🇸 · C.W. Johnson🇺🇸
We present for the first-time the photonuclear cross section of $^{10}$ B calculated within the ab-initio No Core Shell Model framework. Realistic two-nucleon (NN) chiral forces up to next-to-next-to-next-order (N3LO), which have been softened by the similarity renormalization group method (SRG) to $λ = 2.02$ fm $^{- 1}$ , were utilized. The electric-dipole response function is calculated using the Lanczos method. The effects of the continuum were accounted for by including neutron escape widths derived from R-matrix theory. The calculated cross section agrees well with experimental data in terms of structure as well as in absolute peak height, $σ_{max} = 4.85 mb$ at photon energy $ω = 23.61 MeV$ , and integrated cross section $85.36 MeV \cdot mb$ . We test the Brink hypothesis by calculating the electric-dipole response for the first five positive-parity states in $^{10}$ B and verify that dipole excitations built upon the ground- and excited states have similar characteristics.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1502.03464 [pdf]
1 citation
02
[Submitted on 12 Feb 2015]
Ab initio-driven nuclear energy density functional method. A proposal for safe/correlated/improvable parametrizations of the off-diagonal EDF kernels
T. Duguet · M. Bender · J.-P. Ebran · T. Lesinski · V. Somà
This programmatic paper lays down the possibility to reconcile the necessity to resum many-body correlations into the energy kernel with the fact that safe multi-reference energy density functional (EDF) calculations cannot be achieved whenever the Pauli principle is not strictly enforced, as is for example the case when many-body correlations are parametrized under the form of empirical density dependencies. Our proposal is to exploit a newly developed ab initio many-body formalism to guide the construction of safe, explicitly correlated and systematically improvable parametrizations of the {\it off-diagonal} energy and norm kernels that lie at the heart of the nuclear EDF method. The many-body formalism of interest relies on the concepts of symmetry breaking {\it and} restoration that have made the fortune of the nuclear EDF method and is, as such, amenable to this guidance. After elaborating on our proposal, we briefly outline the project we plan to execute in the years to come.
Comments:
14 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.03672 [pdf]
EPJA(2015)·16 citations
03
[Submitted on 12 Feb 2015]
Fitting Single Particle Energies in $s d g h$ Major Shell
E. Dikmen · O. Öztürk · Y. Cengiz
We have performed two kinds of non-linear fitting procedures to the single-particle energies in the $s d g h$ major shell to obtain better shell model results. The low-lying energy eigenvalues of the light Sn isotopes with $A = 103 - 110$ in the $s d g h$ -shell are calculated in the framework of the nuclear shell model by using CD-Bonn two-body effective nucleon-nucleon interaction. The obtained energy eigenvalues are fitted to the corresponding experimental values by using two different non-linear fitting procedures, i.e., downhill simplex method and clonal selection method. The unknown single-particle energies of the states $2 s_{1/2}$ , $1 d_{3/2}$ , and $0 h_{11/2}$ are used in the fitting methods to obtain better spectra of the $^{104, 106, 108, 110}$ Sn isotopes. We compare the energy spectra of the $^{104, 106, 108, 110}$ Sn and $^{103, 105, 107, 109}$ Sn isotopes with/without a nonlinear fit to the experimental results.
Comments:
8 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.03677 [pdf]
Commun.Theor.Phys.(2015)·2 citations
04
[Submitted on 12 Feb 2015]
Charge splitting of directed flow and charge-dependent effects in pion spectra in heavy ion collisions
A. Rybicki🇵🇱 · A. Szczurek🇵🇱 · M. Klusek-Gawenda🇵🇱 · M. Kielbowicz🇵🇱
The large and rapidly varying electric and magnetic fields induced by the spectator systems moving at ultrarelativistic velocities induce a charge splitting of directed flow, $v_{1}$ , of positive and negative pions in the final state of the heavy ion collision. The same effect results in a very sizeable distortion of charged pion spectra as well as ratios of charged pions ( $π^{+} / π^{-}$ ) emitted at high values of rapidity. Both phenomena are sensitive to the actual distance between the pion emission site and the spectator system. This distance $d_{E}$ appears to decrease with increasing rapidity of the pion, and comes below $\sim$ 1~fm for pions emitted close to beam rapidity. In this paper we discuss how these findings can shed new light on the space-time evolution of pion production as a function of rapidity, and on the longitudinal evolution of the system created in heavy ion collisions.
Comments:
8 pages, 3 figures a talk by A. Rybicki at the X Workshop on Particle Correlations and Femtoscopy (WPCF 2014), Gyöngyös, Hungary, 2014
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1502.03689 [pdf]
3 citations
05
[Submitted on 12 Feb 2015]
Toward a solution to the $R_{AA}$ and $v_{2}$ puzzle for heavy quarks
Santosh K. Das🇮🇹 · Francesco Scardina🇮🇹 · Salvatore Plumari🇮🇹 · Vincenzo Greco🇮🇹
The heavy quarks constitutes a unique probe of the quark-gluon plasma properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA} (p_{T})$ and the elliptic flow $v_{2} (p_{T})$ has been observed which challenged all the existing models, especially for D mesons. We discuss how the temperature dependence of the heavy quark drag coefficient is responsible for a large part of such a puzzle. In particular, we have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA} (p_{T})$ observed in experiments at RHIC and LHC energy. We point out that for the same $R_{AA} (p_{T})$ one can generate 2-3 times more $v_{2}$ depending on the temperature dependence of the heavy quark drag coefficient. A non-decreasing drag coefficient as $T \to T_{c}$ is a major ingredient for a simultaneous description of $R_{AA} (p_{T})$ and $v_{2} (p_{T})$ .
Comments:
7 pages, 6 figures, Accepted for publication in Physics Letters B
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1502.03757 [pdf]
PLB(2015)·227 citations
06
[Submitted on 1 Feb 2015] (cross-list from cond-mat.mes-hall)
Interplay of relativistic and nonrelativistic transport in atomically precise segmented graphene nanoribbons
Constantine Yannouleas🇺🇸 · Igor Romanovsky🇺🇸 · Uzi Landman🇺🇸
Graphene's isolation launched explorations of fundamental relativistic physics originating from the planar honeycomb lattice arrangement of the carbon atoms, and of potential technological applications in nanoscale electronics. Bottom-up fabricated atomically-precise segmented graphene nanoribbons, SGNRs, open avenues for studies of electrical transport, coherence, and interference effects in metallic, semiconducting, and mixed GNRs, with different edge terminations. Conceptual and practical understanding of electric transport through SGNRs is gained through nonequilibrium Green's function (NEGF) conductance calculations and a Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. The continuum model reproduces the NEGF results, including optical Dirac Fabry-Perot (FP) equidistant oscillations for massless relativistic carriers in metallic armchair SGNRs, and an unequally-spaced FP pattern for mixed armchair-zigzag SGNRs where carriers transit from a relativistic (armchair) to a nonrelativistic (zigzag) regime. This provides a unifying framework for analysis of coherent transport phenomena and interpretation of forthcoming experiments in SGNRs.
Comments:
12 pages, 6 figures. For related papers, see http://www.prism.gatech.edu/~ph274cy/
Subjects:
Mesoscale and Nanoscale Physics (cond-mat.mes-hall); cond-mat.mtrl-sci (cond-mat.mtrl-sci); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.00205 [pdf]
Sci.Rep.(2015)·1 citation
07
[Submitted on 11 Feb 2015] (cross-list from hep-ph)
Flavor dependence of baryon melting temperature in effective models of QCD
Juan M. Torres-Rincon🇫🇷 · Benjamin Sintes🇫🇷 · Joerg Aichelin🇫🇷
We apply the three-flavor (Polyakov-)Nambu-Jona-Lasinio model to generate baryons as quark-diquark bound states using many-body techniques at finite temperature. All the baryonic states belonging to the octet and decuplet flavor representations are generated in the isospin-symmetric case. For each state we extract the melting temperature at which the baryon may decay into a quark-diquark pair. We seek for an evidence of the strangeness dependence of the baryon melting temperature as suggested by the statistical thermal models and supported by lattice-QCD results. A clear and robust signal for this claim is found, pointing to a flavor dependence of the hadronic deconfinement temperature.
Comments:
23 pages, 12 figures, 6 appendices. v2: Quark condensates and susceptibilities are presented. One parameter of the PNJL model is modified to account for its dependence on the number of flavors; this brings a better agreement between the NJL and PNJL models. Typos are corrected and new references added. Version accepted for its publication in the Physical Review C journal
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.03459 [pdf]
PRC(2015)·34 citations
08
[Submitted on 12 Feb 2015] (cross-list from nucl-ex)
Assessment of molecular effects on neutrino mass measurements from tritium beta decay
L.I. Bodine🇺🇸 · D.S. Parno🇺🇸 · R.G.H. Robertson🇺🇸
The beta decay of molecular tritium currently provides the highest sensitivity in laboratory-based neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino-mass experiments agree with spectroscopic data. Moreover, when neutrino-mass experiments performed in the 1980s with gaseous tritium are re-evaluated using these modern calculations, the extracted neutrino mass-squared values are consistent with zero instead of being significantly negative. On the other hand, the calculated molecular final-state branching ratios are in tension with dissociation experiments performed in the 1950s. We re-examine the theory of the final-state spectrum of molecular tritium decay and its effect on the determination of the neutrino mass, with an emphasis on the role of the vibrational- and rotational-state distribution in the ground electronic state. General features can be reproduced quantitatively from considerations of kinematics and zero-point motion. We summarize the status of validation efforts and suggest means for resolving the apparent discrepancy in dissociation rates.
