Nuclear Theory·nucl-th

Tuesday·October 2, 2018

15 papers—8 primary·7 cross-listed

01
[Submitted on 28 Sept 2018]
Towards the Minimal Spectrum of Excited Baryons
J. Landay🇺🇸 · M. Mai🇺🇸 · M. Döring🇺🇸 · H. Haberzettl🇺🇸 · K. Nakayama🇺🇸
In the light baryon sector resonances can be broad and overlapping and are in most cases not directly visible in the cross section data. Automatized model selection techniques that introduce penalties for resonances can be used to determine the minimally needed set of resonances to describe the data. Several possible penalization schemes are compared. As an application we perform a blindfold identification of hyperon resonances in the $K ˉ N \to K Ξ$ reaction based on the Least Absolute Shrinkage and Selection Operator (LASSO) in combination with the Bayesian Information Criterion (BIC). We find ten resonances --- out of the 21 above-threshold hyperon resonances with spin $J \leq 7/2$ listed by the Particle Data Group. In traditional analyses, it is practically impossible to test the relevance of all resonances and their combinations that may potentially contribute to the reaction. By contrast, the present method proves capable of determining the relevant resonances among a large pool of candidates.
Comments:
19 pages, 11 figures, version accepted by journal
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.00075 [pdf]
PRD(2019)·23 citations
02
[Submitted on 29 Sept 2018]
Thermal vorticity and spin polarization in heavy-ion collisions
De-Xian Wei🇨🇳 · Wei-Tian Deng🇨🇳 · Xu-Guang Huang🇨🇳
The hot and dense matter generated in heavy-ion collisions contains intricate vortical structure in which the local fluid vorticity can be very large. Such vorticity can polarize the spin of the produced particles. We study the event-by-event generation of the so-called thermal vorticity in Au + Au collisions at energy region $s = 7.7 - 200$ GeV and calculate its time evolution, spatial distribution, etc., in a multiphase transport (AMPT) model. We then compute the spin polarization of the $Λ$ and $Λ ˉ$ hyperons as a function of $s$ , transverse momentum $p_{T}$ , rapidity, and azimuthal angle. Furthermore, we study the harmonic flow of the spin, in a manner analogous to the harmonic flow of the particle number. The measurement of the spin harmonic flow may provide a way to probe the vortical structure in heavy-ion collisions. We also discuss the spin polarization of $Ξ^{0}$ and $Ω^{-}$ hyperons which may provide further information about the spin polarization mechanism of hadrons.
Comments:
V2: 8 pages, 10 figures, references updated, published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1810.00151 [pdf]
PRC(2019)·181 citations
03
[Submitted on 29 Sept 2018]
A new and finite family of solutions of hydrodynamics: Part III: Advanced estimate of the life-time parameter
Tamás Csörgő · Gábor Kasza
We derive a new formula for the longitudinal HBT-radius of the two particle Bose-Einstein correlation function from a new family of finite and exact, accelerating solution of relativistic perfect fluid hydrodynamics for a temperature independent speed of sound. The new result generalizes the Makhlin-Sinyukov and Herrmann-Bertsch formulae and leads to an advanced life-time estimate of high energy heavy ion and proton-proton collisions.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.00154 [pdf]
Acta Phys. Pol. B Proc. Suppl. vol. 12 (2…·3 citations
04
[Submitted on 30 Sept 2018]
Ab-initio description of excited states of a one-dimensional nuclear matter with the Hohenberg-Kohn-theorem-inspired functional-renormalization-group method
Takeru Yokota🇯🇵 · Kenichi Yoshida🇯🇵 · Teiji Kunihiro🇯🇵
We demonstrate for the first time that a functional-renormalization-group aided density-functional theory (FRG-DFT) describes well the characteristic features of the excited states as well as the ground state of an interacting many-body system with infinite number of particles in a unified manner. The FRG-DFT is applied to a $(1 + 1)$ -dimensional spinless nuclear matter. For the excited states, the density--density spectral function is calculated at the saturation point obtained in the framework of FRG-DFT, and it is found that our result reproduces a notable feature of the density--density spectral function of the non-linear Tomonaga-Luttinger liquid: The spectral function has a singularity at the edge of its support of the lower-energy side. These findings suggest that the FRG-DFT is a promising first-principle scheme to analyze the excited states as well as the ground states of quantum many-body systems starting from the inter-particle interaction.
Comments:
10 pages, 3 figures, v2: two figures removed, sentences modified, title changed, to appear in PTEP letter
Subjects:
Nuclear Theory (nucl-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th)
arXiv:
1810.00422 [pdf]
PTEP(2019)·19 citations
05
[Submitted on 1 Oct 2018]
Gravitational Wave from Phase Transition inside Neutron Stars
Gaoqing Cao🇨🇳 · Shu Lin🇨🇳
In this work, we propose a new source for gravitational wave (GW) radiation associated with the quantum chromodynamics (QCD) phase transition in the inner cores of neutron stars. The mechanism is based on the bubble dynamics during the first-order phase transition from nuclear matter to quark matter. We identify the characteristic frequency to be of order $ω_{c} \sim 1 0^{6} rad/s$ for this kind of sources and the strain magnitude ( $h \sim 1 0^{- 24}$ for a neutron star at a distance of $0.1 Mpc$ ) reachable by future GW detectors. The GW spectra are shown to be useful to check the transition nature at high baryon chemical potential as well as to constrain the radius and density of the inner cores, which are still indistinct up to now.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
arXiv:
1810.00528 [pdf]
7 citations
06
[Submitted on 1 Oct 2018]
Many-body effects in (p,pN) reactions within a unified approach
R. Crespo · A. Arriaga · R.B. Wiringa · E. Cravo · A. Mecca · A. Deltuva
We study knockout reactions with proton probes within a theoretical framework where {\it ab initio} Quantum Monte Carlo wave functions are combined with the Faddeev/Alt-Grassberger-Sandhas few-body reaction formalism. New Quantum Monte Carlo wave functions are used to describe $^{12}$ C, yielding, for the first time, results consistent with the experimental point rms radii, electron scattering data and (p,2p) total cross sections data. Our results for $A \leq 12$ and $(N - Z) \leq 3$ nuclei show that the theoretical ratios between the (i) {\it ab initio} and Mean Field Approximation theoretical cross sections, $R_{σ}$ , (ii) corresponding ratios between the spectroscopic factors, $R_{Σ}$ , summed over states below particle emission, depend moderately on the nucleon separation energy S $_{N}$ . These ratios are determined by a delicate interplay between the radii of the parent and the residual nuclei and the nucleon separation energy, and were found to be always smaller for the knockout of the more correlated deficient species nucleon. In the case of the symmetric $^{12}$ C nucleus, the theoretical ratios still appear to indicate that protons are more correlated than neutrons.
Comments:
submitted for publication
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.00640 [pdf]
PLB(2020)·9 citations
07
[Submitted on 1 Oct 2018]
General predictions for the neutron star crustal moment of inertia
Thomas Carreau🇫🇷 · Francesca Gulminelli🇫🇷 · Jérôme Margueron🇫🇷
The neutron star crustal EoS and transition point properties are computed within a unified meta-modeling approach. A Bayesian approach is employed including two types of filters: bulk nuclear properties are controlled from low density effective field theory (EFT) predictions as well as the present knowledge from nuclear experiments, while the surface energy is adjusted on experimental nuclear masses. Considering these constraints, a quantitative prediction of crustal properties can be reached with controlled confidence intervals and increased precision with respect to previous calculations: { $\approx 11%$ } dispersion on the crustal width and { $\approx 27%$ } dispersion on the fractional moment of inertia. The crust moment of inertia is also evaluated as a function of the neutron star mass, and predictions for mass and radii are given for different pulsars. The possible crustal origin of Vela pulsar glitches is discussed within the present estimations of crustal entrainment, disfavoring a large entrainment phenomenon if the Vela mass is above $1.4 M_{⊙}$ . Further refinement of the present predictions requires a better estimation of the high order isovector empirical parameters, e.g. $K_{sy m}$ and $Q_{sy m}$ , and a better control of the surface properties of extremely neutron rich nuclei.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1810.00719 [pdf]
PRC(2019)·41 citations
08
[Submitted on 1 Oct 2018]
Automated Discovery of Jet Substructure Analyses
Yue Shi Lai🇺🇸
The study of the substructure of collimated particles from quarks and gluons, or jets, has the promise to reveal the details how color charges interact with the QCD plasma medium created in colliders such as RHIC and the LHC. Traditional jet substructure observables have been constructed using expert knowledge, and are largely transplanted, unmodified, from the high-energy physics, where the goal is primarily the study of boosted hadronic decays. A novel neural network architecture is described that is capable of examining theoretical models, and constructs, on its own, an analysis procedure that is sensitive to the internal model features. This architecture, in combination with symbolic regression, further allows the extraction of closed-form algebraic expressions from the learned result -- enabling the automatically constructed jet substructure analysis to be subsequently understood and reproduced by humans. This system is then tasked to construct an analysis that infers the plasma temperature from observing jets, which is demonstrated using both JEWEL and the Linearized Boltzmann Transport model, and at the presence of a realistic remnant of the plasma, or underlying event, that the measurement has to overcome. In a demonstration how algorithms can produce original research in direct competition to human experts, the resulting jet substructure variables and analyses are capable of determining the initial temperature of the plasma medium from analyzing 1200--2500 jets, a performance not seen in existing, manually designed analyses. Comparison of an incidentally discovered observable with the existing literature further indicates that the system described is capable of examining the model phase spaces to a detail at least comparable to the current field of human experts.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.00835 [pdf]
11 citations

Affiliations

first authorsco-authorsvia INSPIRE