Showing papers in "International Journal of Modern Physics E-nuclear Physics in 2008"

New hadron states

Abstract: In the past four years we have witnessed the renaissance of the hadron spectroscopy. Many interesting new hadron states were discovered experimentally, some of which do not fit into the quark model easily. I will give a concise overview of these states and their possible interpretations. Topics covered in this review are: (1) candidates of new light hadrons including $p\bar p$ threshold enhancement, X(1835), X(1576), f0(1810), recent candidates of the 1-+ exotic mesons, Y(2175), $p\bar\Lambda$ threshold enhancement etc. (2) charmed mesons including p-wave non-strange charmed mesons, Dsj(2317) and Dsj(2460), recent candidates of higher excited charmed mesons, Dsj(2632) etc. (3) charmonium and charmonium-like states such as X(3872), Y(4260), X(3940), Y(3940), Z(3930) etc. The effect from the nearby S-wave open channels on the quark model spectrum above or near strong decay threshold is emphasized. Dynamical lattice simulations of DK and $D^0\bar D^{\ast 0}$ scattering and the extraction of their phase shift...

Open and hidden charm in proton-nucleus and heavy-ion collisions

Abstract: We review dynamical and thermal models for the collectivity and the suppression pattern of charmed mesons — produced in proton–nucleus and nucleus–nucleus collisions at SPS (~158 A GeV) and RHIC energies (~21 A TeV). In particular, we examine the charmonium "melting" and the "comover dissociation" scenarios — implemented in a microscopic transport approach — in comparison to the available data from the SPS and RHIC. The analysis shows that the dynamics of c and quarks. quarks at RHIC are dominated by partonic or "pre-hadronic" interactions in the strongly coupled plasma stage and can neither be modeled by "hadronic" interactions nor described appropriately by color screening alone. Both the "charmonium melting" and the hadronic "comover absorption and recreation model" are found, however, to be compatible with the experimental observation at SPS energies; the experimental ratio of Ψ′/J/Ψ versus centrality clearly favors the "hadronic comover" scenario. We find that the collective flow of charm in the purely hadronic Hadron-String Dynamics (HSD) transport appears compatible with the data at SPS energies, but the data at top RHIC energies are substantially underestimated. Thus, the large elliptic flow v2 of D-mesons and the low RAA(pT) of J/Ψ seen experimentally have to be attributed to early interactions of non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic interactions are mandatory in order to describe the narrowing of the J/Ψ rapidity distribution from pp to central Au + Au collisions at the top RHIC energy of . Additionally we demonstrate that the strong quenching of high-pTJ/Ψ's in central Au + Au collisions indicates that a large fraction of final J/Ψ mesons is created by a coalescence mechanism close to the phase boundary. Throughout this review we, furthermore, provide predictions for charm observables from Au + Au collisions at FAIR energies of 25–35 A GeV.

Covariant Hamiltonian Field Theory

Abstract: A consistent, local coordinate formulation of covariant Hamiltonian field theory is presented. Whereas the covariant canonical field equations are equivalent to the Euler–Lagrange field equations, the covariant canonical transformation theory offers more general means for defining mappings that preserve the form of the field equations than the usual Lagrangian description. It is proven that Poisson brackets, Lagrange brackets, and canonical 2-forms exist that are invariant under canonical transformations of the fields. The technique to derive transformation rules for the fields from generating functions is demonstrated by means of various examples. In particular, it is shown that the infinitesimal canonical transformation furnishes the most general form of Noether's theorem. Furthermore, we specify the generating function of an infinitesimal space-time step that conforms to the field equations.

Nuclear matrix elements for double beta decay

Abstract: The neutrinoless double beta (0νββ) decay of atomic nuclei plays a key role in the search for massive Majorana neutrinos and their mass scale. To extract the necessary information from the measured data the nuclear-structure effects have to be accounted for by computation of the associated nuclear matrix elements (NME's). In this article the NME's for the light-neutrino exchange mechanism are discussed. They are computed by using the proton-neutron quasiparticle random-phase approximation (pnQRPA). Recent developments in this field relate to the handling of the nucleon-nucleon short-range correlations and independent experimental probes of the wave functions relevant for the NME's.

BOUND-STATES OF A SEMI-RELATIVISTIC EQUATION FOR THE ${\cal PT}$-SYMMETRIC GENERALIZED HULTHÉN POTENTIAL BY THE NIKIFOROV–UVAROV METHOD

Abstract: The one-dimensional semi-relativistic equation has been solved for the ${\cal PT}$-symmetric generalized Hulthen potential. The Nikiforov–Uvarov (NU) method which is based on solving the second-order linear differential equations by reduction to a generalized equation of hypergeometric type, is used to obtain exact energy eigenvalues and corresponding eigenfunctions. We have investigated the positive and negative exact bound states of the s-states for different types of complex generalized Hulthen potentials.

SEMI-EMPIRICAL SYSTEMATICS OF (n, 2n), (n, α) REACTIONS CROSS SECTIONS AT 14–15 MeV NEUTRON ENERGY

Abstract: In this study we propose new semi-empirical formulas by modifying the formula of Levkovskii with the new parameters for (n, 2n) and (n, α) reactions cross-sections at 14–15 MeV neutron incident energy The cross sections have been calculated using the asymmetry parameter depending on empirical formulas for the incoming energies of 14–15 MeV neutrons The parameters obtained by modifying the original formula of Levkovskii and Konno et al have been determined by applying the least squares fitting method to the experimental cross sections, and the systematics of the (n, 2n) and (n, α) reactions have been studied We have also suggested different parameters for the empirical formula to reproduce the cross sections of the (n, 2n) and (n, α) reactions for the neutron incident energy of 14–15 MeV The modified formulas yielded cross sections representing markedly smaller chi-square (χ2) deviations from experimental values, and values much closer to units as compared with those calculated using Levkovskii's and Konno et al original formulas The results obtained have been discussed and compared with the other empirical formulas, and found to be well in agreement when used to correlate the available experimental σ(n, 2n) and σ(n, σ) data of different nuclei

Hadronic Interactions from Lattice QCD

Abstract: We present an overview of recent efforts to calculate the interactions among hadrons using lattice QCD. After outlining the techniques that are used to extract scattering parameters, we detail the latest calculations of meson–meson scattering, baryon–baryon scattering and multi-meson systems obtained with domain-wall valence quarks on the staggered MILC lattices by the NPLQCD collaboration. Estimates of the computational resources required to achieve precision results in the baryon sector are presented.

Time-dependent hartree-fock description of heavy ions fusion

Abstract: A microscopic mean-field description of heavy ions fusion is performed in the framework of the Time-Dependent Hartree-Fock (TDHF) theory using a Skyrme interaction with the SLy4d parametrization. A good agreement with experiments is obtained on the position of the fusion barriers for various total masses, mass asymmetries and deformations. The excitation function of the 16O+208Pb is overestimated by about 16% above the barrier. The restriction to an independent particles state in the mean-field dynamics prevents the description of sub-barrier fusion. Effect of transfer on fusion is discussed.

Tddft with skyrme forces: effect of time-odd densities on electric giant resonances

Abstract: Time-odd densities and their effect on electric giant resonances are investigated within the self-consistent separable random-phase-approximation (SRPA) for a variety of Skyrme forces (SkT6, SkO, SkM*, SIII, SGII, SLy4, SLy6, SkI3). Time-odd densities are essential for maintaining the Galilean invariance of the Skyrme functional. Their contribution is determined by the values and signs of the isovector and isoscalar effective-mass parameters of the force. In even-even nuclei these densities are not active in the ground state but can affect the dynamics. As a particular case, we explore the role of the current density in the description of isovector E1 and isoscalar E2 giant resonances in a chain of spherical and deformed Nd isotopes with A=134-158. The relation of the current to the effective masses and relevant parameters of the Skyrme functional is analyzed. It is shown that the current contributes substantially to E1 and E2 and the contribution is the same for all the isotopes along the chain, i.e. for both standard and exotic nuclei.

CENTRALITY EVOLUTION OF pt AND yt SPECTRA FROM Au–Au COLLISIONS AT $\sqrt{s_{NN}} = 200\, {\rm GeV}$

Abstract: A two-component analysis of spectra to pt = 12 GeV/c for identified pions and protons from 200 GeV Au–Au collisions is presented. The method is similar to an analysis of the nch dependence of pt spectra from p–p collisions at 200 GeV, but applied to Au–Au centrality dependence. The soft-component reference is a Levy distribution on transverse mass mt. The hard-component reference is a Gaussian on transverse rapidity yt with exponential (pt power-law) tail. Deviations of data from the reference are described by hard-component ratio rAA, which generalizes nuclear modification factor RAA. The analysis suggests that centrality evolution of pion and proton spectra is dominated by changes in parton fragmentation. The structure of rAA suggests that parton energy loss produces a negative boost Δyt of a large fraction (but not all) of the minimum-bias fragment distribution, and that lower-energy partons suffer relatively less energy loss, possibly due to color screening. The analysis also suggests that the anomalous p/π ratio may be due to differences in the parton energy-loss process experienced by the two hadron species. This analysis provides no evidence for radial flow.

ISOSPIN DEPENDENCE OF REACTIONS 48Ca+243-251Bk

Abstract: The fusion process of 48Ca induced reactions is studied with the two-step model. In this model, the fusion process is devided into two stages: first, the sticking stage where projectile and target come to the touching point over the Coulomb barrier from infinite distance, and second, the formation stage where the di-nucleus formed with projectile and target evolve to form the spherical compound nucleus from the touching point. By the use of the statistical evaporation model, the residue cross sections for different neutron evaporation channels are analyzed. From the results, optimum reactions are given to synthesize Z=117 element with 48Ca induced reactions.

Exact Solution of the SCHRÖDINGER Equation for the Modified Kratzer's Molecular Potential with Position-Dependent Mass

Abstract: Exact solutions of Schrodinger equation are obtained for the modified Kratzer and the corrected Morse potentials with the position-dependent effective mass. The bound state energy eigenvalues and the corresponding eigenfunctions are calculated for any angular momentum for target potentials. Various forms of point canonical transformations are applied.

Study of "condensate" states in 12c and 16o by inelastic scattering

Abstract: Study of some properties of the lowest states of 12C, including the second 0+, 7.65 MeV (Hoyle) state by inelastic scattering of alpha-particles and 3He were carried out. Two independent methods of measuring the radii of the short-lived excited states based on the analysis of diffraction and rainbow patterns of the angular distributions were proposed. Both methods showed that Hoyle state radius is by factor ~ 1.2 – 1.3 larger than that of the ground state. 8Be transfer reaction was identified. The probability of L = 0 configuration in Hoyle state occurred to be 3 times larger than in the ground state indicating to the significant presence of condensate configuration in the former one.

Neutron-proton isovector pairing effect on the nuclear moment of inertia

Abstract: The neutron-proton (n-p) isovector pairing effect on the nuclear moment of inertia has been studied within the framework of the BCS approximation. An analytical expression of the moment of inertia, that explicitly depends upon the n-p pairing, has been established using the Inglis cranking model. The model was first tested numerically for nuclei such as N = Z and whose experimental values of the moment of inertia are known (i.e. such as 16 ≤ Z ≤ 40). It has been shown that the n-p pairing effect is non-negligible and clearly improves the theoretical predictions when compared to those of the pairing between like particles. Secondly, predictions have been established for even-even proton-rich rare-earth nuclei. It has been shown that the n-p pairing effect is non-negligible when N = Z and rapidly decreases with increasing values of (N-Z).

Cluster states in 13c and 11b

Abstract: The cluster structures of the excited states in 11B and 13C were discussed by measuring the isoscalar monopole strengths in the inelastic α scattering at Eα = 388 MeV. It was found that the , , and states in 13C are candidates for the α cluster states with a 3α + n molecular configuration.

The azimuth structure of nuclear collisions — i

Abstract: We describe azimuth structure commonly associated with elliptic and directed flow in the context of 2D angular autocorrelations for the purpose of precise separation of so-called nonflow (mainly minijets) from flow. We extend the Fourier-transform description of azimuth structure to include power spectra and autocorrelations related by the Wiener–Khintchine theorem. We analyze several examples of conventional flow analysis in that context and question the relevance of reaction plane estimation to flow analysis. We introduce the 2D angular autocorrelation with examples from data analysis and describe a simulation exercise which demonstrates precise separation of flow and nonflow using the 2D autocorrelation method. We show that an alternative correlation measure based on Pearson's normalized covariance provides a more intuitive measure of azimuth structure.

Charmed (70, 1-) baryon multiplet

Abstract: The masses of negative parity (70, 1-) charmed nonstrange baryons are calculated in the relativistic quark model. The relativistic three-quark equations of the (70, 1-) charmed baryon multiplet are found in the framework of the dispersion relation technique. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitude are obtained. The calculated mass values of the (70, 1-) charmed baryons are in good agreement with the experimental data.

Cluster states and alpha particle condensation in 13c

Abstract: The structure of 13C is studied with the semi-microscopic cluster model, 3α+n orthogonality condition model (OCM). The energy spectra of four 1/2- states and three 1/2+ states up to Ex ~ 13 MeV are successfully reproduced, in particular, three monopole transition strengths are in fair agreement with the observed ones. We discuss the cluster states and alpha particle condensation in the 1/2± states appearing around the 12C+n, 9Be+α and 3α+n thresholds.

First results with the rising active stopper

Abstract: This paper outlines some of the physics opportunities available with the GSI RISING active stopper and presents preliminary results from an experiment aimed at performing beta-delayed gamma-ray spectroscopic studies in heavy-neutron-rich nuclei produced following the projectile fragmentation of a 1 GeV per nucleon 208Pb primary beam. The energy response of the silicon active stopping detector for both heavy secondary fragments and beta-particles is demonstrated and preliminary results on the decays of neutron-rich Tantalum (Ta) to Tungsten (W) isotopes are presented as examples of the potential of this technique to allow new structural studies in hitherto experimentally unreachable heavy, neutron-rich nuclei. The resulting spectral information inferred from excited states in the tungsten daughter nuclei are compared with results from axially symmetric Hartree–Fock calculations of the nuclear shape and suggest a change in ground state structure for the N = 116 isotone 190W compared to the lighter isotopes of this element.

N/z dependence of projectile fragmentation

Abstract: The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of ΔA/A ≈ 1.5%, lighter isotopes with atomic numbers Z ≤ 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations.

Lessons after the evidence for neutrinoless double beta decay — the next step

Abstract: This paper describes the lessons we have to draw after the observation of neutrinoless ββ decay by the enriched 76Ge experiment, for present and future experiments so as (a) to fulfill the task to confirm the present result (b) to deliver additional information on the main contributions of effective neutrino mass and right-handed weak currents etc. to the 0νββ amplitude. It is shown that presently running and planned experiments are probably not sensitive enough to check the evidence on a reasonable time scale. It is further demonstrated that, the only way to get more information on the individual contributions of m, η, λ etc. to the 0νββ amplitude is to go to completely different types of experiments, rather than those under construction and preparation at present, e.g. to mixed-mode β+/EC decay experiments, such as 124Xe decay. It is pointed out that the sometimes observed "tension" between the result of 0νββ decay and cosmological experiments like WMAP, SDSS etc. does not exist and is an artificial product of improper analysis of the latter.

PROPERTIES OF Fe, Ni AND Zn ISOTOPES NEAR THE DRIP-LINES

Abstract: The position of the neutron and proton drip-lines as well as properties of the isotopes Fe, Ni and Zn with neutron excess and neutron deficit are studied within the Hartree–Fock approach with the Skyrme interaction (Ska, SkM*, Sly4). The pairing is taken into account on the basis of the BCS approach with the pairing constant G = (19.5/A)[1 ± 0.51(N-Z)/A]. Our calculations predict that for Ni isotopes around N = 62 there appears a sudden increase of the deformation parameter up to β = 0.4. The zone with such big deformation, where Ni isotopes are stable against one neutron emission stretches up to N = 78. The magic numbers effects for the isotopes 48Ni, 56Ni, 78Ni, 110Ni are discussed. The universality of the reasons standing behind the enhancement of stability of the isotopes 40O and 110Ni which are beyond the drip-line is demonstrated. Calculated values of the two-neutron separation energy, and proton and neutron root mean square radii for the chain of Ni isotopes show a good agreement with existing Hartree–Fock–Bogoliubov calculations of these values.

Entrance-Channel Effects in Suppression of Fusion of Heavy Nuclei

Abstract: A set of 28 reactions of heavy and superheavy systems for which measured evaporation cross sections are available in the literature was analyzed with the aim to extract information on the fusion hindrance factor. Systematics of the deduced "experimental" hindrance factors (or in other words – fusion probabilities Pfus), based on the dependence of Pfus on the Coulomb interaction parameter and the excess of energy above the interaction barrier, E - B0, is presented.

B c Spectroscopy in the Shifted l-EXPANSION Technique

Abstract: In the framework of static and QCD-motivated model potentials for heavy quarkonium, we present a further comprehensive calculation of the mass spectrum of system and its ground state spin-dependent splittings in the context of the shifted l-expansion technique. We also predict the leptonic constant fBc of the lightest pseudoscalar Bc, and of the vector states taking into account the one-loop and two-loop QCD corrections. Furthermore, we use the scaling relation to predict the leptonic constant of the nS-states of the system. Our predicted results are generally in high agreement with some earlier numerical methods. The parameters of each potential are adjusted to obtain best agreement with the experimental spin-averaged data (SAD).

A computational model for lesion dynamics in multiple sclerosis of the brain

Abstract: Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system (CNS) that is characterized by lesions with inflammatory cells, axons with the insulating myelin sheath damaged, and axonal loss. The causes of MS are not known and there is as yet no cure. The purpose of this research was to evaluate a physically motivated network model for lesion formation in the brain. The parsimonious network model contained two elements: (i) a spatially spreading pathological process causing cell damage and death leading to neuro-degeneration and, (ii) generation of alarm signals by the damaged cells that lead to activation of programmed death of cells surrounding the lesions in an attempt to contain the spatial spread of the pathologic process. Simulation results with a range of network geometries indicated that the model was capable of describing lesion progression and arrest. The modeling results also demonstrated dynamical complexity with sensitivity to initial conditions.

FOLDING MODEL ANALYSIS OF 6He+120Sn ELASTIC SCATTERING

Abstract: In this study, the elastic scattering of 6He projectile from 120Sn nucleus has been analyzed in terms of optical model (OM). Microscopic double folding (DF) model has been used to generate the real central part of the OM potential. The imaginary part has been restricted to Woods–Saxon phenomenological form. Skyrme–Hartree–Fock, Symmetrized Fermi and Gaussian-Exponential densities for 6He nucleus while Hartree–Fock–Bogolyubov (HFB) density of 120Sn nucleus have been used to construct the real DF potential. For the effective interaction, the widely used M3Y has been adopted in the DF procedure. The results of DF have been compared with both literature experimental data and phenomenological analysis.

Cluster Radioactivity of th Isotopes in the Mean-Field Hfb Theory

Abstract: Cluster radioactivity is described as a very mass asymmetric fission process. The reflection symmetry breaking octupole moment has been used in a mean field HFB theory as leading coordinate instead of the quadrupole moment usually used in standard fission calculations. The procedure has been applied to the study of the "very mass asymmetric fission barrier" of several even-even Thorium isotopes. The masses of the emitted clusters as well as the corresponding half-lives have been evaluated on those cases where experimental data exist.

Measurement and analysis of excitation functions and forward recoil range distributions in 12 C + 59 Co system

Abstract: With the motivation of studying complete and incomplete fusion reactions in a 12C+59Co projectile target system, the excitation functions for (C, p3n), (C, 2p2n), (C, αn), (C, α2n), (C, αp3n) and (C, 2α2n) reactions have been measured up to 80 MeV. The well-known activation technique followed by offline high purity Ge γ-ray spectroscopy was used. The measured experimental values were compared with the statistical model calculations by using the ALICE-91 and CASCADE codes. For the calculations obtained by CASCADE, the variation of parameter Fθ, which is the ratio of actual moment of inertia to the rigid body value have also been studied. Considerable enhancement of the measured excitation functions compared to theoretical predictions for some channels clearly indicates the presence of incomplete fusion with complete fusion in the present projectile energy range. The measurements of forward recoil range distribution of evaporation residues at 80 MeV projectile energy confirm these observations.

Strange quark matter in the framework of one gluon exchange and density and temperature dependent particle mass models

Abstract: We calculate the thermodynamic properties of strange quark matter by using the density and temperature dependent particle mass model of Wen et al. For the interaction Hamiltonian we use the one gluon exchange interaction obtained from the Fermi liquid picture. We let the QCD coupling (αc) be constant or vary with density and temperature. A new set of mass scalings for quarks is evaluated from the present interaction, which can be used with thermodynamic formulas derived by Wen et al. Similar to β-stable matter, no stability is found in strange quark matter. Finally, it is shown that the present equation of state of strange quark matter becomes harder with respect to that obtained using the string model, specially with non-constant QCD coupling.

Directed flow as an effect of transient matter rotation in hadron and nucleus collisions

Abstract: We discuss directed flow v1, an observable introduced for the description of nucleus collisions. We consider its possible origin in hadronic reactions as a result of rotation of the transient matter and trace the analogy with nucleus collisions.