Nuclear Theory·nucl-th

Monday·October 23, 2017

10 papers—4 primary·6 cross-listed

01
[Submitted on 19 Oct 2017]
Three-cluster dynamics within the ab initio no-core shell model with continuum: How many-body correlations and $α$ -clustering shape $^{6}$ He
Sofia Quaglioni (1) · Carolina Romero-Redondo (1) · Petr Navratil (2) · Guillaume Hupin (3) ((1) Lawrence Livermore National Laboratory, (2) TRIUMF, (3) CEA, DAM, DIF)
We realize the treatment of bound and continuum nuclear systems in the proximity of a three-body breakup threshold within the ab initio framework of the no-core shell model with continuum. Many-body eigenstates obtained from the diagonalization of the Hamiltonian within the harmonic-oscillator expansion of the no-core shell model are coupled with continuous microscopic three-cluster states to correctly describe the nuclear wave function both in the interior and asymptotic regions. We discuss the formalism in detail and give algebraic expressions for the case of core+ $n$ + $n$ systems. Using similarity-renormalization-group evolved nucleon-nucleon interactions, we analyze the role of $^{4}$ He+ $n$ + $n$ clustering and many-body correlations in the ground and low-lying continuum states of the Borromean $^{6}$ He nucleus, and study the dependence of the energy spectrum on the resolution scale of the interaction. We show that $^{6}$ He small binding energy and extended radii compatible with experiment can be obtained simultaneously, without recurring to extrapolations. We also find that a significant portion of the ground-state energy and the narrow width of the first $2^{+}$ resonance stem from many-body correlations that can be interpreted as core-excitation effects.
Comments:
25 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.07326 [pdf]
PRC(2018)·30 citations
02
[Submitted on 18 Oct 2017]
Nuclear medium effects in muonic neutrino interaction with energies from 0.2 GeV to 1.5 GeV
D. Vargas🇧🇷 · A.R. Samana🇧🇷 · F.G. Velasco🇧🇷 · O.R. Hoyos🇧🇷 · F. Guzmán🇧🇷 · J.L. Bernal-Castillo🇧🇷 · E. Andrade-II🇧🇷 · R. Perez🇧🇷 · A. Deppman🇧🇷 · C.A. Barbero🇦🇷 · A.E. Mariano🇦🇷
Nuclear reactions induced by muon neutrino with energies in the range from 0.2 to 1.5 GeV in Monte Carlo calculations framework in the intra-nuclear cascade model are studied. This study was done by comparison between the available experimental data and theoretical values of total cross section, and the energy distribution of emitted lepton energy in the reaction muon neutrino-nucleus, using the targets: $^{12}$ C, $^{16}$ O, $^{27}$ Al, $^{40}$ Ar, $^{56}$ Fe and $^{208}$ Pb. A phenomenological toy model of primary neutrino-nucleon interaction gives a good agreement of our theoretical inclusive neutrino nucleus cross in comparison with the available experimental data. Some interesting results on the behavior of the cross section as function of 1p-1n and higher contributions are also sketched. The previous results on the percentage of fake events related in available experiments in $^{12}$ C were expanded for the set studied nuclei. With the increase of mass target, the nuclear effects in the cross sections were observed along with the importance to take into account fake events in the reactions.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1710.07351 [pdf]
PRC(2017)·3 citations
03
[Submitted on 20 Oct 2017]
Comparison between the Lipkin-Nogami and Richardson solutions with complex single particle energy in the Lipkin's model
R. M. Id Betan
The pairing interaction is one of the most important contribution of the residual interaction and then, it is of major importance for the study of many-body systems. One can get solutions of the pairing Hamiltonian throught the Bardeen-Cooper-Schieffer (BCS) or the Lipkin-Nogami (LN) approximations but, the pairing Hamiltonian admit exact solution worked out by Richardson. Nuclei far away from the stability line have important correlations with the continuum part of the energy spectrum, due that the Fermi level is very close to the contiuum thershold. The correlations with the continuum can be included in the many-body description through the complex energy states, called Gamow states. In this work we compare the approximates and exact solutions of the pairing Hamiltonian in real and complex-energy representations. In the application of this formulation to the symmetric Lipkin model, we found that the LN solution is in a good agreement with the exact one; besides, the extension of the BCS solution to the complex energy plane gives solution even for strength below the critical one, which is purely imaginary.
