Showing papers in "Physical Review C in 2015"

EPOS LHC: Test of collective hadronization with data measured at the CERN Large Hadron Collider

Abstract: EPOS is a Monte-Carlo event generator for minimum bias hadronic interac- tions, used for both heavy ion interactions and cosmic ray air shower simulations. Since the last public release in 2009, the LHC experiments have provided a number of very inter- esting data sets comprising minimum bias p-p, p-Pb and Pb-Pb interactions. We describe the changes required to the model to reproduce in detail the new data available from LHC and the consequences in the interpretation of these data. In particular we discuss the effect of the collective hadronization in p-p scattering. A different parametrization of flow has been introduced in the case of a small volume with high density of thermalized matter (core) reached in p-p compared to large volume produced in heavy ion collisions. Both parametrizations depend only on the geometry and the amount of secondary particles en- tering in the core and not on the beam mass or energy. The transition between the two flow regimes can be tested with p-Pb data. EPOS LHC is able to reproduce all minimum bias results for all particles with transverse momentum from pt = 0 to a few GeV/c.

Accurate nuclear radii and binding energies from a chiral interaction

Abstract: With the goal of developing predictive ab initio capability for light and medium-mass nuclei, two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named NNLOsat, yield accurate binding energies and radii of nuclei up to Ca-40, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective J(pi) = 3(-) states in O-16 and 40Ca are described accurately, while spectra for selected p- and sd-shell nuclei are in reasonable agreement with experiment.

Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions

Abstract: We introduce a new parametric initial-condition model for high-energy nuclear collisions based on eikonal entropy deposition via a ``reduced-thickness'' function. The model simultaneously describes experimental proton-proton, proton-nucleus, and nucleus-nucleus multiplicity distributions and generates nucleus-nucleus eccentricity harmonics consistent with experimental flow constraints. In addition, the model is compatible with ultracentral uranium-uranium data unlike existing models that include binary collision terms.

0 ν β β and 2 ν β β nuclear matrix elements in the interacting boson model with isospin restoration

Abstract: We introduce a method for isospin restoration in the calculation of nuclear matrix elements (NMEs) for $0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ and $2\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ decay within the framework of the microscopic interacting boson model (IBM-2). With this method, we calculate the NMEs for all processes of interest in $0\ensuremath{ u}{\ensuremath{\beta}}^{\ensuremath{-}}{\ensuremath{\beta}}^{\ensuremath{-}}$ and $2\ensuremath{ u}{\ensuremath{\beta}}^{\ensuremath{-}}{\ensuremath{\beta}}^{\ensuremath{-}}$ and in $0\ensuremath{ u}{\ensuremath{\beta}}^{+}{\ensuremath{\beta}}^{+}$, $0\ensuremath{ u}\mathrm{EC}{\ensuremath{\beta}}^{+}$, $R0\ensuremath{ u}\mathrm{ECEC}$, $2\ensuremath{ u}{\ensuremath{\beta}}^{+}{\ensuremath{\beta}}^{+}$, $2\ensuremath{ u}\mathrm{EC}{\ensuremath{\beta}}^{+}$, and $2\ensuremath{ u}\mathrm{ECEC}$. With this method, the Fermi matrix elements for $2\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ vanish, and those for $0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ are considerably reduced.

Superallowed 0 + → 0 + nuclear β decays: 2014 critical survey, with precise results for V u d and CKM unitarity

Abstract: Precise measurements of the $\ensuremath{\beta}$ decay between nuclear states of spin-parity ${0}^{+}$ and isospin 1 provide fundamental tests of the properties of the electroweak interaction. Collectively, these transitions sensitively probe the conservation of the vector weak current, set tight limits on the presence of scalar currents, and provide the most precise value for ${V}_{u\phantom{\rule{0}{0ex}}d}$. The latter result has become a linchpin in the most demanding test of the unitarity of the CKM matrix.

K∗(892)0 and φ(1020) production in Pb-Pb collisions at sNN =2.76 TeV

Abstract: The yields of the K*(892)(0) and phi(1020) resonances are measured in Pb-Pb collisions at root s(NN) = 2.76 TeV through their hadronic decays using the ALICE detector. The measurements are performed in multiple centrality intervals at mid-rapidity (vertical bar y vertical bar <0.5) in the transverse-momentum ranges 0.3

Centrality dependence of particle production in p-Pb collisions at root s(NN)=5.02 TeV

Abstract: We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at root s(NN) = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N-part) or the number of nucleon-nucleon binary collisions (N-coll) are described. We show that, in contrast to Pb-Pb collisions, in p-Pb collisions large multiplicity fluctuations together with the small range of participants available generate a dynamical bias in centrality classes based on particle multiplicity. We propose to use the zero-degree energy, which we expect not to introduce a dynamical bias, as an alternative event-centrality estimator. Based on zero-degree energy-centrality classes, the N-part dependence of particle production is studied. Under the assumption that the multiplicity measured in the Pb-going rapidity region scales with the number of Pb participants, an approximate independence of the multiplicity per participating nucleon measured at mid-rapidity of the number of participating nucleons is observed. Furthermore, at high-pT the p-Pb spectra are found to be consistent with the pp spectra scaled by N-coll for all centrality classes. Our results represent valuable input for the study of the event-activity dependence of hard probes in p-Pb collisions and, hence, help to establish baselines for the interpretation of the Pb-Pb data.

Quantifying truncation errors in effective field theory

Abstract: Bayesian procedures designed to quantify truncation errors in perturbative calculations of quantum chromodynamics observables are adapted to expansions in effective field theory (EFT). In the Bayesian approach, such truncation errors are derived from degree-of-belief (DOB) intervals for EFT predictions. Computation of these intervals requires specification of prior probability distributions (``priors'') for the expansion coefficients. By encoding expectations about the naturalness of these coefficients, this framework provides a statistical interpretation of the standard EFT procedure where truncation errors are estimated using the order-by-order convergence of the expansion. It also permits exploration of the ways in which such error bars are, and are not, sensitive to assumptions about EFT-coefficient naturalness. We first demonstrate the calculation of Bayesian probability distributions for the EFT truncation error in some representative examples and then focus on the application of chiral EFT to neutron-proton scattering. Epelbaum, Krebs, and Mei\ss{}ner recently articulated explicit rules for estimating truncation errors in such EFT calculations of few-nucleon-system properties. We find that their basic procedure emerges generically from one class of naturalness priors considered and that all such priors result in consistent quantitative predictions for 68% DOB intervals. We then explore several methods by which the convergence properties of the EFT for a set of observables may be used to check the statistical consistency of the EFT expansion parameter.

Nuclear matrix elements for 0 ν β β decays with light or heavy Majorana-neutrino exchange

Abstract: We compute the nuclear matrix elements (NMEs) corresponding to the neutrinoless double beta ($0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$) decays of nuclei which attract current experimental interest. We concentrate on ground-state-to-ground-state decay transitions mediated by light (l-NMEs) or heavy (h-NMEs) Majorana neutrinos. The computations are done in realistic single-particle model spaces using the proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon interactions based on the Bonn one-boson-exchange $G$ matrix. Both the l-NMEs and the h-NMEs include the appropriate short-range correlations, nucleon form factors, and higher-order nucleonic weak currents. In addition, both types of NMEs are corrected for the isospin symmetry by the recently proposed method in which the particle-particle proton-neutron interaction parameter (${g}_{\mathrm{pp}}$) is decomposed into isoscalar (${g}_{\mathrm{pp}}^{T=0}$) and isovector (${g}_{\mathrm{pp}}^{T=1}$) parts. A detailed analysis of the l-NMEs and the h-NMEs is performed to benchmark our computer code and to compare with other recent calculations which produce h-NMEs that are in tension with each other.

Linear Boltzmann Transport for Jet Propagation in the Quark-Gluon Plasma: Elastic Processes and Medium Recoil

Abstract: A Linear Boltzmann Transport model within perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions and angular distribution of reconstructed jets.

Evidence for transverse-momentum- and pseudorapidity-dependent event-plane fluctuations in PbPb and pPb collisions

Abstract: A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of pT and nu of both particles and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at root sNN = 2.76 TeV and pPb collisions at root sNN = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pT and nu. When measured with particles of different pT, the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different nu. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very-high-multiplicity pPb collisions. The nu-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions.

Neutron skin thickness from the measured electric dipole polarizability in Ni 68 , Sn 120 , and Pb 208

Abstract: The authors use recent available experimental data on the electric dipole polarizability of ${}^{68}$Ni, ${}^{120}$Sn, and ${}^{208}$Pb to constrain physically important quantities including the symmetry energy, its slope, and the neutron skin thickness. The strong correlation between the electric dipole polarizabilities of two nuclei is instrumental in predicting the values of electric dipole polarizabilities in other nuclei. The results are of interest for future observational, experimental, and theoretical work on these interconnected nuclear quantities.

Minimally nonlocal nucleon-nucleon potentials with chiral two-pion exchange including Δ resonances

Abstract: In this study, we construct a coordinate-space chiral potential, including Δ-isobar intermediate states in its two-pion-exchange component up to order Q3 (Q denotes generically the low momentum scale). The contact interactions entering at next-to-leading and next-to-next-to-next-to-leading orders (Q2 and Q4, respectively) are rearranged by Fierz transformations to yield terms at most quadratic in the relative momentum operator of the two nucleons. The low-energy constant multiplying these contact interactions are fitted to the 2013 Granada database, consisting of 2309 pp and 2982 np data (including, respectively, 148 and 218 normalizations) in the laboratory-energy range 0–300 MeV. For the total 5291 $pp$ and $np$ data in this range, we obtain a Χ2 /datum of roughly 1.3 for a set of three models characterized by long- and short-range cutoffs, RL and RS respectively, ranging from (RL,RS)=(1.2,0.8) fm down to (0.8,0.6) fm. The long-range (short-range) cutoff regularizes the one- and two-pion exchange (contact) part of the potential.

Peripheral nucleon-nucleon scattering at fifth order of chiral perturbation theory

Abstract: The authors report results for $N\phantom{\rule{0}{0ex}}N$ scattering in higher partial waves based on chiral perturbation theory to 5th order in the expansion. As the first such calculation to this order, the work sets a new standard for the derivation of the $N\phantom{\rule{0}{0ex}}N$ interaction in chiral perturbation theory. The results are not very sensitive to the single cut-off parameter.

Estimation of the shear viscosity at finite net-baryon density from A + A collision data at s NN = 7.7 – 200 GeV

Abstract: Hybrid approaches based on relativistic hydrodynamics and transport theory have been successfully applied for many years for the dynamical description of heavy-ion collisions at ultrarelativistic energies. In this work a new viscous hybrid model employing the hadron transport approach UrQMD for the early and late nonequilibrium stages of the reaction, and 3+1 dimensional viscous hydrodynamics for the hot and dense quark-gluon plasma stage, is introduced. This approach includes the equation of motion for finite baryon number and employs an equation of state with finite net-baryon density to allow for calculations in a large range of beam energies. The parameter space of the model is explored and constrained by comparison with the experimental data for bulk observables from Super Proton Synchrotron and the phase I beam energy scan at Relativistic Heavy Ion Collider. The favored parameter values depend on energy but allow extraction of the effective value of the shear viscosity coefficient over entropy density ratio $\ensuremath{\eta}/s$ in the fluid phase for the whole energy region under investigation. The estimated value of $\ensuremath{\eta}/s$ increases with decreasing collision energy, which may indicate that $\ensuremath{\eta}/s$ of the quark-gluon plasma depends on baryochemical potential ${\ensuremath{\mu}}_{B}$.

Centrality dependence of low-momentum direct-photon production in Au plus Au collisions at root s(NN)=200 GeV

Abstract: The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au+Au collisions at sNN−−−√=200 GeV down to pT=0.4 GeV/c. Photons are detected via photon conversions to e+e− pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low pT. We find an excess of direct photons above the Ncoll-scaled yield measured in p+p collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240MeV/c in the pT range 0.6–2.0 GeV/c. While the shape of the pT distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with Nαpart, where α=1.38±0.03(stat)±0.07(syst).

Systematic study of nuclear matrix elements in neutrinoless double-β decay with a beyond-mean-field covariant density functional theory

Abstract: We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-$\ensuremath{\beta}$ decays with a state-of-the-art beyond-mean-field covariant density functional theory. The dynamic effects of particle-number and angular-momentum conservations as well as quadrupole shape fluctuations are taken into account with projections and generator coordinate method for both initial and final nuclei. The full relativistic transition operator is adopted to calculate the NMEs. The present systematic studies show that in most of the cases there is a much better agreement with the previous nonrelativistic calculation based on the Gogny force than in the case of the nucleus $^{150}\mathrm{Nd}$ found by Song et al. [Phys. Rev. C 90, 054309 (2014)]. In particular, we find that the total NMEs can be well approximated by the pure axial-vector coupling term with a considerable reduction of the computational effort.

Nuclear robustness of the r process in neutron-star mergers

Abstract: We have performed $r$-process calculations for matter ejected dynamically in neutron star mergers based on a complete set of trajectories from a three-dimensional relativistic smoothed particle hydrodynamic simulation with a total ejected mass of $\ensuremath{\sim}1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{M}_{\ensuremath{\bigodot}}$. Our calculations consider an extended nuclear network, including spontaneous, $\ensuremath{\beta}$- and neutron-induced fission and adopting fission yield distributions from the abla code. In particular we have studied the sensitivity of the $r$-process abundances to nuclear masses by using different models. Most of the trajectories, corresponding to 90% of the ejected mass, follow a relatively slow expansion allowing for all neutrons to be captured. The resulting abundances are very similar to each other and reproduce the general features of the observed $r$-process abundance (the second and third peaks, the rare-earth peak, and the lead peak) for all mass models as they are mainly determined by the fission yields. We find distinct differences in the predictions of the mass models at and just above the third peak, which can be traced back to different predictions of neutron separation energies for $r$-process nuclei around neutron number $N=130$. In all simulations, we find that the second peak around $A\ensuremath{\sim}130$ is produced by the fission yields of the material that piles up in nuclei with $A\ensuremath{\gtrsim}250$ due to the substantially longer $\ensuremath{\beta}$-decay half-lives found in this region. The third peak around $A\ensuremath{\sim}195$ is generated in a competition between neutron captures and $\ensuremath{\beta}$ decays during $r$-process freeze-out. The remaining trajectories, which contribute 10% by mass to the total integrated abundances, follow such a fast expansion that the $r$ process does not use all the neutrons. This also leads to a larger variation of abundances among trajectories, as fission does not dominate the $r$-process dynamics. The resulting abundances are in between those associated to the $r$ and $s$ processes. The total integrated abundances are dominated by contributions from the slow abundances and hence reproduce the general features of the observed $r$-process abundances. We find that, at timescales of weeks relevant for kilonova light curve calculations, the abundance of actinides is larger than the one of lanthanides. This means that actinides can be even more important than lanthanides to determine the photon opacities under kilonova conditions. Moreover, we confirm that the amount of unused neutrons may be large enough to give rise to another observational signature powered by their decay.

Real time evolution of non-Gaussian cumulants in the QCD critical regime

Abstract: In this study, we derive a coupled set of equations that describe the nonequilibrium evolution of cumulants of critical fluctuations for spacetime trajectories on the crossover side of the QCD phase diagram. In particular, novel expressions are obtained for the nonequilibrium evolution of non-Gaussian skewness and kurtosis cumulants. UBy utilizing a simple model of the spacetime evolution of a heavy-ion collision, we demonstrate that, depending on the relaxation rate of critical fluctuations, skewness and kurtosis can differ significantly in magnitude as well as in sign from equilibrium expectations. Memory effects are important and shown to persist even for trajectories that skirt the edge of the critical regime. We use phenomenologically motivated parametrizations of freeze-out curves and of the beam-energy dependence of the net baryon chemical potential to explore the implications of our model study for the critical-point search in heavy-ion collisions.

Energy loss, hadronization, and hadronic interactions of heavy flavors in relativistic heavy-ion collisions

Abstract: We construct a theoretical framework to describe the evolution of heavy flavors produced in relativistic heavy-ion collisions. The in-medium energy loss of heavy quarks is described using our modified Langevin equation that incorporates both quasielastic scatterings and the medium-induced gluon radiation. The space-time profiles of the fireball are described by a (2+1)-dimensional hydrodynamics simulation. A hybrid model of fragmentation and coalescence is utilized for heavy quark hadronization, after which the produced heavy mesons together with the soft hadrons produced from the bulk quark-gluon plasma (QGP) are fed into the hadron cascade ultrarelativistic quantum molecular dynamics (UrQMD) model to simulate the subsequent hadronic interactions. We find that the medium-induced gluon radiation contributes significantly to heavy quark energy loss at high ${p}_{\mathrm{T}}$; heavy-light quark coalescence enhances heavy meson production at intermediate ${p}_{\mathrm{T}}$; and scatterings inside the hadron gas further suppress the $D$ meson ${R}_{\mathrm{AA}}$ at large ${p}_{\mathrm{T}}$ and enhance its ${v}_{2}$. Our calculations provide good descriptions of heavy meson suppression and elliptic flow observed at both the Large Hadron Collider and the Relativistic Heavy-Ion Collider.

Systematic study of α -decay energies and half-lives of superheavy nuclei

Abstract: Systematic calculations on the $\ensuremath{\alpha}$-decay energies $({Q}_{\ensuremath{\alpha}})$ and $\ensuremath{\alpha}$-decay half-lives of the superheavy nuclei (SHN) with $Z\ensuremath{\ge}100$ are performed by using 20 models and 18 empirical formulas, respectively. According to the comparisons between the calculated results and experimental data, it is shown that the WS4 mass model is the most accurate one to reproduce the experimental ${Q}_{\ensuremath{\alpha}}$ values of the SHN. Meanwhile it is found that the SemFIS2 formula is the best one to predict the $\ensuremath{\alpha}$-decay half-lives of the SHN because the parameters in this formula are from the experimental $\ensuremath{\alpha}$ emitter data of transuranium nuclei including SHN $(Z=92\text{--}118)$. In addition, the UNIV2 formula with fewest parameters and the VSS, SP and NRDX formulas with fewer parameters work well in prediction on the SHN $\ensuremath{\alpha}$-decay half-lives. Finally, the $\ensuremath{\alpha}$-decay half-lives of $Z=110\text{--}120$ isotopes are predicted within the above mentioned five formulas by inputting the $\mathrm{WS}4 {Q}_{\ensuremath{\alpha}}$ values. By analyzing the ${Q}_{\ensuremath{\alpha}}$ values and the $\ensuremath{\alpha}$-decay half-lives of this region, it is found that for $Z=110\text{--}114$ isotopes $N=162$ and $N=184$ are the submagic number and magic number, respectively. However, for the isotopes of $Z=116\text{--}120$ the submagic number is $N=178$.

Tomography of the Quark-Gluon-Plasma by Charm Quarks

Abstract: We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM) which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross section are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and/or fragmentation depending on transverse momentum. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective lagrangian approach with heavy-quark spin symmetry. Finally, the nuclear modification factor $\rm R_{AA}$ and the elliptic flow $v_2$ of $D^0$ mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at $\sqrt{s_{\rm NN}}$ =200 GeV. We find that in the PHSD the energy loss of $D$ mesons at high $p_T$ can be dominantly attributed to partonic scattering while the actual shape of $\rm R_{AA}$ versus $p_T$ reflects the heavy quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the $\rm R_{AA}$ at low $p_T$ and enhances the $D$-meson elliptic flow $v_2$.

Electric Dipole Moments: A Global Analysis

Abstract: We perform a global analysis of searches for the permanent electric dipole moments (EDMs) of the neutron, neutral atoms, and molecules in terms of six leptonic, semileptonic, and nonleptonic interactions involving photons, electrons, pions, and nucleons. By translating the results into fundamental charge-conjugation-parity symmetry (CP) violating effective interactions through dimension six involving standard model particles, we obtain rough lower bounds on the scale of beyond the standard model CP-violating interactions ranging from 1.5 TeV for the electron EDM to 1300 TeV for the nuclear spin-independent electron-quark interaction. We show that planned future measurements involving systems or combinations of systems with complementary sensitivities to the low-energy parameters may extend the mass reach by an order of magnitude or more.

Fission barriers at the end of the chart of the nuclides

Abstract: We present calculated fission-barrier heights for 5239 nuclides for all nuclei between the proton and neutron drip lines with $171\ensuremath{\le}A\ensuremath{\le}330$. The barriers are calculated in the macroscopic-microscopic finite-range liquid-drop model with a 2002 set of macroscopic-model parameters. The saddle-point energies are determined from potential-energy surfaces based on more than 5 000 000 different shapes, defined by five deformation parameters in the three-quadratic-surface shape parametrization: elongation, neck diameter, left-fragment spheroidal deformation, right-fragment spheroidal deformation, and nascent-fragment mass asymmetry. The energy of the ground state is determined by calculating the lowest-energy configuration in both the Nilsson perturbed-spheroid $(\ensuremath{\epsilon})$ and the spherical-harmonic $(\ensuremath{\beta})$ parametrizations, including axially asymmetric deformations. The lower of the two results (correcting for zero-point motion) is defined as the ground-state energy. The effect of axial asymmetry on the inner barrier peak is calculated in the $(\ensuremath{\epsilon},\ensuremath{\gamma})$ parametrization. We have earlier benchmarked our calculated barrier heights to experimentally extracted barrier parameters and found average agreement to about 1 MeV for known data across the nuclear chart. Here we do additional benchmarks and investigate the qualitative and, when possible, quantitative agreement and/or consistency with data on $\ensuremath{\beta}$-delayed fission, isotope generation along prompt-neutron-capture chains in nuclear-weapons tests, and superheavy-element stability. These studies all indicate that the model is realistic at considerable distances in $Z$ and $N$ from the region of nuclei where its parameters were determined.

Tests of the nuclear equation of state and superfluid and superconducting gaps using the Cassiopeia A neutron star

Abstract: The observed rapid cooling of the Cassiopeia A neutron star can be interpreted as being caused by neutron and proton transitions from normal to superfluid and superconducting states in the stellar core. Here we present two new Chandra ACIS-S Graded observations of this neutron star and measurements of the neutron star mass $M$ and radius $R$ found from consistent fitting of both the x-ray spectra and cooling behavior. This comparison is only possible for individual nuclear equations of state. We test phenomenological superfluid and superconducting gap models which mimic many of the known theoretical models against the cooling behavior. Our best-fit solution to the Cassiopeia A data is one in which the $(M,R)=(1.44\phantom{\rule{0.16em}{0ex}}{M}_{\mathrm{Sun}},12.6\phantom{\rule{4.pt}{0ex}}\text{km})$ neutron star is built with the BSk21 equation of state, strong proton superconductor and moderate neutron triplet superfluid gap models, and a pure iron envelope or a thin carbon layer on top of an iron envelope, although there are still large observational and theoretical uncertainties.

Unified treatment of subsaturation stellar matter at zero and finite temperature

Abstract: The standard variational derivation of stellar matter structure in the Wigner-Seitz approximation is generalized to the finite temperature situation where a wide distribution of different nuclear species can coexist in the same density and proton fraction condition, possibly out of $\beta$-equilibrium. The same theoretical formalism is shown to describe on one side the single-nucleus approximation (SNA), currently used in most core collapse supernova simulations, and on the other side the nuclear statistical equilibrium (NSE) approach, routinely employed in r- and p-process explosive nucleosynthesis problems. In particular we show that in-medium effects have to be accounted for in NSE to have a theoretical consistency between the zero and finite temperature modeling. The bulk part of these in-medium effects is analytically calculated and shown to be different from a van der Waals excluded volume term. This unified formalism allows controlling quantitatively the deviations from the SNA in the different thermodynamic conditions, as well as having a NSE model which is reliable at any arbitrarily low value of the temperature, with potential applications for neutron star cooling and accretion problems. We present different illustrative results with several mass models and effective interactions, showing the importance of accounting for the nuclear species distribution even at temperatures lower than 1 MeV.

Using Neutron Star Observations to Determine Crust Thicknesses, Moments of Inertia, and Tidal Deformabilities

Abstract: We perform a systematic assessment of models for the equation of state (EOS) of dense matter in the context of recent neutron star mass and radius measurements to obtain a broad picture of the structure of neutron stars We demonstrate that currently available neutron star mass and radius measurements provide strong constraints on moments of inertia, tidal deformabilities, and crust thicknesses A measurement of the moment of inertia of PSR J0737-3039A with a 10% error, without any other information from observations, will constrain the EOS over a range of densities to within 50%--60% We find tidal deformabilities between 06 and $6\ifmmode\times\else\texttimes\fi{}{10}^{36}\phantom{\rule{028em}{0ex}}\mathrm{g}\phantom{\rule{016em}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{016em}{0ex}}{\mathrm{s}}^{2}$ (to 95% confidence) for $M=14\phantom{\rule{028em}{0ex}}{M}_{\ensuremath{\bigodot}}$, and any measurement which constrains this range will provide an important constraint on dense matter The crustal fraction of the moment of inertia can be as large as 10% for $M=14\phantom{\rule{028em}{0ex}}{M}_{\ensuremath{\bigodot}}$ permitting crusts to have a large enough moment of inertia reservoir to explain glitches in the Vela pulsar even with a large amount of superfluid entrainment Finally, due to the uncertainty in the equation of state, there is at least a 40% variation in the thickness of the crust for a fixed mass and radius, which implies that future simulations of the cooling of a neutron star crust which has been heated by accretion will need to take this variation into account

Measurement of the correlation between flow harmonics of different order in lead-lead collisions at √sNN = 2.76 TeV with the ATLAS detector

Abstract: Correlations between the elliptic or triangular flow coefficients v(m) (m = 2 or 3) and other flow harmonics v(n) (n = 2 to 5) are measured using root S-NN = 2.76 TeV Pb + Pb collision data collected in 2010 by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 7 mu b(-1). The v(m)-v(n) correlations aremeasured in midrapidity as a function of centrality, and, for events within the same centrality interval, as a function of event ellipticity or triangularity defined in a forward rapidity region. For events within the same centrality interval, v(3) is found to be anticorrelated with v(2) and this anticorrelation is consistent with similar anticorrelations between the corresponding eccentricities, epsilon(2) and epsilon(3). However, it is observed that v(4) increases strongly with v(2), and v(5) increases strongly with both v(2) and v(3). The trend and strength of the v(m) -v(n) correlations for n = 4 and 5 are found to disagree with epsilon(m)-epsilon(n) correlations predicted by initial-geometry models. Instead, these correlations are found to be consistent with the combined effects of a linear contribution to v(n) and a nonlinear term that is a function of v(2)(2) or of v(2)v(3), as predicted by hydrodynamic models. A simple two-component fit is used to separate these two contributions. The extracted linear and nonlinear contributions to v(4) and v(5) are found to be consistent with previously measured event-plane correlations.

Critical density and impact of Δ(1232) resonance formation in neutron stars

Abstract: The critical densities and impact of forming $\mathrm{\ensuremath{\Delta}}(1232)$ resonances in neutron stars are investigated within an extended nonlinear relativistic mean-field (RMF) model. The critical densities for the formation of four different charge states of $\mathrm{\ensuremath{\Delta}}(1232)$ are found to depend differently on the separate kinetic and potential parts of nuclear symmetry energy, the first example of a microphysical property of neutron stars to do so. Moreover, they are sensitive to the in-medium $\mathrm{\ensuremath{\Delta}}$ mass ${m}_{\mathrm{\ensuremath{\Delta}}}$ and the completely unknown $\mathrm{\ensuremath{\Delta}}\text{\ensuremath{-}}\ensuremath{\rho}$ coupling strength ${g}_{\ensuremath{\rho}\mathrm{\ensuremath{\Delta}}}$. In the universal baryon-meson coupling scheme where the respective $\mathrm{\ensuremath{\Delta}}$-meson and nucleon-meson coupling constants are assumed to be the same, the critical density for the first ${\mathrm{\ensuremath{\Delta}}}^{\ensuremath{-}}(1232)$ to appear is found to be ${\ensuremath{\rho}}_{\mathrm{\ensuremath{\Delta}}}^{\mathrm{crit}}=(2.08\ifmmode\pm\else\textpm\fi{}0.02){\ensuremath{\rho}}_{0}$ using RMF model parameters consistent with current constraints on all seven macroscopic parameters usually used to characterize the equation of state of isospin-asymmetric nuclear matter at saturation density ${\ensuremath{\rho}}_{0}$. Moreover, the composition and the mass-radius relation of neutron stars are found to depend significantly on the values of the ${g}_{\ensuremath{\rho}\mathrm{\ensuremath{\Delta}}}$ and ${m}_{\mathrm{\ensuremath{\Delta}}}$.

Strange and nonstrange baryon spectra in the relativistic interacting quark-diquark model with a Gürsey and Radicati-inspired exchange interaction

Abstract: The relativistic interacting quark-diquark model, constructed in the framework of point form dynamics, is extended to strange baryons. The strange and nonstrange baryon spectra are calculated and compared with the experimental data.