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Atomic number dependence of hadron production at large transverse momentum in 300 GeV proton--nucleus collisions

Description: In an experiment at the Fermi National Accelerator Laboratory we have compared the production of large transverse momentum hadrons from targets of W, Ti, and Be bombarded by 300 GeV protons. The hadron yields were measured at 90{sup o} in the proton-nucleon c.m. system with a magnetic spectrometer equipped with 2 Cerenkov counters and a hadron calorimeter. The production cross-sections have a dependence on the atomic number A that grows with P{sub perpendicular}, eventually leveling off proportional to A{sup1.1}.
Date: July 15, 1974
Creator: Cronin, J. W.; Frisch, H. J.; Shochet, M. J.; Boymond, J. P.; Mermod, R.; Piroue, P. A. et al.
Partner: UNT Libraries Government Documents Department

Nucleus--nucleus total cross sections for light nuclei at 1.55 and 2.89 GeV/ C/nucleon

Description: Total cross sections have been measured for protons, deuterons, alphas, and $sup 12$C on hydrogen, deuterium, helium, and carbon targets at 1.55 and 2.89 GeV/c/nucleon using the ''good geometry'' transmission method. In addition, the inelastic cross sections and elastic slope parameters were measured for reactions initiated by deuterons, alphas, and $sup 12$C. The factorization relation sigma/ sub T/(AA) = sigma/sub T/(AB)$sup 2$/sigma/sub T/(BB) is violated for some of these reactions. The results generally agree with Glauber theory predictions except in their detailed energy behavior. It is found that sigma/sub T/ approximately equal to 144 (A/sub T//sup $sup 1$/$sub 3$/ + A/sub P//sup $sup 1$/ $sub 3$/ - 1.48)$sup 2$ and sigma/sub IN/ approximately equal to 78 (A/sub T//sup $sup 1$/$sub 3$/ + A/sub P//sup $sup 1$/$sub 3$/ - 1.25)$sup 2$, where A/sub T/(A/ sub P/) is the atomic mass number of the target (projectile) and the cross sections are given in mb. (auth)
Date: November 1, 1975
Creator: Jaros, J.A.
Partner: UNT Libraries Government Documents Department

Nuclear model tests with neutron resonance data

Description: Previous determinations of the level density parameters, a, as derived from analyses of resonance parameter data, were carried out on the basis of the Gilbert-Cameron theoretical relation for the spin dispersion parameter, {sigma}. However, other different theoretical expressions for {sigma} have been derived previously on the basis of various nuclear models, such as the Fermi gas model, the unified Bohr-Mottelson model with and without inclusion of nucleon pairing correlations, and the Hartree-Fock model. The different expressions for {sigma} would impact the derivation of the a parameter. Because of these considerations, a new examination of the level density parameter, devoid of a reliance on a theoretical expression for {sigma}, is of great importance in various computations in the fields of reactor physics, astrophysics, and spallation neutrons. Here, the spin dispersion parameter of the level density formula, {sigma}, as determined from the spin dependent level spacings of neutron resonances, is compared with theoretical expressions and found to be in agreement with the results of Ericson. On the basis of the present results, the level density parameters, a, for a few nuclides were then derived and found to be lower than previous determinations by about 20%. The impact of the present findings on the LAHET calculations of neutron yields from thick targets of W is discussed.
Date: July 1, 1997
Creator: Mughabghab, S.F. & Dunford, C.
Partner: UNT Libraries Government Documents Department

Spallation neutron production measurements

Description: Measurements of neutron production by proton bombardment of range- thick targets of Pb and W at 0.8, 1.0, 1.2, and 1.4 GeV were made for comparison with calculations based on code LAHET for neutrons with E{sub n}>20 MeV and code MCNP for E{sub n}{le}20 MeV and also to compare with each of two prior experiments dating from about 1965.
Date: October 1, 1996
Creator: Zucker, M.S.; Vanier, P.E.; von Wimmersperg, U.; Mughabghab, S.F.; Schmidt, E. & Tsoupas, N.
Partner: UNT Libraries Government Documents Department

Deuteron and anti-deuteron production in CERN experiment NA44

Description: The abundances of light nuclei probe the later stages of the evolution of a system formed in a relativistic heavy-ion collision. After the system has cooled and expanded, nucleons in close proximity and moving with small relative momenta coalesce to form nuclei. Light nuclei production enables the study of several topics, including the mechanism of composite particle production, freeze-out temperature, size of the interaction region, and entropy of the system. NA44 is the only relativistic heavy-ion experiment to have both deuteron and anti-deuteron results in both pA and AA collisions and the first CERN experiment to study the physics topics addressed by d and {bar d} production.
Date: April 1, 1995
Creator: Simon-Gillo, J.
Partner: UNT Libraries Government Documents Department

Octupole fragmentation and the structure of the O(6)-like Ba nuclei

Description: The low energy octupole states in {sup 134}Ba were examined using proton inelastic scattering. The data show that there is no significant octupole strength in addition to that corresponding to the lowest 3{sup -} state. Consequently, the strong fragmentation of the low energy octupole state expected for a {gamma} soft nucleus does not occur in {sup 134}Ba. The apparent contradiction that the positive parity states in this nucleus present an O(6) type structure and the negative parity ones do not follow the selection rules of the E3 operator for the O(6) symmetry might be explained by noticing that the wave function of an O(6) nucleus has a significant overlap with the wave function of an U(5) - SU(3) transitional nucleus. 9 refs., 3 figs., 2 tabs.
Date: October 1, 1996
Creator: Zamfir, N.V.; Casten, R.F. & Cottle, P.D.
Partner: UNT Libraries Government Documents Department

Extended direct semidirect mechanism and the role of multistep processes in fast nucleon radiative capture

Description: We have recently developed an extension of the direct-semidirect (DSD) radiative capture model to unstable final states and have confirmed its utility in explaining the spectrum of rays from capture of polarized 19.6-MeV protons on {sup 89}Y. It was found that the extended DSD model, supplemented by a Hauser-Feshbach contribution, successfully explains the observed spectra, angular distributions, and analyzing powers, without requiring additional mechanisms, such as precompound or multistep emission, or nucleon-nucleon bremsstrahlung. In this contribution we show that the model also successfully explains data at higher energies (34 MeV incident protons), and that there is no need for additional contributions other than Hauser-Feshbach at this energy as well. The extended DSD model treats capture to unbound final states and also to bound single-particle states that damp into a compound system. An optical (complex) potential is used to describe the propagation of the captured particle. Application of this model to the {gamma} spectrum in the {sup 89}Y(p,{gamma} ) reaction at 19.6 MeV is shown. We have performed new calculations at higher energy (34 MeV protons), and have compared them with the spectra and angular distributions measured in [2] on targets of natural Cu, Ag, and Au. An example of the results, for the spectrum from Cu, is shown in the right-hand part of the figure. In both cases the DSD calculation is shown by a solid line, and a Hauser-Feshbach calculation by a dashed line. The 34-MeV calculations were very similar to those at 19.6 MeV as described in [1]. In both cases, the sum of DSD and Hauser-Feshbach calculations adequately describes the measured spectra. Although not shown, the angular distributions are also well described. There are no significant deficiencies in the comparison with experiment that indicate a need for multistep processes or other additional reaction mechanisms. Such processes are ...
Date: May 1, 1997
Creator: Dietrich, F.S.; Chadwick, M.B. & Kerman, A.K.
Partner: UNT Libraries Government Documents Department

Two-component multistep direct reactions: A microscopic approach

Description: The authors present two principal advances in multistep direct theory: (1) A two-component formulation of multistep direct reactions, where neutron and proton excitations are explicitly accounted for in the evolution of the reaction, for all orders of scattering. While this may at first seem to be a formidable task, especially for multistep processes where the many possible reaction pathways becomes large in a two-component formalism, the authors show that this is not so -- a rather simple generalization of the FKK convolution expression 1 automatically generates these pathways. Such considerations are particularly relevant when simultaneously analyzing both neutron and proton emission spectra, which is always important since these processes represent competing decay channels. (2) A new, and fully microscopic, method for calculating MSD cross sections which does not make use of particle-hole state densities but instead directly calculates cross sections for all possible particle-hole excitations (again including an exact book-keeping of the neutron/proton type of the particle and hole at all stages of the reaction) determined from a simple non-interacting shell model. This is in contrast to all previous numerical approaches which sample only a small number of such states to estimate the DWBA strength, and utilize simple analytical formulae for the partial state density, based on the equidistant spacing model. The new approach has been applied, along with theories for multistep compound, compound, and collective reactions, to analyze experimental emission spectra for a range of targets and energies. The authors show that the theory correctly accounts for double-differential nucleon spectra.
Date: March 1, 1998
Creator: Koning, A.J. & Chadwick, M.B.
Partner: UNT Libraries Government Documents Department

The role of the nuclear level density in spallation neutron studies

Description: The influence of the nuclear level density parameters of the various nuclides determined recently on the neutron yields, produced by 0.8--1.4 GeV proton bombardments of thick tungsten target, was investigated. The results show that better agreement between measurements and LAHET calculations is achieved on the basis of a new set of level density parameters.
Date: August 1, 1998
Creator: Mughabghab, S.F. & Zucker, M.S.
Partner: UNT Libraries Government Documents Department

Scaling between K{sup +} and proton production in nucleus-nucleus collisions

Description: An empirical scaling involving the production of strange particle K{sup +} and protons has been observed at each rapidity over a large range covered by the E-802 spectrometer in reactions from minimum biased p+Be to central Si+Au at 14.6 A-GeV/c. This scaling has implications for the temporal evolution in nucleus-nucleus collisions.
Date: March 1, 1995
Creator: Chen, Ziping & Chasman, C.
Partner: UNT Libraries Government Documents Department

Measurement of color transparency by C(p,2p) reactions at large momentum transfer

Description: The subject of color transparency, the enhancement of the ability of hadrons to penetrate nuclear matter by kinematic selection, is both interesting and controversial. The description of the collision of hadrons with nucleons inside nuclei, and the connection with initial and final state interactions involve fundamental questions of quantum mechanics, and nuclear and particle physics. Interest in color transparency was greatly increased by AGS Experiment 834 which observed dramatic changes with incident momentum for a variety of nuclei. A new experiment, E850, has studied the (p,2p) quasi-elastic reaction near 90{degree} cm for momenta between 5.9 and 9 GeV/c. The quasi-elastic reaction was compared to the elastic reaction on free protons to determine the transparency. With limited statistics, but with better kinematic definition in a new detector, the authors have confirmed the rise in Carbon transparency ratio seen in Expt 834. The Tr(D/H) for deuterium is consistent with no energy dependence. Unlike the free d{sigma}/dt for hydrogen, the d{sigma}/dt from protons in a nucleus is consistent with the exact s{sup {minus}10} scaling. This suggests two components to the pp scattering amplitude; one small and perturbative, the other spatially large and varying, but filtered away by the nuclear matter in the Carbon nucleus. The plan is to complete the repairs of the superconducting solenoid early this fall, reassemble the detector, and collect data starting next spring.
Date: December 1, 1997
Creator: Carroll, A.S. & Collaboration, E850
Partner: UNT Libraries Government Documents Department

Low energy theorem for scalar and vector interactions of a composite spin-1/2 system

Description: Scalar and vector interactions, with the scalar interaction coupled to a composite spin-1/2 system so as to cause a shift of its mass, are shown to obey a low-energy theorem which guarantees that the second order interaction due to z-graphs is the same as for a point Dirac particle. Off-shell and contact interactions appropriate to the composite system cancel and this is verified in a model of a composite fermion. The result provides a justification for the use of the Dirac equation as it has been in relativistic nuclear scattering and mean field theories.
Date: July 1, 1994
Creator: Wallace, S. J.; Gross, Franz & Tjon, J. A.
Partner: UNT Libraries Government Documents Department

Preliminary results of a PWA of the centrally produced {phi}{phi} system

Description: The authors present preliminary results of a Partial Wave Analysis of the centrally produced {phi}{phi} system at 800 GeV/c in the reaction pp {yields} p{sub slow} ({phi}{phi})p{sub fast}. The preliminary results with one and two M = 0 waves, indicate that most of the cross section can be described by two waves, with J{sup PC} LS{sup {eta}} = 2{sup 2}02{sup -1}, 0{sup 2}00{sup -1}.
Date: November 2, 2001
Creator: al., Marco A. Reyes et
Partner: UNT Libraries Government Documents Department

Analysis of gamma-ray spectra from foils activated in a range-thick lead target by 800-MeV protons. Final technical report

Description: Approximately 400 gamma-ray spectra have been analyzed to obtain the types and quantities of radioisotopes produced when 800-MeV protons interact with a range-thick lead target. These spectra were obtained from the radioactive decay of product isotopes in lead disks placed at various depths and radial positions within the target. These spectra were analyzed with the computer code HYPERMET and the photopeak areas were reduced to nuclei produced per incident proton per cubic centimeter of material. Product nuclei ranged from atomic mass 160 to mass 206 and over a range of half lives from a few minutes to several weeks. The results of this analysis have been outlined in this report and transmitted on computer disk to Los Alamos National Laboratory. The consistency of these analyses have been confirmed by a comparison of photopeak areas obtained at LANL with the computer code GAMANAL with those from HYPERMET for two gamma-ray spectra. Also, the nuclear production per proton per cm{sub 3} obtained from these two spectra analyzed both at LANL and at EKU have been found to agree to within the statistical accuracy of the peak-fitting programs. This analysis of these 400 gamma-ray spectra has determined the nuclear production per incident proton per cm{sub 3} at five regularly-spaced radial positions and depths up to 40 cm into a range-thick lead target.
Date: June 12, 1995
Creator: Laird, C.E. & Mullins, D.H.
Partner: UNT Libraries Government Documents Department

Radioisotope yields from 1.85-GeV protons on Mo and 1.85- and 5.0-GeV protons on Te

Description: Radioisotope yields from 1.85-GeV proton interactions in a natural isotopic composition Mo target and those from 1.85- and 5.0-GeV protons in natural Te targets were measured at Lawrence Berkeley Laboratory`s Bevatron. The radioisotope yields were determined by {gamma}-counting the targets using a 100-cm{sup 3} coaxial Ge detector following the irradiations. Cross sections were determined for the production of 31 radioactive nuclides, ranging from Z = 35, A = 74, to Z = 43, A = 97, from the Mo target and for 47 radioactive nuclides, ranging from Z = 35, A = 75, to Z = 53, A = 130 from the Te targets.
Date: May 1, 1995
Creator: Bardayan, D.W.; Hindi, M.M. & Barghouty, A.F.
Partner: UNT Libraries Government Documents Department

Proton--proton analyzing power measurements at 16 MeV

Description: Few attempts have been made to measure accurately the proton-proton analyzing powers at low energies. With the advent of polarized particle beams the measurement can now be made with high accuracy. Analyzing powers were measured at nine scattering angles from 10$sup 0$ to 35$sup 0$ in the laboratory system. As a check on systematic errors, analyzing power measurements were also made by scattering protons from $sup 4$He. In the p Vector-p case the measured values are in very good agreement with the phase shift predictions. The p Vector- $sup 4$He measurements, while giving the same form and sign as the phase shift predictions, differ from the predictions by as much as 11 standard deviations. The p Vector-p analyzing powers had a maximum value of -0.0043 +- 0.0004 at 10$sup 0$ (laboratory) and decreased to zero near 25$sup 0$. A new technique to measure analyzing powers without symmetric detectors is explained. This technique preserves the advantages of the symmetric arm method in that current integration, target density, detector efficiencies, and geometry are cancelled from the final expressions. A new scattering chamber, named the Supercube, is described. The Supercube was designed primarily to perform scattering experiments with a polarized beam. It contains both left-right and up-down detectors for use with both spin-1/2 and spin-1 measurements. The Supercube was designed to make analyzing power measurements to an accuracy of 0.001 routine. The Supercube has proved to have low systematic errors and to perform as expected. The systematic errors were found to be equal to or less than 0.0002. (23 figures, 14 tables) (auth)
Date: July 1, 1975
Creator: Lovoi, P.A.
Partner: UNT Libraries Government Documents Department

Search for massive long lived particles in aluminum targets irradiated by 300 GeV and 400 GeV protons

Description: A directional gas Cherenkov counter, which employed six phototubes to sample Cherenkov light from single particles having a gamma greater than ~10 was used to achieve accidental rates of less than one per day if operated near targets with surface radiation levels of as high as 10/sup +3/ r/hr. The cosmic ray background measured by the apparatus was reduced to less than one per day by mounting our directional Cherenkov counter above the irradiated targets and facing toward the earth. Two searches of a few days duration, after bombardments at energies of 300 and 400 GeV with >10/sup 16/ protons at NAL, were made in four inch thick targets of aluminum, mounted just down stream from another aluminum target. No long-lived particles were observed with cross sections for production and capture of approximately less than a micro-micro barn in a lifetime range of a few to a few thousand hours. (auth) from the decay of a long-lived intermediate state. (auth)
Date: September 11, 1973
Creator: Frankel, S.; Frati, W.; Resvanis, L.; Yang, W. & Nezrick, F.
Partner: UNT Libraries Government Documents Department