Comments:
Published in the Anales de la Asociación Física Argentina. Vol. 28 N. 3, 87 (2017). six pages, seven figures, twenty references. Keywords: Lipkin-Nogami, Richardson, complex energy, Lipkin model, exact solution, pairing
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.07570 [pdf]
Anales AFA Vol. 28 Nro. 3, 87 (2017)·0 citations
04
[Submitted on 20 Oct 2017]
Fully coupled-channel study of $K^{-} pp$ resonance in a chiral SU(3)-based $K ˉ N$ potential
Akinobu Doté🇯🇵 · Takashi Inoue🇯🇵 · Takayuki Myo🇯🇵
We have investigated the most essential kaonic nucleus " $K^{-} pp$ " as a resonant state of the $K ˉ N N$ - $π Σ N$ - $π Λ N$ coupled channel system using a chiral SU(3)-based $K ˉ N$ potential. We treat the " $K^{-} pp$ " resonance adequately with a fully coupled-channel complex scaling method (full ccCSM). Self-consistency needs to be considered for the energy dependence of the chiral SU(3)-based potential. In the present study, we propose a simple prescription for the treatment of self-consistency, considering the {\it averaged threshold} and {\it averaged binding energy of mesons}. With this prescription, we have successfully found the self-consistent solutions of the " $K^{-} pp$ " three-body resonance. The results indicate that the " $K^{-} pp$ " system is bound rather shallowly. In particular, when the potential parameters are constrained with the latest $K ˉ N$ scattering length, the binding energy and half of the mesonic decay width are obtained as $14 - 50$ MeV and $8 - 19$ MeV, respectively.
Comments:
7 pages, 2 figures, accepted by Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.07589 [pdf]
PLB(2018)·33 citations
05
[Submitted on 19 Oct 2017] (cross-list from hep-ph)
Constraints on the hadronic spectrum from Lattice QCD
Paolo Parotto🇺🇸
The spectrum of hadronic resonances continually receives updates from the Particle Data Group, which lists every state with a status representing how established the state is. Moreover, the existence of additional states is predicted by relativistic quark models. It has been suggested that further states might need to be included in the hadronic spectrum in order to improve the agreement between the hadron resonance gas model predictions and lattice QCD data. Such an inclusion would also affect the results of many areas of heavy-ion collision physics that make use of hadronic degrees of freedom, such as hydrodynamical simulations afterburners. However, for some selected observables, the inclusion of further states worsens the agreement with the lattice results. We propose new observables, sensitive to the spectrum content divided by quantum numbers, which allow us to gauge the contribution of additional states. The comparison of Lattice QCD results and predictions from the Hadron Resonance Gas model for these observables, helps to clarify the situation and determine how many, and which new states are needed.
Comments:
5 pages, 4 figures, contribution to the proceedings of FAIRness 2017 conference in Sitges, Spain
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1710.07364 [pdf]
J.Phys.Conf.Ser.(2018)·0 citations
06
[Submitted on 20 Oct 2017] (cross-list from hep-ph)
Jet Quenching in The Most Vortical Fluid: A Holographic Approach
Brett McInnes🇸🇬
The STAR collaboration at the RHIC facility has recently announced the exciting discovery of direct evidence for extremely large vorticity in the Quark-Gluon Plasma generated in peripheral collisions, seen in the form of global polarization of $Λ$ and $Λ ˉ$ hyperons. This prompts the question: does this vorticity have any effect on other observed phenomena, such as jet quenching? Using a simple gauge-gravity model, we suggest that such an effect may be detectable, in data from near-future experiments, as a reduction in the jet quenching parameter. This is predicted to be most prominent in collisions corresponding to a narrow range of centralities around $10%$ . The relative reduction (compared to collisions at zero or, alternatively, large centrality) is predicted to behave in an unexpected and characteristic manner: the model suggests that it is independent of the impact energy.
Comments:
21 pages, no figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1710.07442 [pdf]
7 citations
07
[Submitted on 20 Oct 2017] (cross-list from nucl-ex)
Structure of 55Sc and development of the N=34 subshell closure
D. Steppenbeck · S. Takeuchi · N. Aoi · P. Doornenbal · M. Matsushita · H. Wang · H. Baba · S. Go · J. D. Holt · J. Lee · K. Matsui · S. Michimasa and 13 other authors
The low-lying structure of $^{55}$ Sc has been investigated using in-beam $γ$ -ray spectroscopy with the $^{9}$ Be( $^{56}$ Ti, $^{55}$ Sc+ $γ$ ) $X$ one-proton removal and $^{9}$ Be( $^{55}$ Sc, $^{55}$ Sc+ $γ$ ) $X$ inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory. Transitions with energies of 572(4), 695(5), 1539(10), 1730(20), 1854(27), 2091(19), 2452(26), and 3241(39) keV are reported, and a level scheme has been constructed using $γ γ$ coincidence relationships and $γ$ -ray relative intensities. The results are compared to large-scale shell-model calculations in the $s d$ - $p f$ model space, which account for positive-parity states from proton-hole cross-shell excitations, and to it ab initio shell-model calculations from the in-medium similarity renormalization group that includes three-nucleon forces explicitly. The results of proton-removal reaction theory with the eikonal model approach were adopted to aid identification of positive-parity states in the level scheme; experimental counterparts of theoretical $1/ 2_{1}^{+}$ and $3/ 2_{1}^{+}$ states are suggested from measured decay patterns. The energy of the first $3/ 2^{-}$ state, which is sensitive to the neutron shell gap at the Fermi surface, was determined. The result indicates a rapid weakening of the $N = 34$ subshell closure in $p f$ -shell nuclei at $Z > 20$ , even when only a single proton occupies the $π f_{7/2}$ orbital.
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1710.07465 [pdf]
PRC(2017)·29 citations
08
[Submitted on 20 Oct 2017] (cross-list from hep-lat)
Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime
Giuseppe Gagliardi🇩🇪 · Jangho Kim🇩🇪 · Wolfgang Unger🇩🇪
We present the computation of invariants that arise in the strong coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this limiting case $β \to 0$ are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the $μ_{B} - T$ plane has been established in the strong coupling limit. We present numerical simulations away from the strong coupling limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of $β$ .
Comments:
16 pages, 10 figures, Proceedings of the 35th International Symposium on Lattice Field Theory, Granada, Spain
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1710.07564 [pdf]
EPJ Web Conf.(2018)·20 citations
09
[Submitted on 20 Oct 2017] (cross-list from nucl-ex)
Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems
Peng Huo🇺🇸 · Katarina Gajdosova🇩🇰 · Jiangyong Jia🇺🇸 · You Zhou🇩🇰
Recently CMS Collaboration measured mixed-harmonic four-particle azimuthal correlations, known as symmetric cumulants SC(n,m), in pp and pPb collisions, and interpreted the non-zero SC(n,m) as evidence for long-range collectivity in these small collision systems. Using the PYTHIA and HIJING models which do not have genuine long-range collectivity, we show that the CMS results, obtained with standard cumulant method, could be dominated by non-flow effects associated with jet and dijets, especially in $pp$ collisions. We show that the non-flow effects are largely suppressed using the recently proposed subevent cumulant methods by requiring azimuthal correlation between two or more pseudorapidity ranges. We argue that the reanalysis of SC(n,m) using the subevent method in experiments is necessary before they can used to provide further evidences for a long-range multi-particle collectivity and constraints on theoretical models in small collision systems.
Comments:
7 pages and 6 figures, replace with published version
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1710.07567 [pdf]
PLB(2018)·53 citations
10
[Submitted on 20 Oct 2017] (cross-list from hep-ph)
Novel subjet observables for jet quenching in heavy-ion collisions
Liliana Apolinário🇵🇹 · José Guilherme Milhano🇵🇹 · Mateusz Ploskon🇺🇸 · Xiaoming Zhang🇨🇳
Using a novel observable that relies on the momentum difference of the two most energetic subjets within a jet $Δ S_{12}$ we study the internal structure of high-energy jets simulated by several Monte Carlo event generators that implement the partonic energy-loss in a dense partonic medium. Based on inclusive jet and di-jet production we demonstrate that $Δ S_{12}$ is an effective tool to discriminate between different models of jet modifications over a broad kinematic range. The new quantity, while preserving the colinear and infrared safety of modern jet algorithms, it is experimentally attractive because of its inherent resiliance against backgrounds of heavy-ion collisions.
Comments:
v1: 10 pages. v2: Includes (i) additional discussion about best discriminant by calculating the RSD (ii) new section about hadronization effects on the reconstructed subjets; version to be published in European Physical Journal C
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1710.07607 [pdf]
EPJC(2018)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE