Showing papers in "Physical Review C in 1993"
TL;DR: A complete and consistent description for the hadron spectra from heavy ion collisions in terms of a few collective variables, in particular temperature, longitudinal, and transverse flow is developed.
Abstract: We develop a complete and consistent description for the hadron spectra from heavy ion collisions in terms of a few collective variables, in particular temperature, longitudinal, and transverse flow. To achieve a meaningful comparison with presently available data, we also include the resonance decays into our picture. To disentangle the influences of transverse flow and resonance decays in the ${\mathit{m}}_{\mathit{T}}$ spectra, we analyze in detail the shape of the ${\mathit{m}}_{\mathit{T}}$ spectra.
859 citations
TL;DR: A multienergy partial-wave analysis of all NN scattering data below £350 MeV, published in a regular physics journal between 1955 and 1992, finds all phase shifts and mixing parameters can be determined accurately.
Abstract: We present a multienergy partial-wave analysis of all NN scattering data below ${\mathit{T}}_{\mathrm{lab}}$=350 MeV, published in a regular physics journal between 1955 and 1992. After careful examination, our final database consists of 1787 pp and 2514 np scattering data. Our fit to these data results in ${\mathrm{\ensuremath{\chi}}}^{2}$/${\mathit{N}}_{\mathrm{df}}$=1.08, with ${\mathit{N}}_{\mathrm{df}}$=3945 the total number of degrees of freedom. All phase shifts and mixing parameters can be determined accurately.
565 citations
TL;DR: Energy-dependent global Dirac optical model potentials are found by fitting proton elastic scattering data in the energy range 20--1040 MeV for C, O, Ca,Ca, Zr, and Pb and the mean free path, the effective mass, and the relativistic energy shift are calculated.
Abstract: Energy-dependent global Dirac optical model potentials are found by fitting proton elastic scattering data in the energy range 20--1040 MeV for $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, $^{40}\mathrm{Ca}$, $^{90}\mathrm{Zr}$, and $^{208}\mathrm{Pb}$. Three different energy- and atomic-mass-number-dependent global Dirac optical potentials are also obtained. A number of characteristic features of the potentials are discussed. In addition, the mean free path, the effective mass ${\mathit{m}}_{\mathit{e}}^{\mathrm{*}}$, the Dirac mass ${\mathit{M}}^{\mathrm{*}}$, and the relativistic energy shift ${\mathit{E}}^{\mathrm{*}}$ are calculated.
262 citations
TL;DR: A set of rate equations describing the chemical equilibration of gluons and quarks including medium effects on the relevant QCD transport coefficients are derived, and their consequences for parton equilibrations in heavy ion collisions are discussed.
Abstract: We investigate the processes leading to phase-space equilibration of parton distributions in nuclear interactions at collider energies. We derive a set of rate equations describing the chemical equilibration of gluons and quarks including medium effects on the relevant QCD transport coefficients, and discuss their consequences for parton equilibration in heavy ion collisions.
183 citations
TL;DR: In this paper, the authors developed semi-empirical total reaction cross section formulas for proton nucleus and nucleus-nucleus reactions for incident energies above 15 MeV and 100 MeV/nucleon respectively.
Abstract: We have developed semiempirical total reaction cross section formulas for proton-nucleus (with ${\mathit{Z}}_{\mathit{t}}$\ensuremath{\le}26) and nucleus-nucleus (with ${\mathit{Z}}_{\mathit{p}}$ and ${\mathit{Z}}_{\mathit{t}}$\ensuremath{\le}26) reactions. These formulas apply for incident energies above \ensuremath{\approxeq}15 MeV and \ensuremath{\approxeq}100 MeV/nucleon, respectively. We have also constructed a procedure for calculating the projectile-fragment production cross sections, by scaling semiempirical proton-nucleus partial cross section systematics. The scaling is done by a scaling parameter, which is based on a Bradt-Peters-type law and also takes advantage of the weak-factorization property of projectile fragments. All products from the Z of the projectile down to Z=2 can be calculated. The agreement between the calculated partial cross sections and the experimental data is better than all earlier published results.
