Measurements of a Hamiltonian system and their description by a diffusive model.
The dynamics of transverse particle oscillations in the Fermilab Tevatron, artificially made nonlinear, is studied by observing beam profiles over periods up to an hour. A ``diffusive'' model with amplitude-dependent diffusion coefficient gives a quantitatively accurate description of beam evolution. The evolution is influenced strongly by nonlinear resonance.

title: RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES
abstract: Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved, and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual gas and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) has been built, and a series of detailed experiments is planned at the Argonne Wakefield Accelerator. These experiments will be followed by additional experiments using a second test cell operating at 402.5 MHz.

title: Nonlinear dynamics experiment in the Tevatron
abstract: Results of the continuing analysis of the nonlinear dynamics experiment, E778, are presented. Sixteen special sextupoles introduced nonlinearities in the Tevatron. Smear, which is one of the parameters used to quantify the degree of nonlinearity, was extracted from the data and compared with calculation. Injection efficiency in the presence of nonlinearities was studied. Measurements of the dynamic aperture were performed. The final results in one degree of freedom of the smear, the injection efficiency, and the dynamic aperture are presented. Particles captured on nonlinear resonance islands were directly observed and measurements were taken. The capture efficiency was extracted from the data and compared with prediction. The influence of tune modulation on the stability of these islands was investigated. Plans for future measurements are discussed.<<ETX>>

title: Simulations of a Gas-Filled Helical Muon Beam Cooling Channel
abstract: A helical cooling channel (HCC) has been proposed to quickly reduce the six dimensional phase space of muon beams for muon colliders, neutrino factories, and intense muon sources. The HCC is composed of solenoidal, helical dipole, and helical quadrupole current coils to provide focusing and dispersion needed for emittance exchange as the beam follows an equilibrium helical orbit. Inside the coils constituting the HCC examined here, a series of RF cavities filled with dense hydrogen gas acts as the energy absorber for ionization cooling and also suppressed RF breakdown. Two Monte Carlo simulation programs have been developed to compare HCC performance with analytic predictions and to begin the process of optimizing practical designs that could be built in the near future. We discuss the programs, the comparisons with the analytical theory, and the prospects for a HCC design with the capability to reduce the six-dimensional phase space emittance of a muon beam by a factor of over five orders of magnitude in a linear channel less than 100 meters long.

title: Commissioning the LSU synchrotron light source
abstract: The first commercially supplied synchrotron light source to be built in the USA has been installed and commissioned at LSU. The machine was built by MLI/Brobeck on a fixed price basis with a guaranteed performance of 400 mA at 1.2 GeV. The contract called for 200 mA circulating current at 1.2 GeV before the machine was turned over to LSU. Despite some unanticipated delays, this first commissioning phase was completed on schedule, some 15 months after the building was available to start installation. Vacuum conditioning has continued under LSU direction with present best operation above 300 mA at 1.3 GeV. A description of the commissioning process is given, including the conditioning of the vacuum chamber using synchrotron radiation from circulating beam.

title: EPIC Muon Cooling Simulations using COSY INFINITY
abstract: Next gen­er­a­tion mag­net sys­tems need­ed for cool­ing chan­nels in both neu­tri­no fac­to­ries and muon col­lid­ers will be in­no­va­tive and com­pli­cat­ed. De­sign­ing, sim­u­lat­ing and op­ti­miz­ing these sys­tems is a chal­lenge. Using COSY IN­FIN­I­TY, a dif­fer­en­tial al­ge­bra-based code, to sim­u­late com­pli­cat­ed el­e­ments can allow the com­pu­ta­tion and cor­rec­tion of a va­ri­ety of high­er order ef­fects, such as spher­i­cal and chro­mat­ic aber­ra­tions, that are dif­fi­cult to ad­dress with other sim­u­la­tion tools. As an ex­am­ple, a he­li­cal dipole mag­net has been im­ple­ment­ed and sim­u­lat­ed, and the per­for­mance of an epicyclic para­met­ric ion­iza­tion cool­ing sys­tem for muons is stud­ied and com­pared to sim­u­la­tions made using G4Beam­line, a GEAN­T4 toolk­it.

title: Massive hadron pair production by 800 GeV/c protons on nuclear targets.
abstract: We report data on proton-nucleon collisions obtained on Fermilab experiment E711, in which high transverse momentum hadrons are produced near 90[degree] in the proton-nucleon center of mass forming high mass states, using an 800 GeV/[ital c] proton beam on targets of beryllium, aluminum, iron, and tungsten. The data presented cover the mass range from 7 to 15 GeV/[ital c][sup 2], the three dihadron charge states ++, +[minus], and [minus][minus], and parton-parton scattering angles up to cos[theta][sup *]=0.50. We present the differential mass dihadron cross section, as well as the angular and charge dependence of the measurement. The cross section as a function of the parton-parton scattering angle for the three charge states is shown to vary linearly with the value of the atomic weight. While the angular distributions are shown to be independent of the target type, a small dependence on the charge state of the distributions is observed. The data are shown to be in good agreement with extrapolations from previous measurements and phenomenological QCD calculations.

title: Bag formation in the presence of vector mesons. II. Inclusion of scalars.
abstract: We construct an effective Lagrangian of pions, the vector mesons rho and ..omega.., as well as a scalar meson and a scalar glueball which incorporates chiral symmetry and the QCD trace anomaly. The scalar sector is set up so that it contains particles in a realistic mass range with physically narrow widths. We calculate static nucleon properties and demonstrate that shallow bags with typical confinement sizes of Rapprox.1/2 fm are favored by phenomenology.

title: Strongly coupled quarks in the standard model.
abstract: For sufficiently strong Yukawa couplings the standard model goes over to the linear sigma model. We point out that the associated heavy quarks may behave like strongly interacting low-energy u and d quarks so one cannot argue that very-heavy-quark systems will provide an easy test of QCD. An upper-quark-mass bound of about 1.5 TeV is found. This should also apply to techniquarks.) Experimental confirmation of the scheme might come from the observation of very tightly bound baryons made from three heavy quarks.

title: Scale anomaly and the scalars.
abstract: We investigate the properties of a possible low-lying scalar glueball as well as the ordinary scalar-quark states using an effective chiral Lagrangian which satisfies the trace anomaly and U(1)/sub A/ anomaly of QCD. An interesting mass bound for the lightest particle in the scalar-singlet channel is discussed. Detailed arguments against the existence of a very light (less than 400 MeV) scalar glueball are presented. It is shown that the introduction of a derivative-coupling term in the usual type of linear sigma model cures the problem of excessively large widths for the ordinary (nonet) scalar mesons. In fact, chiral symmetry enables one to nicely correlate the widths of the entire scalar nonet. It is noted that the same derivative-coupling term allows a heavy (1-2 GeV) scalar glueball to have sufficiently narrow width to permit its observation as an ordinary resonance, in contrast with a recent claim. Our model can naturally explain the unusually large partial width for the etaeta' mode of the glueball candidate G(1590). A symmetrical ansatz for the anomaly terms is suggested which enables one to successfully calculate the eta' mass as the ratio of gluon condensate to pion-decay constant. In addition, the theoretically interesting limit where the glueballmore » becomes a true dilaton is formulated in a new and illustrative way.« less

title: Charm production in neutron-nucleon interactions.
abstract: Hadronic production of charmed particles in association with muons from their semileptonic decay has been observed in a high-resolution streamer-chamber experiment performed at Fermilab. A miss-distance analysis of the pictures gives a signal of 17.3 +- 4.7 events. Depending on the production model this corresponds to a range of neutron-nucleon cross sections from 8 to 50 ..mu..b, assuming an A/sup 2/3/ dependence.