Nuclear Theory·nucl-th

Friday·December 21, 2018

16 papers—7 primary·9 cross-listed

01
[Submitted on 19 Dec 2018]
Chiral symmetry restoration by parity doubling and the structure of neutron stars
Michał Marczenko · David Blaschke · Krzysztof Redlich · Chihiro Sasaki
Recent lattice QCD studies at vanishing density exhibit the parity-doubling structure for the low-lying baryons around the chiral crossover temperature. This finding is likely an imprint of the chiral symmetry restoration in the baryonic sector of QCD, and is expected to occur also in cold dense matter, which makes it of major relevance for compact stars. By contrast, typical effective models for compact star matter embody chiral physics solely in the deconfined sector, with quarks as degrees of freedom. In this contribution, we present a description of QCD matter based on the effective hybrid quark-meson-nucleon model. Its characteristic feature is that, under neutron-star conditions, the chiral symmetry is restored in a first-order phase transition deep in the hadronic phase, before the deconfinement of quarks takes place. We discuss the implications of the parity doubling of baryons on the mass-radius relation for compact stars obtained in accordance with the modern constraints on the mass from PSR J0348+0432, the compactness from GW170817, as well as the direct URCA process threshold. We show that the existence of high-mass stars might not necessarily signal the deconfinement of quarks.
Comments:
prepared for the XIIIth Quark Confinement and the Hadron Spectrum Proceedings
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.08250 [pdf]
PoS(2018)·0 citations
02
[Submitted on 19 Dec 2018]
Iterative approaches to the self-consistent nuclear energy density functional problem. Heavy ball dynamics and potential preconditioning
W. Ryssens🇺🇸 · M. Bender🇫🇷 · P.-H. Heenen🇧🇪
Large-scale applications of energy density functional (EDF) methods depend on fast and reliable algorithms to solve the associated non-linear self-consistency problem. When dealing with large single-particle variational spaces, existing solvers can become very slow, and their performance dependent on manual fine-tuning of numerical parameters. In addition, convergence can sensitively depend on particularities of the EDF's parametrisation under consideration. Using the widely-used Skyrme EDF as an example, we investigate the impact of the parametrisation of the EDF, both in terms of the operator structures present and the size of coupling constants, on the convergence of numerical solvers. We focus on two aspects of the self-consistency cycle, which are the diagonalisation of a fixed single-particle Hamiltonian on one hand and the evolution of the mean-field densities and potentials on the other. Throughout the article we use a coordinate-space representation, for which the behaviour of algorithms can be straightforwardly analysed. We propose two algorithmic improvements that are easily implementable in existing solvers, heavy-ball dynamics and potential preconditioning. We demonstrate that these methods can be made virtually parameter-free, requiring no manual fine-tuning to achieve near-optimal performance except for isolated cases. The combination of both methods decreases substantially the CPU time required to obtain converged results. The improvements are illustrated for the MOCCa code that solves the self-consistent HFB problem in a 3d coordinate space representation for parametrisations of the standard Skyrme EDF at next-to-leading order in gradients and its extension to next-to-next-to-leading order.
Comments:
29 pages, 18 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.08262 [pdf]
EPJA(2019)·19 citations
03
[Submitted on 20 Dec 2018]
Dilute Fermi gas at fourth order in effective field theory
C. Wellenhofer🇩🇪 · C. Drischler🇺🇸 · A. Schwenk🇩🇪
Using effective field theory methods, we calculate for the first time the complete fourth-order term in the Fermi-momentum or $k_{F} a_{s}$ expansion for the ground-state energy of a dilute Fermi gas. The convergence behavior of the expansion is examined for the case of spin one-half fermions and compared against quantum Monte-Carlo results, showing that the Fermi-momentum expansion is well-converged at this order for $∣ k_{F} a_{s} ∣ ≲ 0.5$ .
Comments:
6 pages, 2 figures; v2: minor improvements in text, references updated, matches published version
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1812.08444 [pdf]
PLB(2020)·20 citations
04
[Submitted on 20 Dec 2018]
Low-lying dipole strengths for probable $p$ -wave one-neutron halos in the medium mass region
Manju (IITR) · J. Singh (Uni Hokkaido) · Shubhchintak (ULB) · R. Chatterjee (IITR)
The one-neutron halos lying in the island of inversion around $N = 20$ has provided the podium, to study the variation of total low-lying dipole strength with the neutron separation energy. We study three probable p-wave one-neutron halo candidates 31Ne and 34Na and 37Mg lying in the island of inversion. A simple analytic model has been used for the calculation of the total low-lying dipole strength for the medium mass p-wave one-neutron halos. A correction factor to this analytical model has been estimated with a realistic Woods-Saxon potential. A comparison of these analytic calculations has been made with the those performed by a finite-range distorted-wave Born approximation theory of the Coulomb dissociation. We also make an estimate of the one-neutron separation energies of 31Ne, 34Na and 37Mg.
Comments:
7 pages latex, 4 figures, to appear in EPJA
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1812.08482 [pdf]
EPJA(2019)·14 citations
05
[Submitted on 20 Dec 2018]
Bottom Production in $pp$ Collisions at Large Hadron Collider Energies using Parton Cascade Model
Rupa Chatterjee · Dinesh K. Srivastava
We study the production of bottom quarks in $pp$ collisions at Large Hadron Collider energies using previously developed parton cascade model to explore the impact of Landau Pomeranchuk Midgal (LPM) effect on their dynamics. In contrast to the case for charm quarks reported recently, we find only a marginal impact of the suppression of multiple scatterings of partons due to the LPM effect on their production. It is felt that this happens as they are only produced in very hard collisions.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1812.08661 [pdf]
1 citation
06
[Submitted on 20 Dec 2018]
Proton elastic scattering on calcium isotopes from chiral nuclear optical potentials
T. R. Whitehead · Y. Lim · J. W. Holt
We formulate microscopic optical potentials for nucleon-nucleus scattering from chiral two- and three-nucleon forces. The real and imaginary central terms of the optical potentials are obtained from the nucleon self energy in infinite nuclear matter at a given density and isospin asymmetry, calculated self-consistently to second order in many-body perturbation theory. The real spin-orbit term is extracted from the same chiral potential using an improved density matrix expansion. The density-dependent optical potential is then folded with the nuclear density distributions of 40Ca, 42Ca, 44Ca, and 48Ca from which we study proton-nucleus elastic scattering and total reaction cross sections using the reaction code TALYS. We compare the results of the microscopic calculations to those of phenomenological models and experimental data up to projectile energies of E = 180 MeV. While overall satisfactory agreement with the available experimental data is obtained, we find that the elastic scattering and total reaction cross sections can be significantly improved with a weaker imaginary optical potential, particularly for larger projectile energies.
Comments:
12 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.08725 [pdf]
PRC(2019)·37 citations
07
[Submitted on 20 Dec 2018]
Ab initio no-core shell model study of $^{18 - 23}$ O and $^{18 - 24}$ F isotopes
Archana Saxena · Praveen C. Srivastava
In the present work, we have done a comprehensive study of low-lying energy spectrum for oxygen and fluorine chains using $ab ini t i o$ no core shell model. We have used inside nonlocal outside Yukawa (INOY) potential, which is a two body interaction but also has the effect of three body forces by short range and nonlocal character. Also, we have performed calculations with N3LO and N2LOopt interactions and compared corresponding results with the experimental data and phenomenological USDB interaction. We have reached up to $N_{ma x}$ =6 for $^{18 - 21}$ O and $^{18 - 19}$ F, $N_{ma x}$ =4 for other oxygen and fluorine isotopes, respectively. We have also discussed the binding energy of oxygen and fluorine chains. Over binding in the ground state (g.s.) energy in neutron rich oxygen isotopes is observed in our largest model space calculations.
Comments:
Accepted in Journal of Physics G: Nuclear and Particle Physics (2020)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.08744 [pdf]
J.Phys.G(2020)·19 citations
08
[Submitted on 19 Dec 2018] (cross-list from hep-ph)
PHOTON-2017 conference proceedings
David d'Enterria · Albert de Roeck · Michelangelo Mangano (eds.) · Jaroslav Adam · Massimiliano Alvioli · Christopher D. Anson · Hamed Bakhshiansohi · Cristian Baldenegro · Valerio Bertone · Stanley J. Brodsky · Peter J. Bussey · Chav Chhiv Chau and 69 other authors
This document collects the proceedings of the PHOTON 2017 conference ("International Conference on the Structure and the Interactions of the Photon", including the 22th "International Workshop on Photon-Photon Collisions", and the "International Workshop on High Energy Photon Colliders") held at CERN (Geneva) in May 2017. The latest experimental and theoretical developments on the topics of the PHOTON conference series are covered: (i) $γ γ$ processes in e $^{+}$ e $^{-}$ , proton-proton (pp) and nucleus-nucleus (AA) collisions at current and future colliders, (ii) $γ$ -hadron interactions in e $^{\pm}$ p, pp, and AA collisions, (iii) final-state photon production (including Standard Model studies and searches beyond it) in pp and AA collisions, and (iv) high-energy $γ$ -ray astrophysics. These proceedings are dedicated to the memory of Maria Krawczyk.
Comments:
296 pages. CERN-Proceedings-2018-001 (CERN, Geneva, 2018), to appear. arXiv admin note: substantial text overlap with arXiv:1804.05614, arXiv:1708.06683, arXiv:1709.09044, arXiv:1708.00912, arXiv:1708.07173, arXiv:1709.02985, arXiv:1709.00176, arXiv:1709.05167, arXiv:1708.05756, arXiv:1708.09759, arXiv:1708.07531, arXiv:1703.08450, arXiv:1711.02551, arXiv:1511.07794, arXiv:1712.10104, arXiv:1708.05776, arXiv:1712.10202, arXiv:1709.07110, arXiv:1702.08730, arXiv:1709.02648, arXiv:1411.6397
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1812.08166 [pdf]
CERN Proc.(2018)·6 citations
09
[Submitted on 19 Dec 2018] (cross-list from astro-ph.HE)
Equation of state sensitivities when inferring neutron star and dense matter properties
S. K. Greif · G. Raaijmakers · K. Hebeler · A. Schwenk · A. L. Watts
Understanding the dense matter equation of state at extreme conditions is an important open problem. Astrophysical observations of neutron stars promise to solve this, with NICER poised to make precision measurements of mass and radius for several stars using the waveform modelling technique. What has been less clear, however, is how these mass-radius measurements might translate into equation of state constraints and what are the associated equation of state sensitivities. We use Bayesian inference to explore and contrast the constraints that would result from different choices for the equation of state parametrization; comparing the well-established piecewise polytropic parametrization to one based on physically motivated assumptions for the speed of sound in dense matter. We also compare the constraints resulting from Bayesian inference to those from simple compatibility cuts. We find that the choice of equation of state parametrization and particularly its prior assumptions can have a significant effect on the inferred global mass-radius relation and the equation of state constraints. Our results point to important sensitivities when inferring neutron star and dense matter properties. This applies also to inferences from gravitational wave observations.
Comments:
to appear in MNRAS
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1812.08188 [pdf]
MNRAS(2019)·195 citations
10
[Submitted on 19 Dec 2018] (cross-list from hep-ph)
Subleading Power Rapidity Divergences and Power Corrections for $q_{T}$
Markus A. Ebert🇺🇸 · Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Frank J. Tackmann🇩🇪 · Gherardo Vita🇺🇸 · Hua Xing Zhu🇨🇳
A number of important observables exhibit logarithms in their perturbative description that are induced by emissions at widely separated rapidities. These include transverse-momentum ( $q_{T}$ ) logarithms, logarithms involving heavy-quark or electroweak gauge boson masses, and small- $x$ logarithms. In this paper, we initiate the study of rapidity logarithms, and the associated rapidity divergences, at subleading order in the power expansion. This is accomplished using the soft collinear effective theory (SCET). We discuss the structure of subleading-power rapidity divergences and how to consistently regulate them. We introduce a new pure rapidity regulator and a corresponding $MS$ -like scheme, which handles rapidity divergences while maintaining the homogeneity of the power expansion. We find that power-law rapidity divergences appear at subleading power, which give rise to derivatives of parton distribution functions. As a concrete example, we consider the $q_{T}$ spectrum for color-singlet production, for which we compute the complete $q_{T}^{2} / Q^{2}$ suppressed power corrections at $O (α_{s})$ , including both logarithmic and nonlogarithmic terms. Our results also represent an important first step towards carrying out a resummation of subleading-power rapidity logarithms.
Comments:
40 pages + appendices, 3 figures; v2: TMD collaboration included in acknowledgement; v3: minor changes, journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.08189 [pdf]
JHEP(2019)·163 citations
11
[Submitted on 19 Dec 2018] (cross-list from hep-ph)
QCD Sum Rules Approach to the $X, Y$ and $Z$ States
Raphael M. Albuquerque🇧🇷 · Jorgivan M. Dias🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷 · Fernando S. Navarra🇧🇷 · Marina Nielsen🇧🇷 · Carina M. Zanetti🇧🇷
In the past decade, due to the experimental observation of many charmonium-like states, there has been a revival of hadron spectroscopy. In particular, the experimental observation of charged charmonium-like, $Z_{c}$ states, and bottomonium-like, $Z_{b}$ states, represents a challenge since they can not be accommodated within the naive quark model. These charged states are good candidates of either tetraquark or molecular states and their observation motivated a vigorous theoretical activity. This is a rapidly evolving field with enormous amount of new experimental information. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. The present review is written from the perspective of the QCD sum rules approach, where we present the main steps of concrete calculations and compare the results with other approaches and with experimental data.
Comments:
90 pages, 27 figures; to be published in Journal of Physics G
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.08207 [pdf]
J.Phys.G(2019)·152 citations
12
[Submitted on 19 Dec 2018] (cross-list from hep-ph)
Slow neutron production as a probe of hadron formation in high-energy $γ^{*} A$ reactions
A.B. Larionov🇩🇪 · M. Strikman🇺🇸
Deep Inelastic Scattering (DIS) experiments at the planned Electron-Ion Collider will be affected by details of the hadron formation inside the nuclear volume. Besides semi-inclusive particle production experiments decays of the target nucleus via emission of neutrons provide an additional opportunity to probe this domain. This paper reports on the hybrid dynamical+statistical calculations of low-energy neutron production in muon- and virtual photon-induced collisions with nuclei. We confirm the conclusion that the E665 data on neutron production in $μ^{-}$ + Pb DIS at 470 GeV indicate a strong suppression of the final state interaction for hadrons with momenta above $\sim 1$ GeV/c. Ultraperipheral heavy-ion collisions at the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC) can be used to test this suppression. The calculations of the neutron multiplicity distributions and $p_{t}$ -spectra in photon - nucleus collisions at the energies accessible at the LHC and RHIC are presented for several models of hadron formation. We argue that studies of neutron production in ultraperipheral heavy ion collisions open a new window on the small- $x$ dynamics and hadron component of the photon wave function.
Comments:
34 pages, 10 figures, revised sec. 1 and 2, main results and conclusions unchanged, version accepted in Phys. Rev. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1812.08231 [pdf]
PRC(2020)·13 citations
13
[Submitted on 19 Dec 2018] (cross-list from physics.data-an)
Event-shape engineering and heavy-flavour observables in relativistic heavy-ion collisions
A. Beraudo🇮🇹 · A. De Pace🇮🇹 · M. Monteno🇮🇹 · M. Nardi🇮🇹 · F. Prino🇮🇹
Traditionally, events collected at relativistic heavy-ion colliders are classified according to some centrality estimator (e.g. the number of produced charged particles) related to the initial energy density and volume of the system. In a naive picture the latter are directly related to the impact parameter of the two nuclei, which sets also the initial eccentricity of the system: zero in the case of the most central events and getting larger for more peripheral collisions. A more realistic modelling requires to take into account event-by-event fluctuations, in particular in the nucleon positions within the colliding nuclei: collisions belonging to the same centrality class can give rise to systems with different initial eccentricity and hence different flow harmonics for the final hadron distributions. This issue can be addressed by an event-shape-engineering analysis, consisting in selecting events with the same centrality but different magnitude of the average bulk anisotropic flow and therefore of the initial-state eccentricity. In this paper we present the implementation of this analysis in the POWLANG transport model, providing predictions for the transverse-momentum and angular distributions of charm and beauty hadrons for event-shape selected collisions. In this way it is possible to get information on how the heavy quarks propagating (and hadronizing) in a hot environment respond both to its energy density and to its geometric asymmetry, breaking the perfect correlation between eccentricity and impact parameter which characterizes a modelling of the medium based on smooth average initial conditions
Subjects:
Data Analysis, Statistics and Probability (physics.data-an); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1812.08337 [pdf]
EPJC(2019)·20 citations
14
[Submitted on 20 Dec 2018] (cross-list from hep-ph)
A theoretical analysis of the doubly radiative decays $η^{(')} \to π^{0} γ γ$ and $η^{'} \to η γ γ$
Rafel Escribano🇪🇸 · Sergi Gonzàlez-Solís🇨🇳 · Renata Jora🇷🇴 · Emilio Royo🇪🇸
The scalar and vector meson exchange contributions to the doubly radiative decays $η^{(')} \to π^{0} γ γ$ and $η^{'} \to η γ γ$ are analysed within the Linear Sigma Model and Vector Meson Dominance frameworks, respectively. Predictions for the diphoton invariant mass spectra and the associated integrated branching ratios are given and compared with current available experimental data. Whilst a satisfactory description of the shape of the $η \to π^{0} γ γ$ and $η^{'} \to π^{0} γ γ$ decay spectra is obtained, thus supporting the validity of the approach, the corresponding branching ratios cannot be reproduced simultaneously. A first theoretical prediction for the recently measured $η^{'} \to η γ γ$ by the BESIII collaboration is also presented.
Comments:
16 pages, 4 figures, 2 tables; v2: includes experimental measurement for the $η^{'} \to η γ γ$ , a better treatment for the $σ$ propagator and a new discussion on the values of the $V P γ$ couplings
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1812.08454 [pdf]
PRD(2020)·42 citations
15
[Submitted on 20 Dec 2018] (cross-list from hep-lat)
Finite-density gauge correlation functions in QC2D
Tamer Boz🇮🇪 · Ouraman Hajizadeh🇦🇹 · Axel Maas🇦🇹 · Jon-Ivar Skullerud🇮🇪
2-color QCD is the simplest QCD-like theory which is accessible to lattice simulations at finite density. It therefore plays an important role to test qualitative features and to provide benchmarks to other methods and models, which do not suffer from a sign problem. To this end, we determine the minimal-Landau-gauge propagators and 3-point vertices in this theory over a wide range of densities, the vacuum, and at both finite temperature and density. The results show that there is essentially no modification of the gauge sector in the low-temperature, low-density phase. Even outside this phase only mild modifications appear, mostly in the chromoelectric sector.
Comments:
45 pages, 23 figures, 1 table; v2: Some technical details added, minor modifications
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.08517 [pdf]
PRD(2019)·40 citations
16
[Submitted on 20 Dec 2018] (cross-list from hep-lat)
Consistency between Lüscher's finite volume method and HAL QCD method for two-baryon systems in lattice QCD
Takumi Iritani🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵
There exist two methods to study two-baryon systems in lattice QCD: the direct method which extracts eigenenergies from the plateaux of the temporal correlator and the HAL QCD method which extracts observables from the non-local potential associated with the tempo-spatial correlator. Although the two methods should give the same results theoretically, qualitatively different results have been reported. Recently, we pointed out that the separation of the ground state from the excited states is crucial to obtain sensible results in the former, while both states provide useful signals in the latter. In this paper, we identify the contribution of each state in the direct method by decomposing the two-baryon correlators into the finite-volume eigenmodes obtained from the HAL QCD method. We consider the $ΞΞ$ system in the $^{1}$ S $_{0}$ channel at $m_{π} = 0.51$ GeV in 2+1 flavor lattice QCD using the wall and smeared quark sources. We demonstrate that the "pseudo-plateau" at early time slices (t = 1~2 fm) from the smeared source in the direct method indeed originates from the contamination of the excited states, and the true plateau with the ground state saturation is realized only at t > 5~15 fm corresponding to the inverse of the lowest excitation energy. We also demonstrate that the two-baryon operator can be optimized by utilizing the finite-volume eigenmodes, so that (i) the finite-volume energy spectra from the HAL QCD method agree with those from the optimized temporal correlator and (ii) the correct spectra would be accessed in the direct method only if highly optimized operators are employed. Thus we conclude that the long-standing issue on the consistency between the Lüscher's finite volume method and the HAL QCD method for two baryons is now resolved: They are consistent with each other quantitatively only if the excited contamination is properly removed in the former.
Comments:
34 pages, 17 figurs, published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1812.08539 [pdf]
JHEP(2019)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE