Nuclear Theory·nucl-th

Thursday·May 3, 2018

11 papers—3 primary·8 cross-listed

01
Marchenko method with incomplete data and singular nucleon scattering
Mahmut Elbistan · Pengming Zhang · Janos Balog
We apply the Marchenko method of quantum inverse scattering to study nucleon scattering problems. Assuming a $β / r^{2}$ type repulsive core and comparing our results to the Reid93 phenomenological potential we estimate the constant $β$ , determining the singularity strength, in various spin/isospin channels. Instead of using Bargmann type S-matrices which allows only integer singularity strength, here we consider an analytical approach based on the incomplete data method, which is suitable for fractional singularity strengths as well.
nucl-thmath-phmath.MPPTEP(2019)·1 citation
02
Net-charge fluctuation in Au+Au collisions at energies available at the Facility for Antiproton and Ion Research using the UrQMD model
Somnath Ghosh🇮🇳 · Provash Mali🇮🇳 · Amitabha Mukhopadhyay🇮🇳
We have studied the dynamical fluctuation of net-charge of hadrons produced in Au+Au collisions at energies that in near future will be available at the Facility for Antiproton and Ion Research (FAIR). Data simulated by a microscopic transport model based on ultra-relativistic quantum molecular dynamics are analyzed for the purpose. The centrality and pseudorapidity dependence of the net-charge fluctuation of hadrons are examined. Our simulated results are compared with the results available for nucleus-nucleus collision experiments held at similar energies. The gross features of our simulated results on net-charge fluctuations are found to be consistent with the experiment. At incident beam energy $E_{lab} = 10 A$ GeV the magnitude of net-charge fluctuation is very large, and in comparison with the rest its centrality dependence appears to be a little unusual. The effect of global charge conservation is expected to be very crucial at FAIR energies. The charge fluctuations measured with varying pesudorapidity window size depend on the collision centrality. The dependence is however exactly opposite in nature to that observed in the Pb+Pb collision at $s_{_{N N}} = 2.76$ TeV.
nucl-thhep-phPRC(2017)·13 citations
03
A short walk through the physics of neutron stars
Isaac Vidana🇮🇹
In this work we shortly review several aspects of the physics of neutron stars. After the introduction we present a brief historical overview of the idea of neutron stars as well as of the theoretical and observational developments that followed it from the mid 1930s to the present. Then, we review few aspects of their observation discussing, in particular, the different types of telescopes that are used, the many astrophysical manifestations of these objects, and several observables such as masses, radii or gravitational waves. Finally, we briefly summarize some of theoretical issues like their composition, structure equations, equation of state, and neutrino emission and cooling.
nucl-thEur.Phys.J.Plus(2018)·45 citations
04
Coulomb Potential Is Not a Part of The QCD Potential
Gouranga C Nayak🇺🇸
The Coulomb plus linear potential is widely used in QCD. However, in this paper we show that the Coulomb potential of the form $\frac{1}{r}$ is not a part of the QCD potential. This is because the form $\frac{g ^{2}}{r}$ is for abelian theory (not QCD) and the form $\frac{g ^{2} ( μ )}{r}$ in QCD at short distance is not of the Coulomb form $\frac{1}{r}$ because $g (μ)$ depends on the mass/length scale $μ$ . Similarly at long distance the QCD potential corresponds to the potential in the classical Yang-Mills theory which does not have the Coulomb form $\frac{1}{r}$ because the fundamental color charge of the quark is time dependent in the classical Yang-Mills theory. This is unlike the QED potential which reduces to Coulomb potential at long distance.
↳ hep-phhep-latnucl-th0 citations
05
Nonperturbatively-renormalized glue momentum fraction at physical pion mass from Lattice QCD
Yi-Bo Yang🇺🇸 · Ming Gong🇨🇳 · Jian Liang🇺🇸 · Huey-Wen Lin🇺🇸 · Keh-Fei Liu🇺🇸 · Dimitra Pefkou🇺🇸 · Phiala Shanahan🇺🇸
We present the first nonperturbatively-renormalized determination of the glue momentum fraction $⟨ x ⟩_{g}$ in the nucleon, based on lattice-QCD simulations at physical pion mass using the cluster-decomposition error reduction (CDER) technique. We provide the first practical strategy to renormalize the glue energy-momentum tensor (EMT) nonperturbatively in the RI/MOM scheme, and convert the results to the $MS$ scheme with 1-loop matching. The simulation results show that the CDER technique can reduce the statistical uncertainty of its renormalization constant by a factor of $O$ (300) in calculations using typical state-of-the-art lattice volume, and the nonperturbatively-renormalized $⟨ x ⟩_{g}$ is shown to be independent of the lattice definitions of the glue EMT up to discretization errors. We determine the renormalized $⟨ x ⟩_{g}^{MS} (2 GeV)$ to be 0.47(4)(11) at physical pion mass, which is consistent with the experimentally-determined value.
↳ hep-lathep-phnucl-thPRD(2018)·60 citations
06
Charged pion condensation under parallel electromagnetic fields
Jingyi Chao🇨🇳 · Mei Huang🇨🇳 · Andrey Radzhabov🇨🇳
The formation of charged pion condensate under parallel electromagnetic fields is studied within the two-flavor Nambu--Jona-Lasinio model. The technique of Schwinger proper time method is extended to explore the quantity locating in the off-diagonal flavor space, i.e., charged pion. We obtain the associated effective potential as a function of the strength of the electromagnetic fields and find out that it contains a sextic term which possibly induce weakly first order phase transition. Dependence of pion condensation on model parameters is investigated.
↳ hep-phnucl-thCPC(2020)·16 citations
07
Nonequilibrium axial charge production in expanding glasma flux tubes
Naoto Tanji🇮🇹
Axial charge production at the early stage of heavy-ion collisions is investigated within the framework of real-time lattice simulations at leading order in QCD coupling. Starting from color glass condensate initial conditions, the time evolution of quantum quark fields under classical color gauge fields is computed on a lattice in longitudinally expanding geometry. We consider simple color charge distributions in Lorentz contracted nuclei that realize flux tube-like configurations of color fields carrying nonzero topological charge after a collision. By employing the Wilson fermion extended to the longitudinally expanding geometry, we demonstrate the realization of the axial anomaly on the real-time lattice.
↳ hep-phhep-latnucl-thPRD(2018)·9 citations
08
Enhanced low-energy $γ$ -decay strength of $^{70}$ Ni and its robustness within the shell model
A. C. Larsen · J. E. Midtbø · M. Guttormsen · T. Renstrøm · S. N. Liddick · A. Spyrou · S. Karampagia · B. A. Brown · O. Achakovskiy · S. Kamerdzhiev · D. L. Bleuel · A. Couture and 10 other authors
Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their $γ$ -emission probability at very low $γ$ energies. In this work, we present measurements of the $γ$ -decay strength of $^{70}$ Ni over the wide range $1.3 \leq E_{γ} \leq 8$ MeV. A significant enhancement is found in the $γ$ -decay strength for transitions with $E_{γ} < 3$ MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed $E 1$ -strength calculations within the quasiparticle time-blocking approximation, which describe our data above $E_{γ} ≃ 5$ MeV very well. Moreover, large-scale shell-model calculations indicate an $M 1$ nature of the low-energy $γ$ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich $^{72, 74, 76} Ni$ .
↳ nucl-exnucl-thPRC(2018)·48 citations
09
Holographic Bjorken flow of a hot and dense fluid in the vicinity of a critical point
Renato Critelli (Sao Paulo U.)🇧🇷 · Romulo Rougemont (Rio de Janeiro State U.)🇧🇷 · Jorge Noronha (Sao Paulo U.)🇧🇷
In this paper we use the gauge/gravity duality to perform the first systematic study of the onset of hydrodynamic behavior in a hot and dense far-from-equilibrium strongly coupled relativistic fluid with a critical point. By employing a top-down holographic construction that stems from string theory, we numerically obtain the full nonlinear evolution of the far-from-equilibrium system undergoing a Bjorken expansion and address the following question: how does hydrodynamic behavior emerge in the vicinity of a critical point in the phase diagram? For the top-down holographic system analyzed in the present work, we find that the approach to hydrodynamics is strongly affected by the presence of the critical point: the closer the ratio between the chemical potential and the temperature is to its critical value, the longer it takes for the system to be well described by the equations of viscous hydrodynamics.
↳ hep-thhep-phnucl-thPRD(2019)·38 citations
10
Nucleon axial form factor from a Bayesian neural-network analysis of neutrino-scattering data
Luis Alvarez-Ruso🇪🇸 · Krzysztof M. Graczyk🇵🇱 · Eduardo Saul-Sala🇪🇸
The Bayesian approach for feed-forward neural networks has been applied to the extraction of the nucleon axial form factor from the neutrino-deuteron scattering data measured by the Argonne National Laboratory (ANL) bubble chamber experiment. This framework allows to perform a model-independent determination of the axial form factor from data.. When the low $0.05 < Q^{2} < 0.10$ GeV $^{2}$ data is included in the analysis, the resulting axial radius disagrees with available determinations. Furthermore, a large sensitivity to the corrections from the deuteron structure is obtained. In turn, when the low- $Q^{2}$ region is not taken into account, with or without deuteron corrections, no significant deviations from the dipole ansatz have been observed. A more accurate determination of the nucleon axial form factor requires new precise measurements of neutrino-induced quasielastic scattering on hydrogen and deuterium.
↳ hep-phhep-exnucl-exnucl-thPRC(2019)·35 citations
11
On the Properties of Neutrinos
A. Baha Balantekin🇺🇸 · Boris Kayser🇺🇸
Our present understanding of neutrino properties is reviewed with a particular emphasis on observable differences between Majorana and Dirac neutrinos. Current and future experimental efforts towards measuring neutrino properties are summarized. Consequences of the Majorana vs.Dirac nature of neutrinos on neutrino masses, neutrino decays, and neutrino electromagnetic properties are described.
↳ hep-phhep-thnucl-thAnn.Rev.Nucl.Part.Sci.(2018)·95 citations

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