Showing papers in "Physical Review C in 2002"
Joint Institute for Nuclear Research1, Hungarian Academy of Sciences2, Polish Academy of Sciences3, University of Birmingham4, University of Marburg5, Goethe University Frankfurt6, GSI Helmholtz Centre for Heavy Ion Research7, Comenius University in Bratislava8, CERN9, University of Washington10, Max Planck Society11, Eötvös Loránd University12, National and Kapodistrian University of Athens13, University of California, Los Angeles14, Kent State University15, University of Houston16, University of Warsaw17, Massachusetts Institute of Technology18
TL;DR: In this article, the mean pion multiplicity per wounded nucleon increases approximately linearly with a change of slope starting in the region 15--40 A GeV, and the change from pion suppression with respect to $p+p$ interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40A GeV.
Abstract: Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80, and 158 A GeV are presented. These are compared with data at lower and higher energies as well as with results from $p+p$ interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with ${s}_{\mathrm{NN}}^{1/4}$ with a change of slope starting in the region 15--40 A GeV. The change from pion suppression with respect to $p+p$ interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40A GeV. A nonmonotonic energy dependence of the ratio of ${K}^{+}$ to ${\ensuremath{\pi}}^{+}$ yields is observed, with a maximum close to 40A GeV and an indication of a nearly constant value at higher energies. The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.
549 citations
TL;DR: In this paper, the three-nucleon force at the next-to-next-leading order in chiral effective field theory was analyzed. But only the two-and three-and four-and five-and six-and seven-and eight-nule interactions were taken into account.
Abstract: We perform the first fully consistent analysis of $\mathrm{nd}$ scattering at next-to-next-to-leading order in chiral effective field theory including the corresponding three-nucleon force and extending our previous work, where only the two-nucleon interaction has been taken into account. The three-nucleon force appears first at this order in the chiral expansion and depends on two unknown parameters. These two parameters are determined from the triton binding energy and $\mathrm{nd}$ doublet scattering length. We find an improved description of various scattering observables in relation to the next-to-leading order results especially at moderate energies ${(E}_{\mathrm{lab}}=65\mathrm{MeV}).$ It is demonstrated that the long-standing ${A}_{y}$ problem in $\mathrm{nd}$ elastic scattering is still not solved by the leading 3NF, although some visible improvement is observed. We discuss possibilities of solving this puzzle. The predicted binding energy for the $\ensuremath{\alpha}$ particle agrees with the empirical value.
487 citations
KEK1
TL;DR: In this article, the authors investigated the possible existence of deeply bound nuclear states with binding energies of 108, 86, and 113 MeV and widths of 20, 34, and 38 MeV, respectively.
Abstract: The possible existence of deeply bound nuclear $\overline{K}$ states is investigated theoretically for few-body systems. The nuclear ground states of a ${K}^{\ensuremath{-}}$ in ${}^{3}\mathrm{He},$ ${}^{4}\mathrm{He},$ and ${}^{8}\mathrm{Be}$ are predicted to be discrete states with binding energies of 108, 86, and 113 MeV and widths of 20, 34, and 38 MeV, respectively. The smallness of the widths arises from their energy-level locations below the $\ensuremath{\Sigma}\ensuremath{\pi}$ emission threshold. It is found that a substantial contraction of the surrounding nucleus is induced due to the strong attraction of the $I=0$ $\overline{K}N$ pair, thus forming an unusually dense nuclear medium. Formation of the $T=0{K}^{\ensuremath{-}}{\ensuremath{\bigotimes}}^{3}\mathrm{He}+{K}^{0}{\ensuremath{\bigotimes}}^{3}\mathrm{H}$ state in the ${}^{4}\mathrm{He}$ (stopped ${K}^{\ensuremath{-}},$ $n)$ reaction is proposed, with a calculated branching ratio of about 2%.
459 citations
TL;DR: In this paper, an extensive systematization of theoretical and experimental nuclear densities and of optical potential strengths extracted from heavy-ion elastic scattering data analyses at low and intermediate energies is presented.
Abstract: Extensive systematizations of theoretical and experimental nuclear densities and of optical potential strengths extracted from heavy-ion elastic scattering data analyses at low and intermediate energies are presented. The energy dependence of the nuclear potential is accounted for within a model based on the nonlocal nature of the interaction. The systematics indicates that the heavy-ion nuclear potential can be described in a simple global way through a double-folding shape, which basically depends only on the density of nucleons of the partners in the collision. The possibility of extracting information about the nucleon-nucleon interaction from the heavy-ion potential is investigated.
365 citations
TL;DR: In this article, the effect of early chemical freeze-out on radial flow, elliptic flow, and Hanbury Brown-Twiss (HBT) radii was investigated by using a fully three-dimensional hydrodynamic model.
Abstract: We investigate the effect of early chemical freeze-out on radial flow, elliptic flow, and Hanbury Brown--Twiss (HBT) radii by using a fully three-dimensional hydrodynamic model. When we take account of the early chemical freeze-out, the space-time evolution of temperature in the hadron phase is considerably different from the conventional model in which chemical equilibrium is always assumed. As a result, we find that radial and elliptic flows are suppressed and that the lifetime and the spatial size of the fluid are reduced. We analyze the ${p}_{t}$ spectrum, the differential elliptic flow, and the HBT radii at the Relativistic Heavy-Ion Collider energy by using hydrodynamics with a chemically nonequilibrium equation of state.
356 citations
TL;DR: In this article, a new version of the Li-ge intranuclear cascade (INC) model is proposed for the description of spallation reactions, which can accommodate a diffuse nuclear surface, removing unphysical features linked with the use of statistical blocking factors, and pion dynamics is improved, especially concerning the delta lifetime.
Abstract: A new version of the Li\`ege intranuclear cascade (INC) model is proposed for the description of spallation reactions. Compared to the previous version, it incorporates new features: (i) it can accommodate a diffuse nuclear surface, (ii) the treatment of the Pauli blocking effect is improved, removing unphysical features linked with the use of statistical blocking factors, (iii) collisions between moving spectator nucleons are explicitly suppressed, (iv) pion dynamics is improved, especially concerning the delta lifetime, (v) it can accommodate light ions as incoming projecticles, (vi) the remnant angular momentum is included in the output of the model. Another important feature is the self-consistent determination of the stopping time, i.e., the time at which the INC calculation is terminated and coupled to evaporation. The predictions of the model, used with the Schmidt evaporation code, are tested against a large body of experimental data, in the 200-MeV--2-GeV range for incident energy per nucleon, including total reaction cross sections, neutron, proton, pion, and composite double differential cross sections, particle multiplicities, residue mass and charge distributions, and residue recoil velocity distributions. Good agreement is generally obtained without additional varying parameters. It is shown that the introduction of a diffuse surface considerably improves the description of the total reaction cross sections, of the intensity of the quasielastic peak in proton and neutron double differential cross sections and of the residue production yield for isotopes close to the target. High energy neutron spectra are found to be sensitive to details of the deuteron structure in deuteron-induced reactions. The shape of the fragmentation peaks in residue mass spectra is shown to be closely related to the shape of the distribution of the excitation energy left after the cascade stage. The longitudinal residue recoil velocity and its fluctuations display typical random-walk characterics, which are interpreted as a direct consequence of the independence of successive binary collisions occurring during the cascade process and therefore provide a strong support of the basic hypotheses of the INC model. Small but systematic discrepancies between model predictions and experiment are identified and possible further improvements to reduce them are discussed. The influence of the evaporation model is investigated. A comparison with similar approaches is presented.
322 citations
TL;DR: In this article, the authors show that four-particle correlation analyses can reliably separate flow and non-flow correlation signals, with the latter account for on average about 15 percent of the observed second-harmonic azimuthal correlation.
Abstract: Elliptic flow holds much promise for studying the early-time thermalization attained in ultrarelativistic nuclear collisions. Flow measurements also provide a means of distinguishing between hydrodynamic models and calculations which approach the low density (dilute gas) limit. Among the effects that can complicate the interpretation of elliptic flow measurements are azimuthal correlations that are unrelated to the reaction plane (non-flow correlations). Using data for Au + Au collisions at {radical}s{sub NN} = 130 GeV from the STAR TPC, it is found that four-particle correlation analyses can reliably separate flow and non-flow correlation signals. The latter account for on average about 15 percent of the observed second-harmonic azimuthal correlation, with the largest relative contribution for the most peripheral and the most central collisions. The results are also corrected for the effect of flow variations within centrality bins. This effect is negligible for all but the most central bin , where the correction to the elliptic flow is about a factor of two. A simple new method for two-particle flow analysis based on scalar products is described. An analysis based on the distribution of the magnitude of the flow vector is also described.
313 citations
TL;DR: In this article, the ground and low-lying excited states of 9,10-nucleon nuclei were obtained using a constrained path algorithm. But the ground state was not obtained for all nuclei.
