119236559
Some remarks on a paper by G.-S. Yang and H.-C.Kim: Mass splitting of SU(3) baryons within a chiral soliton model
In a recent paper Yang and Kim discuss the lowest baryon mass formulas using a chiral soliton model. However, contrary to their assertion, their result is not equivalent to a generalized Gell Mann-Okubo mass formula derived (G.Morpurgo,1992) using only general properties of QCD (The General Parameterization method). The reason for the non equivalence is that the generalized mass formula includes all the main terms that break flavor at second order, whereas the Authors above do not go beyond first order flavor breaking (and should therefore find the usual Gell Mann Okubo formula). This is not so, due to some inconsistencies. Below we confine to the part of the Yang-Kim paper dealing with the mass formula. We will not consider the other items of their paper. 1.Second order versus first order in flavor breaking. As stated in the Abstract, I will consider only the part of the paper of Yang and Kim [1] dealing with the Gell Mann-Okubo mass formula (see the generalized Gell Mann-Okubo mass formula Eqs.(1) below) derived [2] many years ago. In the Eqs.(1,2) below the particle symbols stay for the particle masses. 1 2 (p+ Ξ) + T = 1 4 (3Λ + 2Σ − Σ) (1) where T stays for T ≡ Ξ∗− − 1 2 (Ω + Σ∗−) (2) The fit to the data depends on whether we use the conventional or the pole values for the masses of the resonances appearing in T : l.h.s. = 1132.36± 0.7MeV, r.h.s. = 1133.93± 0.04MeV (conventional) l.h.s. = 1133.86± 1.25MeV, r.h.s. = 1133.93± 0.04MeV (pole) (3) In Eq.(1) the value of T is 5.7±0.7MeV . The Eq.(1), written with the signs of the charges indicated in it, includes correctly the effects of the e.m. contributions to the masses. (See in Ref.[2], the text and the footnote 9). Note from Eq.(3) e-mail morpurgo@ge.infn.it
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.
117632815
The QCD parametrization of baryon magnetic moments
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.
123073842
QCD with pion exchange, double counting and the baryon magnetic moments
126324552
Magnetic moments of the Deltas in QCD
180753764
PRACTICAL DIAGNOSTIC MEASUREMENTS
119009661
Determination of coupled-lattice properties using turn-by-turn data
A formalism for extracting coupled betatron parameters from multiturn, shock excited, beam position monitor data is described. The most important results are nonperturbative in that they do not rely on the underlying ideal lattice model. Except for damping, which is assumed to be exponential and small enough to be removed empirically, the description is symplectic. As well as simplifying the description, this leads to self-consistency checks that are applied to the data. The most important of these is a {open_quotes}magic ratio{close_quotes} of Fourier coefficients that is required to be a lattice invariant, the same at every beam position monitor. All formulas are applied to both real and simulated data. The real data was acquired June, 1992 at LEP as part of decoupling studies, using the LEP beam orbit measurement system. Simulated data, obtained by numerical tracking (TEAPOT) in the same (except for unknown errors) lattice, agrees well with real data when subjected to identical analysis. For both datasets, deviations between extracted and design parameters and deviations from self-consistency can be accounted for by noise and signal processing limitations. This investigation demonstrates that the LEP beam position system yields reliable local coupling measurements. It can be conservatively assumed that systems of similar design at the SSC and LHC will provide the measurements needed for local decoupling.
55091650
Betatron function measurement at LEP using the BOM 1000 turns facility
A new method for measuring the beta function around LEP is presented. The method uses phase difference measurements between three adjacent beam position monitors to obtain the value for the beta function at the monitors and in their neighbourhood, e.g. at interaction points, electrostatic separators etc. The phase differences are obtained from measuring coherent betatron oscillations for 1024 turns at the 504 beam position monitors. After a discussion of the accuracy of the method the measured values for the beta function are compared with the theoretical values for different lattices. In regular parts of the lattice (e.g. arcs) the beating of the beta function measured using this method agrees well with the beating obtained by another method using a fit of the phase over 15 monitors.<<ETX>>
12798237
Overview of LEP operation in 1998
After the installation of 32 additional RF cavities in the 1997-1998 shutdown LEP was operated at a beam energy of 94.5 GeV. The total integrated luminosity for the year 1998 clearly surpassed its target and reached 198 pb/sup -1/. Vertical beam-beam tuneshifts of more than 0.07 were obtained. The performance did not seem to be beam-beam limited, but the total beam current was limited by power dissipation problems to around 6 mA. A high phase advance optics (102/spl deg/, 90/spl deg/), with a smaller natural emittance, was used for regular operation in 1998. This contributed to the excellent performance of LEP, together with the further reduction of both the horizontal and vertical beta function at the interaction points. No dynamic aperture problems were encountered.
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.