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Nuclear hadrodynamics

Description: The role of hadron dynamics in the nucleus is illustrated to show the importance of nuclear medium effects in hadron interactions. The low lying hadron spectrum is considered to provide the natural collective variables for nuclear systems. Recent studies of nucleon-nucleon and delta-nucleon interactions are reviewed, with emphasis on the type of experimental phenomena which signal the importance of the many-body dynamics. 28 references.
Date: January 1, 1984
Creator: Geesaman, D.F.
Partner: UNT Libraries Government Documents Department

Nucleon parton distributions and nuclear structure

Description: The current experimental status of measurements of nucleon structure functions in deep inelastic lepton scattering is presented. Recent BCDMS and SLAC results provide a consistent data set for charged lepton scattering. New probes of parton distributions: direct photons, Drell Yan di-muon production, W, Z and heavy quark production are providing information on the gluon an antiquark distributions. The implications of these data on our understanding of the structure of the nucleon, and the structure of the nucleon in the nucleus are discussed. 26 refs., 9 figs.
Date: January 1, 1990
Creator: Geesaman, D.F.
Partner: UNT Libraries Government Documents Department

Nuclear structure in pion scattering and charge exchange

Description: Data from pion inelastic scattering and charge-exchange experiments are discussed within the framework of a DWIA analysis. The properties of the pion-nucleon interaction transformed to the pion-nuclear system are used to infer new nuclear-structure information for both discrete states and giant resonances.
Date: January 1, 1982
Creator: Zeidman, B. & Geesaman, D.F.
Partner: UNT Libraries Government Documents Department

Overview of nuclear structure with electrons

Description: Following a broad summary of the author's view of nuclear structure in 1974, he will discuss the key elements they have learned in the past 25 years from the research at the M.I.T. Bates Linear Accelerator center and its sister electron accelerator laboratories. Electron scattering has provided the essential measurements for most of the progress. The future is bright for nuclear structure research as their ability to realistically calculate nuclear structure observables has dramatically advanced and they are increasingly able to incorporate an understanding of quantum chromodynamics into their picture of the nucleus.
Date: December 3, 1999
Creator: Geesaman, D. F.
Partner: UNT Libraries Government Documents Department

Deep inelastic muon scattering with hadron detection

Description: The physics motivation and experimental apparatus of FNAL E665 are described. E665 is a new experiment to study the hadrons in coincidence with muons deep inelastically scattered from nuclei. One of the goals of the experiment is to examine nuclear medium effects not only on the baryon quark distributions (the EMC effect) but also on the process of hadronization in high energy collisions. 17 refs., 5 figs.
Date: January 1, 1985
Creator: Geesaman, D.F. & Green, M.C.
Partner: UNT Libraries Government Documents Department

Recent results for (e,e{prime}p) reactions at Jefferson Lab

Description: Coincidence cross sections for (e, e{prime}p) quasi-elastic scattering were measured at CEBAF with high statistical precision for C, Fe, and Au targets for 0.6 < Q{sup 2} < 3.3 GeV{sup 2}. Missing energy and missing momentum distributions obtained from a preliminary analysis are in reasonable agreement with prior data from SLAC. The preliminary analysis are compared with a PWIA calculation to determine the nuclear transparency as a function of Q{sup 2} and A. A Rosenbluth analysis to extract the longitudinal and transverse cross sections from these data is anticipated.
Date: September 1, 1997
Creator: Potterveld, D.; Cummings, W.J. & Geesaman, D.F.
Partner: UNT Libraries Government Documents Department

Delta-nucleus dynamics: proceedings of symposium

Description: The appreciation of the role in nuclear physics of the first excited state of the nucleon, the delta ..delta..(1232), has grown rapidly in the past decade. The delta resonance dominates nuclear reactions induced by intermediate energy pions, nucleons, and electromagnetic probes. It is also the most important non-nucleonic degree of freedom needed to resolve many fundamental problems encountered in the study of low-energy nuclear phenomena. Clearly, a new phase of nuclear physics has emerged and conventional thinking must be extended to account for this new dimension of nuclear dynamics. The most challenging problem we are facing is how a unified theory can be developed to describe ..delta..-nucleus dynamics at all energies. In exploring this new direction, it is important to have direct discussions among researchers with different viewpoints. Separate entries were prepared for the 49 papers presented. (WHK)
Date: October 1, 1983
Creator: Lee, T.S.H.; Geesaman, D.F. & Schiffer, J.P. (eds.)
Partner: UNT Libraries Government Documents Department

Data acquisition for FNAL E665

Description: The data acquisition system for FNAL E665, an experiment to study deep inelastic muon scattering from nucleons and nuclei, is described. The system is built with the FNAL VAXONLINE and RSX DA building blocks. The structure, capabilities and limitations for data flow, control and monitoring are discussed. 20 refs., 1 fig.
Date: January 1, 1989
Creator: Geesaman, D.F.; Green, M.C.; Kaufman, S.; Tentindo-Repond, S.; Bartlett, J.F.; Melanson, H.L. et al.
Partner: UNT Libraries Government Documents Department

Resonant structures in heavy-ion reactions

Description: An investigation of heavy-ion resonance structures using the /sup 24/Mg(/sup 16/O, /sup 12/C)/sup 28/Si reaction is presented. The data are analyzed in the context of Breit-Wigner resonances added to a direct-reaction background.
Date: January 1, 1980
Creator: Sanders, S.J.; Henning, W.; Ernst, H.; Geesaman, D.F.; Jachcinski, C.; Kovar, D.G. et al.
Partner: UNT Libraries Government Documents Department

Two-body photodisintegration of the deuteron above 1 GeV

Description: One of the central issues in nuclear physics is the identification of clear signatures for quarks in nuclei. A guiding principle in this search is to perform experiments with high energy electromagnetic probes of the simplest nucleus, the deuteron, a system which is particularly amenable to theoretical interpretation. It has long been known that the quark counting rules seem to apply for electron elastic scattering from the pion and nucleon. However, the rapid decline in the cross section for electron scattering from the deuteron, a six-quark system, renders an experiment at high momentum transfer unfeasible. Clearly, the dimensional-scaling region is not reached for electron-deuteron elastic scattering as indicated. This led Brodsky and Chertok to analyze these data in terms of the reduced nuclear amplitudes and produce, in effect, scaling at a lower momentum transfer. Presently, this is the only known case where the reduced nuclear amplitude analysis seems to apply. In the present work we abandon elastic electron scattering in favor of an exclusive photoreaction with the deuteron. The simplest process involving a nucleus is the ..gamma..d ..-->.. pn reaction. Here, n = 13 and an s/sup -11/ dependence is expected where the quark counting rules are valid. Naively, one would expect that the energy region where the quark counting rules are valid to be most naturally described in terms of a quark or parton basis rather than a nucleon basis, and thereby provide a signature quark effects in nuclei. Hitherto no s/sup -11/ dependence has been observed for the data below 1 GeV. As a test of the energy-dependence for the ..gamma..d ..-->.. pn reaction, we have performed the first measurements for this process above 1 GeV.
Date: January 1, 1988
Creator: Holt, R.J.; Freedman, S.J.; Geesaman, D.F.; Gilman, R.; Green, M.C.; Jackson, H.E. et al.
Partner: UNT Libraries Government Documents Department

Prospect for observation of polarization in electron-deuteron elastic scattering at high momentum transfer

Description: A measurement of the charge and quadrupole form factors of the deuteron would address the most fundamental questions in nuclear physics: validity of perturbative QCD at relatively low momentum transfer, effect of isoscalar meson-exchange currents, and the deuteron structure at short range. Polarization methods will be required in order to provide the separation of these form factors. We propose that the high current of electrons in a storage ring be employed in order to scatter electrons from a gaseous, tensor-polarized, deuterium target.
Date: January 1, 1985
Creator: Holt, R.J.; Green, M.C.; Young, L.; Kowalczyk, R.S.; Geesaman, D.F.; Zeidman, B. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the light quark flavor asymmetry in the nucleon sea.

Description: Fermilab experiment E866 has performed a precision measurement of the ratio of Drell-Yan yields from 800 GeV/c protons incident on deuterium and hydrogen targets. The measurement is used to determine the ratio of down antiquarks({bar d}) to up antiquarks({bar u}) in the proton over a broad range in the fraction of the proton momentum carried by the antiquark, 0.02 &lt; x &lt; 0.345. For x &lt; 0.15, the data is in reasonable agreement with pre-existing parton distributions while for x &gt; 0.20 the data is much closer to unity than these parton functions had indicated. The light quark asymmetry provides valuable information on the relative role perturbative and non-perturbative mechanisms play in generating the nucleon sea. A proposal to extend the Drell-Yan measurement to higher values of x using 120 GeV protons from the Fermilab main injector will be discussed.
Date: June 25, 1999
Creator: Awes, T. C.; Beddo, M. E.; Brown, C. N.; Bush, J. D.; Collaboration, FNAL E866 /NuSea; Geesaman, D. F. et al.
Partner: UNT Libraries Government Documents Department

Deuteron photodisintegration : new results from TJNAF.

Description: The first measurements of the differential cross section from d({gamma},p)n up to 4.0 GeV were performed at the Thomas Jefferson National Accelerator Facility (TJNAF, formerly CEBAF). Bremsstrahlung photons from electron beam impinging on a copper radiator and a liquid deuterium target were employed for this experiment. The experiment was performed in Hall C where the photoprotons at forward angles in the center-of-mass were detected in the High Momentum Spectrometer (HMS) and photoprotons at backward angles were detected in the Short Orbit Spectrometer (SOS). The bremsstrahlung photon energy was reconstructed from the measured proton momentum and angle using the two-body kinematics. We report the cross section results at the proton center-of-mass angles of 37{degree} and 90{degree}. These results are in good agreement with previous lower energy measurements. The 90{degree} data continue to show the constituent-counting-rule behavior up to 4 GeV. The results will be compared with models based on QCD as well as those based on meson-exchange theory.
Date: November 18, 1997
Creator: Abbott, D. J.; Ahmidouch, A.; Armstrong, C. S.; Arrington, J.; Cummings, W. J.; Geesaman, D. F. et al.
Partner: UNT Libraries Government Documents Department

Fragmentation of high-spin particle-hole states in sup 26 Mg

Description: The inelastic scattering of 134 MeV protons to seven 6{sup -} states in {sup 26}Mg has been studied. By combining the results with those of a companion electron scattering study, and utilizing DWIA calculations, it has been possible to extract isoscalar and isovector excitation amplitudes. Shell model calculations using (1d{sub 5/2}){sup 10-n-p} (2s{sub 1/2}){sup n} (1f{sub 7/2}){sup p}, with p = 0 and 1, model spaces can reproduce the general features of the fragmentation, but not the structure of the yrast 6{sup -} state. 28 refs., 10 figs., 2 tabs.
Date: January 1, 1989
Creator: Segel, R.E.; Amusa, A.; Geesaman, D.F.; Lawson, R.D.; Zeidman, B.; Olmer, C. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the deep-inelastic spin-dependent structure functions of the proton and neutron at HERA

Description: It is possible to measure the deep-inelastic spin-dependent structure functions g/sub 1//sup p/(x) and g/sub 1//sup n/(x) for the proton and neutron using internal polarized hydrogen, deuterium, and /sup 3/He targets of polarization 50% and thickness 10/sup 14/ to 10/sup 15/ cm/sup -2/ and the 60 mA longitudinally polarized 30 GeV electron beam in the HERA electron storage ring. The measurement of the deep-inelastic spin-structure of both isospin states of the nucleon at the same kinematics and using the same apparatus allows the Bjorken sum rule to be experimentally checked. In addition, it uniquely constrains the spin distribution of the u and d quarks as a function of x in any model of the nucleon. Possible target and detector configurations are described and an estimate of the accuracy of such a measurement is presented.
Date: January 1, 1988
Creator: Beck, D.H.; Filippone, B.W.; Jourdan, J.; McKeown, R.D.; Milner, R.G.; Woodward, C.E. et al.
Partner: UNT Libraries Government Documents Department

Hyperon-nucleon bound states and electroproduction of strangeness on light nuclei.

Description: The A(e,e{prime}K{sup +})Y X reaction has been investigated in Hall C at Jefferson Lab. Data were taken for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at a beam energy of 3.245 GeV for {sup 1}H, {sup 2}H, {sup 3}He and {sup 4}He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations including {Lambda}, {Sigma}{sup 0}, {Sigma}{sup -} hyperon production. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for {Lambda}-hypernuclear bound states is seen for {sup 3,4}He targets.
Date: June 25, 2002
Creator: Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J. et al.
Partner: UNT Libraries Government Documents Department

Electroproduction of Kaons on light nuclei.

Description: The A(e,e{prime}K{sup +})YX reaction on H, D, {sup 3}He, and {sup 4}He was investigated in Hall C at CEBAF. Data were obtained for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at 3.245 GeV. The missing mass spectra for both H and D are fitted with Monte-Carlo simulations incorporating peaks corresponding to {Lambda} production on the proton and {Sigma} production on both the proton and neutron. For D, the cross section ratio {Sigma}{sup 0}/{Sigma}{sup {minus}} {approx} 2, and excess yield close to the thresholds for {Lambda} and {Sigma} production can be attributed to final-state interactions that are compared to the data. The analysis of the data for the He targets is in a more preliminary state with broader quasi-free peaks resulting from the higher Fermi momenta. Evidence for bound {Lambda}-hypernuclear states is seen and other structure may be present.
Date: December 7, 2000
Creator: Zeidman, B.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J. et al.
Partner: UNT Libraries Government Documents Department

Electroproduction of strangeness on light nuclei.

Description: The A(e,e{prime} K{sup +})YX reaction has been investigated in Hall C at Jefferson Laboratory for 6 different targets. Data were taken for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at a beam energy of 3.245 GeV for {sup 1}H, {sup 2}H, {sup 3}He, {sup 4}He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations taking into account the production of {Lambda} and {Sigma}{sup 0} hyperon production off the proton, and {Sigma}{sup -} off the neutron. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for {Lambda}-hypernuclear bound states is seen for {sup 3,4}He targets.
Date: May 16, 2002
Creator: Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the LIght Quark Flavor Asymmetry in the Nucleon Sea

Description: The Drell-Yan cross section ratios, s(p+d)/s(p+p), measured in Fermilab E866, have led to the first determination of d(x)/u(x), d(x)-(x), and the integral of d(x)-u(x) for the proton over the range 0.02 &lt; x &lt; 0.345. The E866 results are compared with predictions based on parton distribution functions and various theoretical models. The relationship between the E866 results and the NMC measurements of the Gottfried integral is discussed. The agreement between the E866 results and models employing virtual mesons indicates these non-perturbative processes play an important role in the origin of the d, u asymmetry in the nucleon sea.
Date: July 23, 1998
Creator: Peng, J.C.; Awes, T.C.; Beddo, M.E.; Brooks, M.L.; Brown, C.N.; Bush, J.D. et al.
Partner: UNT Libraries Government Documents Department

Quasifree (e,e'p) Reactions and Proton Propagation in Nuclei

Description: The (e,e'p) reaction was studies on targets of C, Fe, and Au at momentum transfers squared Q{sup 2} of 0.6, 1.3, 1.8 and 3.3 GeV{sup 2} in a region of kinematics dominated by quasifree electron-proton scattering. Missing energy and missing momentum distributions are reasonably well described by plane wave impulse approximation calculations with Q{sup 2} and A dependent corrections that measure the attenuation of the final state protons.
Date: June 1, 1998
Creator: Abbott, David; Ahmidouch, A.; Amatuni, Ts.A.; Armstrong, C.; Arrington, J.; Assamagan, J.A. et al.
Partner: UNT Libraries Government Documents Department