Nuclear Theory·nucl-th

Tuesday·January 8, 2019

12 papers—6 primary·6 cross-listed

01
[Submitted on 4 Jan 2019]
Shrinking the Quark Gluon Plasma
Matthew D. Sievert🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
In recent years the understanding on the limits of the smallest possible droplet of the Quark Gluon Plasma has been called into question. Experimental results from both the Large Hadron Collider and the Relativistic Heavy Ion Collider have provided hints that the Quark Gluon Plasma may be produced in systems as small as that formed in pPb or dAu collisions. Yet alternative explanations still exist from correlations arising from quarks and gluons in a color glass condensate picture. In order to resolve these two scenarios, a system size scan has been proposed at the Large Hadron Collider for collisions of ArAr and OO. Here we make predictions for a possible future run of ArAr and OO collisions at the Large Hadron Collider and study the system size dependence of a variety of flow observables. We find that linear response (from the initial conditions to the final flow harmonics) becomes more dominant in smaller systems whereas linear+cubic response can accurately predict multi-particle cumulants for a wide range of centralities in large systems.
Comments:
21 pages, 25 figure; v2 Fig 3-5 replaced, Fig. 7 added
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1901.01319 [pdf]
PRC(2019)·90 citations
02
[Submitted on 5 Jan 2019]
What is wrong with our current nuclear forces?
R. Machleidt
I discuss ab initio predictions for light and intermediate-mass nuclei as well as nuclear matter. Problems and open issues are outlined and an attempt is made to relate them to specific deficiencies of the chiral two- and many-nucleon forces currently in use. In particular, I identify the softness of the NN potential (due to non-locality) as one important factor for the improvement of microscopic predictions. This finding is very much in tune with the recent investigation by Lu et al. (arXiv:1812.10928) where---within a simple, but realistic model---it is shown that proper nuclear matter saturation requires a considerable amout of non-locality in the NN interaction.
Comments:
7 pages, 2 figures; contribution to the Proceedings of the International Conference `Nuclear Theory in the Supercomputing Era 2018' (NTSE-2018), Daejeon, South Korea, October 29 - November 2, 2018, eds. A. M. Shirokov and A. I. Mazur, Pacific National University, Khabarovsk, Russia, 2019
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1901.01473 [pdf]
Nucl.Theor.(2018)·3 citations
03
[Submitted on 6 Jan 2019]
Open Heavy Flavors in Nuclear Collisions: Theory Overview
Pol Bernard Gossiaux🇫🇷
I review the current status and some prospects of theoretical studies on open heavy flavor physics in nuclear collisions at RHIC and LHC energies.
Comments:
Proceedings from Quark Matter 2018 plenary talk (Venezia)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1901.01606 [pdf]
NPA(2019)·7 citations
04
[Submitted on 6 Jan 2019]
The QCD Kondo phase in quark stars
R. Fariello · Juan C. Macías🇧🇷 · F. S. Navarra🇧🇷
We study light (u, d) quark matter with charm impurities. These impurities are added to the Lagrangian density. We derive the equation of state (EOS) of this kind of quark matter, which contains a Kondo phase. We explore this EOS and study the structure of stars, identifying the effects of the Kondo phase. Solving the TOV equations and computing the mass-radius diagram, we find that the presence of a Kondo phase leads to smaller and lighter stars.
Comments:
12 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1901.01623 [pdf]
15 citations
05
[Submitted on 7 Jan 2019]
Phenomenological view on baryon-baryon potentials from lattice QCD simulations
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪
A qualitative discussion on the range of the potentials as they result from the phenomenological meson-exchange picture and from lattice simulations by the HAL QCD Collaboration is presented. For the former pion- and/or $η$ -meson exchange are considered together with the scalar-isoscalar component of correlated $π π / K K ˉ$ exchange. It is observed that the intuitive expectation for the behavior of the baryon-baryon potentials for large separations, associated with the exchange of one and/or two pions, does not always match with the potentials extracted from the lattice simulations. Only in cases where pion exchange provides the longest ranged contribution, like in the $Ξ N$ system, a reasonable qualitative agreement between the phenomenological and the lattice QCD potentials is found for baryon-baryon separations of $r ≳ 1$ fm. For the $Ω N$ and $ΩΩ$ interactions where isospin conservation rules out one-pion exchange a large mismatch is observed, with the potentials by the HAL QCD Collaboration being much longer ranged and much stronger at large distances as compared to the phenomenological expectation. This casts some doubts on the applicability of using these potentials in few- or many-body systems.
Comments:
8 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1901.01801 [pdf]
EPJA(2019)·12 citations
06
[Submitted on 7 Jan 2019]
Jets in non-equilibrium quark-gluon plasma
Sigtryggur Hauksson🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Jets are a promising way to probe the non-equilibrium physics of quark-gluon plasma (QGP). We study how an out-of-equilibrium medium induces a jet particle to emit gluons. Evaluation of the emission rate is complicated by Weibel instabilities which lead to an exponential growth of chromomagnetic fields. Deriving a quantum field theoretical description of an unstable QGP medium, we show that the chromomagnetic fields deflect jet particles during the gluon emission.
Comments:
Proceedings for Hard Probes 2018
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1901.01924 [pdf]
PoS(2018)·0 citations
07
[Submitted on 5 Jan 2019] (cross-list from astro-ph.HE)
Origin of the Heaviest Elements: the Rapid Neutron-Capture Process
John J. Cowan🇺🇸 · Christopher Sneden🇺🇸 · James E. Lawler🇺🇸 · Ani Aprahamian🇺🇸 · Michael Wiescher🇺🇸 · Karlheinz Langanke🇩🇪 · Gabriel Martínez-Pinedo🇩🇪 · Friedrich-Karl Thielemann🇨🇭
The production of about half of the heavy elements found in nature is assigned to a specific astrophysical nucleosynthesis process: the rapid neutron capture process (r-process). Although this idea has been postulated more than six decades ago, the full understanding faces two types of uncertainties/open questions: (a) The nucleosynthesis path in the nuclear chart runs close to the neutron-drip line, where presently only limited experimental information is available, and one has to rely strongly on theoretical predictions for nuclear properties. (b) While for many years the occurrence of the r-process has been associated with supernovae, more recent studies have cast substantial doubts on this environment. Alternative scenarios include the mergers of neutron stars, neutron-star black hole mergers, but possibly also rare classes of supernovae as well as hypernovae/collapsars with polar jet ejecta and also accretion disk outflows related to the collapse of fast rotating massive stars with high magnetic fields. Stellar r-process abundance observations, have provided insights into, and constraints on the frequency of and conditions in the responsible stellar production sites. One of them, neutron star mergers, was just identified and related to the Gravitational Wave event GW170817. High resolution observations, increasingly more precise due to improved experimental atomic data, have been particularly important in defining the heavy element abundance patterns of the old halo stars, and thus determining the extent, and nature, of the earliest nucleosynthesis in our Galaxy. Combining new results and important breakthroughs in the related nuclear, atomic and astronomical fields of science, this review attempts to provide an answer to the question "How Were the Elements from Iron to Uranium Made?" (Abridged)
Comments:
96 pages, 42 figures, 2 tables, author copy manuscript published in Reviews of Modern Physics
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1901.01410 [pdf]
RMP(2021)·574 citations
08
[Submitted on 5 Jan 2019] (cross-list from hep-ph)
Radiative corrections to the jet quenching parameter in dilute and dense media
Jean-Paul Blaizot🇫🇷 · Fabio Dominguez🇪🇸
We extend the calculation of radiative corrections to momentum broadening in a QCD medium to include processes where single scattering dominates over multiple soft scatterings. Our analysis focusses on processes that are enhanced by a potentially large double logarithmic contribution. We demonstrate that such double logarithmic contributions emerge in calculations of momentum broadening in dilute systems where only single scattering occurs. We show how the different regimes, multiple versus single scattering, constrain different parts of the phase space.
