45798253
Aspects of the chiral quark model.
We point out intriguing connections between the chiral quark model in which the nucleon is treated as a soliton and the ordinary potential-binding quark model. The axial-vector coupling comes out near the value (5/3 rather than around 0.7 as in the Skyrme description and can be easily ''fine-tuned'' to its experimental value. A ''linear potential'' in some sense is generated as a collective effect of the ''meson cloud.'' Contact with QCD is made by introducing a gluonium field so as to satisfy the trace-anomaly equation. In the simplest treatment of this field one predicts a scalar-isoscalar state at 900 MeV in agreement with a recent analysis of experiments. The model is used to discuss how a ''nontrivial winding number'' emerges for the meson fields. A number of additional features of the model are treated.
122953784
A hamiltonian structure from gauge transformations of the Zakharov-Shabat system
Abstract We study a hamiltonian structure for nonlinear evolution equations arising from a class of gauge transformations of the Zakharov-Shabat system.
91179466
Beam commissioning of the PEP-II High Energy Ring
The PEP-II High Energy Ring (HER), a 9 GeV electron storage ring, has been in commissioning since spring 1997. Initial beam commissioning activities focused on systems checkout and commissioning and on determining the behaviour of the machine systems at high beam currents, This phase culminated with the accumulation of 0.75 A of stored beam-sufficient to achieve design luminosity-in January 1998 after 3.5 months of beam time. Collisions with the 3 GeV positron beam of the Low Energy Ring (LER) were achieved in Summer of 1998. At high beam currents, collective instabilities have been seen. Since then, commissioning activities for the HER have shifted in focus towards characterization of the machine and a rigorous program to understand the machine and the beam dynamics is presently underway.
18232712
Chandra observations of the nearby spiral galaxy NGC6503
We have observed the nearby spiral galaxy NGC6503 using Chandra. Seven discrete sources associated with the galaxy have been found, one of them coincident with its Liner-starburst nucleus. One of the sources corresponds to a ULX with Lx >~ 10e39 ergs/s. Previous ROSAT observations of the galaxy show that this source has varied by at least a factor 3 in the last 6 years. No evidence is found for strong diffuse emission in the nuclear region or the presence of a low luminosity AGN.
181733866
LASER WELDING OF STEEL PLATES WITH UNMACHINED EDGES
119337087
Investigating the process of star formation in young LMC star clusters
The rich star clusters in the Large Magellanic Cloud (LMC) are ideal for studying the process of star formation. Here we focus on the determination of age spreads amongst the massive stars in two young clusters, NGC1818 and NGC1805. We present colour magnitude diagrams (derived from HST data) for these clusters, and discuss the difficulties in age spread determination.
32539092
Measurement of the mass of the tau lepton.
The mass of the [tau] lepton has been measured at the Beijing Electron-Positron Collider using the Beijing Spectrometer. A search near threshold for [ital e][sup +][ital e[minus]][r arrow][tau][sup +][tau][sup [minus]] was performed. Candidate events were identified by requiring that one [tau] decay via [tau][r arrow][ital e][nu][bar [nu]], and the other via [tau][r arrow][mu][nu][bar [nu]]. The mass value, obtained from a fit to the energy dependence of the [tau][sup +][tau][sup [minus]] cross section, is [ital m][sub [tau]]=1776.9[sub [minus]0.5][sup +0.4][plus minus]0.2 MeV.
54066498
OO design and implementation: Java and Java analysis studio
We present an overview of the Java language, Java virtual machine, and the large set of standard libraries and extensions available for Java, and provide a discussion of issues that effect Java performance. This is followed by an introduction to Java Analysis Studio (JAS), a tool written in Java, and in which Java is the language used to perform data analysis. We will also explore how OO techniques have been used to built a system from modular components including visualization, fitting and data-access components that can be used together, or on their own.
26932934
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.
32203233
Massive hadron pair production by 800 GeV/c protons on nuclear targets.
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.
31307451
Double analog state in odd-A nuclei.
Measurements were performed using pion double charge exchange to observe the double isobaric analog state (DIAS) in the odd-[ital A] nuclei [sup 54]V, [sup 59]Co, [sup 115]In, and [sup 197]Au. These results are combined with data for other odd-[ital A] targets and used to investigate the [ital N], [ital Z], and [ital A] dependence of DIAS cross sections.