Nuclear Theory·nucl-th

Friday·December 9, 2016

9 papers—2 primary·7 cross-listed

03
[Submitted on 7 Dec 2016] (cross-list from astro-ph.SR)
Impact of $(α, n)$ reactions on weak r-process in neutrino-driven winds
Julia Bliss · Almudena Arcones · Fernando Montes · Jorge Pereira
After a successful core-collapse supernova, a neutrino-driven wind develops where it is possible to synthesize lighter heavy elements ( $30 < Z < 45$ ). In the early galaxy, the origin of these elements is associated to the r-process and to an additional process. Here we assume the additional process corresponds to the weak r-process or alpha-process taking place in neutrino-driven winds. Based on a trajectory obtained from hydrodynamical simulations we study the astrophysics and nuclear physics uncertainties with our main focus on the $(α, n)$ reactions. These are critical to redistribute the matter and allow to further move it from light to heavy elements after nuclear statistical equilibrium freezes out. In this first sensitivity study, we vary all $(α, n)$ reactions by given constant factors which are justified based on the uncertainties of the statistical model and its nuclear physics input, mainly alpha optical potentials under the conditions found in the wind. Our results show that $(α, n)$ reactions are indeed very important to predict abundances. Therefore, further studies will follow to identify individual critical reactions. Since the nucleosynthesis path is close to stability, these reactions can be measured in the near future. This will uniquely allow to reduce the nuclear physics uncertainties and thus to use observations to constrain and understand the astrophysical conditions in the wind.
Comments:
15 pages, 8 figures
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1612.02435 [pdf]
J.Phys.G(2017)·52 citations
04
[Submitted on 7 Dec 2016] (cross-list from hep-ph)
Hunting the Gluon Orbital Angular Momentum at the Electron-Ion Collider
Xiangdong Ji🇺🇸 · Feng Yuan🇺🇸 · Yong Zhao🇺🇸
Applying the connection between the parton Wigner distribution and orbital angular momentum (OAM), we investigate the probe of the gluon OAM in hard scattering processes at the planned electron-ion collider. We show that the single longitudinal target-spin asymmetry in the hard diffractive dijet production is very sensitive to the gluon OAM distribution. The associated spin asymmetry leads to a characteristic azimuthal angular correlation of $sin (ϕ_{q} - ϕ_{Δ})$ , where $ϕ_{Δ}$ and $ϕ_{q}$ are the azimuthal angles of the proton momentum transfer and the relative transverse momentum between the quark-antiquark pair. This study will enable a first measurement of the gluon OAM in the proton spin sum rule.
Comments:
8 pages, 2 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1612.02438 [pdf]
PRL(2017)·74 citations
05
[Submitted on 7 Dec 2016] (cross-list from hep-ph)
Gluon orbital angular momentum at small- $x$
Yoshitaka Hatta🇯🇵 · Yuya Nakagawa🇯🇵 · Bowen Xiao🇺🇸 · Feng Yuan🇺🇸 · Yong Zhao🇨🇳
We present a general analysis of the orbital angular momentum (OAM) distribution of gluons $L_{g} (x)$ inside the nucleon with particular emphasis on the small- $x$ region. We derive a novel operator representation of $L_{g} (x)$ in terms of Wilson lines and argue that it is approximately proportional to the gluon helicity distribution $L_{g} (x) \approx - 2Δ G (x)$ at small- $x$ . We also compute longitudinal single spin asymmetry in exclusive diffractive dijet production in lepton-nucleon scattering in the next-to-eikonal approximation and show that the asymmetry is a direct probe of the gluon helicity/OAM distribution as well as the QCD odderon exchange.
Comments:
22 pages. v2 significantly expands the previous version with all the details of derivation as well as a number of new results and discussions. The title and abstract are changed, and an author is added
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1612.02445 [pdf]
PRD(2017)·124 citations
06
[Submitted on 7 Dec 2016] (cross-list from hep-lat)
Non-equilibrium study of the Chiral Magnetic Effect from real-time simulations with dynamical fermions
Mark Mace🇺🇸 · Niklas Mueller🇩🇪 · Sören Schlichting🇺🇸 · Sayantan Sharma🇺🇸
We present a real-time lattice approach to study the non-equilibrium dynamics of vector and axial charges in $S U (N) \times U (1)$ gauge theories. Based on a classical description of the non-Abelian and Abelian gauge fields, we include dynamical fermions and develop operator definitions for (improved) Wilson and overlap fermions that allow us to study real-time manifestations of the axial anomaly from first principles. We present a first application of this approach to anomalous transport phenomena such as the Chiral Magnetic Effect (CME) and Chiral Separation Effect (CSE) by studying the dynamics of fermions during and after a $S U (N)$ sphaleron transition in the presence of a $U (1)$ magnetic field. We investigate the fermion mass and magnetic field dependence of the suggested signatures of the CME and CSE and point out some important aspects which need to be accounted for in the macroscopic description of anomalous transport phenomena.
Comments:
21 pages, 13 figures. RevTeX. V2: small clarifications and added references. To be published in Phys. Rev. D
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.02477 [pdf]
PRD(2017)·71 citations
07
[Submitted on 8 Dec 2016] (cross-list from physics.atom-ph)
Nuclear excitation by two-photon electron transition
A. V. Volotka · A. Surzhykov · S. Trotsenko · G. Plunien · Th. Stöhlker · S. Fritzsche
A new mechanism of nuclear excitation via two-photon electron transitions (NETP) is proposed and studied theoretically. As a generic example, detailed calculations are performed for the $E 1 E 1$ $1 s 2 s^{1} S_{0} \to 1 s^{2}^{1} S_{0}$ two-photon decay of He-like $^{225}$ Ac $^{87 +}$ ion with the resonant excitation of the $3/2 +$ nuclear state with the energy 40.09(5) keV. The probability for such a two-photon decay via the nuclear excitation is found to be $P_{NETP} = 3.5 \times 1 0^{- 9}$ and, thus, is comparable with other mechanisms, such as nuclear excitation by electron transition and by electron capture. The possibility for the experimental observation of the proposed mechanism is thoroughly discussed.
Comments:
5 pages, 4 figures
Subjects:
Atomic Physics (physics.atom-ph); Nuclear Theory (nucl-th)
arXiv:
1612.02570 [pdf]
PRL(2016)·3 citations
08
[Submitted on 8 Dec 2016] (cross-list from hep-ph)
Faddeev fixed center approximation to $π K ˉ K^{*}$ system and the $π_{1} (1600)$
Xu Zhang🇨🇳 · Ju-Jun Xie🇨🇳 · Xurong Chen🇨🇳
We investigate the three-body system of $π K ˉ K^{*}$ by using the fixed-center approximation to the Faddeev equation, taking the interaction between $π$ and $K ˉ$ , $π$ and $K^{*}$ , and $K ˉ$ and $K^{*}$ from the chiral unitary approach. The study is made assuming scattering of a $π$ on a $K ˉ K^{*}$ cluster, which is known to generate the $f_{1} (1285)$ state. The resonant structure around $1650$ MeV shows up in the modulus squared of the $π$ - $(K ˉ K^{*})_{f_{1} (1285)}$ scattering amplitude and suggests that a $π$ - $(K ˉ K^{*})_{f_{1} (1285)}$ state, with "exotic" quantum numbers $J^{P C} = 1^{-+}$ , can be formed. This state can be identified as the observed $π_{1} (1600)$ resonance. We suggest that this is the origin of the present $π_{1} (1600)$ resonance and propose to look at the $π f_{1} (1285)$ mode in future experiments to clarify the issue.
Comments:
6 pages, 5 figures. To match the published version in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1612.02613 [pdf]
PRD(2017)·7 citations
09
[Submitted on 8 Dec 2016] (cross-list from astro-ph.HE)
Charged current neutrino interactions in hot and dense matter
Luke F. Roberts🇺🇸 · Sanjay Reddy🇺🇸
We derive the charged current absorption rate of electron and anti-electron neutrinos in dense matter using a fully relativistic approach valid at arbitrary matter degeneracy. We include mean field energy shifts due to nuclear interactions and the corrections due to weak magnetism. The rates are derived both from the familiar Fermi's Golden Rule, and from the techniques of finite temperature field theory, and shown to be equivalent. In various limits, these results can also be used to calculate neutral current opacities. We find that some pieces of the response have been left out in previous derivations and their contribution at high density can be significant. Useful formulae and detailed derivations are presented and we provide a new open source implementation of these opacities for use in radiation hydrodynamic simulations of core-collapse supernovae and neutron star mergers.
Comments:
20 pages, 5 figures. Accepted to PRC
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1612.02764 [pdf]
PRC(2017)·83 citations

Affiliations

first authorsco-authorsvia INSPIRE

Impact of (α,n) reactions on weak r-process in neutrino-driven winds

Hunting the Gluon Orbital Angular Momentum at the Electron-Ion Collider

Gluon orbital angular momentum at small-x

Non-equilibrium study of the Chiral Magnetic Effect from real-time simulations with dynamical fermions

Nuclear excitation by two-photon electron transition

Faddeev fixed center approximation to πKˉK∗ system and the π1​(1600)

Charged current neutrino interactions in hot and dense matter

Affiliations

Impact of $(α, n)$ reactions on weak r-process in neutrino-driven winds

Gluon orbital angular momentum at small- $x$

Faddeev fixed center approximation to $π K ˉ K^{*}$ system and the $π_{1} (1600)$