Nuclear Theory·nucl-th

Tuesday·April 11, 2017

11 papers—8 primary·3 cross-listed

01
Bottomonia suppression in heavy-ion collisions
Brandon Krouppa🇺🇸 · Radoslaw Ryblewski🇵🇱 · Michael Strickland🇺🇸
The thermal suppression of heavy quark bound states represents an ideal observable for determining if one has produced a quark-gluon plasma in ultrarelativistic heavy-ion collisions. In recent years, a paradigm shift has taken place in the theory of quarkonium suppression due to new first principles calculations of the thermal widths of these states. These thermal widths are large, e.g. O(20-100 MeV) for the Upsilon(1S), and cause in-medium suppression of the states at temperatures below their traditionally defined disassociation temperatures. In order to apply the newly developed understanding to phenomenology, however, one must make detailed 3+1d dissipative hydrodynamical models of the plasma including the effects of finite shear viscosity. These effects include not only the modification of the time evolution of the temperature of the system, flow, etc., but also non-equilibrium modifications of the heavy quark potential itself. In this proceedings contribution, we briefly review the setup for these model calculations and present comparisons of theory with data from RHIC 200 GeV/nucleon Au-Au collisions, LHC 2.76 TeV/nucleon Pb-Pb, and LHC 5.02 TeV/nucleon Pb-Pb collisions as a function of number of participants, rapidity, and transverse momentum.
nucl-thhep-phNPA(2017)·15 citations
02
Natural orbitals for the no-core configuration interaction approach
Chrysovalantis Constantinou🇺🇸
Ab initio calculations face the challenge of describing a complex multiscale quantum many-body system. The nuclear wave function has both strong short-range correlations and long-range contributions. Natural orbitals provide a means of adapting the single-particle basis for ab initio no-core configuration interaction (NCCI) calculations to better match the many-body wave function. Natural orbitals are obtained by diagonalizing the one-body density matrix from a calculation using an initial single-particle reference basis, such as the traditional harmonic oscillator basis. The natural orbital basis builds in contributions from high-lying oscillator shells, thus accelerating convergence of wave functions, energies, and other observables. The convergence of the ground and excited state energies, radii, and electromagnetic observables of He, Li, and Be isotopes calculated using natural orbitals in ab initio NCCI calculations is discussed. It is found that electromagnetic observables involving the M1 operator fully converge, while the calculated energies, radii, and observables involving the E2 operator converge significantly faster with the natural orbital basis than with the harmonic oscillator basis. The use of infrared (IR) extrapolation schemes with the natural orbital calculations is also explored.
nucl-th2 citations
03
A New Paradigm for Hadronic Parity Nonconservation and its Experimental Implications
Susan Gardner🇺🇸 · W.C. Haxton🇺🇸 · Barry R. Holstein🇺🇸
For decades the primary experimental goal in studies of hadronic parity nonconservation (PNC) has been the isolation of the isovector weak nucleon-nucleon interaction, expected to be dominated by long-range pion exchange and enhanced by the neutral current. In meson-exchange descriptions this interaction together with an isoscalar interaction generated by rho and omega exchange dominate most observables. Consequently these two amplitudes have been used to compare and check the consistency of the field's experiments. Yet to date, despite sensitive searches like that performed with 18F, no evidence for isovector hadronic PNC has been found. Here we argue, based on recent large-Nc treatments and new global analyses, that the emphasis on isovector hadronic PNC was misplaced. Large-Nc provides an alternative and theoretically better motivated simplification of effective field theories (EFTs) of hadronic PNC, separating the five low-energy constants (LECs) into two of leading order (LO), and three others that are NNLO. This scheme pivots the isospin coordinates we have traditionally used, placing one dominant axis in the isoscalar plane, and a second along the isotensor direction. We show that this large-Nc LEC hierarchy accurately describes all existing data on hadronic PNC, and we discuss opportunities to further test the predicted large-Nc hierarchy of LECs, illustrating the kind of analyses experimentalists can use to better constrain the LO theory and to determine the size of NNLO corrections.
nucl-thhep-phAnn.Rev.Nucl.Part.Sci.(2017)·43 citations
04
How tightly is nuclear symmetry energy constrained by unitary Fermi gas?
Nai-Bo Zhang · Bao-Jun Cai · Bao-An Li · William G. Newton · Jun Xu
We examine critically how tightly the density dependence of nuclear symmetry energy \esym is constrained by the universal equation of state (EOS) of the unitary Fermi gas $E_{UG} (ρ)$ considering currently known uncertainties of higher order parameters describing the density dependence of the Equation of State of isospin-asymmetric nuclear matter. We found that $E_{UG} (ρ)$ does provide a useful lower boundary for the \esym. However, it does not tightly constrain the correlation between the magnitude $E_{sym} (ρ_{0})$ and slope $L$ unless the curvature $K_{sym}$ of the symmetry energy at saturation density $ρ_{0}$ is more precisely known. The large uncertainty in the skewness parameters affects the $E_{sym} (ρ_{0})$ versus $L$ correlation by the same almost as significantly as the uncertainty in $K_{sym}$ .
nucl-thnucl-exNucl.Sci.Tech.(2017)·59 citations
05
Scale-Invariant Hidden Local Symmetry, Topology Change and Dense Baryonic Matter II
Won-Gi Paeng🇰🇷 · Thomas T. S. Kuo🇺🇸 · Hyun Kyu Lee🇰🇷 · Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷
Exploiting certain robust topological inputs from the skyrmion description of compressed baryonic matter with a scale-chiral symmetric Lagrangian, we predict the equation of state that is consistent with the properties of nuclear matter at the equilibrium density, supports the maximum mass of massive compact star $\sim 2 M_{⊙}$ and surprisingly gives the sound velocity close to the "conformal velocity" $1/ 3$ at densities $≳ 3 n_{0}$ . At the core of this result is the observation that parity-doubling occurs in the nucleon structure as density goes above $\sim 2 n_{0}$ with a chiral-singlet mass $m_{0} \sim (0.6 - 0.9) m_{N}$ , hinting at a possible up-to-date unsuspected source of proton mass and an emergence at high density of scale symmetry and flavor local symmetry, both hidden in the QCD vacuum.
nucl-thastro-ph.HEhep-phPRD(2017)·73 citations
06
Pseudorapidity profile of transverse momentum fluctuations in heavy ion collisions
Sandeep Chatterjee🇵🇱 · Piotr Bozek🇵🇱
We investigate pseudorapidity correlations of the average transverse flow of particles emitted in relativistic heavy-ion collisions. We employ 3+1 dimensional viscous relativistic hydrodynamics with initial conditions from the quark Glauber Monte Carlo model to confront the recent measurements on the pseudorapidity correlations of the transverse momentum fluctuations in Pb+Pb collisions at $s_{N N} = 2760$ GeV. We find good agreement between the model predictions and data. Further, we study two other observables build with the covariance of the average transverse momentum in different rapidity bins. These observables have better stability under various systematics, thus allowing for a robust comparison between data and model. The transverse flow-transverse flow correlation coefficient is directly related to correlations of the underlying collective flow at different pseudorapidities. The 3-bin measure of $p_{T}$ factorization breaking in pseudorapidity gives an estimate of possible decorrelation of the average transverse flow in the longitudinal direction.
nucl-thhep-phnucl-exPRC(2017)·18 citations
07
Beam energy scan theory: Status and open questions
H. Petersen🇩🇪
The goal of heavy ion reactions at low beam energies is to explore the QCD phase diagram at high net baryon chemical potential. To relate experimental observations with a first order phase transition or a critical endpoint, dynamical approaches for the theoretical description have to be developed. In this summary of the corresponding plenary talk, the status of the dynamical modeling including the most recent advances is presented. The remaining challenges are highlighted and promising experimental measurements are pointed out.
nucl-thhep-phnucl-exNPA(2017)·11 citations
08
Saturation with chiral interactions and consequences for finite nuclei
J. Simonis · S. R. Stroberg · K. Hebeler · J. D. Holt · A. Schwenk
We explore the impact of nuclear matter saturation on the properties and systematics of finite nuclei across the nuclear chart. Using the ab initio in-medium similarity renormalization group (IM-SRG), we study ground-state energies and charge radii of closed-shell nuclei from $^{4}$ He to $^{78}$ Ni, based on a set of low-resolution two- and three-nucleon interactions that predict realistic saturation properties. We first investigate in detail the convergence properties of these Hamiltonians with respect to model-space truncations for both two- and three-body interactions. We find one particular interaction that reproduces well the ground-state energies of all closed-shell nuclei studied. As expected from their saturation points relative to this interaction, the other Hamiltonians underbind nuclei, but lead to a remarkably similar systematics of ground-state energies. Extending our calculations to complete isotopic chains in the $s d$ and $p f$ shells with the valence-space IM-SRG, the same interaction reproduces not only experimental ground states but two-neutron-separation energies and first excited $2^{+}$ states. We also calculate radii with the valence-space IM-SRG for the first time. Since this particular interaction saturates at too high density, charge radii are still too small compared with experiment. Except for this underprediction, the radii systematics is, however, well reproduced. Our results highlight the importance of nuclear matter as a theoretical benchmark for the development of next-generation chiral interactions.
nucl-thnucl-exPRC(2017)·233 citations
09
General equilibrium second-order hydrodynamic coefficients for free quantum fields
M. Buzzegoli (U. Florence)🇮🇹 · E. Grossi (U. Heidelberg)🇩🇪 · F. Becattini (U. Florence)🇮🇹
We present a systematic calculation of the corrections of the stress-energy tensor and currents of the free boson and Dirac fields up to second order in thermal vorticity, which is relevant for relativistic hydrodynamics. These corrections are non-dissipative because they survive at general thermodynamic equilibrium with non vanishing mean values of the conserved generators of the Lorentz group, i.e. angular momenta and boosts. Their equilibrium nature makes it possible to express the relevant coefficients by means of correlators of the angular-momentum and boost operators with stress-energy tensor and current, thus making simpler to determine their so-called "Kubo formulae". We show that, at least for free fields, the corrections are of quantum origin and we study several limiting cases and compare our results with previous calculations. We find that the axial current of the free Dirac field receives corrections proportional to the vorticity independently of the anomalous term.
↳ hep-thgr-qcnucl-thJHEP(2017)·91 citations
10
More quantum centrifugal effect in rotating frame
J.-P. Gazeau🇫🇷 · T. Koide🇧🇷 · R. Murenzi🇫🇷
The behaviour of quantum systems in non-inertial frames is revisited from the point of view of affine coherent state (ACS) quantization. We restrict our approach to the one-particle dynamics confined in a rotating plane about a fixed axis. This plane is considered as punctured due to the existence of the rotation center, which is viewed as a singularity. The corresponding phase space is the affine group of the plane and the ACS quantization enables us to quantize the system by respecting the affine symmetry of the true phase space. Our formulation predicts the appearance of an additional quantum centrifugal term, besides the usual angular momentum one, which prevents the particle to reach the singular rotation center. Moreover it helps us to understand why two different non-inertial Schrödinger equations are obtained in previous works. The validity of our equation can be confirmed experimentally by observing the harmonic oscillator bound states and the critical angular velocity for their existence.
↳ quant-phhep-thnucl-thEPL(2017)·5 citations
11
Production of doubly charmed baryons nearly at rest
Stefan Groote🇪🇪 · Sergey Koshkarev🇪🇪
We investigate the production cross sections, momentum distributions and rapidity distributions for doubly charmed baryons which according to the intrinsic heavy quark mechanism are produced nearly at rest. These events should be measurable at fixed-target experiments like STAR@RHIC and AFTER@LHC.
↳ hep-phnucl-thEPJC(2017)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE