Nuclear Theory·nucl-th

Wednesday·July 26, 2017

10 papers—5 primary·5 cross-listed

01
[Submitted on 24 Jul 2017]
Analysis of the Daya Bay Reactor Antineutrino Flux Changes with Fuel Burnup
Anna Hayes🇺🇸 · Gerard Jungman🇺🇸 · Libby McCutchan🇺🇸 · Alejandro Sonzogni🇺🇸 · Gerry Garvey🇺🇸 · Xiaobao Wang🇨🇳
We investigate the recent Daya Bay results on the changes in the antineutrino flux and spectrum with the burnup of the reactor fuel. We find that the discrepancy between current model predictions and the Daya Bay results can be traced to the original measured $^{235}$ U/ $^{239}$ Pu ratio of the fission beta spectra that were used as a base for the expected antineutrino fluxes. An analysis of the antineutrino spectra that is based on a summation over all fission fragment beta-decays, using nuclear database input, explains all of the features seen in the Daya Bay evolution data. However, this summation method still predicts an anomaly. Thus, we conclude that there is currently not enough information to use the antineutrino flux changes to rule out the possible existence of sterile neutrinos.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1707.07728 [pdf]
PRL(2018)·53 citations
02
[Submitted on 25 Jul 2017]
Fixed-t analyticity as a constraint in single energy partial wave analyses of meson photoproduction reactions
H. Osmanović🇧🇦 · M. Hadžimehmedović🇧🇦 · R. Omerović🇧🇦 · J. Stahov🇧🇦 · V. Kashevarov🇩🇪 · K. Nikonov🇩🇪 · M. Ostrick🇩🇪 · L. Tiator🇩🇪 · A. Švarc🇭🇷
Partial wave amplitudes of meson photoproduction reactions are an important source of information in baryon spectroscopy. We investigate a new approach in single-energy partial wave analyses of these reactions. Instead of using a constraint to theoretical models in order to achieve solutions which are continuous in energy, we enforce the analyticity of the amplitudes at fixed values of the Mandelstam variable $t$ . We present an iterative procedure with successive fixed- $t$ amplitude analyses which constrain the single-energy partial wave analyses and apply this method to the $γ p \to η p$ reaction. We use pseudo data, generated by the EtaMAID model, to test the method and to analyze ambiguities. Finally, we present an analytically constrained partial wave analysis using experimental data for four polarization observables recently measured at MAMI and GRAAL in the energy range from threshold to $s = 1.85$ GeV.
Comments:
46 pages, 24 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1707.07891 [pdf]
PRC(2018)·15 citations
03
[Submitted on 25 Jul 2017]
Evolution of pressures and correlations in the Glasma produced in high energy nuclear collisions
M. Ruggieri🇨🇳 · J. H. Liu🇮🇹 · L. Oliva. G. X. Peng🇨🇳 · V. Greco🇮🇹
We consider the SU(2) Glasma with gaussian fluctuations and study its evolution by means of classical Yang-Mills equations solved numerically on a lattice. Neglecting in this first study the longitudinal expansion we follow the evolution of the pressures of the system and compute the effect of the fluctuations in the early stage up to $t \approx 2$ fm/c, that is the time range in which the Glasma is relevant for high energy collisions. We measure the ratio of the longitudinal over the transverse pressure, $P_{L} / P_{T}$ , and we find that unless the fluctuations carry a substantial amount of the energy density at the initial time, they do not change significantly the evolution of $P_{L} / P_{T}$ in the early stage, and that the system remains quite anisotropic. We also measure the longitudinal fields correlators both in the transverse plane and along the longitudinal direction: while at initial time fields appear to be anticorrelated in the transverse plane, this anticorrelation disappears in the very early stage and the correlation length in the transverse plane increases; on the other hand, we find that the longitudinal correlator decreases for a small longitudinal separation while being approximately constant for larger separation, which we interpret as a partial loss of longitudinal correlation induced by the dynamics.
