117632815
The QCD parametrization of baryon magnetic moments
120776511
The non-relativistic quark model
The classification scheme and decay properties of hadron states are investigated in the framework of the non relativistic quark model. The main successes and the unsolved difficulties of the model are presented indicating the future work which could be done to understand and exploit the non-relativistic quark ideas.РезюмеИсследованы схема классификации и распадные свойства адронов в рамках статической модели кварков. Изложены главные успехи и нерешенные проблемы модели, указывая задачи, которые должны быть решены для лучшего понимания и использования нерелятивистских идей.
14665617
Comment on "Chiral symmetry and the intrinsic structure of the nucleon"- by D.B.Leinweber,A.W.Thomas and R.D.Young
Some remarks are presented on a recent paper (Leinweber,Thomas and Young, Phys.Rev.Lett. 86, 5011, 2001). In particular a statement of the above paper on the fact that the ratio between the magnetic moments of proton and neutron should remain constant at -3/2, independent of the change of the quark mass is discussed on the basis of the general parameterization.
35083522
Field theory and the nonrelativistic quark model: A parametrization of the meson masses.
We apply the method developed in previous papers (Phys. Rev. D 40, 2997 (1989); 40, 3111 (1989)) to write a general parametrization of the masses of the lowest meson nonets. We compare the mass formulas obtained in this way with those used currently in a nonrelativistic quark model (NRQM). As in the previous work, the aim is to separate the features specific to the NRQM from those that follow from a relativistic field theory satisfying a few rather general conditions (satisfied by QCD). For the meson masses it turns out that the formulas obtained from field theory have essentially the same structure and number of parameters as those in the NRQM. This explains the good fit that the NRQM provides in this case; the internal {ital v}/{ital c} of the {ital q{bar q}} pair is irrelevant. As a by- product, the mixing angle for the {ital I}=0 mesons (e.g., {eta} and {eta}{prime}) predicted from the masses turns out to be model independent to first order in flavor breaking. We discuss the question of the linear versus quadratic or, say, square-root mixing angles.
122238217
A relation between the charge radii of π+,K+,K0 derived by the general QCD parametrization
We derive, using the general QCD parametrization, the approximate relation r2(π+) − r2(K+) − r2(K0) where the r's are the charge radii. The relation is satisfied but the experimental errors are still sizeable. The derivation is similar to (but even simpler than) that for r2(p) − r2(n) r2(Δ+) (Phys. Lett. B, 448 (1999) 107).
119592224
New Results in the Search of Quarks in Matter by the Magnetic Levitation Electrometer
Abstract The results of many runs performed levitating in succession several spheres without opening the levitation chamber show the existence of an additional (magneto-electric) force acting on the sphere. Ignoring this force in the analysis of the data produces “spurious” fractional charges.
5752960
THE CERN DETECTOR SAFETY SYSTEM FOR THE LHC EXPERIMENTS
The Detector Safety System (DSS), developed at CERN in common for the four LHC experiments under the auspices of the Joint Controls Project (JCOP), will be responsible for assuring the equipment protection for these experiments. Therefore, the DSS requires a high degree of both availability and reliability. It is composed of a Front-end and a Back-end part. The Front-end is based on a redundant Siemens PLC, to which the safetycritical part of the DSS task is delegated. The PLC Frontend is capable of running autonomously and of automatically taking predefined protective actions whenever required. It is supervised and configured by the CERN-chosen PVSS SCADA system via a Siemens OPC server. The supervisory layer provides the operator with a status display and with limited online reconfiguration capabilities. Configuration of the code running in the PLCs is completely data driven via the contents of a “Configuration Database”. Thus, the DSS can easily adapt to the different and constantly evolving requirements of the LHC experiments during their construction, commissioning and exploitation phases. Currently, the DSS is being installed and commissioned for the construction of the CMS and LHCb experiments.
18819445
Measurements and Visualization of the Transverse Phase-Space Topology at LEP
The LEP Beam Orbit Measurement system (BOM) allows for the acquisition of the beam position at each Beam Position Monitor (BPM) for over 1000 consecutive turns. By synchronizing the acquisition with a kick given to the beam, we can investigate the behavior of the beam under different conditions. In particular, starting from the data of one BPM, we can apply a simple mathematical manipulation to build a ”virtual” BPM, with a phase advance of 90 degrees. Plotting the real BPM against the virtual one, we can observe the evolution of the beam in the phase-space. An appropriate coloring technique is used, to help the User finding his way through the data. Fixed points in the phasespace can be put in evidence, as well as the beam behavior in their neighbourhood. Quantities like the tune, the beam detuning as function of the position amplitude and the beam damping can be studied in this way. Significant examples from real life will be shown.
55383466
LEP performance at 91.5 GeV
The 1997 LEP collider run was the first year of the LEP2 program devoted to stable high luminosity running. The good performance of the LEP superconducting RF system allowed to run at beam energies of 91.5 GeV. In addition to the to usual optimisation procedures to minimise the vertical beam emittances, the horizontal beam sizes were reduced by increasing the horizontal damping partition number and reducing the betatron function at the interaction points. Vertical beam-beam tune shifts in excess of 0.05 were achieved with total beam currents of 5 mA. The total integrated luminosity of 73 pb-1 is the highest ever recorded in a single year of LEP operation.
54676169
Measurement of chromatic effects in LEP
The chromaticity produced by the insertions and the lattice of LEP is corrected in the FODO lattice of the arcs which has horizontal and vertical phase advances of 90/spl deg/ and 60/spl deg/ for the LEP optics presently used. This is done with two horizontal and three vertical sextupole families. To check this correction scheme the non-linear chromaticities have been measured by observing the betatron tunes as a function of RF-frequency, i.e. of momentum deviation. The differences between the results and the expected effects of the sextupoles are interpreted in terms of octupole and decapole components in the dipole magnets. To check the distribution around the ring of the chromaticities and their corrections the betatron phase advances have been measured as a function of momentum deviation. This was done by observing an excited betatron oscillation for 1024 turns in all beam position monitors for different RF-frequencies. The results clearly show the negative chromaticity produced in the straight sections and its correction in the arcs. The parasitic sextupole components are found to be spread uniformly in the arcs within the measurement errors. Under this condition one finds that they have a negligible effect on the dynamic aperture.
59433578
Electron-positron collisions at 209 GeV in LEP
The Large Electron-Positron Collider (LEP) at CERN closed down in November 2000. During the year 2000 electron-positron collisions were established at centre-of-mass energies of up to 209 GeV. The energy reach of LEP was thus extended by another 7 GeV compared to the year 1999. At the same time the luminosity production was kept high and the total delivered luminosity for the year was 233 pb/sup -1/. High beam energy and high luminosity extended the discovery reach of LEP. The successful energy increase of LEP is analysed and the operation and performance in the regime of ultra-strong damping is described.