162 citations
TL;DR: In-medium nucleon-nucleon cross sections in a microscopic model based upon the Bonn NN potential and the Dirac-Brueckner approach for nuclear matter is derived.
Abstract: We derive in-medium nucleon-nucleon (NN) cross sections in a microscopic model. Our calculations are based upon the Bonn NN potential and the Dirac-Brueckner approach for nuclear matter. We consider energies up to 300 MeV (in the laboratory frame) and densities up to twice nuclear matter density. Our results deviate substantially from cross section parametrizations that are commonly used in the nuclear medium.
158 citations
TL;DR: The generalized superfluid model, with a level-density parameter and a spin-cutoff factor that are both energy dependent, does give a good fit, and the resulting best-fit parameter values are consistent with those found in other applications of this model as discussed by the authors.
Abstract: Model fits were made to the cumulative distribution of all known levels (with spins [ital J][le]10) in [sup 116]Sn below an excitation energy of 4.1 MeV identified in a variety of experiments, and simultaneously to the density of [ital J]=0 and [ital J]=1 resonances inferred from neutron capture and total cross-section measurements in [sup 115]Sn+[ital n]. Neither the back-shifted Fermi-gas model nor the constant-temperature model provides a satisfactory fit over the entire energy range. The generalized superfluid model, with a level-density parameter and a spin-cutoff factor that are both energy dependent, does give a good fit, and the resulting best-fit parameter values are consistent with those found in other applications of this model.
158 citations
TL;DR: A formulation of the shell model as a path integral and Monte Carlo techniques for its evaluation, which linearizes the two-body interaction by an auxiliary field and proves that a wide class of interactions are free of this limitation.
Abstract: We present in detail a formulation of the shell model as a path integral and Monte Carlo techniques for its evaluation. The formulation, which linearizes the two-body interaction by an auxiliary field, is quite general, both in the form of the effective ‘‘one-body’’ Hamiltonian and in the choice of ensemble. In particular, we derive formulas for the use of general (beyond monopole) pairing operators, as well as a novel extraction of the canonical (fixed-particle-number) ensemble via an activity expansion. We discuss the advantages and disadvantages of the various formulations and ensembles and give several illustrative examples. We also discuss and illustrate calculation of the imaginary-time response function and the extraction, by maximum entropy methods, of the corresponding strength function. Finally, we discuss the "sign problem" generic to fermion Monte Carlo calculations, and prove that a wide class of interactions are free of this limitation.
158 citations
TL;DR: In this article, the Coulomb dissociation of 28 MeV/nucleon into two neutrons by a Pb target was measured and a kinematically complete measurement was performed.
Abstract: We have performed a kinematically complete measurement of the Coulomb dissociation of 28 MeV/nucleon $^{11}\mathrm{Li}$ into $^{9}\mathrm{Li}$ and two neutrons by a Pb target. From the energies and angles of the emitted neutrons and of $^{9}\mathrm{Li}$, the excitation energy E of $^{11}\mathrm{Li}$ was determined on an event-by-event basis, and the Coulomb dissociation cross section as a function of excitation energy was constructed. The photonuclear cross section ${\mathrm{\ensuremath{\sigma}}}_{\mathit{E}1}$(E) and the dipole strength function dB(E1)/dE were determined from the Coulomb dissociation cross section. ${\mathrm{\ensuremath{\sigma}}}_{\mathit{E}1}$(E) has a peak at E=1.0 MeV and a width \ensuremath{\Gamma}=0.8 MeV. These parameters are consistent with the picture of a soft dipole mode. However, a significant post-breakup Coulomb acceleration of $^{9}\mathrm{Li}$ suggests instead a direct breakup. The complete kinematical measurement also allowed neutron and $^{9}\mathrm{Li}$ momentum distributions to be constructed in the rest frame of the $^{11}\mathrm{Li}$. The momentum distributions were fitted with Gaussian functions, yielding width parameters ${\mathrm{\ensuremath{\sigma}}}_{9}$=18\ifmmode\pm\else\textpm\fi{}4 MeV/c and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{n}}$=13\ifmmode\pm\else\textpm\fi{}3 MeV/c. A more general feature of the breakup mechanism of $^{11}\mathrm{Li}$ could be deduced from these measurements. It was found that the $^{9}\mathrm{Li}$ and neutron momentum distributions and the neutron-neutron relative momentum distribution could be reproduced if the $^{11}\mathrm{Li}$ excitation energy was partitioned between the $^{9}\mathrm{Li}$ and the neutrons by a three-body phase space distribution. This indicates there is no directional correlation between the halo neutrons, and shows that the halo neutrons do not exist as a dineutron bound to a $^{9}\mathrm{Li}$ core.
139 citations
TL;DR: Pulsed-beam time-of-flight techniques are used in a transmission measurement with a continuous spectrum of neutrons to determine neutron total cross sections with good precision up to 600 MeV, representing steps in the development of a neutron-nucleus optical potential at intermediate energy and important input for the clarification of isovector effects in the nucleon- nucleus interaction.
Abstract: Pulsed-beam time-of-flight techniques are used in a transmission measurement with a continuous spectrum of neutrons to determine neutron total cross sections with good precision up to 600 MeV. Neutrons are produced by spallation of the 800 MeV proton beam from the Los Alamos Meson Physics Facility accelerator incident on a thick, heavily shielded tungsten target at the Weapons Neutron Research facility at Los Alamos National Laboratory. Transmission measurements were completed for fifteen elements with 9\ensuremath{\le}A\ensuremath{\le}209 and three isotopically enriched samples of $^{40}\mathrm{Ca}$, $^{90}\mathrm{Zr}$, and $^{208}\mathrm{Pb}$. Principal features of the experiment are the intensity and time structure of the neutron source, tight collimation of the neutron beam line, good geometry, rapid cycling of the samples, stable electronics, and a small, fast neutron detector. Errors due to counting statistics were generally less than 1% for each of several hundred energy bins for each target. The measurements represent steps in the development of a neutron-nucleus optical potential at intermediate energy and important input for the clarification of isovector effects in the nucleon-nucleus interaction. The data also provide insight into the long-standing discussion of mean free paths of the nucleon in the nucleus.
135 citations
TL;DR: The ratio of cross sections of quasielastic electron scattering for heavy and light nuclei at xg1 and g1 (GeV/c${)}^{2}$ should exhibit simple scaling relations which are ultimately expressed through the ratio of the light-cone nucleon distributions in nuclei, and these cross section ratios are extracted from existing data in a practically model independent way.
Abstract: We argue that the ratio of cross sections of quasielastic electron scattering for heavy and light nuclei at xg1 and ${\mathit{Q}}^{2}$g1 (GeV/c${)}^{2}$ should exhibit simple scaling relations which are ultimately expressed through the ratio of the light-cone nucleon distributions in nuclei. We extract these cross section ratios from existing data in a practically model independent way. The results are found to be in reasonable agreement with our x-scaling relations for the region of 2gx\ensuremath{\ge}1.4 where the contribution of two-nucleon short-range correlations are expected to dominate. The ratios exhibit scaling in the light-cone fraction, \ensuremath{\alpha}, of the struck nucleon for the range 2gx\ensuremath{\ge}0.9. The \ensuremath{\alpha} scaling is in agreement with the expectations of the light-cone quantum mechanics of nuclei, providing further evidence for the dominance of short-range correlations in nuclei at kg0.3 GeV/c. An extension of this analysis to the interpretation of color transparency experiments is discussed.
TL;DR: A comprehensive analysis is made of the experimental information on Gamow-Teller beta decay for the light nuclei, using a recently constructed shell-model Hamiltonian operating in the first four major shells to calculate 83 decay matrix elements.
Abstract: A comprehensive analysis is made of the experimental information on Gamow-Teller beta decay for the light (A\ensuremath{\le}18) nuclei. Experimental data on half-lives, Q values, and branching ratios are tabulated. Experimental logft values and beta-decay matrix elements are deduced from these data. The one-body-transition densities necessary to predict the beta-decay matrix elements are then calculated using a recently constructed shell-model Hamiltonian operating in the first four major shells. Using these parameters, effective Gamow-Teller operators are deduced for the 0p shell from a least-squares fit to 16 experimental matrix elements. The effective operators are used to calculate 83 decay matrix elements. Some specific decays are discussed.
TL;DR: Comment on several recent papers addressing the issue of the pion-nucleon coupling constant and criticizing the Nijmegen analyses and presents additional information which may clarify several points of discussion.
Abstract: In view of the persisting misunderstandings about the determination of the pion-nucleon coupling constants in the Nijmegen multienergy partial-wave analyses of pp, np, and p\ifmmode\bar\else\textasciimacron\fi{}p scattering data, we present additional information which may clarify several points of discussion. We comment on several recent papers addressing the issue of the pion-nucleon coupling constant and criticizing the Nijmegen analyses.
TL;DR: It is found that the present complete data set is not adequate to limit the range of nuclear matter compressibility to better than about a factor of 1.7 (200 to 350 MeV).
Abstract: We examine the status of the nuclear matter compressibility ${\mathit{K}}_{\mathrm{nm}}$ obtained from experimental data of the strength distribution of the giant monopole resonance in nuclei and employing a least-squares fit to a semiempirical expansion of the nucleus compressibility ${\mathit{K}}_{\mathit{A}}$ in ${\mathit{A}}^{\mathrm{\ensuremath{-}}1/3}$. We present arguments indicating that all the coefficients of this expansion must be determined by a fit to the data. In our analysis we have used the entire data set, correcting for systematic energy differences between data sets measured in different laboratories, and applying the same criteria to all sets in extracting the uncertainties. Contrary to recent statements by Sharma and collaborators, we find that the present complete data set is not adequate to limit the range of ${\mathit{K}}_{\mathrm{nm}}$ to better than about a factor of 1.7 (200 to 350 MeV).
TL;DR: This work considers the dependence of collective flow on the nuclear surface thickness in a Boltzmann-Uehling-Uhlenbeck transport model of heavy ion collisions and finds that balance energy scales with the mass number as ${\mathit{A}}^{\mathrm{\ensuremath{-}}\ mathit{y}}$, where y has a numerical value between 0.35 and 0.5, depending on the assumptions about the in-medium nucleon-nucleon cross
Abstract: We consider the dependence of collective flow on the nuclear surface thickness in a Boltzmann-Uehling-Uhlenbeck transport model of heavy ion collisions Well-defined surfaces are introduced by giving test particles a Gaussian density profile of constant width Zeros of the flow excitation function are as much influenced by the surface thickness as the nuclear equation of state, and the dependence of this effect is understood in terms of a simple potential scattering model Realistic calculations must also take into account medium effects for the nucleon-nucleon cross section, and impact parameter averaging We find that balance energy scales with the mass number as ${\mathit{A}}^{\mathrm{\ensuremath{-}}\mathit{y}}$, where y has a numerical value between 035 and 05, depending on the assumptions about the in-medium nucleon-nucleon cross section
TL;DR: In this paper, the authors present results for spectroscopic factors of the outermost shells in NIKHEF-K data, which have been derived from the comparsion between the available quasielastic (e, e'p) data and the corresponding calculated cross sections obtained within a fully relativistic formalism.
Abstract: We present results for spectroscopic factors of the outermost shells in $^{40}\mathrm{Ca}$ and $^{208}\mathrm{Pb}$, which have been derived from the comparsion between the available quasielastic (e,e'p) data from NIKHEF-K and the corresponding calculated cross sections obtained within a fully relativistic formalism. We include exactly the effect of Coulomb disortion on the electron wave functions and discuss its role in the extraction of the spectroscopic factors from experiment. Without any adjustable parameter, we find spectroscopic factors of about 70%, consistent with theoretical predictions. We compare our results with previous relativistic and nonrelativistic analyses of (e,e'p) data. In addition to Coulomb distortion effects, we discuss different choices of the nucleon current operator and also analyze the effects due to the relativistic treatment of the outgoing-distorted and bound nucleon wave functions.
TL;DR: Strong evidence was found for an [ital E]1 strength function which is based on a generalized Lorentzian, enhanced compared to spherical nuclei, with an energy-dependent spreading width and a nonzero limit as the energy tends to zero.
Abstract: The distribution of [ital E]1 and [ital M]1 strength in [sup 157]Gd compound nucleus has been studied. An investigation of capture of 2 and 24 keV neutrons in a [sup 156]Gd target resulted in resonance-averaged intensities of primary gamma rays between 3.7 and 6.4 MeV. From these intensities the gamma-ray strength functions have been derived for [ital E]1 and [ital M]1 radiation. We compare several formulations of strength functions to these resonance capture and/or photoabsorption data. Further we use these prescriptions in calculations of the total average radiation width, radiative capture cross sections, and gamma-ray spectra, and compare them to available experimental information. By analyzing these results strong evidence was found for an [ital E]1 strength function which is based on a generalized Lorentzian, enhanced compared to spherical nuclei, with an energy-dependent spreading width and a nonzero limit as the energy tends to zero. For [ital M]1 radiation the giant resonance spin-flip mode is favored.
TL;DR: It is shown that the striking energy variation in the [ital pd][r arrow]He [eta] cross section near threshold is probably due to a final state interaction associated with a large (complex) [eta][minus][sup 3]He scattering length.
Abstract: It is shown that the striking energy variation in the pd${\ensuremath{\rightarrow}}^{3}$He \ensuremath{\eta} cross section near threshold is probably due to a final state interaction associated with a large (complex) \ensuremath{\eta}${\mathrm{\ensuremath{-}}}^{3}$He scattering length. The consequences of this hypothesis are studied for the production of the meson in the \ensuremath{\eta}${\mathrm{\ensuremath{-}}}^{4}$He and \ensuremath{\eta}${\mathrm{\ensuremath{-}}}^{7}$Be channels.
TL;DR: The cross section for the electromagnetic production of different particles in heavy-ion collision is derived within the external field approach and the impact-parameter dependent production of scalar and pseudoscalar bosons, charged (spin 0) boson pairs, and fermion pairs is discussed.
Abstract: The cross section for the electromagnetic production of different particles in heavy-ion collision is derived within the external field approach. Introducing polarized photon-fusion cross sections, it is possible to generalize the equivalent photon method to describe the impact-parameter dependence of the particle production. The impact-parameter dependent production of scalar and pseudoscalar (spin 0) bosons, charged (spin 0) boson pairs, and fermion pairs is discussed.
TL;DR: Values for the strange vector and axial-vector form factors of the proton, including the axial vector dipole mass, are obtained, although with large errors due to correlations.
Abstract: A previous [nu][ital p] elastic scattering experiment at BNL is reanalyzed, taking into account the strange vector and axial-vector form factors of the proton [ital F][sub 1][sup [ital s]], [ital F][sub 2][sup [ital s]], and [ital G][sub 1][sup [ital s]]. Values for these form factors are obtained, although with large errors due to correlations between [ital F][sub 1][sup [ital s]] and [ital F][sub 2][sup 2] and between [ital G][sub 1][sup [ital s]] and the axial vector dipole mass [ital M][sub [ital A]]. Future [nu][ital p] elastic scattering experiments could significantly improve the knowledge of these form factors.
TL;DR: In this paper, the effect of breakup on heavy-ion fusion reactions induced by a halo nucleus was discussed based on a semiclassical method, and it was shown that although the large enhancement of the fusion cross section is moderated by the breakup, the Halo nucleus still leads to a larger fusion cross-section than the other Li isotopes.
Abstract: We discuss the effect of breakup on heavy-ion fusion reactions induced by a halo nucleus $^{11}\mathrm{Li}$ based on a semiclassical method. Our formula leads to a smaller effect of breakup than that calculated in a recent paper using unitarity. We show that although the large enhancement of the fusion cross section is moderated by the breakup, the halo nucleus $^{11}\mathrm{Li}$ still leads to a larger fusion cross section than the other Li isotopes. This trend is especially significant at low energies, but occurs also at energies near the Coulomb barrier where experimental study is feasible.
TL;DR: In this article, the decay properties of the very neutron-rich S and Cl isotopes were studied by a doubly achromatic spectrometer LISE (Ligne d'Ions Super Epluch\'es).
Abstract: Beta-decay half-lives and \ensuremath{\beta}-delayed neutron-emission probabilities of the very neutron-rich nuclei $^{44}\mathrm{S}$ and $^{45--47}\mathrm{Cl}$ have been measured. These isotopes, which lie at or close to the N=28 magic shell, were produced in interactions of a 60 MeV/u $^{48}\mathrm{Ca}$ beam from GANIL (Grand Acc\'el\'erateur National d'Ions Lourds) with a $^{64}\mathrm{Ni}$ target, and were separated by the doubly achromatic spectrometer LISE (Ligne d'Ions Super Epluch\'es). Their decay was studied by a \ensuremath{\beta}-n time correlation measurement. The results are compared to recent model predictions and indicate a rapid weakening of the N=28 shell effect below $_{20}^{48}\mathrm{Ca}_{28}$. The nuclear structure effects reflected in the decay properties of the exotic S and Cl isotopes may be the clue for the astrophysical understanding of the unusual $^{48}\mathrm{Ca}$${/}^{46}$Ca abundance ratio measured in the solar system as well as the Ca-Ti-Cr anomalies observed in E. King inclusions of the Allende meteorite.
TL;DR: In this paper, the double beta decay of Te has been confirmed and the ratio of half-lives for δ-beta decay was precisely determined as δ = 3.11.
Abstract: Double beta decay of $^{128}\mathrm{Te}$ has been confirmed and the ratio of half-lives for \ensuremath{\beta}\ensuremath{\beta} decay of $^{130}\mathrm{Te}$ and $^{128}\mathrm{Te}$ has been precisely determined as ${\mathit{T}}_{1/2}^{130}$/${\mathit{T}}_{1/2}^{128}$=(3.52\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ by ion-counting mass spectrometry of Xe in ancient Te ores, using techniques that reduce interferences due to trapped Xe. We have also detected excesses of $^{126}\mathrm{Xe}$ originating in high energy reactions of cosmic ray muons and their secondaries on Te; such reactions make minor contributions to the measured $^{128}\mathrm{Xe}$ excesses in the Te ores. The Xe measurements, combined with common Pb dating of the ores, yield a $^{130}\mathrm{Te}$ half-life of (2.7\ifmmode\pm\else\textpm\fi{}0.1)\ifmmode\times\else\texttimes\fi{}${10}^{21}$ yr and thus a $^{128}\mathrm{Te}$ half-life of (7.7\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}${10}^{24}$ yr, the longest radioactive decay lifetime measured to date. These results give limits on the effective Majorana mass of the neutrino (1.1--1.5 eV) and right-handed currents (\ensuremath{\Vert}〈\ensuremath{\eta}〉\ensuremath{\Vert}5.3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$) comparable to the best obtained from direct neutrinoless \ensuremath{\beta}\ensuremath{\beta}-decay searches. They also imply new limits on unconventional Majorons not constrained by measurements of the ${\mathit{Z}}^{0}$ decay width.
TL;DR: The present model describes the exotic decay of nuclei by considering the molecular phase of the fragments in an effective liquid drop description of the process by using the Werner-Wheeler approximation for the velocity field of the nuclear flow.
Abstract: The present model describes the exotic decay of nuclei by considering the molecular phase of the fragments in an effective liquid drop description of the process. Shell corrections are included via experimental values of energy released in the disintegration (Q value), which is used to define the effective surface tension of the drop. The Coulomb potential energy is the exact solution of the Poisson equation for a uniform charge distribution in the nuclear volume. The inertial coefficient of the barrier penetrability problem is determined by using the Werner-Wheeler approximation for the velocity field of the nuclear flow. The model is successful in calculating the half-life for both the exotic decay and the \ensuremath{\alpha} disintegration processes.
TL;DR: The proton Compton effect has been studied in the region between the threshold for pion photoproduction and the \ensuremath{\Delta}(1232) and the dispersion sum rule constraint is found to be consistent with the best previous measurements.
Abstract: The proton Compton effect has been studied in the region between the threshold for pion photoproduction and the \ensuremath{\Delta}(1232). The measurements were performed using bremmstrahlung from the high duty-factor electron beam available at the Saskatchewan Accelerator Laboratory. Elastically scattered photons were detected with an energy resolution of approximately 1.5% using a large NaI total absorption scintillation detector. Differential cross sections were measured for photon energies in the range 136 MeV\ensuremath{\le}${\mathit{E}}_{\ensuremath{\gamma}}$\ensuremath{\le}289 MeV and for angles in the range 25\ifmmode^\circ\else\textdegree\fi{}${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$135\ifmmode^\circ\else\textdegree\fi{}. The angular distributions and the excitation functions derived from these data are in agreement with recent theoretical analyses. The results were interpreted within a formalism based in part on dispersion relations to obtain model-dependent estimates of the electric and magnetic polarizabilities, \ensuremath{\alpha}\ifmmode\bar\else\textasciimacron\fi{} and \ensuremath{\beta}\ifmmode\bar\else\textasciimacron\fi{}. We find, subject to the dispersion sum rule constraint \ensuremath{\alpha}\ifmmode\bar\else\textasciimacron\fi{}+\ensuremath{\beta}\ifmmode\bar\else\textasciimacron\fi{}=(14.2\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ ${\mathrm{fm}}^{3}$, that \ensuremath{\alpha}\ifmmode\bar\else\textasciimacron\fi{}=(9.8\ifmmode\pm\else\textpm\fi{}0.4\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ ${\mathrm{fm}}^{3}$ and \ensuremath{\beta}\ifmmode\bar\else\textasciimacron\fi{}=(4.4\ensuremath{\mp}0.4\ensuremath{\mp}1.1)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ ${\mathrm{fm}}^{3}$, which are consistent with the best previous measurements.
TL;DR: The reliability and accuracy of the method used have been corroborated independently by three other ways: by directly solving the inverse problem for d${\mathrm{\ensuremath{-}}}^{4}$He scattering and by two different methods for finding a solution for the three-body (n+p) problem as mentioned in this paper.
Abstract: The $^{6}\mathrm{Li}$(${1}^{+}$0)${\ensuremath{\rightarrow}}^{4}$He+d virtual decay vertex constant ${\mathit{G}}_{0}$ and the respective asymptotic coefficient ${\mathit{C}}_{0}$ of the $^{6}\mathrm{Li}$ wave function in the $^{4}\mathrm{He}$+d channel are found using the analytic continuation of the solution of a novel energy-dependent phase-shift analysis of elastic d${\mathrm{\ensuremath{-}}}^{4}$He scattering to the pole corresponding to the $^{6}\mathrm{Li}$ ground state. The reliability and accuracy of the method used have been corroborated independently by three other ways: by directly solving the inverse problem for d${\mathrm{\ensuremath{-}}}^{4}$He scattering and by two different methods for finding a solution for the three-body (\ensuremath{\alpha}+n+p) problem. The values ${\mathit{G}}_{0}^{2}$=0.42\ifmmode\pm\else\textpm\fi{}0.02 fm and ${\mathit{C}}_{0}$=2.93\ifmmode\pm\else\textpm\fi{}0.15 have been found, which seem to be the most accurate and reliable among the values obtained so far.
TL;DR: Computation of the corrected data of interest such as reaction energy and scattering angle as well as the reconstructed trajectories in terms of position measurements in two planes near the focal plane.
Abstract: A method is presented that allows the reconstruction of trajectories in particle spectrographs and the reconstructive correction of residual aberrations that otherwise limit the resolution. Using a computed or fitted high order transfer map that describes the uncorrected aberrations of the spectrograph, it is possible to calculate a map via an analytic recursion relation that allows the computation of the corrected data of interest such as reaction energy and scattering angle as well as the reconstructed trajectories in terms of position measurements in two planes near the focal plane. The technique is only limited by the accuracy of the position measurements, the incoherent spot sizes, and the accuracy of the transfer map. In practice the method can be expressed as an inversion of a nonlinear map and implemented in the differential algebraic framework. The method is applied to correct residual aberrations in the S800 spectrograph which is under construction at the National Superconducting Cyclotron Laboratory at Michigan State University and to two other high resolution spectrographs.
TL;DR: The complete development of this model, which gives a very good fit to all the data up to 600 MeV, is presented.
Abstract: Pion nucleon scattering up to 600 MeV lab kinetic energy is described by a manifestly covariant wave equation in which the pion is restricted to its mass-shell.The kernel of the equation includes nucleon (N), Roper (N*), delta, and D(sub)13 poles, with their corresponding crossed pole terms approximated by contact interactions, and contact sigma and rho-like exchange terms.The pi-NN vertex is treated as a mixture of gamma^5 and gamma^mu gamma^5 coupling, with a mixingparameter lambda chosen so that the dressed nucleon pole will be unshifted by the interaction.Chiral symmetry is maintained at threshold.The resonance contributions are fully unitarized by the equation, with their widths determined by the dynamics included in the model.The delta and D(sub)13 are treated as a pure spin 3/2 particles, with no spin 1/2 amplitude in the S-channel.The complete development of this model, which gives a very good fit to all the data up to 600 MeV, is presented.
TL;DR: A unified description of scattering cross sections as well as bound and quasibound states for the systems [alpha]+[sup 16]O and [alpha]-N is presented and strong resonances in the compound system are observed.
Abstract: A unified description of scattering cross sections as well as bound and quasibound states for the systems \ensuremath{\alpha}${+}^{16}$O and \ensuremath{\alpha}${+}^{15}$N is presented. Optical potentials have been extracted from the analysis of elastic \ensuremath{\alpha}-scattering data on $^{16}\mathrm{O}$ and $^{15}\mathrm{N}$ in a wide range of energies. Special emphasis was given to the \ensuremath{\alpha}${+}^{16}$O scattering at energies near the Coulomb barrier. The real part of the potential was calculated using the double-folding procedure. Effective nucleon-nucleon interactions with different density dependence as well as zero-range and finite-range knock-on-exchange potentials are investigated. The dispersive part of the real potential was calculated using the dispersion relation of the optical potential. Together with the dominating channel potential it reproduces the observed energy dependence of the volume integral of the real part of the potential. We calculate the energies and other properties of bound and resonance \ensuremath{\alpha}-cluster states in $^{20}\mathrm{Ne}$ and $^{19}\mathrm{F}$ and find good agreement with the experimental data. As an application of the derived energy dependence of the optical potential we calculate \ensuremath{\alpha}${+}^{16}$O excitation functions in the energy range from 10 to 30 MeV. In this region strong resonances in the compound system are observed.
TL;DR: The response function of nuclei in the quasielastic region at large momentum transfer ([bold q][le]10 fm[sup [minus]1]) is measured for a series ofuclei up to large values of the Bjorken scaling variables.
Abstract: The response function of nuclei in the quasielastic region at large momentum transfer (q\ensuremath{\le}10 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$) is measured for a series of nuclei, $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, $^{27}\mathrm{Al}$, $^{56}\mathrm{Fe}$, and $^{197}\mathrm{Au}$, up to large values of the Bjorken scaling variables x2.5.