Comments:
14 pages, 10 figures. To appear on Phys. Rev. D. In V2 the discussion about isotropization has been resized, while a broad discussion about the gauge invariant correlators along the longitudinal direction and the breaking of the Glasma color strings has been added. In V3 a mistake about the definition of the parallel transporter has been corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Theory (hep-th)
arXiv:
1707.07956 [pdf]
PRD(2018)·19 citations
04
[Submitted on 25 Jul 2017]
Collective longitudinal polarization in relativistic heavy-ion collisions at very high energy
F. Becattini (1)🇮🇹 · Iu. Karpenko (2) ((1) U. Florence (2) INFN Florence)🇮🇹
We study the polarization of particles in relativistic heavy-ion collisions at very high energy along the beam direction within a relativistic hydrodynamic framework. We show that this component of the polarization decreases much slower with center-of-mass energy compared to the transverse component, even in the ideal longitudinal boost-invariant scenario with non-fluctuating initial state, and that it can be measured by taking advantage of its quadrupole structure in the transverse momentum plane. In the ideal longitudinal boost-invariant scenario, the polarization is proportional to the gradient of temperature at the hadronization and its measurement can provide important information about the cooling rate of the Quark Gluon Plasma around the critical temperature.
Comments:
5 pages, 3 figures, final version published in Phys. Rev. Lett
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1707.07984 [pdf]
PRL(2018)·242 citations
05
[Submitted on 21 Jul 2017]
Extended Chiral Quark Models in the Framework of Quantum Chromodynamic: Theory and their Applications in Hot and Dense Mediums
M. Abu-Shady🇪🇬
In this review article, we give overview on the extended chiral quark models. In particular, how these models are extended to include the higher-order interactions, quantized fields, logarithmic potential and the effect of these modifications on hadron properties at hot and dense mediums. In addition, how we deal with non-normalization of the Nambu-Jona-Lasinio (NJL) model by using mid-point technique. Therefore, the extended quark models give satisfied results in comparison with lattice QCD at finite temperature and baryonic chemical potential. The extra effort is needed to deal with chiral quark models in the presence of external magnetic field at finite temperature and density.
Comments:
12 pages, 7 figures, and 3 Tables. arXiv admin note: text overlap with arXiv:1507.02214
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1707.08045 [pdf]
Open Access Journal of Physics, Volume 1,…·1 citation
06
[Submitted on 21 Jul 2017] (cross-list from hep-ph)
DPS in CGC: Double Quark Production and Effects of Quantum Statistics
Alex Kovner🇨🇱 · Amir H. Rezaeian🇨🇱
We consider forward inclusive production of two quarks in the high energy p-A collisions in the CGC formalism. We demonstrate that the production cross-section is determined by the convolution of the proton generalized double transverse momentum-dependent distribution (2GTMD) functions with two independent eikonal scattering amplitudes: the product of two dipoles and a quadrupole. We explicitly demonstrate that the quadrupole amplitude term accounts for all the (initial and final state) effects of quantum statistics for identical fermions, and the correlations due to these effects. We also demonstrate that the effects due to quantum statistics (entirely encoded in the quadrupole) are parametrically leading contributions to the correlated particle production at large $N_{c}$ . For non-identical quarks the quadrupole term also leads to correlated production which has characteristics similar to the HBT effect.
Comments:
15 pages, 1 figure; v3: results unchanged, clarifying comments added. The version to appear in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1707.06985 [pdf]
PRD(2017)·33 citations
07
[Submitted on 24 Jul 2017] (cross-list from hep-ph)
Nucleon form factors in dispersively improved Chiral Effective Field Theory I: Scalar form factor
J. M. Alarcón🇺🇸 · C. Weiss🇺🇸
We propose a method for calculating the nucleon form factors (FFs) of $G$ -parity-even operators by combining Chiral Effective Field Theory ( $χ$ EFT) and dispersion analysis. The FFs are expressed as dispersive integrals over the two-pion cut at $t > 4 M_{π}^{2}$ . The spectral functions are obtained from the elastic unitarity condition and expressed as products of the complex $π π \to N N ˉ$ partial-wave amplitudes and the timelike pion FF. $χ$ EFT is used to calculate the ratio of the partial-wave amplitudes and the pion FF, which is real and free of $π π$ rescattering in the $t$ -channel ( $N / D$ method). The rescattering effects are then incorporated by multiplying with the squared modulus of the empirical pion FF. The procedure results in a marked improvement compared to conventional $χ$ EFT calculations of the spectral functions. We apply the method to the nucleon scalar FF and compute the scalar spectral function, the scalar radius, the $t$ -dependent FF, and the Cheng-Dashen discrepancy. Higher-order chiral corrections are estimated through the $π N$ low-energy constants. Results are in excellent agreement with dispersion-theoretical calculations. We elaborate several other interesting aspects of our method. The results show proper scaling behavior in the large- $N_{c}$ limit of QCD because the $χ$ EFT calculation includes $N$ and $Δ$ intermediate states. The squared modulus of the timelike pion FF required by our method can be extracted from Lattice QCD calculations of vacuum correlation functions of the operator at large Euclidean distances. Our method can be applied to the nucleon FFs of other operators of interest, such as the isovector-vector current, the energy-momentum tensor, and twist-2 QCD operators (moments of generalized parton distributions).
Comments:
17 pages and 11 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1707.07682 [pdf]
PRC(2017)·31 citations
08
[Submitted on 24 Jul 2017] (cross-list from hep-ph)
Multi-angle calculation of the matter-neutrino resonance near an accretion disk
Shashank Shalgar🇺🇸
We perform a numerical study of the matter-neutrino resonance in a multi-angle calculation in the vicinity of an accretion disk. We assume thermally distributed neutrino and anti-neutrino fields emitted by two-dimensional disk that is homogeneous and isotropic; the electrons are assumed to be at constant density. We compare the the result of this computation to that obtained using single-angle approximation. We investigate the robustness of matter-neutrino resonance in environment surrounding accretion disks by progressively relaxing the single angle approximation. We find that the multi-angle results in the present simplified model do not support a robust resonance mechanism as suggested by the single angle treatment. We also discuss the context under which matter-neutrino resonance may be important in future studies.
Comments:
10 pages, 3 figures. Version accepted in JCAP
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1707.07692 [pdf]
JCAP(2018)·20 citations
09
[Submitted on 25 Jul 2017] (cross-list from astro-ph.HE)
Entrainment in Superfluid Neutron Star Crusts: Hydrodynamic Description and Microscopic Origin
N. Chamel
In spite of the absence of viscous drag, the neutron superfluid permeating the inner crust of a neutron star cannot flow freely, and is entrained by the nuclear lattice similarly to laboratory superfluid atomic gases in optical lattices. The role of entrainment on the neutron superfluid dynamics is reviewed. For this purpose, a minimal hydrodynamical model of superfluidity in neutron-star crusts is presented. This model relies on a fully four-dimensionally covariant action principle. The equivalence of this formulation with the more traditional approach is demonstrated. In addition, the different treatments of entrainment in terms of dynamical effective masses or superfluid density are clarified. The nuclear energy density functional theory employed for the calculations of all the necessary microscopic inputs is also reviewed, focusing on superfluid properties. In particular, the microscopic origin of entrainment and the different methods to estimate its importance are discussed.
Comments:
30 pages, 4 figures
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
1707.07854 [pdf]
J.Low Temp.Phys.(2017)·44 citations
10
[Submitted on 25 Jul 2017] (cross-list from hep-ph)
Entropy Production During Hadronization of a Quark-Gluon Plasma
Tamas S. Biro🇭🇺 · Zsolt Schram🇭🇺 · Laszlo Jenkovszky🇺🇦
We revisit the physical pictures for the hadronization of quark-gluon plasma, concentrating on the problem of entropy production during processes where the number of degrees of freedom is seemingly reduced due to color confinement. Based on observations on Regge trajectories we propose not having an infinite tower of hadronic resonances. We discuss possible entropy production mechanisms far from equilibrium in terms of stochastic dynamics.
Comments:
Submitted to EPJ A Topical Issue on "Frontiers in nuclear, heavy ion and strong field physics", in memoriam Walter Greiner
Subjects:
High Energy Physics — Phenomenology (hep-ph); Statistical Mechanics (cond-mat.stat-mech); Nuclear Theory (nucl-th)
arXiv:
1707.07912 [pdf]
EPJA(2018)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE