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Baryon-baryon mixing in hypernuclei

Description: Implications of few-body hypernuclei for the understanding of the baryon-baryon interaction are examined. Octet-octet coupling effects not present in conventional, non strange nuclei are the focus. The need to identify strangeness {minus}2 hypernuclei to test model predictions is emphasized.
Date: May 1998
Creator: Gibson, B. F.
Partner: UNT Libraries Government Documents Department

S = {minus}1 and S = {minus}2 few-body hypernuclei

Description: The S = {minus}1 and S = {minus}2 few-body bound states are the focus of this discussion. Implications for the understanding of the baryon-baryon interaction are examined. Octet-octet coupling effects not found in conventional, non-strange nuclei are highlighted. TJNAF wave function tests for the S = {minus}1 sector are noted. The need to identify S = {minus}2 hypernuclei to explore the S = {minus}2 strong interaction and to test model predictions is emphasized.
Date: November 1997
Creator: Gibson, B. F.
Partner: UNT Libraries Government Documents Department

{psi}{prime} and J/{psi} suppression in high-energy nucleon-nucleus and nucleus-nucleus collisions

Description: The observed features of {psi}` to J/{psi} suppression in pA and nucleus-nucleus collisions can be explained in terms of a two-component absorption model. For the hard component of the absorption due to the interaction of the produced c{bar c} systems with baryons at high relative energies, the absorption cross sections are insensitive to the radii of the c{bar c} systems, as described by the Additive Quark Model. For the soft component due to the low energy c{bar c} interactions with soft particles produced by other baryon-baryon collisions, the absorption cross sections are greater for {psi}` than for J/{psi}, because the breakup threshold for {psi}` is much smaller than for {psi}.
Date: December 31, 1995
Creator: Wong, Cheuk-Yin
Partner: UNT Libraries Government Documents Department

Proposal to study 50,000 Sigman- n multiprong events at 240-GeV/c by means of the 15 foot bubble chamber

Description: In contrast to the large amount of data accumulated in non strange baryon-baryon interactions, there is only a limited amount of information available on {Sigma}N interactions. As a {Sigma}{sup -}p experiment at 240 GeV/c has already been approved with the 15', we propose to complete this experiment by studying the {Sigma}{sup -}n interactions at the same incident momentum. This will allow us to make a comparison between {Sigma}{sup -}n and {Sigma}{sup -}p reactions and to detect thus the isospin influence on the {Sigma}N interactions. Furthermore, as previous bubble chamber experiments at FNAL have shown that four constraint reactions can be studied, the use of a neutron target will give us access to four constraint final states which cannot be obtained from the {Sigma}{sup -}p experiment. The utilization of a deuteron target will of course complicate somewhat the data analysis. Nevertheless this is a convenient method to study the pure 1=3/2 EN isospin state as {Sigma}{sup +}p experiments are more difficult to carry out than {Sigma}{sup -}n. In a first step we would like to have a statistics corresponding to 50,000 multiprong events, i.e., events having more than two prongs.
Date: January 1, 1975
Creator: Braun, H.; Brick, D.; Fridaman, A.; Gerberm, J.P.; Jegham, E.; Juillot, P. et al.
Partner: UNT Libraries Government Documents Department

Status of heavy-lepton searches

Description: Searches for heavy leptons using e{sup +}e{sup -} annihilation, lepton-hadron collisions, photon-hadron collisions, hadron-hadron collisions, and studies of macroscopic matter are reviewed. The present experimental status and future possibilities are summarized.
Date: June 1, 1981
Creator: Perl, M.L.
Partner: UNT Libraries Government Documents Department


Description: The general character of 4-quark (mesonic) and strange 6-quark (baryonic) quark systems is very briefly reviewed a la Jaffe, i.e. in the MIT bag, and so far still possibly viable candidates are indicated. The concentration is on the latter (S = -2) systems, with some attention given to more likely to be discoverable light, doubly-strange nuclei. The two modes for generating doubly strange, generally double-{Lambda} nuclear systems, are considered and related to each other. Traditionally, one employs the (K{sup -},K{sup +}) reaction on a relatively light target and hopes to retain two units of strangeness on a single final state fragment. Alternatively, heavy ion reactions can be used to produce {Lambda}-hyperons copiously and one seeks to observe coalescence of two of these particles into the lightest S=-2 nucleus, the H-dibaryon. The complications arising from the presence of a repulsive core in the baryon-baryon interaction on the production of the H are discussed. Also considered is the possible presence in the data from the AGS experiment E906, of slightly heavier S=-2 nuclei, in particular in the system {sub {lambda}{lambda}}{sup 4}H.
Date: June 10, 2002
Creator: KAHANA,D.E. & KAHANA,S.H.
Partner: UNT Libraries Government Documents Department

High statistics analysis using anisotropic clover lattices: (III) Baryon-baryon interactions

Description: Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic clover gauge-field configurations at a pion mass of m{sub {pi}} {approx} 390 MeV, a spatial volume of L{sup 3} {approx} (2.5 fm){sup 3}, and a spatial lattice spacing of b {approx} 0.123 fm. Luescher's method is used to extract nucleon-nucleon, hyperon-nucleon and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The isospin-3/2 N{Sigma} interactions are found to be highly spin-dependent, and the interaction in the {sup 3}S{sub 1} channel is found to be strong. In contrast, the N{Lambda} interactions are found to be spin-independent, within the uncertainties of the calculation, consistent with the absence of one-pion-exchange. The only channel for which a negative energy-shift is found is {Lambda}{Lambda}, indicating that the {Lambda}{Lambda} interaction is attractive, as anticipated from model-dependent discussions regarding the H-dibaryon. The NN scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN-sector at this pion mass. This is consistent with our previous Lattice QCD calculation of NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio of correlation functions that yields the ground-state energy splitting is explored. In particular, focus is placed on the window of time slices for which the signal-to-noise ratio does not degrade exponentially, as this provides the opportunity to extract quantitative information about multi-baryon systems.
Date: January 19, 2010
Creator: Beane, S; Detmold, W; Lin, H; Luu, T; Orginos, K; Savage, M et al.
Partner: UNT Libraries Government Documents Department

Hypernuclear physics: A brief past and bright future

Description: A primary reason for investigating the structure and reactions of baryon systems is to achieve an understanding the fundamental baryon-baryon force in the realm of non-perturbative QCD. Few-baryon systems play an essential role, because one can calculate complete solutions to test a particular baryon-baryon interaction ansatz. Hypernuclei, exotic nuclei containing one or more hyperons (Y = {Lambda}, {Sigma}, or {Xi}) are crucial to this investigation, because they permit one to probe models based upon our experience in the nonstrange sector; they lie outside of the conventional world where our models were developed. That is, we can test whether our sophisticated models of the nucleon-nucleon (NN) interaction extrapolate successfully beyond the zero strangeness region in which the parameters were determined, or whether the models merely interpolate. The presence of the strangeness degree of freedom (flavor) adds a new dimension to our evolving picture of nuclear physics. We shall see that the physics of hypernuclei is both novel and puzzling, stretching our intuition and analysis capability beyond that developed during the more than half century that we have explored conventional nuclear physics. The hypernuclear sector of hadronic physics is not just a simple extension of zero-strangeness phenomena.
Date: October 1, 2000
Creator: Gibson, B.F.
Partner: UNT Libraries Government Documents Department

Nucleon-nucleon scattering at LAMPF and KEK

Description: A review of current measurements of spin-dependent observables in p-p and n-p scattering is given for experiments done at two laboratories, Clinton P. Anderson Meson Physics Facility at Los Alamos (LAMPF) and the National Laboratory for High Energy Physics in Japan (KEK). 18 refs., 12 figs.
Date: January 1, 1988
Creator: Glass, G.
Partner: UNT Libraries Government Documents Department

Empirical proton-neutron interaction strengths

Description: An empirical technique to extract proton-neutron interaction energies for specific protons and neutrons in a wide variety of nuclei is described. The results shed light on the roles of the monopole and quadrupole components of the p-n interaction, their orbit dependence, the microscopic basis of the N/sub p/N/sub n/ scheme, and the saturation of collectively observed in deformed nuclei. 3 refs., 4 figs.
Date: January 1, 1989
Creator: Casten, R.F.; Zhang, J.Y. & Brenner, D.S.
Partner: UNT Libraries Government Documents Department

Mean field and collisions in hot nuclei

Description: Collisions between heavy nuclei produce nuclear matter of high density and excitation. Brueckner methods are used to calculate the momentum and temperature dependent mean field for nucleons propagating through nuclear matter during these collisions. The mean field is complex and the imaginary part is related to the ''two-body'' collision, while the real part relates to ''one-body'' collisions. A potential model for the N-N interactions is avoided by calculating the Reaction matrix directly from the T-matrix (i.e., N-N phase shifts) using a version of Brueckner theory previously published by the author. Results are presented for nuclear matter at normal and twice normal density and for temperatures up to 50 MeV. 23 refs., 7 figs.
Date: June 1, 1989
Creator: K /umlt o/hler, H.S.
Partner: UNT Libraries Government Documents Department

Nucleon-nucleon theory and phenomenology. Progress report and renewal proposal

Description: Progress is outlined on five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction with the new dramatically altered ..pi pi.. s-wave interaction and using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the ..pi..N and ..pi pi.. physical regions of the N anti N ..-->.. ..pi pi.. amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly, and determining which phases are given by theory at which energies; (4) the introduction of our K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated and verified permanent nucleon-nucleon data bank in the 0 to 1200 MeV range that can be used by all nucleon-nucleon researchers (or anyone else) via Telenet dial-in and by means of a published compendium. (WHK)
Date: January 1, 1981
Creator: Signell, P.
Partner: UNT Libraries Government Documents Department

Neutron-antineutron oscillations in nuclei

Description: We briefly review the state of the art for extracting the period of neutron-antineutron oscillations from the lifetime of nuclei. The most recent data on nuclear stability provide a limit of 10{sup 8} s for the oscillation period. 13 refs.
Date: January 1, 1989
Creator: Dover, C.B.; Gal, A.; Richard, J.M. (Brookhaven National Lab., Upton, NY (USA); Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics & Grenoble-1 Univ., 38 (France). Inst. des Sciences Nucleaires)
Partner: UNT Libraries Government Documents Department

Nonrelativistic theory of heavy-ion collisions

Description: A wide range of phenomena is observed in heavy-ion collisions, calling for a comprehensive theory based on fundamental principles of many-particle quantum mechanics. At low energies, the nuclear dynamics is controlled by the mean field, as we know from spectroscopic nuclear physics. We therefore expect the comprehensive theory of collisions to contain mean-field theory at low energies. The mean-field theory is the subject of the first lectures in this chapter. This theory can be studied quantum mechanically, in which form it is called TDHF (time-dependent Hartree-Fock), or classically, where the equation is called the Vlasov equation. 25 references, 14 figures.
Date: July 17, 1984
Creator: Bertsch, G.
Partner: UNT Libraries Government Documents Department

Multiple particle production processes in the light'' of quantum optics

Description: Ever since the observation that high-energy nuclear active'' cosmic-ray particles create bunches of penetrating particles upon hitting targets, a controversy has raged about whether these secondaries are created in a single act'' or whether many hadrons are just the result of an intra-nuclear cascade, yielding one meson in every step. I cannot escape the impression that: the latter kind of model appeals naturally as a consequence of an innate bio-morphism in our way of thinking and that in one guise or another it has tenaciously survived to this day, also for hadron-hadron collisions, via multi-peripheral models to the modern parton shower approach. Indeed, from the very beginning of theoretical consideration of multiparticle production, the possibility of many particles arising from a single hot'' system has been explored, with many fruitful results, not the least of which are the s{sup 1/4} dependence of the mean produced particle multiplicity and the thermal'' shape of the P{sub T} spectra. An important consequence of the thermodynamical-hydrodynamical models is that particle emission is treated in analogy to black-body radiation, implying for the secondaries a set of specific Quantum-Statistical properties, very similar to those observed in quantum optics. From here on I shall try to review a number of implications and applications of this QS analogy in the study of multiplicity distributions of the produced secondaries. I will touch only in passing another very important topic of this class, the Bose-Einstein two-particle correlations.
Date: September 1, 1990
Creator: Friedlander, E.M.
Partner: UNT Libraries Government Documents Department

Charge-independence-breaking in the triton

Description: We find the effect of the observed charge-independence-breaking in {sup 1}S{sub 0} nucleon-nucleon scattering on the binding energy of the triton to be of order 80 keV. When corrections for this effect are made in an 18-channel momentum-space Faddeev calculation, we find the Paris and Argonne v{sub 14} potentials triton binding energies that differ by only 20 keV.
Date: January 1, 1990
Creator: Gloeckle, W.; Lee, T.S.H. & Wiringa, R.B.
Partner: UNT Libraries Government Documents Department

Multifractal structures in multiparticle production in p -p interactions at radical s = 1800 GeV

Description: Fractal structure in multiparticle production of {bar p} {minus} p minimum-bias'' interactions at {radical}s = 1800 GeV has been studied using the Collider Detector at Fermilab. Preliminary results are shown and compared with very simple Monte Carlo models.
Date: August 1, 1990
Creator: Rimondi, F. (Bologna Univ. (Italy) Istituto Nazionale di Fisica Nucleare, Bologna (Italy))
Partner: UNT Libraries Government Documents Department

A quark-gluon plasma search in anti p --p at radical s = 1. 8 TeV

Description: The search by E-735 for QGP evidence in centrally produced particles in {bar p}p collisions has revealed several interesting results in the behavior with variation of dN{sub c}/d{eta} in the measured interval from 2--18. In {l angle}P{sub t}{r angle} we see a decrease in slope for all particles near dN{sub c}/d{eta} {approx equal} 9 corresponding to a Bjorken initial energy density of 2.2 GeV/{sub fm}{sup 3}. Above dN{sub c}/d{eta} = 10, the increase of {l angle}P{sub t}{r angle} is small except for {bar p}'s where the data suggest a 25% increase in the region 13--18. In the particle ratios, normalizing to {pi}'s, they (K, {bar p}, {Lambda}{sup 0}, {gamma}) are all independent of dN{sub c}/d{eta} within errors of {plus minus} 15% except for K{sup {plus minus}}/{pi}{sup {plus minus}} which increases by 30% in the interval 7 to 18. Based on the E-735 data analyzed to data, one can conclude that QGP is not manifest in {bar p}p collisions at 1.8 TeV. Nonetheless, there are the two effects mentioned above, which can be explored with much improved sensitivity using the high-statistics data of the '88--'89 run.
Date: October 8, 1990
Creator: Turkot, F.
Partner: UNT Libraries Government Documents Department

The Missing Top: Prospects at the Tevatron

Description: A new run has begun at the Tevatron Collider, and two detectors, CDF and D0, have started taking data. After a short review of the situation of the top search in both the single and dilepton channel, we present the expectations for the near and far future. There have already been accelerator and detector upgrades, and more are to come. Important improvements are also expected from new analysis tools.
Date: December 1, 1992
Creator: Cobal, M.
Partner: UNT Libraries Government Documents Department

Investigations of the structure and electromagnetic interactions of few-body systems

Description: In order to make it easy for the reader to see the specific research carried out and the progress made, the following report of progress is done by topic. Each item has a format layout of Topic, Investigators, Objective, Significance, and Description of Progress, followed at the end by the relevant references. As is clear from the topics listed, the emphasis of the George Washington University (GWU) theory group has been on the structure and electromagnetic interactions of few-body nuclei. Both low- and intermediate-energy electromagnetic disintegration of these nuclei is considered. When the excitation energy of the target nucleus is low, the aim has been to handle the continuum part of the theoretical work numerically with no approximations, that is, by means of full three- or four-body dynamics. When structure questions axe the issue, numerically accurate calculations axe always carried through, limited only by the underlying two-body or three-body interactions used as input. Implicit in our work is the question of how far one can go within the traditional nuclear physics framework, i.e., nucleons and mesons in a nonrelativistic setting. Our central goal is to carry through state-of-the-art fewbody calculations that wig serve as a means of determining at what point standard nuclear physics requires quark degrees of freedom in order to understand the phenomena in question. So far, in the problems considered, there has been no evidence of the necessity to go beyond the traditional approach, though we always keep in mind that possibility. As our work is involved with questions in the intermediate-energy realm, moving from a nonrelativistic framework to a relativistic one is always a consideration. Currently, for the problems that have been pursued in this domain of energy, the issues concern far more the mechanisms of the reactions and structural questions than the need to move ...
Date: July 1, 1992
Creator: Lehman, D. R.; Haberzettl, H.; Maximon, L. C. & Parke, W. C.
Partner: UNT Libraries Government Documents Department

The Fermilab PBAR-P Collider: Present status and future plans

Description: The Tevatron Collider is performing beyond expectations for its first physics run. The peak luminosity is already 1.6 times the design goal of 10/sup 30/ cm/sup /minus/2/ s/sup /minus/1/. The anticipated integrated luminosity recorded by the major detector, CDF, is 3 inverse picobarns which should be sufficient to see the top quark if its mass is less than 110 GeV. The next two Collider runs will have improved performance with luminosity approaching 10/sup 31/ at two interaction regions. In the years between 1993 and 2000, the Collider energy will be increased by using the highest field superconducting magnets then available, where 8.8 T would give 2 TeV on 2 TeV pbar-p collisions with a luminosity above 10/sup 31/. To facilitate this possibility and to improve the general Collider capabilities, a new 150 GeV Main Injector is now being designed. 3 figs., 2 tabs.
Date: November 1, 1988
Creator: Johnson, R.
Partner: UNT Libraries Government Documents Department

Is nuclear structure really so simple The P-factor revisited

Description: The parameter, P = N{sub p}N{sub n}/(N{sub p}+N{sub n}) is the number of valence protons (neutron) relative to the nearest shell or subshell closure, provides a simple and physically intuitive framework for understanding the evolution of collectivity in medium and heavy nuclei in terms of the competition between the spherical-driving, like-particle interaction and the deformation-driving, proton-neutron (p-n) interaction. In the past several years the P factor has been used to correlate a variety of properties of nuclear ground states and structures at low excitation energy. Here we present two new applications of this simple scheme: The isotopic systematics of 2{sub 1}{sup +} states and the linearization of intruder 0+ states in the Pb region. The results show the versatility of the P-factor as a simple embodiment of the competition and balance between the p-n and pairing residual interactions that seem to determine much of the behavior of ground and excited configurations of medium and heavy nuclei.
Date: January 1, 1992
Creator: Brenner, D. S. (Clark Univ., Worcester, MA (United States)); Casten, R. F. (Brookhaven National Lab., Upton, NY (United States)); Chou, W. T. (Clark Univ., Worcester, MA (United States) Brookhaven National Lab., Upton, NY (United States)) & Zhang, J. Y. (Brookhaven National Lab., Upton, NY (United States) Tennessee Univ., Knoxville, TN (United States) Institute of Modern Physics, Lanzhou, PRC (China))
Partner: UNT Libraries Government Documents Department

Neutron-proton bremsstrahlung experiments

Description: It is well known that charged particles emit bremsstrahlung radiation when they are accelerated. Classical electron bremsstrahlung occurs when a photon is emitted by an electron accelerated in the field of a nucleus. The bremsstrahlung process also occurs in the scattering of nucleons, for which it is the lowest energy inelastic process that can occur. Like electron bremsstrahlung, nucleon-nucleon bremsstrahlung also requires the exchange of a virtual particle to conserve energy and momentum. In electron bremsstrahlung a virtual photon is exchanged but with two nucleons a meson can be exchanged. Unlike electron bremsstrahlung, in nucleon-nucleon bremsstrahlung the photon can originate from the exchanged meson. This exchange contribution has been shown in calculations to be a significant fraction of bremsstrahlung events. Thus bremsstrahlung serves as a probe of exchange currents in the nucleon-nucleon interaction. Because of a lack of a free neutron target or an intense neutron beam, few measurements of neutron-proton bremsstrahlung exist, each having poor statistical accuracy and poor energy resolution. The white neutron source at the Weapons Neutron Research (WNR) target area at the Los Alamos Meson Physics Facility (LAMPF) produces neutrons with energies from below 50 to above 400 MeV. Using time-of-flight techniques and a liquid hydrogen target, we are measuring the outgoing photons of energies up to 250 MeV at gamma ray angles of around 90[degree] relative to the incident beam. Protons scattered at very forward angles are also detected in coincidence with the gamma rays.
Date: January 1, 1992
Creator: Koster, J.E.; Nelson, R.O.; Schillaci, M.E.; Wender, S.A. (Los Alamos National Lab., NM (United States)); Mayo, D.; Brady, F.P. et al.
Partner: UNT Libraries Government Documents Department