Nuclear Theory·nucl-th

Tuesday·October 3, 2017

25 papers—15 primary·10 cross-listed

01
Nuclear deformation in the laboratory frame
C.N. Gilbreth · Y. Alhassid · G.F. Bertsch
We develop a formalism for calculating the distribution of the axial quadrupole operator in the laboratory frame within the rotationally invariant framework of the configuration-interaction shell model. The calculation is carried out using a finite-temperature auxiliary-field quantum Monte Carlo method. We apply this formalism to isotope chains of even-mass samarium and neodymium nuclei, and show that the quadrupole distribution provides a model-independent signature of nuclear deformation. Two technical advances are described that greatly facilitate the calculations. The first is to exploit the rotational invariance of the underlying Hamiltonian to reduce the statistical fluctuations in the Monte Carlo calculations. The second is to determine quadruple invariants from the distribution of the axial quadrupole operator. This allows us to extract effective values of the intrinsic quadrupole shape parameters without invoking an intrinsic frame or a mean-field approximation.
nucl-thcond-mat.mes-hallPRC(2018)·15 citations
02
Revealing Fine Structure in the Antineutrino Spectra From a Nuclear Reactor
A. A. Sonzogni🇺🇸 · M. Nino🇺🇸 · E. A. McCutchan🇺🇸
We calculate the Inverse Beta Decay (IBD) antineutrino spectrum generated by nuclear reactors using the summation method to understand deviations from the smooth Huber-Mueller model due to the decay of individual fission products, showing that plotting the ratio of two adjacent spectra points can effectively reveal these deviations. We obtained that for binning energies of 0.1 MeV or lower, abrupt changes in the spectra due to the jagged nature of the individual antineutrino spectra could be observed for highly precise experiments. Surprisingly, our calculations also reveal a peak-like feature in the adjacent points ratio plot at 4.5 MeV even with a 0.25 MeV binning interval, which we find is present in the IBD Daya Bay spectrum published in 2016. We show that this 4.5 MeV feature is caused by the contributions of just four fission products, 95Y, 98,101N and 102Tc. This would be the first evidence of the decay of a few fission products in the IBD antineutrino spectrum from a nuclear reactor.
nucl-thhep-exhep-phnucl-exPRC(2018)·40 citations
03
Correlated Prompt Fission Data in Transport Simulations
P. Talou · R. Vogt · J. Randrup · M.E. Rising · S.A. Pozzi · J. Verbeke · M.T. Andrews · S.D. Clarke · P. Jaffke · M. Jandel · T. Kawano · M.J. Marcath and 6 other authors
Detailed information on the fission process can be inferred from the observation, modeling and theoretical understanding of prompt fission neutron and $γ$ -ray~observables. Beyond simple average quantities, the study of distributions and correlations in prompt data, e.g., multiplicity-dependent neutron and \gray~spectra, angular distributions of the emitted particles, $n$ - $n$ , $n$ - $γ$ , and $γ$ - $γ$ ~correlations, can place stringent constraints on fission models and parameters that would otherwise be free to be tuned separately to represent individual fission observables. The FREYA~and CGMF~codes have been developed to follow the sequential emissions of prompt neutrons and $γ$ -rays~from the initial excited fission fragments produced right after scission. Both codes implement Monte Carlo techniques to sample initial fission fragment configurations in mass, charge and kinetic energy and sample probabilities of neutron and $γ$ ~emission at each stage of the decay. This approach naturally leads to using simple but powerful statistical techniques to infer distributions and correlations among many observables and model parameters. The comparison of model calculations with experimental data provides a rich arena for testing various nuclear physics models such as those related to the nuclear structure and level densities of neutron-rich nuclei, the $γ$ -ray~strength functions of dipole and quadrupole transitions, the mechanism for dividing the excitation energy between the two nascent fragments near scission, and the mechanisms behind the production of angular momentum in the fragments, etc. Beyond the obvious interest from a fundamental physics point of view, such studies are also important for addressing data needs in various nuclear applications. (See text for full abstract.)
nucl-thnucl-exEPJA(2018)·46 citations
04
Alternative methods to measure global polarization of $Λ$ hyperons
Irfan Siddique🇨🇳 · Zuo-tang Liang🇨🇳 · Michael Annan Lisa🇺🇸 · Qun Wang🇨🇳 · Zhang-bu Xu🇨🇳
We propose alternative methods to measure the global polarization of $Λ$ hyperons. These methods involve event averages of proton's and $Λ$ 's momenta in the lab frame. We carry out simulations using these methods and show that all of them work equivalently well in obtaining the global polarization of $Λ$ hyperons.
nucl-thCPC(2019)·5 citations
05
Peeling off neutron skins from neutron-rich nuclei: Constraints on the symmetry energy from neutron-removal cross sections
T. Aumann · C.A. Bertulani · F. Schindler · S. Typel
An experimentally constrained equation of state of neutron-rich matter is fundamental for the physics of nuclei and the astrophysics of neutron stars, mergers, core-collapse supernova explosions and the synthesis of heavy elements. To this end, we investigate the potential of constraining the density dependence of the symmetry energy close to saturation density through measurements of neutron-removal cross sections in high-energy nuclear collisions of a few hundreds MeV/nucleon to GeV/nucleon. We show that the sensitivity of the total neutron-removal cross section is high enough so that the required accuracy can be reached experimentally with the recent developments of new detection techniques. We quantify two crucial points to minimize the model dependence of the approach and to reach the required accuracy: the contribution to the cross section from inelastic scattering has to be measured separately in order to allow a direct comparison of experimental cross sections to theoretical cross sections based on density functional theory and eikonal theory. The accuracy of the reaction model should be investigated and quantified by the energy and target dependence of various nucleon-removal cross sections. Our calculations explore the dependence of neutron-removal cross sections on the neutron skin of medium-heavy neutron-rich nuclei, and we demonstrate that the slope parameter L of the symmetry energy could be constrained down to +/-10 MeV by such a measurement with a 2% accuracy of the measured and calculated cross sections.
nucl-thnucl-exPRL(2017)·58 citations
06
Partial restoration of spin-isospin SU(4) Symmetry and the One-QRPA method in Double Beta Decay
V. dos S. Ferreira🇧🇷 · F. Krmpotić🇦🇷 · C.A. Barbero🇦🇷 · A. R. Samana🇧🇷
The one-QRPA method is used to describe simultaneously both double decay beta modes, giving special attention to the partial restoration of spin-isospin SU(4) symmetry. To implement this restoration and to fix the model parameters, we resort to the energetics of Gamow-Teller resonances and to the minima of the single $β^{+}$ -decay strengths. This makes the theory predictive regarding the $β β_{2 ν}$ -decay, producing the $2 ν$ moments in $^{48}$ Ca, $^{76}$ Ge, $^{82}$ Se, $^{96}$ Zr, $^{100}$ Mo, $^{128, 130}$ Te, and $^{150}$ Nd, that are of the same order of magnitude as the experimental ones; however, the agreement with $β β_{2 ν}$ data is only modest. To include contributions coming from induced nuclear weak currents, we extend the $β β_{0 ν}$ -decay formalism employed previously in C. Barbero et. al, Nuc. Phys. A628, 170 (1998). The numerical results for the $β β_{0 ν}$ moments in the above mentioned nuclei are similar to those obtained in other theoretical studies although smaller on averag by $\sim 40%$ . We attribute this difference basically to the one-QRPA-method, employed here for the first time, instead of the currently used two-QRPA-method. The difference is partially due to the way of carrying out the restoration of the spin-isospin symmetry. It is hard to say which is the best way to make the restoration, since the $β β_{0 ν}$ moments are not experimentally measurable. The numerical uncertainties in the $β β$ moments, related with i) their strong dependence on the residual interaction in the p-p channel when evaluated within the QRPA, and ii) lack of proper knowledge of single-particle energies, have been quantified. It is concluded that the partial restoration of the SU (4) symmetry is crucial in the description of the $β β$ -decays, regardless of the nuclear model used.
nucl-thPRC(2017)·9 citations
07
Charmonium Coherent Photoproduction and Hadroproduction with Effects of Quark Gluon Plasma
Wei Shi · Wangmei Zha🇨🇳 · Baoyi Chen
We study the charmonium coherent photoproduction and hadroproduction consistently with modifications from both cold and hot nuclear matters. The strong electromagnetic fields from fast moving nucleus interact with the other target nucleus, producing abundant charmonium in the extremely low transverse momentum region $p_{T} < 0.1$ GeV/c. This results in significative enhancement of $J / ψ$ nuclear modification factor in semi-central and peripheral collisions. In the middle $p_{T}$ region such as $p_{T} < 3 \sim 5$ GeV/c, $J / ψ$ final yield is dominated by the combination process of single charm and anti-charm quarks moving in the deconfined matter, $c + c ˉ \to J / ψ + g$ . In the higher $p_{T}$ region, $J / ψ$ production are mainly from parton initial hard scatterings at the beginning of nucleus-nucleus collisions and decay of B hadrons. We include all of these production mechanisms and explain the experimental data well in different colliding centralities and transverse momentum regions.
nucl-thnucl-exPLB(2018)·41 citations
08
Two neutrino double- $β$ decay of $94 \leq A \leq 150$ nuclei for the 0 $^{+} \to$ 2 $^{+}$ transition
Yash Kaur Singh · R. Chandra · P.K. Raina · P.K. Rath
Within the PHFB approach, the $0^{+} \to 2^{+}$ transition of two neutrino double- $β$ decay of $^{94, 96}$ Zr, $^{100}$ Mo, $^{104}$ Ru, $^{110}$ Pd, $^{128, 130}$ Te and $^{150}$ Nd isotopes is studied employing wave functions generated with four different parametrizations of the pairing plus multipole type of two-nucleon interaction and the summation method. In comparison to the $0^{+} \to 0^{+}$ transition, the nuclear transition matrix elements $M_{2 ν} (2^{+})$ are quite sensitive to the deformation of the yrast 2 $^{+}$ state. Consideration of the available theoretical and experimental results suggest that the observation of the 02 $^{+}$ transition of $2 ν β^{-} β^{-}$ decay may be possible in $^{96}$ Zr, $^{100}$ Mo, $^{130}$ Te and $^{150}$ Nd isotopes. The effect of deformation on the $M_{2 ν} (2^{+})$ is also studied.
nucl-thEPJA(2017)·5 citations
09
Cluster formation in pre-compound nuclei in the time-dependent framework
Bastian Schuetrumpf · Witold Nazarewicz
Background: Applications of nuclear time-dependent density functional theory (TDDFT) are often capable of providing quantitative description of heavy ion reactions. However, the structure of pre-compound states produced in heavy ion reactions are difficult to assess theoretically in TDDFT as the s.p. density alone is a weak indicator of shell structure and cluster states. Purpose: We employ the time-dependent nucleon localization function (NLF) to reveal structure of pre-compound states in nuclear reactions involving light and medium-mass ions. We primarily focus on spin saturated systems with N = Z. Furthermore, we study reactions with oxygen and carbon ions, for which experimental evidence for {\alpha} clustering in pre-compound states exists. Method: We utilize the symmetry-free TDDFT approach and compute the NLFs to describe $^{16}$ O + $^{16}$ O, $^{40}$ Ca + $^{16}$ O, $^{40}$ Ca + $^{40}$ Ca, and $^{16, 18}$ O + $^{12}$ C collisions at energies above the Coulomb barrier. Results: We show that NLFs reveal a variety of time-dependent modes involving cluster structures. For instance, the $^{16}$ O + $^{16}$ O collision results in a vibrational mode of a quasi-molecular \alpha- $^{12}$ C- $^{12}$ C-\alpha{} state. For heavier ions, a variety of cluster configurations are predicted. For the collision of $^{16, 18}$ O + $^{12}$ C, we showed that the pre-compound system has a tendency to form {\alpha} clusters. This result supports the experimental findings that the presence of cluster structures in the projectile and target nuclei gives rise to strong entrance channel effects and enhanced {\alpha} emission. Conclusion: The time-dependent NLF is a good indicator of clusters structures in complex pre-compound states formed in heavy-ion fusion reactions. The localization reveals the presence of collective vibrations involving cluster structures, which dominate the initial dynamics of the fusing system.
nucl-thPRC(2017)·42 citations
10
Hyperspherical harmonics expansion on Lagrange meshes for bosonic systems in one dimension
N.K. Timofeyuk · D. Baye
A one-dimensional system of bosons interacting with contact and single-Gaussian forces is studied with an expansion in hyperspherical harmonics. The hyperradial potentials are calculated using the link between the hyperspherical harmonics and the single-particle harmonic-oscillator basis while the coupled hyperradial equations are solved with the Lagrange-mesh method. Extensions of this method are proposed to achieve good convergence with small numbers of mesh points for any truncation of hypermomentum. The convergence with hypermomentum strongly depends on the range of the two-body forces: it is very good for large ranges but deteriorates as the range decreases, being the worst for the contact interaction. In all cases, the lowest-order energy is within 4.5 $%$ of the exact solution and shows the correct cubic asymptotic behaviour at large boson numbers. Details of the convergence studies are presented for 3, 5, 20 and 100 bosons. A special treatment for three bosons was found to be necessary. For single-Gaussian interactions, the convergence rate improves with increasing boson number, similar to what happens in the case of three-dimensional systems of bosons.
nucl-thFew Body Syst.(2017)·7 citations
11
Beth-Uhlenbeck approach for repulsive interactions between baryons in a hadron gas
Volodymyr Vovchenko🇩🇪 · Anton Motornenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Horst Stoecker🇩🇪
The quantum mechanical Beth-Uhlenbeck (BU) approach for repulsive hard-core interactions between baryons is applied to the thermodynamics of a hadron gas. The second virial coefficient $a_{2}$ -- the "excluded volume" parameter -- calculated within the BU approach is found to be temperature dependent, and it differs dramatically from the classical excluded volume (EV) model result. At temperatures $T = 100 - 200$ MeV, the widely used classical EV model underestimates the EV parameter for nucleons at a given value of the nucleon hard-core radius by large factors of 3-4. Previous studies, which employed the hard-core radii of hadrons as an input into the classical EV model, have to be re-evaluated using the appropriately rescaled EV parameters. The BU approach is used to model the repulsive baryonic interactions in the hadron resonance gas (HRG) model. Lattice data for the second and fourth order net baryon susceptibilities are described fairly well when the temperature dependent BU baryonic excluded volume parameter corresponds to nucleon hard-core radii of $r_{c} = 0.25 - 0.3$ fm. Role of the attractive baryonic interactions is also considered. It is argued that HRG model with a constant baryon-baryon EV parameter $v_{N N} ≃ 1$ fm $^{3}$ provides a simple yet efficient description of baryon-baryon interaction in the crossover temperature region.
nucl-thhep-phPRC(2018)·34 citations
12
Optical Potentials Derived from Nucleon-Nucleon Chiral Potentials at N4LO
M. Vorabbi🇨🇦 · P. Finelli🇮🇹 · C. Giusti🇮🇹
Background: Elastic scattering is probably the main event in the interactions of nucleons with nuclei. Even if this process has been extensively studied in the last years, a consistent description, i.e., starting from microscopic two- and many-body forces connected by the same symmetries and principles, is still under development. Purpose: In a previous paper we derived a theoretical optical potential from NN chiral potentials at fourth order (N3LO). In the present work we use NN chiral potentials at fifth order (N4LO), with the purpose to check the convergence and to assess the theoretical errors associated with the truncation of the chiral expansion in the construction of an optical potential. Methods: The optical potential is derived as the first-order term within the spectator expansion of the nonrelativistic multiple scattering theory and adopting the impulse approximation and the optimum factorization approximation. Results: The pp and np Wolfenstein amplitudes and the cross section, analyzing power, and spin rotation of elastic proton scattering from 16O, 12C, and 40Ca nuclei are presented at an incident proton energy of 200 MeV. The results obtained with different versions of chiral potentials at N4LO are compared. Conclusions: Our results indicate that convergence has been reached at N4LO. The agreement with the experimental data is comparable with the agreement obtained in our previous work. We confirm that building an optical potential within chiral perturbation theory is a promising approach for describing elastic proton-nucleus scattering.
nucl-thPRC(2017)·22 citations
13
Constant temperature description of the nuclear level densities
Mihai Horoi · Jayani Dissanayake
The spin and parity dependent nuclear level densities (NLD) are calculated for medium-heavy nuclei using shell model techniques. The NLD are used to calculate cross sections and reaction rates of interest for nuclear astrophysics and nuclear energy applications. We investigate a new approach of describing the shell model NLD via a constant temperature parametrization. This approach provides new information about the effects of symmetries on the temperature of the low-lying nuclear states, and it is shown to be more versatile for applications.
nucl-thAIP Conf.Proc.(2017)·2 citations
14
Neutron width statistics in a realistic resonance-reaction model
P. Fanto · G. F. Bertsch · Y. Alhassid
A recent experiment on s-wave neutron scattering from $^{192, 194, 196}$ Pt found that the reduced neutron width distributions deviate significantly from the expected Porter-Thomas distribution (PTD), and several explanations have been proposed within the statistical model of compound nucleus reactions. Here, we study the statistics of reduced neutron widths in the reaction $n +^{194}$ Pt within a model that combines the standard statistical model with a realistic treatment of the neutron channel. We find that, if the correct secular energy dependence of the average neutron widths is used, then the reduced neutron width distribution is in excellent agreement with the PTD for a reasonable range of the neutron-nucleus coupling strength and depth of the neutron channel potential. Within our parameter range, there can be a near-threshold bound or virtual state of the neutron channel potential that modifies the energy dependence of the average width from the $E$ dependence, commonly assumed in experimental analysis, in agreement with the proposal of H. A. Weidenmüller [1]. In these cases, the reduced neutron width distributions extracted using the $E$ dependence are significantly broader than the PTD. We identify a relatively narrow range of parameters where this effect is significant.
nucl-thcond-mat.mes-hallPRC(2018)·15 citations
15
A data-driven analysis for the temperature and momentum dependence of the heavy quark diffusion coefficient in relativistic heavy-ion collisions
Yingru Xu🇺🇸 · Marlene Nahrgang🇺🇸 · Shanshan Cao🇺🇸 · Jonah E. Bernhard🇫🇷 · Steffen A. Bass🇺🇸
By applying a Bayesian model-to-data analysis, we estimate the temperature and momentum dependence of the heavy quark diffusion coefficient in an improved Langevin framework. The posterior range of the diffusion coefficient is obtained by performing a Markov chain Monte Carlo random walk and calibrating on the experimental data of $D$ -meson $R_{AA}$ and $v_{2}$ in three different collision systems at RHIC and the LHC: AuAu collisions at 200 GeV, PbPb collisions at 2.76 and 5.02 TeV. The spatial diffusion coefficient is found to be consistent with lattice QCD calculations and comparable with other models' estimation. We demonstrate the capability of our improved Langevin model to simultaneously describe the $R_{AA}$ and $v_{2}$ at both RHIC and the LHC energies, as well as the higher order flow coefficient such as $D$ -meson $v_{3}$ . We show that by applying a Bayesian analysis, we are able to quantitatively and systematically study the heavy flavor dynamics in heavy-ion collisions.
nucl-thPRC(2018)·166 citations
16
A Two-band Model for p-wave Superconductivity
Heron Caldas · F. S. Batista · Mucio A. Continentino · Fernanda Deus · David Nozadze
In this paper we study the effects of hybridization in the superconducting properties of a two-band system. We consider the cases that these bands are formed by electronic orbitals with angular momentum, such that, the hybridization $V (k)$ among them can be symmetric or antisymmetric under inversion symmetry. We take into account only intra-band attractive interactions in the two bands and investigate the appearance of an induced inter-band pairing gap. We show that (inter-band) superconducting orderings are induced in the total absence of attractive interaction between the two bands, which turns out to be completely dependent on the hybridization between them. For the case of antisymmetric hybridization we show that the induced inter-band superconductivity has a p-wave symmetry.
↳ cond-mat.supr-concond-mat.str-elnucl-thAnnals Phys.(2017)·3 citations
17
Superfluidity and Superconductivity in Neutron Stars
Brynmor Haskell · Armen Sedrakian
This review focuses on applications of the ideas of superfluidity and superconductivity in neutron stars in a broader context, ranging from the microphysics of pairing in nucleonic superfluids to macroscopic manifestations of superfluidity in pulsars. The exposition of the basics of pairing, vorticity and mutual friction can serve as an introduction to the subject. We also review some topics of recent interest, including the various types of pinning of vortices, glitches, and oscillations in neutron stars containing superfluid phases of baryonic matter.
↳ astro-ph.HEgr-qcnucl-thAstrophys.Space Sci.Libr.(2018)·89 citations
18
Factorization and Resummation for Groomed Multi-Prong Jet Shapes
Andrew J. Larkoski🇺🇸 · Ian Moult🇺🇸 · Duff Neill🇺🇸
Observables which distinguish boosted topologies from QCD jets are playing an increasingly important role at the Large Hadron Collider (LHC). These observables are often used in conjunction with jet grooming algorithms, which reduce contamination from both theoretical and experimental sources. In this paper we derive factorization formulae for groomed multi-prong substructure observables, focusing in particular on the groomed $D_{2}$ observable, which is used to identify boosted hadronic decays of electroweak bosons at the LHC. Our factorization formulae allow systematically improvable calculations of the perturbative $D_{2}$ distribution and the resummation of logarithmically enhanced terms in all regions of phase space using renormalization group evolution. They include a novel factorization for the production of a soft subjet in the presence of a grooming algorithm, in which clustering effects enter directly into the hard matching. We use these factorization formulae to draw robust conclusions of experimental relevance regarding the universality of the $D_{2}$ distribution in both $e^{+} e^{-}$ and $pp$ collisions. In particular, we show that the only process dependence is carried by the relative quark vs. gluon jet fraction in the sample, no non-global logarithms from event-wide correlations are present in the distribution, hadronization corrections are controlled by the perturbative mass of the jet, and all global color correlations are completely removed by grooming, making groomed $D_{2}$ a theoretically clean QCD observable even in the LHC environment. We compute all ingredients to one-loop accuracy, and present numerical results at next-to-leading logarithmic accuracy for $e^{+} e^{-}$ collisions, comparing with parton shower Monte Carlo simulations. Results for $pp$ collisions, as relevant for phenomenology at the LHC, are presented in a companion paper.
↳ hep-phhep-exnucl-thJHEP(2018)·50 citations
19
Hot Spaghetti: Viscous Gravitational Collapse
Berndt Müller🇺🇸 · Andreas Schäfer🇩🇪
We explore the fate of matter falling into a macroscopic Schwarzschild black hole for the simplified case of a radially collapsing thin spherical shell for which the back reaction of the geometry can be neglected. We treat the internal dynamics of the infalling matter in the framework of viscous relativistic hydrodynamics and calculate how the internal temperature of the collapsing matter evolves as it falls toward the Schwarzschild singularity. We find that viscous hydrodynamics fails when either, the dissipative radial pressure exceeds the thermal pressure and the total radial pressure becomes negative, or the time scale of variation of the tidal forces acting on the collapsing matter becomes shorter than the characteristic hydrodynamic response time.
↳ gr-qchep-phnucl-thEPJA(2018)·0 citations
20
Nonlinear Responses of Chiral Fluids from Kinetic Theory
Yoshimasa Hidaka🇯🇵 · Shi Pu🇯🇵 · Di-Lun Yang🇯🇵
The second-order nonlinear responses of inviscid chiral fluids near local equilibrium are investigated by applying the chiral kinetic theory (CKT) incorporating side-jump effects. It is shown that the local equilibrium distribution function can be non-trivially introduced in a co-moving frame with respect to the fluid velocity when the quantum corrections in collisions are involved. For the study of anomalous transport, contributions from both quantum corrections in anomalous hydrodynamic equations of motion and those from the CKT and Wigner functions are considered under the relaxation-time (RT) approximation, which result in anomalous charge Hall currents propagating along the cross product of the background electric field and the temperature (or chemical-potential) gradient and of the temperature and chemical-potential gradients. On the other hand, the nonlinear quantum correction on the charge density vanishes in the classical RT approximation, which in fact satisfies the matching condition given by the anomalous equation obtained from the CKT.
↳ hep-thcond-mat.mes-hallcond-mat.stat-mechnucl-thPRD(2018)·165 citations
21
Cumulant Expansion in Gluon Saturation, and Five and Six-Gluon Azimuthal Correlations
Sener Ozonder🇹🇷
Correlations between the momenta of the final state hadrons measured in proton or nucleus collisions contain information that sheds light on the initial conditions and evolutionary dynamics of the collision system. These correlation measurements have revealed the long-range rapidity correlations in p-p and p-Pb systems, and they have also made it possible to extract the elliptic flow coefficient from hadron correlation measurements. In this work, we calculate five- and six-gluon correlation functions in the framework of saturation physics by using superdiagrams. We also derive the cumulant expansion of the gluon correlators that is valid in the gluon saturation limit. We show that the cumulant expansion of the gluon correlators that is used for counting the number of diagrams to be calculated does not follow the standard cumulant expansion. We also explain how these findings can be used in obtaining experimentally relevant observables such as flow coefficients calculated from correlations as well as ratios of the correlation functions of different orders.
↳ hep-phhep-thnucl-thPRD(2017)·3 citations
22
Baryons in the plasma: in-medium effects and parity doubling
Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Davide de Boni🇬🇧 · Simon Hands🇬🇧 · Benjamin Jäger🇨🇭 · Chrisanthi Praki🇬🇧 · Jon-Ivar Skullerud🇮🇪
We investigate the fate of baryons made out of u, d and s quarks in the hadronic gas and the quark-gluon plasma, using nonperturbative lattice simulations, employing the FASTSUM anisotropic Nf=2+1 ensembles. In the confined phase a strong temperature dependence is seen in the masses of the negative-parity groundstates, while the positive-parity groundstate masses are approximately temperature independent, within the error. At high temperature parity doubling emerges. A noticeable effect of the heavier s quark is seen. We give a simple description of the medium-dependent masses for the negative-parity states and speculate on the relevance for heavy-ion phenomenology via the hadron resonance gas.
↳ hep-lathep-phnucl-thEPJ Web Conf.(2018)·16 citations
23
Functional Renormalization Group and Kohn-Sham scheme in Density Functional Theory
Haozhao Liang🇯🇵 · Yifei Niu🇷🇴 · Tetsuo Hatsuda🇯🇵
Deriving accurate energy density functional is one of the central problems in condensed matter physics, nuclear physics, and quantum chemistry. We propose a novel method to deduce the energy density functional by combining the idea of the functional renormalization group and the Kohn-Sham scheme in density functional theory. The key idea is to solve the renormalization group flow for the effective action decomposed into the mean-field part and the correlation part. Also, we propose a simple practical method to quantify the uncertainty associated with the truncation of the correlation part. By taking the $φ^{4}$ theory in zero dimension as a benchmark, we demonstrate that our method shows extremely fast convergence to the exact result even for the highly strong coupling regime.
↳ cond-mat.str-elhep-thnucl-thquant-phPLB(2018)·33 citations
24
Elliptic flow coefficients from transverse momentum conservation
Adam Bzdak🇵🇱 · Guo-Liang Ma🇨🇳
We calculate the $k$ -particle ( $k = 2, 4, 6, 8$ ) azimuthal cumulants resulting from the conservation of transverse momentum. We find that $c_{2} {k} > 0$ and depending on the transverse momenta, $c_{2} {k}$ can reach substantial values even for a relatively large number of particles. The impact of our results on the understanding of the onset of collectivity in small systems is emphasized.
↳ hep-phhep-exnucl-exnucl-thPRC(2018)·11 citations
25
Baryon-antibaryon annihilation and reproduction in relativistic heavy-ion collisions
E. Seifert🇩🇪 · W. Cassing🇩🇪
The quark rearrangement model for baryon-antibaryon annihilation and reproduction ( $B B ˉ \leftrightarrow 3 M$ ) - incorporated in the Parton-Hadron-String Dynamics (PHSD) transport approach - is extended to the strangeness sector. A derivation of the transition probabilities for the three-body processes is presented and a strangeness suppression factor for the invariant matrix element squared is introduced to account for the higher mass of the strange quark compared to the light up and down quarks. In simulations of the baryon-antibaryon annihilation and reformation in a box with periodic boundary conditions we demonstrate that our numerical implementation fulfills detailed balance on a channel-by-channel basis for more than 2000 individual $2 \leftrightarrow 3$ channels. Furthermore, we study central Pb+Pb collisions within PHSD from 11.7 $A$ GeV to 158 $A$ GeV and investigate the impact of the additionally implemented reaction channels in the strangeness sector. We find that the new reaction channels have a visible impact essentially only on the rapidity spectra of antibaryons. The spectra with the additional channels in the strangeness sector are closer to the experimental data than without for all antihyperons. Due to the chemical redistribution between baryons/antibaryons and mesons we find a slightly larger production of antiprotons thus moderately overestimating the available experimental data. We additionally address the question if the antibaryon spectra (with strangeness) from central heavy-ion reactions at these energies provide further information on the issue of chiral symmetry restoration and deconfinement. However, by comparing transport results with/without partonic phase as well as including/excluding effects from chiral symmetry restoration we find no convincing signals in the strange antibaryon sector for either transition due to the strong final-state interactions.
↳ hep-phnucl-thPRC(2018)·28 citations

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