Comments:
15 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1901.01448 [pdf]
PRD(2019)·17 citations
09
[Submitted on 6 Jan 2019] (cross-list from hep-ph)
Chiral Kinetic Theory from Effective Field Theory Revisited
Shu Lin🇨🇳 · Aradhya Shukla🇨🇳
We revisit the chiral kinetic equation from high density effective theory approach, finding a chiral kinetic equation differs from counterpart derived from field theory in high order terms in the $O (1/ μ)$ expansion, but in agreement with the equation derived in on-shell effective field theory upon identification of cutoff. By using reparametrization transformation properties of the effective theory, we show that the difference in kinetic equations from two approaches are in fact expected. It is simply due to different choices of degree of freedom by effective theory and field theory. We also show that they give equivalent description of the dynamics of chiral fermions.
Comments:
26 pages, extend discussion on reparametrization transformation and its relation with side-jump
Subjects:
High Energy Physics — Phenomenology (hep-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Nuclear Theory (nucl-th)
arXiv:
1901.01528 [pdf]
JHEP(2019)·45 citations
10
[Submitted on 6 Jan 2019] (cross-list from hep-ph)
The dispersion relation of the fast neutrino oscillation wave
Changhao Yi🇺🇸 · Lei Ma🇺🇸 · Joshua D. Martin🇺🇸 · Huaiyu Duan (UNM)
A dense neutrino medium can support flavor oscillation waves which are coherent among different momentum modes of the neutrinos. The dispersion relation (DR) branches of such a wave with complex frequencies and/or wave numbers can lead to the exponential growth of the wave amplitude which in turn will engender a collective flavor transformation in the neutrino medium. In this work we propose that the complex DR branches of the neutrino oscillation wave should be bound by the critical points of the DR. We demonstrate how this theory can be applied to the neutrino medium with an (approximate) axial symmetry about the propagation direction of the neutrino oscillation wave. We also show how the flavor instabilities in this medium can be identified by tracing the critical points of the DR as the electron lepton number distribution of the neutrino medium is changed continuously.
Comments:
11 pages, 4 figures. Small textual changes for clarification
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1901.01546 [pdf]
PRD(2019)·86 citations
11
[Submitted on 7 Jan 2019] (cross-list from cond-mat.quant-gas)
Time fractals and discrete scale invariance with trapped ions
Dean Lee · Jacob Watkins · Dillon Frame · Gabriel Given · Rongzheng He · Ning Li · Bing-Nan Lu · Avik Sarkar
We show that a one-dimensional chain of trapped ions can be engineered to produce a quantum mechanical system with discrete scale invariance and fractal-like time dependence. By discrete scale invariance we mean a system that replicates itself under a rescaling of distance for some scale factor, and a time fractal is a signal that is invariant under the rescaling of time. These features are reminiscent of the Efimov effect, which has been predicted and observed in bound states of three-body systems. We demonstrate that discrete scale invariance in the trapped ion system can be controlled with two independently tunable parameters. We also discuss the extension to n-body states where the discrete scaling symmetry has an exotic heterogeneous structure. The results we present can be realized using currently available technologies developed for trapped ion quantum systems.
Comments:
4 + 5 pages (main + supplemental materials), 2 + 3 figures (main + supplemental materials), version to appear in Physical Review A Rapid Communications
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1901.01661 [pdf]
PRA(2019)·6 citations
12
[Submitted on 7 Jan 2019] (cross-list from nucl-ex)
Observation of excited states in $^{20}$ Mg sheds light on nuclear forces and shell evolution
J. S. Randhawa · R. Kanungo · M. Holl · J. D. Holt · P. Navratil · S. R. Stroberg · G. Hagen · G. R. Jansen · M. Alcorta · C. Andreoiu · C. Barnes · C. Burbadge and 26 other authors
The exotic Borromean nucleus $^{20}$ Mg with $N$ = 8, located at the proton drip-line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in $^{20}$ Mg from the $^{20}$ Mg( $d$ , $d^{'}$ ) reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and {\it ab initio} calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of $β_{n}$ =0.46 $\pm$ 0.21. This provides the first indication of a possible weakening of the $N$ = 8 shell closure at the proton drip-line.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1901.01741 [pdf]
PRC(2019)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE