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INDEPENDENT PARTICLE ASPECTS OF NUCLEAR DYNAMICS

Description: A generalization of the independent particle model from nuclear statics to nuclear dynamics is sought. Attention is centered on the average behavior of nuclear dynamics, as opposed to detailed behavior, such as that characteristic of shell effects in nuclear statics. In many situations, all that is needed is a model of dissipation in nuclear dynamics. Completely independent nucleons produce dissipation only when they interact with the surface of a nucleus or when they cross from one nucleus to another. The first possibility manifests itself whenever a nuclear surface deforms. Dissipation is then described by a simple 'wall formula.' The second mechanism for dissipation is relevant whenever two nuclei are moving relative to one another and are in sufficient contact that nucleons can move between them. Another simple expression, the 'window formula,' describes dissipation in this case. Neither of the two formulae has any free parameters.
Date: May 1, 1979
Creator: Robel, M.C.
Partner: UNT Libraries Government Documents Department

Longitudinal double-spin asymmetry for inclusive jet production in vec p + vec p collisions at sqrt s = 200 GeV

Description: We report a new STAR measurement of the longitudinal double-spin asymmetry A{sub LL} for inclusive jet production at mid-rapidity in polarized p + p collisions at a center-of-mass energy of {radical}s = 200 GeV. The data, which cover jet transverse momenta 5 < p{sub T} < 30 GeV/c, are substantially more precise than previous measurements. They provide significant new constraints on the gluon spin contribution to the nucleon spin through the comparison to predictions derived from one global fit of polarized deep-inelastic scattering measurements.
Date: October 7, 2007
Creator: Coll, STAR
Partner: UNT Libraries Government Documents Department

PARTICIPANT INTIMACY - A CLUSTER ANALYSIS OF THE INTRANUCLEAR CASCADE

Description: The intranuclear cascade for relativistic nuclear collisions is analyzed in terms of 'clusters' consisting of groups of nucleons which are dynamically linked to each other by violent interactions. The formation cross sections for the different cluster types as well as their intrinsic dynamics are studied and compared with the predictions of the linear cascade model ('rows-on-rows').
Date: August 1, 1980
Creator: Cugnon, J.; Knoll, J. & Randrup, J.
Partner: UNT Libraries Government Documents Department

Overview of reaction mechanisms for calculating the high energy component of fast-nucleon induced gamma spectra

Description: This presentation reviews the current status of quantum mechanical models for understanding the high-energy component of gamma spectra resulting from radiative capture of fast nucleons; i.e., the part of the spectrum that is not amenable to standard statistical model (Hauser-Feshbach) treatments. These models are based on the direct-semidirect (DSD) model and its variants. Included are recent results on the extension of the DSD model to unbound final states, a discussion of problems and improvements in understanding the form factors in this model, and a brief discussion of a model closely related to the DSD, the pure-resonance model.
Date: February 21, 1995
Creator: Dietrich, F.S.
Partner: UNT Libraries Government Documents Department

Status of the N* Program at JLAB

Description: Recent results in electromagnetic excitation of nucleon resonance are presented, and confronted with theoretical predictions. Preliminary data in the search for missing states are discussed as well.
Date: June 1, 2002
Creator: Burkert, Volker D.
Partner: UNT Libraries Government Documents Department

Excitations of the nucleon with dynamical fermions

Description: We measure the spectrum of low-lying nucleon resonances using Bayesian fitting methods. We compare the masses obtained in the quenched approximation to those obtained with two flavours of dynamical fermions at a matched lattice spacing. At the pion masses employed in our simulations, we find that the mass of the first positive-parity nucleon excitation is always greater than that of the parity partner of the nucleon.
Date: June 1, 2002
Creator: Maynard, C.M. & Richards, D.G.
Partner: UNT Libraries Government Documents Department

Gluon density in nuclei

Description: In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.
Date: October 1996
Creator: Ayala, A. L.; Ducati, M. B. G. & Levin, E. M.
Partner: UNT Libraries Government Documents Department

Shadowing and absorption effects on J/psi production in dA collisions

Description: The authors study medium modifications of J/{psi} production in cold nuclear media in deuterium-nucleus collisions. They discuss several parameterizations of the modifications of the parton densities in the nucleus, known as shadowing, an initial-state effect. They also include absorption of the produced J/{psi} by nucleons, a final-state effect. Both spatially homogeneous and inhomogeneous shadowing and absorption are considered. They use the number of binary nucleon-nucleon collisions as a centrality measure. Results are presented for d+Au collisions at {radical}S{sub NN} = 200 GeV and for d+Pb collisions at {radical}S{sub NN} = 6.2 TeV. To contrast the centrality dependence in pA and dA collisions, they also present pPb results at {radical}S{sub NN} = 8.8 TeV.
Date: November 1, 2004
Creator: Vogt, R.
Partner: UNT Libraries Government Documents Department

Dark Matter before the LHC in a Natural Supersymmetric StandardModel

Description: We show that the solid lower bound of about 10{sup -44} cm{sup 2} is obtained for the cross section between the supersymmetric dark matter and nucleon in a theory in which the supersymmetric fine-tuning problem is solved without extending the Higgs sector at the weak scale. This bound arises because of relatively small superparticle masses and a fortunate correlation that the two dominant diagrams for the dark matter detection always interfere constructively if the constraint from the b {yields} s{gamma} measurements is obeyed. It is, therefore, quite promising in the present scenario that the supersymmetric dark matter is discovered before the LHC, assuming that the dark matter is the lightest supersymmetric particle.
Date: September 21, 2005
Creator: Ryuichiro, Kitano & Yasunori, Nomura
Partner: UNT Libraries Government Documents Department

HOLE-HOLE INTERACTIONS AND THE PROPERTIES OF NUCLEAR MATTER

Description: Recently a number of authors have suggested modifications of the Brueckner theory of nuclear matter so as to include hole-hole interactions, as well as particle-particle interactions. Iwamoto has demonstrated that in a perturbation theory calculation the inclusion of hole-hole interaction makes no change in the ground-state energy through second order. The singular two-body potential between nucleons makes it difficult, however, to conclude anything about the contribution of these terms in nuclear matter. The formal similarity between the equation of Iwamoto and the equation for the energy gap in nuclear matter, coupled with the fact that the energy gap is very small at normal density, indicates that the effect of hole-hole interactions is probably only a very small change in the ground-state energy of nuclear matter. It is the point of this note to show that this conclusion is in fact correct, the demonstration proceeding by use of the separation method for evaluating the energy of nuclear matter.
Date: April 4, 1960
Creator: Moszkowski, S.A. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

Off-forward parton distribution

Description: Recent developments in studying off-forward parton distributions are discussed. In this talk, the author discusses the recent developments in studying the off-forward parton distributions (OFPD`s). He has written a topical review article on the subject, which will soon be published in Journal of Physics G. The interested audience can consult that article for details. His talk consists of three parts: definition of the new distributions, their physical significance, and experimental measurements.
Date: December 1, 1998
Creator: Ji, X.
Partner: UNT Libraries Government Documents Department

Excitation Function of the Reaction C12(p,pn)C11 at High Energies

Description: Chupp and McMillan have recently measured the excitation curve for the reaction C{sup 12}(pnpn)C{sup 11} at high energies. Using the model of the nucleus described by Serber, the excitation curve of the above reaction has been calculated for energies up to 100 Mev. The excitation of the nucleus is determined on the basis that the incident proton makes individual collisions with the nucleons, the transferred energy exciting the nucleus. n-p collisions are taken to be three times more probable than n-n or p-p collisions. Charge exchange is assumed. The calculations were made for both 50% and 100% charge exchange. The decay of the excited nucleus is treated by the usual evaporation mode.
Date: November 1, 1947
Creator: Heckrotte, W. & Wolff, Peter
Partner: UNT Libraries Government Documents Department

Energy and system size dependence of phi meson production in Cu+Cu and Au+Au collisions

Description: We study the beam-energy and system-size dependence of {phi} meson production (using the hadronic decay mode {phi} {yields} K{sup +}K{sup -}) by comparing the new results from Cu + Cu collisions and previously reported Au + Au collisions at {radical}s{sub NN} = 62.4 and 200 GeV measured in the STAR experiment at RHIC. Data presented are from midrapidity (|y| < 0.5) for 0.4 < p{sub T} < 5 GeV/c. At a given beam energy, the transverse momentum distributions for {phi} mesons are observed to be similar in yield and shape for Cu + Cu and Au + Au colliding systems with similar average numbers of participating nucleons. The {phi} meson yields in nucleus-nucleus collisions, normalized by the average number of participating nucleons, are found to be enhanced relative to those from p + p collisions with a different trend compared to strange baryons. The enhancement for {phi} mesons is observed to be higher at {radical}s{sub NN} = 200 GeV compared to 62.4 GeV. These observations for the produced {phi}(s{bar s}) mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.
Date: October 28, 2008
Creator: Coll, STAR
Partner: UNT Libraries Government Documents Department

(e,e'N) Reactions

Description: With the advent of a new generation of high energy, high duty cycle electron accelerators, a whole range of new nuclear and subnuclear phenomena can be investigated, in particular through coincidence experiments.This contribution focuses on one and two nucleon emission studies below pion threshold.After a brief review of recent experimental and theoretical work, the study of single nucleon densities through high energy (e,e'N) experiments is discussed.New insights in short-range multihadron phenomena are likely to be obtained through (e,e'p), (e,e'd) and (e,e'2N) reactions.Coincidence experiments, some of them involving polarization measurement, are described to study the free and bound nucleon electromagnetic responses.
Date: January 1, 1987
Creator: Mougey, Jean
Partner: UNT Libraries Government Documents Department

Relativistic Models of the Structure of Light Nuclei

Description: In this talk, I will discuss how relativistic meson theory is developed and applied to the description of few nucleon systems, and show how the ideas which emerge from this discussion provide a natural, theoretical foundation for the Dirac treatment of proton-nucleus scattering.
Date: January 1, 1985
Creator: Gross, Franz
Partner: UNT Libraries Government Documents Department

d/u Asymmetry in the Nucleon Sea

Description: Fermilab E866 has performed a precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on hydrogen and deuterium targets, leading to the first determinations of {bar d}/{bar u} and {bar d}-{bar u} in the proton as functions of {chi}. The results show that {bar d} > {bar u} over a broad range of {chi} and provide valuable information regarding the origins of the {bar d}/{bar u} asymmetry and the antiquark sea in the nucleon. No known symmetry requires equality of the {bar d} and {bar u} distributions in the proton. However, until recently it had been generally assumed that {bar d}({chi}) {approx} {bar u}({chi}), where {chi} is the fraction of the proton's momentum (Bjorken-{chi}) carried by the antiquark, based both on the assumption that the majority of the antiquark sea in the nucleon originates from gluon splitting into q - {bar q} pairs and the lack of experimental evidence to the contrary. The first clear evidence that {bar d} {ne} {bar u} came from the NMC measurements of the structure functions F{sub 2}{sup p}({chi}) and F{sub 2}{sup n}({chi}) in deep-inelastic muon scattering on hydrogen and deuterium.
Date: August 24, 1998
Creator: Gagliardi, C. A.; Awes, T. C.; Stankus, P. W. & Young, G. R.
Partner: UNT Libraries Government Documents Department