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Flavor mixing and charm decay

Description: The results of mixing matrix determination and their implications on heavy quark decays are given. The decays of charm mesons D/sup 0/, D/sup +/, F/sup +/ into two pseudoscalar mesons are discussed in the framework of SU(3) symmetry. The charm decays are also discussed in terms of quark diagrams. It is demonstrated that the differences observed in the lifetimes of D/sup 0/ and D/sup +/, and in the branching ratios B(D/sup 0/ ..-->.. K/sup -/K/sup +/) and B(D/sup 0/ ..-->.. ..pi../sup -/..pi../sup +/) can be easily incorporated. 3 figures.
Date: January 1, 1980
Creator: Chau Wang, L.C.
Partner: UNT Libraries Government Documents Department

Baeklund transformations, conservation laws and linearization of the self-dual Yang-Mills and chiral fields

Description: Baecklund Transformations (BT) and the derivation of local conservation laws are first reviewed in the classic case of the Sine-Gordon equation. The BT, conservation laws (local and nonlocal), and the inverse-scattering formulation are discussed for the chiral and the self-dual Yang-Mills fields. Their possible applications to the loop formulation for the Yang-Mills fields are mentioned. 55 references, 1 figure.
Date: January 1, 1980
Creator: Wang, L.C.
Partner: UNT Libraries Government Documents Department

Flavor mixing and quark decay

Description: A brief historical review of the development of the mixing among quarks is given, i.e. the quark states contributing to the weak currents are mixtures of the quark mass eigenstates of strong interactions. The mixing matrix is discussed. Non-leptonic decays of the D meson are covered. (GHT)
Date: January 1, 1980
Creator: Chau Wang, L L
Partner: UNT Libraries Government Documents Department

Highlights of high energy pp, anti pp and e/sup +/e/sup -/ interactions

Description: Topics covered include: the production cross sections of W/sup +-/ and Z/sup 0/; the detection of the Z/sup 0/ and W/sup +-/; some detailed features of the Drell-Yan model; the onia production; and the Higgs boson and technicolor pseudo scalar production. e/sup +/e/sup -/ interactions are compared with the pp and p-anti p interactions. (GHT)
Date: January 1, 1981
Creator: Wang, L.C.
Partner: UNT Libraries Government Documents Department

Phenomenology of quark mixing and the Kobayashi-Maskawa model

Description: The status of the determination of the quark mixing matrix in the Kobayashi-Maskawa model and its phenomenological implications are discussed. Much of the talk reviews current work on the subject. Some new results on the CP violation effects in exclusive and inclusive decays of bottom, charm and strange particles are also given.
Date: April 1, 1981
Creator: Wang, L.L.C.
Partner: UNT Libraries Government Documents Department

Quark flavor mixing and its physical implications. [Review]

Description: Developments on the subject of flavor mixing, especially the Kobayashi-Maskawa model, since the Tokyo conference in 1978 are reviewed. Aspects discussed include the following: history of the development of the understanding of weak interaction quark states, the determination of the mixing matrix V, nonleptonic decays (the ..delta..I = 1/2 rule of K decays, charm nonleptonic decays), the neutron electric dipole moment, decay interference from CP violation, dynamical origin of the quark flavor mixing, and alternatives to the three doublet model. 34 references, 1 figure. (RWR)
Date: January 1, 1980
Creator: Wang, L.L.C.
Partner: UNT Libraries Government Documents Department

Phenomenology of CP violation from the Kobayashi-Maskawa model

Description: The CP violation consequences of the K-M model, which Kobayashi, Maskawa introduced in 1977 for the purpose of incorporating CP violation via the complexity in the mixing matrix of the quarks are discussed. Much of the talk is a review of current work on the subject. Some new results on the CP violation effects in exclusive and inclusive decays of bottom, charm and strange particles are also given.
Date: January 1, 1980
Creator: Wang, L.L.C.
Partner: UNT Libraries Government Documents Department

Way to observe the Higgs boson H/sup 0/ in hadronic interactions

Description: With its single parameter sin/sup 2/ theta/sub W/ = .23 +- .02, the standard SU(2) x U(1) model has impressively fitted many different types of weak interactions. Though the model has the definite predictions of the intermediate bosons W/sup + -/, Z/sup 0/, with Masses M/sub W/ approx. = 80 GeV, M/sub Z/ approx. = 90 GeV, the mass-generating mechanism of the theory has been obscure. Since we are at the threshold of checking the existence of the predicted W/sup + -/ and Z/sup 0/ with definite signatures in the next generation accelerators, it is of great importance to find ways to check the existence of these mass-generating related bosons. Contrasting to the situation with e/sup +/e/sup -/ machines, for which signatures and ways to observe such bosons are rather clear, ways of detecting such bosons have been noticeably missing in hadronic scatterings. Here it is pointed out that the bremsstrahlung of the H/sup 0/ by a Z/sup 0/, produced in hadronic scattering gives a definite signature of a bump in the dilepton mass Q with a sharp fall at Q approx. = M/sub Z/ - M/sub H/. The production is calculated using the Drell-Yan model.
Date: January 1, 1980
Creator: Chau Wang, L.L.
Partner: UNT Libraries Government Documents Department

Geometric Effects on Electron Cloud

Description: The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit the machine performances by inducing beam instabilities, beam emittance increase, beam loss, vacuum pressure increases and increased heat load on the vacuum chamber wall. The electron multipacting is a kind of geometric resonance phenomenon and thus is sensitive to the geometric parameters such as the aperture of the beam pipe, beam shape and beam bunch fill pattern, etc. This paper discusses the geometric effects on the electron cloud build-up in a beam chamber and examples are given for different beams and accelerators.
Date: July 6, 2007
Creator: Wang, L
Partner: UNT Libraries Government Documents Department

Effects of Beam Filling Pattern on Beam Ion Instability and Beam Loading In PEP-X

Description: A proposed high-brightness synchrotron light source (PEP-X) is under design at SLAC. The 4.5-GeV PEP-X storage ring has four theoretical minimum emittance (TME) cells to achieve the very low emittance and two double-bend achromat (DBA) cells to provide spaces for IDs. Damping wigglers will be installed in zero-dispersion straights to reduce the emittance below 0.1 nm. Ion induced beam instability is one critical issue due to its ultra small emittance. Third harmonic cavity can be used to lengthen the bunch in order to improve the beam's life time. Bunch-train filling pattern is proposed to mitigate both the fast ion instability and beam loading effect. This paper investigates the fast ion instability and beam loading for different beam filling patterns.
Date: June 2, 2009
Creator: Wang, L.
Partner: UNT Libraries Government Documents Department

Electron Cloud in the Wigglers of the Positron Damping Ring of the International Linear Collider

Description: The ILC positron damping ring comprises hundreds of meters of wiggler sections, where many more photons than in the arcs are emitted, and with the smallest beampipe aperture of the ring. A significant electron-cloud density can therefore be accumulated via photo-emission and via beam-induced multipacting. In field-free regions the electron-cloud build up may be suppressed by adding weak solenoid fields, but the electron cloud remaining in the wigglers as well as in the arc dipole magnets can still drive single-bunch and multi-bunch beam instabilities. This paper studies the electron-cloud formation in an ILC wiggler section for various scenarios, as well as its character, and possible mitigation schemes.
Date: July 6, 2007
Creator: Wang, L.
Partner: UNT Libraries Government Documents Department

Adaptive Impedance Analysis of Grooved Surface using the Finite Element Method

Description: Grooved surface is proposed to reduce the secondary emission yield in a dipole and wiggler magnet of International Linear Collider. An analysis of the impedance of the grooved surface based on adaptive finite element is presented in this paper. The performance of the adaptive algorithms, based on an element-element h refinement technique, is assessed. The features of the refinement indicators, adaptation criteria and error estimation parameters are discussed.
Date: July 6, 2007
Creator: Wang, L.
Partner: UNT Libraries Government Documents Department

Comments on the integrability of the loop-space chiral equations

Description: A demonstration is given how the ordinary space chiral equations provide the existence conditions for the infinite number of conserved currents and how these currents are related to the so-called inverse-scattering equations, whose integrability is provided by the original chiral equations. Loop-space chiral equations are introduced. The integrability conditions of the non-local currents in two possible different situations are discussed. In the first case, the generating functions are functionals of the loop alone. The integrability conditions are not satisfied and higher order conserved non-local currents do not exist. In the second case, the generating functions are functionals of the loop as well as a parameter the integrability conditions at a restricted point of the parameter are satisfied, however there is an infinite fold of arbitrariness. It indicates that additional guiding principles are needed in addition to the original loop-space chiral equation in order to uniquely determine the infinite conserved non-local currents as functionals of the loop and the parameter.
Date: January 1, 1980
Creator: Gu, C. & Wang, L.L.C.
Partner: UNT Libraries Government Documents Department

Distortion of Crabbed Bunch Due to the Electron Cloud

Description: In order to improve the luminosity, two crab cavities have been installed in KEKB HER and LER [1]. Since there is only one crab cavity in each ring, the crab cavity generates a horizontally titled bunch along the whole ring. The achieved specific luminosity with crabbed bunch is higher, but it is not as high as that from beam-beam simulation [2]. One of the suspicions is the electron cloud. The electron cloud in LER (positron beam) may distort the crabbed bunch and cause the luminosity drop. This note briefly estimates the bunch shape distortion due to the electron cloud in KEKB LER.
Date: May 28, 2008
Creator: Wang, L & Raubenheimer, T.
Partner: UNT Libraries Government Documents Department

Transverse Single Bunch Instability in PEP-X

Description: A proposed high-brightness synchrotron light source (PEP-X) is under design at SLAC. The 4.5- GeV PEP-X storage ring has four theoretical minimum emittance (TME) cells to achieve the very low emittance and two double-bend achromat (DBA) cells to provide spaces for IDs. Damping wigglers will be installed in zero-dispersion straights to reduce the emittance below 0.1nm. In this paper, we present a preliminary estimation of the threshold of the transverse mode coupling instability (TMCI). Three approaches have been used in the estimation and they agree well with each other.
Date: June 2, 2009
Creator: Wang, L. & Stupakov, G.
Partner: UNT Libraries Government Documents Department

Trapping of Electron Cloud LLC/Cesrta Quadrupole and Sextupole Magnets

Description: The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D [1]. One of the primary goals of the CesrTA program is to investigate the interaction of the electron cloud with low emittance positron beam to explore methods to suppress the electron cloud, develop suitable advanced instrumentation required for these experimental studies and benchmark predictions by simulation codes. This paper reports the simulation of the electron-cloud formation in CESRTA and ILC quadrupole and sextupole magnets using the 3D code CLOUDLAND. We found that electrons can be trapped with a long lifetime in a quadrupole and sextupole magnet due to the mirror field trapping mechanism. We study the effects of magnet strength, bunch current, ante-chamber effect, bunch spacing effect and secondary emission yield (SEY) in great detail. The development of an electron cloud in magnets is the main concern where a weak solenoid field is not effective. Quadrupole and sextupole magnets have mirror field configurations which may trap electrons by the mirror field trapping mechanism [2]. Fig.1 shows the orbit of a trapped electron in a quadrupole magnet. The electron makes gyration motion (called transverse motion) and also moves along the field line (called longitudinal motion). At the mirror point (middle of the field line), there is a maximum longitudinal energy and minimum transverse energy. When the electron moves away from the mirror point, its longitudinal energy reduces and the transverse energy increases as the magnetic field increases. If the magnetic field is strong enough, the longitudinal energy becomes zero at one point and then the electron is turned back by the strong field. Note that the electrons are trapped in the region near the middle of the field lines. Although ...
Date: August 18, 2011
Creator: Wang, L. & Pivi, M.
Partner: UNT Libraries Government Documents Department

STUDY ON THE VOLUMETRIC RATIO OF THE HYBRID GM REGENERATOR OVER THE COLD CHAMBER WORKING AT 4K.

Description: This paper presents a computational analysis on the hybrid GM regenerator at liquid helium region. The effects of the ratio of the regenerator volume over the cold chamber volume on cooling performance were simulated numerically. The results show that there exits a minimum ratio of the regenerator volume over the cold chamber volume for a G-M cryocooler at 4K. The cooling capacity of the refrigerator drops sharply with smaller regenerator, and rises slowly with larger regenerator. The effects of the material combinations of the hybrid regenerator on the volumetric ratio were also studied. The design principle of the geometry size of the regenerator working at 4K was discussed.
Date: July 12, 1999
Creator: WANG,L.
Partner: UNT Libraries Government Documents Department

THE EXPERIMENTAL STUDY OF A SINGLE STAGE G-M REFRIGERATOR WITH THE REGENERATOR SET OUTSIDE THE CYLINDER.

Description: In this paper, a single-stage G-M refrigerator with the regenerator set outside the cylinder is presented. The experimental system for testing the performance of the cryocooler was constructed. The lowest temperature was 14K when the operating frequency was 0.6 Hz. The cooling capacity of 4.4W has been obtained at 20K. The effects of operating parameters of the refrigerator on cooling performance were also experimentally studied.
Date: July 12, 1999
Creator: WANG,L.
Partner: UNT Libraries Government Documents Department