Nuclear Theory·nucl-th

Tuesday·November 1, 2016

26 papers—16 primary·10 cross-listed

01
Impact of finite density on spectroscopic parameters of decuplet baryons
K. Azizi🇹🇷 · N. Er🇹🇷 · H. Sundu🇹🇷
The decuplet baryons, $Δ$ , $Σ^{*}$ , $Ξ^{*}$ and $Ω^{-}$ , are studied in nuclear matter by using the in-medium QCD sum rules. By fixing the three momentum of the particles under consideration at the rest frame of the medium, the negative energy contributions are removed. It is obtained that the parameters of the $Δ$ baryon are more affected by the medium against the $Ω^{-}$ state, containing three strange quarks, whose mass and residue do not affected by the medium, considerably. We also find the vector and scalar self energies of these baryons in nuclear matter. By the recent progresses at $P ˉ$ ANDA experiment at FAIR and NICA facility it may be possible to study the in-medium properties of such states even the multi-strange $Ξ^{*}$ and $Ω^{-}$ systems in near future.
nucl-thhep-phPRD(2016)·11 citations
02
Internal and external radiative widths in the combined R-matrix and potential model formalism
A. M. Mukhamedzhanov · Shubhchintak · C. A. Bertulani · T. V. Nhan Hao
Using the $R$ -matrix approach we calculate the radiative width for a resonance decaying to a bound state through electric dipole, $E 1$ , transitions. The total radiative width is determined by the interference of the nuclear internal and external radiative width amplitudes. For a given channel radius the external radiative width amplitude is model independent and is determined by the asymptotic normalization coefficient (ANC) of the bound state to which the resonance decays. It also depends on the partial resonance width. To calculate the internal radiative width amplitude we show that a single particle potential model is appropriate. We compare our results with a few experimental data.
nucl-thPRC(2017)·11 citations
03
Longitudinal correlations in the initial stages of ultra-relativistic nuclear collisions
Wojciech Broniowski🇵🇱 · Piotr Bozek🇵🇱
In this talk we review some of our results for the longitudinal correlations in connection with recent experimental data, in particular for the {\em torque} effect and for the two-particle correlations in pseudorapidity, $C (η_{1}, η_{2})$ . The model framework involves event-by-event fluctuations of the initial conditions, followed with 3D viscous hydrodynamic evolution and statistical hadronization.
nucl-thnucl-exEPJ Web Conf.(2017)·3 citations
04
Limits on hadron spectrum from bulk medium properties
Wojciech Broniowski🇵🇱
We bring up the fact that the bulk thermal properties of the hadron gas, as measured on the lattice, preclude a very fast rising of the number of resonance states in the QCD spectrum, as assumed by the Hagedorn hypothesis, unless a substantial repulsion between hadronic resonances is present. If the Hagedorn growth continued above masses ~1.8 GeV, then the thermodynamic functions would noticeably depart from the measured lattice values at temperatures above 140 MeV, just below the transition temperature to quark-gluon plasma.
nucl-thhep-phBled Workshops Phys.(2016)·3 citations
05
Shape phase mixing in critical point nuclei
R. Budaca · A. I. Budaca
Spectral properties of nuclei near the critical point of the quantum phase transition between spherical and axially symmetric shapes are studied in a hybrid collective model which combines the $γ$ -stable and $γ$ -rigid collective conditions through a rigidity parameter. The model in the lower and upper limits of the rigidity parameter recovers the X(5) and X(3) solutions respectively, while in the equally mixed case it corresponds to the X(4) critical point symmetry. Numerical applications of the model on nuclei from regions known for critical behavior reveal a sizable shape phase mixing and its evolution with neutron or proton numbers. The model also enables a better description of energy spectra and electromagnetic transitions for these nuclei.
nucl-thPRC(2016)·8 citations
06
Delta isobars in relativistic mean-field models with $σ$ -scaled hadron masses and couplings
E.E. Kolomeitsev🇸🇰 · K.A. Maslov🇷🇺 · D.N. Voskresensky🇷🇺
We extend the relativistic mean-field models with hadron masses and meson-baryon coupling constants dependent on the scalar $σ$ field, studied previously to incorporate $Δ (1232)$ baryons. Available empirical information is analyzed to put constraints on the couplings of $Δ$ s with meson fields. Conditions for the appearance of $Δ$ s are studied. We demonstrate that with inclusion of the $Δ$ s our equations of state continue to fulfill majority of known empirical constraints including the pressure-density constraint from heavy-ion collisions, the constraint on the maximum mass of the neutron stars, the direct Urca and the gravitational-baryon mass ratio constraints.
nucl-thastro-ph.HENPA(2017)·69 citations
07
Scalar quanta in Fermi liquids: zero sounds, instabilities, Bose condensation, and a metastable state in dilute nuclear matter
E.E. Kolomeitsev🇸🇰 · D.N. Voskresensky🇷🇺
Spectrum of bosonic scalar-mode excitations in a normal Fermi liquid with a local scalar interaction is investigated for various values and momentum dependence of the scalar Landau parameter $f_{0}$ in the particle-hole channel. For $f_{0} > 0$ the conditions are found when the phase velocity on the spectrum of the zero sound acquires a minimum at a non-zero momentum. For $- 1 < f_{0} < 0$ there are only damped excitations, and for $f_{0} < - 1$ the spectrum becomes unstable against a growth of scalar-mode excitations. An effective Lagrangian for the scalar excitation modes is derived after performing a bosonization procedure. We demonstrate that the instability may be tamed by the formation of a static Bose condensate of the scalar modes. The condensation may occur in a homogeneous or inhomogeneous state relying on the momentum dependence of the scalar Landau parameter. We show that in the isospin-symmetric nuclear matter there may appear a metastable state at a subsaturation nuclear density owing to the condensate. Then we consider a possibility of the condensation of the zero-sound-like excitations in a state with a non-zero momentum in Fermi liquids moving with overcritical velocities, provided an appropriate momentum dependence of the Landau parameter $f_{0} (k) > 0$ . We also argue that in peripheral heavy-ion collisions the Pomeranchuk instability may occur already for $f_{0} > - 1$ .
nucl-thcond-mat.quant-gasEPJA(2016)·7 citations
08
Towards a quantitative understanding of high $p_{T}$ flow harmonics
Jorge Noronha (Sao Paulo U.)
In this proceedings I briefly review the recent progress achieved on the calculation of $v_{n}$ at high $p_{T}$ via the coupling of a jet energy loss model with full event-by-event viscous hydrodynamics. It is shown that that this framework can simultaneously describe experimental data for $R_{AA}$ , $v_{2}$ , and $v_{3}$ at high $p_{T}$ . High $p_{T}$ $v_{2}$ is found to be approximately linearly correlated with the soft $v_{2}$ on an event-by-event basis, which opens up a new way to correlate soft and hard observables in heavy ion collisions.
nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2017)·2 citations
09
Proton radius from electron-proton scattering and chiral perturbation theory
Marko Horbatsch🇨🇦 · Eric A. Hessels🇨🇦 · Antonio Pineda🇪🇸
We determine the root-mean-square proton charge radius, $R_{p}$ , from a fit to low- $Q^{2}$ electron-proton elastic scattering cross section data with the higher moments fixed (within uncertainties) to the values predicted by chiral perturbation theory. We obtain $R_{p} = 0.857 (11)$ fm. This number falls between the value obtained from muonic hydrogen analyses and the CODATA value (based upon atomic hydrogen spectroscopy and electron-proton scattering determinations).
nucl-thhep-phnucl-exphysics.atom-phPRC(2017)·57 citations
10
Mathematical aspects of the nuclear glory phenomenon: from backward focusing to Chebyshev polynomials
Vladimir B. Kopeliovich (INR of RAS, Moscow & MIPT, Moscow)
The angular dependence of the cumulative particles production off nuclei near the kinematical boundary for multistep process is defined by characteristic polynomials in angular variables $J_{N}^{2} (z_{N}^{θ})$ , where $θ$ is the polar angle defining the momentum of the final (cumulative) particle, $z_{N}^{θ} = cos (θ / N)$ , the integer $N$ being the multiplicity of the process (the number of interactions). Physical argumentation, exploring the small phase space method, leads to the appearance of equations for these polynomials $J_{N}^{2} [cos (π / N)] = 0$ . The recurrent relations between polynomials with different $N$ are obtained, and their connection with known in mathematics Chebyshev polynomials of 2-d kind is established. As a result of this equality, differential cross section of the cumulative particle production has characteristic behaviour $d σ \sim 1/ π - θ$ at $θ \sim π$ (the backward focusing effect). Such behaviour takes place for any multiplicity of the interaction, beginning with $n = 3$ , elastic or inelastic (with resonances excitations in intermediate states), and can be called the nuclear glory phenomenon, or 'Buddha's light' of cumulative particles.
nucl-thhep-phJ.Phys.Conf.Ser.(2017)·1 citation
11
Implications of Efimov physics for the description of three and four nucleons in chiral effective field theory
A. Kievsky🇮🇹 · M. Viviani🇮🇹 · M. Gattobigio🇫🇷 · L. Girlanda🇮🇹
In chiral effective field theory the leading order (LO) nucleon-nucleon potential includes two contact terms, in the two spin channels $S = 0, 1$ , and the one-pion-exchange potential. When the pion degrees of freedom are integrated out, as in the pionless effective field theory, the LO potential includes two contact terms only. In the three-nucleon system, the pionless theory includes a three-nucleon contact term interaction at LO whereas the chiral effective theory does not. Accordingly arbitrary differences could be observed in the LO description of three- and four-nucleon binding energies. We analyze the two theories at LO and conclude that a three-nucleon contact term is necessary at this order in both theories. In turn this implies that subleading three-nucleon contact terms should be promoted to lower orders. Furthermore this analysis shows that one single low energy constant might be sufficient to explain the large values of the singlet and triplet scattering lengths.
nucl-thcond-mat.quant-gasPRC(2017)·29 citations
12
Initial conditions for hydrodynamics from weakly coupled pre-equilibrium evolution
Aleksas Mazeliauskas🇺🇸
We use leading order effective kinetic theory to simulate the pre\nobreakdash-equilibrium evolution of transverse energy and flow perturbations in heavy-ion collisions. We provide a Green function which propagates the initial perturbations of the energy-momentum tensor to a time when hydrodynamics becomes applicable. With this map, the pre-thermal evolution from saturated nuclei to hydrodynamics can be modeled in the framework of weakly coupled QCD.
nucl-thhep-phJ.Phys.Conf.Ser.(2017)·0 citations
13
Multiparton interactions: From pp to pA
Christian Bierlich🇸🇪
In the process of understanding nuclear collisions, reliable extrapolations from pp collisions, based on Glauber models, are highly desirable, though seldomly accurate. We review the inclusion of diffractive excitations and argue that they provide an important contribution to centrality observables in pA collisions. We present a method for distinguishing between diffractively and non-diffractively wounded nucleons, and a proof-of-principle for an extrapolation of multiparton interaction models built on this.
nucl-thhep-phNucl.Part.Phys.Proc.(2017)·0 citations
14
Susceptibilities from a black hole engineered EoS with a critical point
Israel Portillo🇺🇸
Currently at the Beam Energy Scan at RHIC experimental efforts are being made to find the QCD critical point. On the theoretical side, the behavior of higher-order susceptibilities of the net-baryon charge from Lattice QCD at $μ_{_{B}} = 0$ may allow us to estimate the position of the critical point in the QCD phase diagram. However, even if the series expansion continues to higher-orders, there is always the possibility to miss the critical point behavior due to truncation errors. An alternative approach is to use a black hole engineered holographic model, which displays a critical point at large densities and matches lattice susceptibilities at $μ_{_{B}} = 0$ . Using the thermodynamic data from this black hole model, we obtain the freeze-out points extracted from the net-protons distribution measured at STAR and explore higher order fluctuations at the lowest energies at the beam energy scan to investigate signatures of the critical point.
nucl-thhep-phJ.Phys.Conf.Ser.(2017)·7 citations
15
How gauge covariance of the fermion and boson propagators in QED constrain the effective fermion-boson vertex
Shaoyang Jia🇺🇸 · M.R. Pennington🇺🇸
We derive the gauge covariance requirement imposed on the QED fermion-photon three-point function within the framework of a spectral representation for fermion propagators. When satisfied, such requirement ensures solutions to the fermion propagator Schwinger-Dyson equation (SDE) in any covariant gauge with arbitrary numbers of spacetime dimensions to be consistent with the Landau-Khalatnikov-Fradkin transformation (LKFT). The general result has been verified by the special cases of three and four dimensions. Additionally, we present the condition that ensures the vacuum polarization is independent of the gauge parameter. As an illustration, we show how the Gauge Technique dimensionally regularized in 4D does not satisfy the covariance requirement.
nucl-thPRD(2016)·13 citations
16
Phenomenological predictions of 3+1d anisotropic hydrodynamics
Mohammad Nopoush🇺🇸 · Michael Strickland🇺🇸 · Radoslaw Ryblewski🇵🇱
We make phenomenological predictions for particle spectra and elliptic flow in heavy-ion collisions using 3+1d anisotropic hydrodynamics (aHydro) including the effects of both shear and bulk viscosities. The dynamical equations necessary are derived by taking moments of the Boltzmann equation allowing for three distinct (diagonal) momentum-space anisotropy parameters. The formulation is based on relaxation-time approximation for the collisional kernel and a lattice-QCD-based equation of state. Evolving the system to late times, we calculate particle production using THERMINATOR 2, modified to account for an ellipsoidal distribution function. We obtain particle spectra for different particle species such as pions, kaons, and protons, and elliptic flow $v_{2}$ as a function of centrality, transverse momentum, and rapidity. In our model, we have four free parameters, i.e. freeze-out temperature, initial central energy density, initial momentum-space anisotropies, and shear viscosity to entropy density ratio. Using a multidimensional fit to LHC experimental data, we make a preliminary extraction of these parameters. We find reasonable agreement between 3+1d aHydro and available experimental data for $η / s \sim 0.23$ .
nucl-thhep-phJ.Phys.Conf.Ser.(2017)·12 citations

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