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.03497 [pdf]
PRC(2015)·76 citations
09
[Submitted on 12 Feb 2015] (cross-list from hep-lat)
Nucleons and parity doubling across the deconfinement transition
Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Simon Hands🇬🇧 · Benjamin Jäger🇬🇧 · Chrisanthi Praki🇬🇧 · Jon-Ivar Skullerud🇮🇪
It is expected that nucleons and their parity partners become degenerate when chiral symmetry is restored. We investigate this question in the context of the thermal transition from the hadronic phase to the quark-gluon plasma, using lattice QCD simulations with N_f=2+1 flavours. We observe a clear sign of parity doubling in the quark-gluon plasma. Besides, we find that the nucleon ground state is, within the uncertainty, largely independent of the temperature, whereas temperature effects are substantial in the negative-parity (N^*) channel, already in the confined phase.
Comments:
5 pages, 5 eps figures, some more details, figure and references added; to appear in PRD
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.03603 [pdf]
PRD(2015)·96 citations
10
[Submitted on 12 Feb 2015] (cross-list from hep-ph)
Mean transverse momenta correlations in hadron-hadron collisions in MC toy model with repulsing strings
Igor Altsybeev🇷🇺
In the present work, Monte-Carlo toy model with repulsing quark-gluon strings in hadron-hadron collisions is described. String repulsion creates transverse boosts for the string decay products, giving modifications of observables. As an example, long-range correlations between mean transverse momenta of particles in two observation windows are studied in MC toy simulation of the heavy-ion collisions.
Comments:
7 pages, 6 figures, proceedings of the XI Quark Confinement and the Hadron Spectrum Conference (2015)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.03608 [pdf]
AIP Conf.Proc.(2016)·14 citations
11
[Submitted on 12 Feb 2015] (cross-list from hep-ph)
Breakdown of the expansion of finite-size corrections to the hydrogen Lamb shift in moments of charge distribution
Franziska Hagelstein🇩🇪 · Vladimir Pascalutsa (KPH, JGU Mainz)🇩🇪
We quantify a limitation in the usual accounting of the finite-size effects, where the leading $[(Z α)^{4}]$ and subleading $[(Z α)^{5}]$ contributions to the Lamb shift are given by the mean-square radius and the third Zemach moment of the charge distribution. In the presence of any non-smooth behaviour of the nuclear form factor at scales comparable to the inverse Bohr radius, the expansion of the Lamb shift in the moments breaks down. This is relevant for some of the explanations of the "proton size puzzle". We find, for instance, that the de Rújula toy model of the proton form factor does not resolve the puzzle as claimed, despite the large value of the third Zemach moment. Without relying on the radii expansion, we show how tiny, milli-percent (pcm) changes in the proton electric form factor at a MeV scale would be able to explain the puzzle. It shows that one needs to know all the soft contributions to proton electric form factor to pcm accuracy for a precision extraction of the proton charge radius from atomic Lamb shifts.
Comments:
5 pages, 3 figures; significant revision, version accepted for publication in Physical Review A (RC)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
1502.03721 [pdf]
PRA(2015)·13 citations
12
[Submitted on 12 Feb 2015] (cross-list from hep-ph)
Parton energy loss and momentum broadening at NLO in high temperature QCD plasmas
Jacopo Ghiglieri🇨🇭 · Derek Teaney🇺🇸
We present an overview of a perturbative-kinetic approach to jet propagation, energy loss, and momentum broadening in a high temperature quark-gluon plasma. The leading-order kinetic equations describe the interactions between energetic jet-particles and a non-abelian plasma, consisting of on-shell thermal excitations and soft gluonic fields. These interactions include 2<->2 scatterings, collinear bremsstrahlung, and drag and momentum diffusion. We show how the contribution from the soft gluonic fields can be factorized into a set of Wilson line correlators on the light cone. We review recent field-theoretical developments, rooted in the causal properties of these correlators, which simplify the calculation of the appropriate Wilson lines in thermal field theory. With these simplifications lattice measurements of transverse momentum broadening have become possible, and the kinetic equations describing parton transport have been extended to next-to-leading order in the coupling g.
Comments:
Review to appear in QGP5, 40 pages, 12 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.03730 [pdf]
IJMPE(2015)·59 citations
13
[Submitted on 12 Feb 2015] (cross-list from hep-ph)
Electromagnetic probes in heavy-ion collisions: Messengers from the hot and dense phase
H. van Hees🇩🇪 · J. Weil🇩🇪 · S. Endres🇩🇪 · M. Bleicher🇩🇪
Due to their penetrating nature, electromagnetic probes, i.e., lepton-antilepton pairs (dileptons) and photons are unique tools to gain insight into the nature of the hot and dense medium of strongly-interacting particles created in relativistic heavy-ion collisions, including hints to the nature of the restoration of chiral symmetry of QCD. Of particular interest are the spectral properties of the electromagnetic current-correlation function of these particles within the dense and/or hot medium. The related theoretical investigations of the in-medium properties of the involved particles in both the partonic and hadronic part of the QCD phase diagram underline the importance of a proper understanding of the properties of various hadron resonances in the medium.
Comments:
8 pages, 2 figures; Contribution to the proceedings of the Resonance Workshop at Catania 2014
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.03767 [pdf]
EPJ Web Conf.(2015)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE