Nuclear Theory·nucl-th

Friday·March 2, 2018

6 papers—4 primary·2 cross-listed

01
[Submitted on 1 Mar 2018]
Nonlinear coupling of flow harmonics: Hexagonal flow and beyond
Giuliano Giacalone🇫🇷 · Li Yan🇨🇦 · Jean-Yves Ollitrault🇫🇷
Higher Fourier harmonics of anisotropic flow ( $v_{4}$ and beyond) get large contributions induced by elliptic and triangular flow through nonlinear response. We present a general framework of nonlinear hydrodynamic response which encompasses the existing one, and allows to take into account the mutual correlation between the nonlinear couplings affecting Fourier harmonics of any order. Using Large Hadron Collider data on Pb+Pb collisions at ~ $s = 2.76$ TeV, we perform an application of our formalism to hexagonal flow, $v_{6}$ , a coefficient affected by several nonlinear contributions which are of the same order of magnitude. We obtain the first experimental measure of the coefficient $χ_{624}$ , which couples $v_{6}$ to $v_{2}$ and $v_{4}$ . This is achieved by putting together the information from several analyses: event-plane correlations, symmetric cumulants, as well as new higher-order moments recently analyzed by the ALICE collaboration. The value of $χ_{624}$ extracted from data is in fair agreement with hydrodynamic calculations, although with large error bars, which would be dramatically reduced by a dedicated analysis. We argue that within our formalism the nonlinear structure of a given higher harmonic can be determined more accurately than the harmonic itself, and we emphasize potential applications to future measurements of $v_{7}$ and $v_{8}$ .
Comments:
9 pages; 5 figures; the Mathematica notebook provided as ancillary file contains a step-by-step analysis of experimental data, with the derivation of all the quantities shown in the paper
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1803.00253 [pdf]
PRC(2018)·14 citations
02
[Submitted on 1 Mar 2018]
Faddeev approach to the reaction $K^{-} d \to π Σ n$ at $p_{K} = 1$ GeV/c
K. Miyagawa🇯🇵 · J. Haidenbauer🇩🇪 · H. Kamada🇯🇵
The reaction $K^{-} d \to π Σ n$ is studied within a Faddeev-type approach, with emphasis on the specific kinematics of the E31 experiment at J-PARC, i.e. $K^{-}$ beam momentum of $p_{K} = 1$ GeV/c and neutron angle of $θ_{n} = 0^{\circ}$ . The employed Faddeev approach requires as main input amplitudes for the two-body subsystems $K ˉ N \to K ˉ N$ and $K ˉ N \to π Σ$ . For the latter results from recently published chiral unitary models of the $K ˉ N$ interaction are utilized. The $K ˉ N \to K ˉ N$ amplitude itself, however, is taken from a recent partial-wave analysis. Due to the large incoming momentum of the $K^{-}$ , the $K ˉ N$ interaction is probed in a kinematical regime where those chiral potentials are no longer applicable. A comparison of the predicted spectrum for various $π Σ$ charge channels with preliminary data is made and reveals a remarkable agreement as far as the magnitude and the line shape in general is concerned. Noticeable differences observed in the $π Σ$ spectrum around the $K ˉ N$ threshold, i.e. in the region of the $Λ$ (1405) resonance, indicate a sensitivity to the details of the employed $K ˉ N \to π Σ$ amplitudes and suggest that pertinent high-precision data could indeed provide substantial constraints on the structure of the $Λ$ (1405).
Comments:
15 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.00330 [pdf]
PRC(2018)·10 citations
03
[Submitted on 1 Mar 2018]
Hyperons: the strange ingredients of the nuclear equation of state
Isaac Vidana🇮🇹
In this article we will review the role and properties of hyperons in finite and infinite nuclear systems. In particular, we will revise different production mechanisms of hypernuclei, as well as several aspects of hypernuclear $γ$ -ray spectroscopy, and the weak decay modes of hypernuclei. Then we will discuss the construction of hyperon-nucleon and hyperon-hyperon interactions on the basis of the meson-exchange and chiral effective field theories. Recent developments based on the so-called V $_{l o w k}$ approach and lattice QCD will also be adressed. Finally, we will go over some of the effects of hyperons on the properties of neutron and proto-neutron stars with an emphasis on the so-called "hyperon puzzle", {\it i.e.,} the problem of the strong softening of the equation of state, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a problem which has become more intringuing and difficult to solve due the recent measurements of $\sim 2 M_{⊙}$ millisecond pulsars. We will discuss some of the solutions proposed to tackle this problem. We will also re-examine the role of hyperons on the cooling properties of newly born neutron stars and on the development of the so-called r-mode instability.
Comments:
Invited review article to be published in the Proceedings of the Royal Society A. 43 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.00504 [pdf]
Proc.Roy.Soc.Lond.A(2018)·96 citations
04
[Submitted on 1 Mar 2018]
Beta Spectrum Generator: High precision allowed $β$ spectrum shapes
Leendert Hayen🇧🇪 · Nathal Severijns🇧🇪
Several searches for Beyond Standard Model physics rely on an accurate and highly precise theoretical description of the allowed $β$ spectrum. Following recent theoretical advances, a C++ implementation of an analytical description of the allowed beta spectrum shape was constructed. It implements all known corrections required to give a theoretical description accurate to a few parts in $1 0^{4}$ . The remaining nuclear structure-sensitive input can optionally be calculated in an extreme single-particle approximation with a variety of nuclear potentials, or obtained through an interface with more state-of-the-art computations. Due to its relevance in modern neutrino physics, the corresponding (anti)neutrino spectra are readily available with appropriate radiative corrections. In the interest of user-friendliness, a graphical interface was developed in Python with a coupling to a variety of nuclear databases. We present several test cases and illustrate potential usage of the code. Our work can be used as the foundation for current and future high-precision experiments related to the beta decay process. Source code: https://github.com/leenderthayen/BSG Documentation: http://bsg.readthedocs.io
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1803.00525 [pdf]
Comput.Phys.Commun.(2019)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nonlinear coupling of flow harmonics: Hexagonal flow and beyond

Faddeev approach to the reaction K−d→πΣn at pK​=1 GeV/c

Hyperons: the strange ingredients of the nuclear equation of state

Beta Spectrum Generator: High precision allowed β spectrum shapes

Affiliations

Faddeev approach to the reaction $K^{-} d \to π Σ n$ at $p_{K} = 1$ GeV/c

Beta Spectrum Generator: High precision allowed $β$ spectrum shapes