Abstract: We report on quantum Monte Carlo calculations of the ground and low-lying excited states of $A=9,10$ nuclei using realistic Hamiltonians containing the Argonne ${v}_{18}$ two-nucleon potential alone or with one of several three-nucleon potentials, including Urbana IX and three of the new Illinois models. The calculations begin with correlated many-body wave functions that have an $\ensuremath{\alpha}$-like core and multiple p-shell nucleons, $\mathrm{LS}$-coupled to the appropriate ${(J}^{\ensuremath{\pi}};T)$ quantum numbers for the state of interest. After optimization, these variational trial functions are used as input to a Green's function Monte Carlo calculation of the energy, using a constrained path algorithm. We find that the Hamiltonians that include Illinois three-nucleon potentials reproduce ten states in ${}^{9}\mathrm{Li},$ ${}^{9}\mathrm{Be},$ ${}^{10}\mathrm{Be},$ and ${}^{10}\mathrm{B}$ with an rms deviation as little as 900 keV. In particular, we obtain the correct ${3}^{+}$ ground state for ${}^{10}\mathrm{B},$ whereas the Argonne ${v}_{18}$ alone or with Urbana IX predicts a ${1}^{+}$ ground state. In addition, we calculate isovector and isotensor energy differences, electromagnetic moments, and one- and two-body density distributions.
257 citations
TL;DR: In this paper, the authors studied the elliptic flow in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) in a multiphase transport model by converting the strings in the high energy density regions into partons.
Abstract: The elliptic flow in heavy ion collisions at the Relativistic Heavy Ion Collider is studied in a multiphase transport model By converting the strings in the high energy density regions into partons, we find that the final elliptic flow is sensitive to the parton scattering cross section To reproduce the large elliptic flow observed in Au+Au collisions at $\sqrt{s}=130 A\mathrm{GeV}$ requires a parton scattering cross section of about 6 mb We also study the dependence of the elliptic flow on the particle multiplicity, transverse momentum, and particle mass
245 citations
TL;DR: In this article, the relativistic Hartree-Bogoliubov (RHB) model is extended to include density-dependent meson-nucleon couplings, and the new densitydependent effective interaction DD-ME1 is tested in the analysis of the equations of state for symmetric and asymmetric nuclear matter, and of groundstate properties of the Sn and Pb isotopic chains.
Abstract: The relativistic Hartree-Bogoliubov (RHB) model is extended to include density-dependent meson-nucleon couplings. The effective Lagrangian is characterized by a phenomenological density dependence of the $\ensuremath{\sigma},$ $\ensuremath{\omega},$ and $\ensuremath{\rho}$ meson-nucleon vertex functions, adjusted to properties of nuclear matter and finite nuclei. Pairing correlations are described by the pairing part of the finite range Gogny interaction. The new density-dependent effective interaction DD-ME1 is tested in the analysis of the equations of state for symmetric and asymmetric nuclear matter, and of ground-state properties of the Sn and Pb isotopic chains. Results of self-consistent RHB calculations are compared with experimental data, and with results previously obtained in the RHB model with nonlinear self-interactions, as well as in the density-dependent relativistic hadron field (DDRH) model. Parity-violating elastic electron scattering on Pb and Sn nuclei is calculated using a relativistic optical model with inclusion of Coulomb distortion effects, and the resulting asymmetry parameters are related to the neutron ground-state density distributions.
242 citations
Abstract: An effective interaction is derived for use in the full pf basis. Starting from a realistic G-matrix interaction, 195 two-body matrix elements and 4 single-particle energies are determined by fitting to 699 energy data in the mass range 47 to 66. The derived interaction successfully describes various structures of pf-shell nuclei. As examples, systematics of the energies of the first 2+ states in the Ca, Ti, Cr, Fe, and Ni isotope chains and energy levels of 56,57,58Ni are presented. The appearance of a new magic number 34 is seen.
TL;DR: In this paper, data from a number of different experimental measurements are used to construct caloric curves for five different regions of nuclear mass, and these curves are qualitatively similar and exhibit plateaus at the higher excitation energies.
Abstract: Data from a number of different experimental measurements are used to construct caloric curves for five different regions of nuclear mass. These curves are qualitatively similar, and exhibit plateaus at the higher excitation energies. The limiting temperatures represented by the plateaus decrease with increasing nuclear mass, and are in very good agreement with results of recent calculations employing either a chiral symmetry model or the Gogny interaction. This agreement strongly favors a soft equation of state. Evidence is presented which suggests that critical excitation energies and critical temperatures might be determined from caloric curve measurements when the mass variations inherent in such measurements are taken into account.
TL;DR: In this article, the effects of coupling to an isovector-scalar meson in a phenomenological hadronic field theory have been investigated for the equation of state and the phase diagram of asymmetric nuclear matter.
Abstract: We try to single out some qualitative effects of coupling to a \ensuremath{\delta}-isovector-scalar meson, introduced in a minimal way in a phenomenological hadronic field theory. Results for the equation of state (EOS) and the phase diagram of asymmetric nuclear matter (ANM) are discussed. We stress the consistency of the \ensuremath{\delta}-coupling introduction in a relativistic approach. Contributions to the slope and curvature of the symmetry energy and to the neutron-proton effective mass splitting appear particularly interesting. A more repulsive EOS for neutron matter at high baryon densities is expected. Effects on the critical properties of warm ANM, mixing mechanical and chemical instabilities and isospin distillation, are also presented. The \ensuremath{\delta} influence is mostly on the isovectorlike collective response. The results are largely analytical, and this makes the physical meaning quite transparent. Implications for nuclear structure properties of drip-line nuclei and for reaction dynamics with radioactive beams are finally pointed out.
TL;DR: In this paper, precise measurements of deuteron vector and tensor analyzing powers were performed via elastic scattering at three incoming deuterons energies of 140, 200, and 270 MeV at the same angles.
Abstract: Precise measurements of deuteron vector and tensor analyzing powers ${A}_{y}^{d},$ ${A}_{\mathrm{xx}},$ ${A}_{\mathrm{yy}},$ and ${A}_{\mathrm{xz}}$ in $d\ensuremath{-}p$ elastic scattering were performed via ${}^{1}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{d},d)p$ and ${}^{1}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{d},p)d$ reactions at three incoming deuteron energies of ${E}_{d}^{\mathrm{lab}}=140,$ 200, and $270 \mathrm{MeV}.$ A wide range of center-of-mass angles from $\ensuremath{\approx}10\ifmmode^\circ\else\textdegree\fi{}$ to $180\ifmmode^\circ\else\textdegree\fi{}$ was covered. The cross section was measured at 140 and 270 MeV at the same angles. These high precision data were compared with theoretical predictions based on exact solutions of three-nucleon Faddeev equations and modern nucleon-nucleon potentials combined with three-nucleon forces. Three-body interactions representing a wide range of present day models have been used: the Tucson-Melbourne $2\ensuremath{\pi}$-exchange model, a modification thereof closer to chiral symmetry, the Urbana IX model, and a phenomenological spin-orbit ansatz. Large three-nucleon force effects are predicted, especially at the two higher energies. However, only some of them, predominantly $d\ensuremath{\sigma}/d\ensuremath{\Omega}$ and ${A}_{y}^{d},$ are supported by the present data. For tensor analyzing powers the predicted effects are in drastic conflict to the data, indicating defects of the present day three-nucleon force models.
TL;DR: In this article, the S-wave interaction of mesons with baryons in the strangeness S = 0 sector in a coupled channel unitary approach is studied and the basic dynamics are drawn from the lowest order meson baryon chiral Lagrangians.
Abstract: We study the S-wave interaction of mesons with baryons in the strangeness S=0 sector in a coupled channel unitary approach. The basic dynamics is drawn from the lowest order meson baryon chiral Lagrangians. Small modifications inspired by models with explicit vector meson exchange in the t-channel are also considered. In addition the pi pi N channel is included and shown to have an important repercussion in the results, particularly in the isospin 3/2 sector.
TL;DR: In this article, the ground-state properties of a set of even-even nuclei are predicted using a Lagrangian whose QCD-scaled coupling constants are all natural (dimensionless and of order one).
Abstract: We present results obtained in the calculation of nuclear ground-state properties in relativistic Hartree approximation using a Lagrangian whose QCD-scaled coupling constants are all natural (dimensionless and of order one). Our model consists of four-, six-, and eight-fermion point couplings (contact interactions) together with derivative terms representing, respectively, two-, three-, and four-body forces and the finite ranges of the corresponding mesonic interactions. The coupling constants have been determined in a self-consistent procedure that solves the model equations for representative nuclei simultaneously in a generalized nonlinear least-squares adjustment algorithm. The extracted coupling constants allow us to predict ground-state properties of a much larger set of even-even nuclei to good accuracy. The fact that the extracted coupling constants are all natural leads to the conclusion that QCD scaling and chiral symmetry apply to finite nuclei.
TL;DR: In this paper, the Hartree-Fock-Bogoliubov model was used to fit the new Audi-Wapstra mass data to the new mass table HFB-2.
Abstract: The two previously published Hartree-Fock (HF) mass formulas, HFBCS-1 and HFB-1 (HF-Bogoliubov), are shown to be in poor agreement with new Audi-Wapstra mass data. The problem lies first with the prescription adopted for the cutoff of the single-particle spectrum used with the $\ensuremath{\delta}$-function pairing force, and second with the Wigner term. We find an optimal mass fit if the spectrum is cut off both above ${E}_{F}+15 \mathrm{MeV}$ and below ${E}_{F}\ensuremath{-}15 \mathrm{MeV},$ ${E}_{F}$ being the Fermi energy of the nucleus in question. In addition to the Wigner term of the form ${V}_{W} \mathrm{exp}(\ensuremath{-}\ensuremath{\lambda}|N\ensuremath{-}Z|/A)$ already included in the two earlier HF mass formulas, we find that a second Wigner term linear in $|N\ensuremath{-}Z|$ leads to a significant improvement in lighter nuclei. These two features are incorporated into our new Hartree-Fock-Bogoliubov model, which leads to much improved extrapolations. The 18 parameters of the model are fitted to the 2135 measured masses for $N,Zg~8$ with an rms error of 0.674 MeV. With this parameter set a complete mass table, labeled HFB-2, has been constructed, going from one drip line to the other, up to $Z=120.$ The new pairing-cutoff prescription favored by the new mass data leads to weaker neutron-shell gaps in neutron-rich nuclei.
TL;DR: In this article, the authors study the hadron-quark phase transition in the interior of neutron stars and calculate the equation of state (EOS) of hadronic matter using the Brueckner-Bethe-Goldstone formalism with realistic two-body and three-body forces, as well as a relativistic mean field model.
Abstract: We study the hadron-quark phase transition in the interior of neutron stars (NS's). We calculate the equation of state (EOS) of hadronic matter using the Brueckner-Bethe-Goldstone formalism with realistic two-body and three-body forces, as well as a relativistic mean field model. For quark matter we employ the MIT bag model constraining the bag constant by using the indications coming from the recent experimental results obtained at the CERN SPS on the formation of a quark-gluon plasma. We find it necessary to introduce a density-dependent bag parameter and the corresponding consistent thermodynamical formalism. We calculate the structure of NS interiors with the EOS comprising both phases, and we find that the NS maximum masses fall in a relatively narrow interval, $1.4{M}_{\ensuremath{\bigodot}}l~{M}_{\mathrm{max}}l~{1.7M}_{\ensuremath{\bigodot}}.$ The precise value of the maximum mass turns out to be only weakly correlated with the value of the energy density at the assumed transition point in nearly symmetric nuclear matter.
TL;DR: In this article, the effect of continuum couplings in the fusion of the halo nucleus around the Coulomb barrier is studied using a three-body model within a coupled discretized continuum channels formalism.
Abstract: The effect of continuum couplings in the fusion of the halo nucleus ${}^{11}\mathrm{Be}$ on ${}^{208}\mathrm{Pb}$ around the Coulomb barrier is studied using a three-body model within a coupled discretized continuum channels formalism. We investigate in particular the role of continuum-continuum couplings. These are found to hinder total, complete, and incomplete fusion processes. Couplings to the projectile ${1p}_{1/2}$ bound excited state redistribute the complete and incomplete fusion cross sections, but the total fusion cross section remains nearly constant. Results show that continuum-continuum couplings enhance the irreversibility of breakup and reduce the flux that penetrates the Coulomb barrier. Converged total fusion cross sections agree with the experimental ones for energies around the Coulomb barrier, but underestimate those for energies well above the Coulomb barrier.
TL;DR: In this article, various measures of net charge (conserved quantities) fluctuations proposed for the identification of critical phenomena in heavy ion collisions are discussed and the dynamical component of fluctuations of the net charge can be expressed simply in terms of integrals of two-and single-particle densities.
Abstract: We discuss various measures of net charge (conserved quantities) fluctuations proposed for the identification of critical phenomena in heavy ion collisions. We show the dynamical component of fluctuations of the net charge can be expressed simply in terms of integrals of two- and single-particle densities. We discuss the dependence of the fluctuation observables on detector acceptance, detection efficiency and colliding system size, and collision centrality. Finally, we present a toy model of particle production including charge conservation and resonance production to gauge the effects of such resonances and finite acceptance on the net-charge fluctuations.
TL;DR: In this paper, a partial-wave analysis of single-pion photoproduction data has been completed, focusing mainly on the influence of new measurements and model-dependence in the choice of parameterization employed above the twopion threshold.
Abstract: A partial-wave analysis of single-pion photoproduction data has been completed. This study extends from threshold to 2 GeV in the laboratory photon energy, focusing mainly on the influence of new measurements and model-dependence in the choice of parameterization employed above the two-pion threshold. Results are used to evaluate sum rules and estimate resonance photo-decay amplitudes. These are compared to values obtained in the MAID analysis.
TL;DR: In this article, a low momentum nucleon-nucleon (NN) potential was derived from meson exchange potentials by integrating out the model dependent high momentum modes of the nucleon.
Abstract: A low momentum nucleon-nucleon (NN) potential ${V}_{low\ensuremath{-}k}$ is derived from meson exchange potentials by integrating out the model dependent high momentum modes of ${V}_{\mathrm{NN}}.$ The smooth and approximately unique ${V}_{low\ensuremath{-}k}$ is used as input for shell model calculations instead of the usual Brueckner G matrix. Such an approach eliminates the nuclear mass dependence of the input interaction one finds in the G matrix approach, allowing the same input interaction to be used in different nuclear regions. Shell model calculations of ${}^{18}\mathrm{O},$ ${}^{134}\mathrm{Te},$ and ${}^{135}\mathrm{I}$ using the same input ${V}_{low\ensuremath{-}k}$ have been performed. For cut-off momentum \ensuremath{\Lambda} in the vicinity of 2 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$, our calculated low-lying spectra for these nuclei are in good agreement with experiments, and are weakly dependent on \ensuremath{\Lambda}.
TL;DR: In this paper, the effects of the spin-isospin channel of the Skyrme energy functional on predictions for Gamow-Teller distributions and superdeformed rotational bands were investigated.
Abstract: We investigate the effects of the spin-isospin channel of the Skyrme energy functional on predictions for Gamow-Teller distributions and superdeformed rotational bands. We use the generalized Skyrme interaction ${\mathrm{SkO}}^{\ensuremath{'}}$ to describe even-even ground states and then analyze the effects of time-odd spin-isospin couplings, first term by term and then together via linear regression. Some terms affect the strength and energy of the Gamow-Teller resonance in finite nuclei without altering the Landau parameter ${g}_{0}^{\ensuremath{'}}$ that to leading order determines spin-isospin properties of nuclear matter. Though the existing data are not sufficient to uniquely determine all the spin-isospin couplings, we are able to fit them locally. Altering these coupling constants does not change the quality with which the Skyrme functional describes rotational bands.
TL;DR: In this article, the PHOBOS experiment has measured the charged particle multiplicity at midrapidity in Au+Au collisions at sqrt(s_NN) = 200 GeV as a function of the collision centrality.
Abstract: The PHOBOS experiment has measured the charged particle multiplicity at mid-rapidity in Au+Au collisions at sqrt(s_NN) = 200 GeV as a function of the collision centrality. Results on dN/deta(eta , are presented as a function of . As was found from similar data at sqrt(s_NN) = 130 GeV, the data can be equally well described by parton saturation models and two-component fits which include contributions that scale as Npart and the number of binary collisions, Ncoll. We compare the data at the two energies by means of the ratio R(200/130) of the charged particle multiplicity for the two different energies as a function of . For events with >100$, we find that this ratio is consistent with a constant value of 1.14+-0.01(stat.)+-0.05(syst.).
TL;DR: In this article, the properties of even-even O, Ca, Ni, Zr, Sn, and Pb isotopes from the stability line to the neutron drip line are studied with the relativistic continuum Hartree-Bogoliubov theory, where both the spin-orbit interaction and continuum are properly taken into account.
Abstract: The properties of even-even O, Ca, Ni, Zr, Sn, and Pb isotopes from the $\ensuremath{\beta}$-stability line to the neutron drip line are studied with the relativistic continuum Hartree-Bogoliubov theory, where both the spin-orbit interaction and continuum are properly taken into account. The available experimental binding energies ${E}_{b}$ and two-neutron separation energies ${S}_{2n}$ are reproduced very well. The predicted neutron drip-line nuclei are, respectively, ${}^{74}\mathrm{Ca},$ ${}^{100}\mathrm{Ni},$ ${}^{140}\mathrm{Zr},$ ${}^{176}\mathrm{Sn},$ and ${}^{268}\mathrm{Pb}.$ Based on the analysis of two-neutron separation energies, single-particle energy levels, the orbital occupation, the contribution of continuum and nucleon density distribution, giant halo phenomena due to pairing, correlation and the contribution from the continuum are suggested to appear in Ca isotopes with $Ag60$ apart from Zr isotopes predicted earlier.
TL;DR: In this article, the authors measured the angular distribution of the cross section, the proton analyzing power, and all proton polarization transfer coefficients at 250 MeV, compared with theoretical predictions based on exact solutions of the three nucleon Faddeev equations and modern realistic nucleon-nucleon potentials combined with three-Nucleon forces (3NF), namely, the Tucson-Melbourne (TM) $2.
Abstract: The angular distributions of the cross section, the proton analyzing power, and all proton polarization transfer coefficients of $\stackrel{\ensuremath{\rightarrow}}{p}d$ elastic scattering were measured at 250 MeV. The range of center-of-mass angles was $10\ifmmode^\circ\else\textdegree\fi{}--165\ifmmode^\circ\else\textdegree\fi{}$ for the cross section and the analyzing power, and about $10\ifmmode^\circ\else\textdegree\fi{}--95\ifmmode^\circ\else\textdegree\fi{}$ for the polarization transfer coefficients. These are the first measurements of a complete set of proton polarization observables for $\stackrel{\ensuremath{\rightarrow}}{p}d$ elastic scattering at intermediate energies. The present data are compared with theoretical predictions based on exact solutions of the three-nucleon Faddeev equations and modern realistic nucleon-nucleon potentials combined with three-nucleon forces (3NF), namely, the Tucson-Melbourne (TM) $2\ensuremath{\pi}$-exchange model, a modification thereof ${(\mathrm{T}\mathrm{M}}^{\ensuremath{'}}$) closer to chiral symmetry, and the Urbana IX model. Large effects of the three-nucleon forces are predicted. The inclusion of the three-nucleon forces gives a good description of the cross section at angles below the minimum. However, appreciable discrepancies between the data and predictions remain at backward angles. For the spin observables the predictions of the TM 3NF model deviate strongly from the other two 3NF models, which are close together, except for ${K}_{y}^{{y}^{\ensuremath{'}}}.$ In the case of the analyzing power all 3NF models fail to describe the data at the upper half of the angular range. In the restricted measured angular range the polarization transfer coefficients are fairly well described by the ${\mathrm{TM}}^{\ensuremath{'}}$ and Urbana IX 3NF models, whereas the TM 3NF model mostly fails. The transfer coefficient ${K}_{y}^{{y}^{\ensuremath{'}}}$ is best described by the Urbana IX but the theoretical description is still insufficient to reproduce the experimental data. These results call for a better understanding of the spin structure of the three-nucleon force and very likely for a full relativistic treatment of the three-nucleon continuum.
TL;DR: In this paper, it was shown that the so-determined numerical values have a remarkable similarity to values extracted from phenomenological one-boson exchange models in a low momentum expansion, and they also extracted these values from various modern high accuracy nucleon-nucleon potentials and found again the same similarity.
Abstract: In the modern description of nuclear forces based on chiral effective field theory, four-nucleon operators with unknown coupling constants appear. These couplings can be fixed by a fit to the low partial waves of nucleon-nucleon scattering. We show that the so-determined numerical values have a remarkable similarity to values extracted from phenomenological one-boson-exchange models in a low momentum expansion. We also extract these values from various modern high accuracy nucleon-nucleon potentials and find again the same similarity. This paves the way for estimating the low-energy constants of operators with more nucleon fields and/or external probes.
TL;DR: In this paper, a Gaussian-basis coupled-rearrangement-based method was used to estimate energy levels of the double-ensuremath-Lambda hypernuclei.
Abstract: Energy levels of the double-\ensuremath{\Lambda} hypernuclei ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{7}\mathrm{He},$ ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{7}\mathrm{Li},$ ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{8}\mathrm{Li},$ ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{9}\mathrm{Li},$ ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{9}\mathrm{Be},$ and ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{10}\mathrm{Be}$ are predicted on the basis of an $\ensuremath{\alpha}+x+\ensuremath{\Lambda}+\ensuremath{\Lambda}$ four-body model, where ${x=n,p,d,t,}^{3}\mathrm{He},$ and $\ensuremath{\alpha},$ respectively. Interactions between the constituent particles are determined so as to reproduce reasonably the observed low-energy properties of the $\ensuremath{\alpha}+x$ nuclei ${(}^{5}\mathrm{He},{}^{5}\mathrm{Li},{}^{6}\mathrm{Li},{}^{7}\mathrm{Li},{}^{7}\mathrm{Be},{}^{8}\mathrm{Be})$ and the existing data for \ensuremath{\Lambda}-binding energies of the $x+\ensuremath{\Lambda}$ and $\ensuremath{\alpha}+x+\ensuremath{\Lambda}$ systems ${(}_{\ensuremath{\Lambda}}^{3}\mathrm{H},{}_{\ensuremath{\Lambda}}^{4}\mathrm{H},{}_{\ensuremath{\Lambda}}^{5}\mathrm{He},{}_{\ensuremath{\Lambda}}^{6}\mathrm{He},{}_{\ensuremath{\Lambda}}^{6}\mathrm{Li},{}_{\ensuremath{\Lambda}}^{7}\mathrm{Li},{}_{\ensuremath{\Lambda}}^{8}\mathrm{Li},{}_{\ensuremath{\Lambda}}^{8}\mathrm{Be},{}_{\ensuremath{\Lambda}}^{9}\mathrm{Be}).$ An effective \ensuremath{\Lambda}\ensuremath{\Lambda} interaction is constructed so as to reproduce, within the \ensuremath{\alpha}+\ensuremath{\Lambda}+\ensuremath{\Lambda} model, the ${B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ of ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{6}\mathrm{He},$ which was extracted from the emulsion experiment, the NAGARA event. With no adjustable parameters for the $\ensuremath{\alpha}+x+\ensuremath{\Lambda}+\ensuremath{\Lambda}$ system, ${B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ of ground and bound excited states of the double-\ensuremath{\Lambda} hypernuclei with $A=7--10$ are calculated within the Gaussian-basis coupled-rearrangement-channel method. The Demachi-Yanagi event, identified recently as ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{10}\mathrm{Be},$ is interpreted as an observation of its ${2}^{+}$ excited state on the basis of the present calculation. Structural changes in the $\ensuremath{\alpha}+x$ core nuclei, due to the interaction of the \ensuremath{\Lambda} particles, are found to be substantial, and these play an important role in estimating the \ensuremath{\Lambda}\ensuremath{\Lambda} bond energies of those hypernuclei.
TL;DR: In this paper, a nucleon resonance analysis by simultaneously considering all pion-and photon-induced experimental data on the final states was presented, and the results on the photoproduction reactions and the electromagnetic properties of the resonances were presented.
Abstract: We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states $\ensuremath{\gamma}N,$ $\ensuremath{\pi}N,$ $2\ensuremath{\pi}N,$ $\ensuremath{\eta}N,$ $K\ensuremath{\Lambda},$ $K\ensuremath{\Sigma},$ and $\ensuremath{\omega}N$ for energies from the nucleon mass up to $\sqrt{s}=2\mathrm{GeV}.$ In this analysis we find strong evidence for the resonances ${P}_{31}(1750),$ ${P}_{13}(1900),$ ${P}_{33}(1920),$ and ${D}_{13}(1950).$ The $\ensuremath{\omega}N$ production mechanism is dominated by large ${P}_{11}(1710)$ and ${P}_{13}(1900)$ contributions. In this second part we present the results on the photoproduction reactions and the electromagnetic properties of the resonances. The inclusion of all important final states up to $\sqrt{s}=2\mathrm{GeV}$ allows for estimates on the importance of the individual states for the GDH sum rule.
TL;DR: In this paper, the Hartree-Fock-Bogoliubov theory and Gogny's D1S force were used to analyze the fission barriers of the nuclei in a fully microscopic way up to the scission point.
Abstract: The fission barriers of the nuclei ${}^{254}\mathrm{Fm},$ ${}^{256}\mathrm{Fm},$ ${}^{258}\mathrm{Fm},$ ${}^{258}\mathrm{No}$, and ${}^{260}\mathrm{Rf}$ are investigated in a fully microscopic way up to the scission point. The analysis is based on the constrained Hartree-Fock-Bogoliubov theory and Gogny's D1S force. The quadrupole, octupole, and hexadecapole moments as well as the number of nucleons in the neck region are used as constraints. Two fission paths, corresponding to the bimodal fission, are found. The decrease with isotope mass of the half-life times of heavy Fm isotopes is also explained.