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Supersymmetry: Theory

Description: If supersymmetric particles are discovered at high-energy colliders, what can one hope to learn about them? In principle, the properties of supersymmetric particles can give a window into the physics of grand unification, or of other aspects of interactions at very short distances. In this article, the author sketches out a systematic program for the experimental study of supersymmetric particles and point out the essential role that e{sup +}e{sup {minus}} linear colliders will play in this investigation.
Date: March 1, 1996
Creator: Peskin, M.E.
Partner: UNT Libraries Government Documents Department

A coaxial ring-sidearm power extraction design

Description: We report a successful klystron power extraction design, in which a TEM coaxial mode is transmitted into TE10 mode of a WR90 rectangular waveguide at 11.42 GHz, with very little TEM reflection and almost vanishing asymmetric (TEM {r_arrow} TE11, or monopole to dipole) reflectance. Our coupler consists of a ring (disk) around the coaxial waveguide, and a coax-WR90 sidearm junction. The methods used in the design are numerical simulation, performed on the MAFIA3 T3 time- domain module and on the High Frequency Structure Simulator, and analytical treatment to guide the numerical runs. The demerit parameters (dipole reflectance and TEM reflection) can be reduced as much as desired (to zero in principle), the only limitation being computer run time and memory. Results are accurate to a few percent.
Date: January 1, 1996
Creator: Ben-Menahem, S. & Yu, D.
Partner: UNT Libraries Government Documents Department

Study of deep inelastic scattering of polarized electrons off polarized deuterons

Description: This thesis describes a 29GeV electron - nucleon scattering experiment carried out at Stanford Linear Accelerator Center (SLAC). Highly polarized electrons are scattered off a polarized ND{sub 3} target. Scattered electrons are detected by two spectrometers located in End Station A (ESA) at angles of 4.5{degrees} and 7{degrees} with respect to the beam axis. We have measured the spin structure function g{sub 1} of deuteron over the range of 0.029 < x < 0.8 and 1. 0 < Q{sup 2} < 12.0(GeV/c){sup 2}. This integral indicates a discrepancy of more than three standard deviations from the prediction of the Ellis-Jaffe sum rule, 0.068{+-}0.005 at Q{sup 2} = 3.0(GeV/c){sup 2} while our result of g{sub 1}{sup d} in good agreement with SMC results. Combined with g{sub 1} of the proton, the measurement of {integral}{sub 0}{sup 1}(g{sub 1}{sup d}-g{sub 1}{sup n}) is 0.169{+-}0.008. We also obtained the strong coupling constant at Q{sup 2} = 3.0(GeV/c){sup 2} to be 0.417{sub -0.110}{sup +0.086}, using the power correction for the sum rule up to third order of {alpha}{sub s}. This result is in agreement with the strong coupling constant {alpha}{sub s}(Q{sup 2}) = 3.0(GeV/c{sup 2}) obtained from various experiments. Using our deuteron results and the axial vector couplings of hyperon decays, the total quark polarization along the nucleon spin is found to be 0.286{+-}.055, implying that quarks carry only 30% of the nucleon spin. The strange sea quark polarization is also determined to be -0.101 {+-} .023. These measurements are in agreement with other experiments and provide the world`s most precise measurement of these quark polarizations. 80 refs., 151 figs., 23 tabs.
Date: March 1, 1996
Creator: Kuriki, M.
Partner: UNT Libraries Government Documents Department

1995 Site environmental report, January 1995--December 1995

Description: This report provides information about environmental programs and compliance with environmental regulations in calendar year 1995 (CY95) at the Stanford Linear Accelerator Center (SLAC). SLAC is a national laboratory operated by Stanford University under contract with the US Department of Energy (DOE) and is devoted to experimental and theoretical research in elementary particle physics, in basic sciences using synchrotron radiation, and in accelerator physics and technology. SLAC`s Environment, Safety, and Health (ES&H) Division consists of five departments and a Program Planning Office (PPO). Their shared goal is to help ensure that SLAC operates in compliance with federal, state, and local regulations, as well as DOE Orders related to environment, safety, and health. The five departments are: (1) Environmental Protection and Restoration (EPR), (2) Operational Health Physics (OHP), (3) Radiation Physics (RP), (4) Safety, Health, and Assurance (SHA), and (5) Waste Management (WM). The EPR Department oversees the majority of SLAC`s environmental programs, including programs for environmental restoration; waste minimization; air quality; storm water and industrial wastewater; polychlorinated biphenyls (PCBs); and groundwater. The WM Department coordinates disposal of hazardous, radioactive, and mixed waste. The OHP Department, in cooperation with the EPR Department, oversees environmental radiological monitoring and dosimetry at SLAC. The SHA Department oversees quality assurance for SLAC`s environmental activities. The RP Department conducts beam checkouts of new experiments to ensure shielding adequacy for the protection of the workers and members of the general public. The most significant information in this report is summarized briefly in the following sections.
Date: September 1, 1996
Partner: UNT Libraries Government Documents Department

Z{sup 0} pole direct measurements of the parity violation parameters A{sub b} and A{sub c} at SLD

Description: This report presents three different techniques used at SLD to measure directly the parity violation parameters of Zb{bar b} and Zc{bar c} couplings from the left-right forward-backward asymmetries. The results have been obtained using 150,000 hadronic Z{sup 0} decays accumulated during the 1993-95 runs with high electron beam polarization.
Date: September 1, 1996
Creator: Mancinelli, G.
Partner: UNT Libraries Government Documents Department

Radiation calculations and shielding considerations for the design of the Next Linear Collider

Description: The authors describe some of the work that they have done as a contribution to the Next Linear Collider (NLC) Zeroth-Order Design Report (ZDR), with specific emphasis placed on radiation-protection issues. However, because of the very nature of this machine--namely, extremely-small beam spots of high intensity--a new approach in accelerator radiation-protection philosophy appears to be warranted. Accordingly, the presentation will first take a look at recent design studies directed at protecting the machine itself, since this has resulted in a much better understanding of the very short exposure times involved whenever beam is lost and radiation sources are created. At the end of the paper, the authors suggest a Beam Containment System (BCS) that would provide an independent, redundant guarantee that exposure times are, indeed, kept very short. This, in turn, has guided them in the determination of the transverse shield thickness for the machine.
Date: November 1, 1996
Creator: Nelson, W.R.; Rokni, S.H. & Vylet, V.
Partner: UNT Libraries Government Documents Department

Wire ageing with the TEA photocathode

Description: Recently several RICH protypes successfully tested a gaseous TEA photocathode. However, its wire ageing behavior is unknown. In principle, TEA is a more strongly bonded molecule than TMAE, and, as a result, one would expect better wire ageing behavior. This paper explores this question.
Date: June 1, 1996
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

Measurement of the B{sup +} and B{sup 0} lifetimes from semileptonic decays at SLD

Description: The lifetimes of B{sup +} and B{sup 0} mesons have been measured using a sample of 150,000 hadronic Z{sup 0} decays collected by the SLD experiment at the SLC between 1993 and 1995. The analysis identifies the semileptonic decays of B mesons with high (p,p{sub t}) leptons and reconstructs the B meson decay length and charge by vertexing the lepton with a partially reconstructed D meson. This method results in a sample of 634 (584) charged (neutral) decays with high charge purity. A maximum likelihood fit finds: {tau}{sub B{sup +}} = 1.60{sub {minus}0.11}{sup +0.12}(stat) {+-} 0.06(syst) ps, {tau}{sub B{sup 0}} = 1.55{sub {minus}0.12}{sup +0.13}(stat) {+-} 0.09(syst) ps, and the ratio {tau}{sub B{sup +}}/{tau}{sub B{sup 0}} = 1.03{sub {minus}0.13}{sup +0.15}(stat) {+-} 0.08(syst).
Date: July 1, 1996
Partner: UNT Libraries Government Documents Department

Neutral current couplings of leptons to polarized Z{sup O}`s in the SLD experiment

Description: The authors study neutral current couplings of leptons to polarized Z{sup 0}`s in the SLD experiment in terms of the leptonic asymmetry parameters A{sub e}, A{sub {mu}}, and A{sub {tau}}. The authors discuss in detail e{sub L,R}{sup {minus}} + e{sup +} {yields} Z{sup 0} {yields} {mu}{sup {minus}}{mu}{sup +} and {tau}{sup {minus}}{tau}{sup +}, with left (L)- or right (R)-handed polarized electron beams. SLD`s most precise measurement of A{sub e} is shown to result from the left-right cross section asymmetry; A{sub LR}; where the dependence on initial state electronic couplings enable use of essentially all of the data. Comparing A{sub {mu}} and A{sub {tau}} with A{sub e} tests the universality of leptonic couplings. A{sub {mu}} = 0.102 {+-} 0.033 {+-} 0.001, A{sub {tau}} = 0.190 {+-} 0.034 {+-} 0.001, and A{sub e} = 0.148 {+-} 0.016 {+-} 0.002 from these two leptonic channels. If lepton universality is assumed, a combined asymmetry parameter A{sub e{mu}{tau}} = 0.147 {+-} 0.013 results, which directly corresponds to an effective value of the weak mixing angle sin{sup 2}{theta}{sub W}{sup eff} = 0.2315 {+-} 0.0017.
Date: December 1, 1996
Creator: Panvini, R.S
Partner: UNT Libraries Government Documents Department

Transfer matrices of superimposed magnets and RF cavity

Description: Superimposed magnets often occur in accelerators, such as in the interaction regions of colliders. This note presents the linear transfer matrices of various superimposed magnets. Since readers of this note are probably well informed, the authors simply list the results without derivation. The method used to calculate the linear transfer matrices is outlined elsewhere. The authors list the Hamiltonian H and the corresponding matrix e{sup :-sH:} for several combinations of common magnets (only sector magnets without fringe field) used in accelerators. Magnetic fields and vector potentials (in Coulomb gauge) are also listed for reference. The usual (x, y, s) coordinate system is used. The transfer matrices are for the commonly used canonical variables (x, P{sub x}, y, P{sub y}, z, {delta}). For those cases when the transfer matrices depend on the gauge selection, the authors also list the matrices for the coordinates and kinetic momenta (x, p{sub x}, y, p{sub y}). The magnetic fields and Hamiltonians are correct only up to the order appropriate for linear optics. In this computer age, complicated analytical results may lose their usefulness and attractiveness in many applications. However, the authors hope their exact analytic results to linear order are still useful for particle dynamics studies in superimposed magnet systems.
Date: November 1, 1996
Creator: Wang, Shun-xi & Chao, A.
Partner: UNT Libraries Government Documents Department

The polarization asymmetry in {gamma}e collisions at the NLC and triple gauge Boson couplings

Description: The capability of the NLC in the {gamma}e collider mode to probe the CP-conserving {gamma}WW and {gamma}ZZ anomalous couplings through the use of the polarization asymmetry is examined. When combined with other measurements, very strong constraints on both varieties of anomalous couplings can be obtained. The author shows that these bounds are complementary to those that can be extracted from data taken at the LHC.
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Study of microwave instability

Description: The microwave instability is usually described by linearizing Vlasov equation in the angle-action variables I, {phi} and assuming that the interaction of azimuthal harmonics {rho}{sub n}(I) of the distribution function {rho} is weak. The argument implied here is that the Hamiltonian flow smears out particles over invariant tori characterized by the action variables, and the remaining azimuthal dependence of the distribution function is small. Indeed, such an approach successfully describes bunch spectrum and the threshold of the microwave instability. However, recently there have been interesting observations of bunch centroid and bunch shape oscillations above instability threshold at LEP and the damping ring at SLAC. There are also indicates that the oscillations sometimes occur in localized region in the longitudinal coordinate instead of affecting the entire longitudinal distribution as one expects by an action-angle analysis. In this paper the authors describe an alternative approach to the problem of bunch stability using decomposition of the Fokker-Plank equation in the system of nonlinear equations for the moments of the distribution function. In particular, this approach allows them to avoid the conventional action-angle decomposition. The physical quantities they are interested in, the moments, are expressed in the Cartesian z {minus} {delta} phase space. To close the infinite hierarchy of moments equations, the authors assume that higher order correlations are small. Although both the action-angle and the Cartesian languages must be equivalent before truncation, they may have different speed of convergence depending on the problem being studied. It is hoped that Cartesian expansion approach would converge faster for the cases corresponding to those observed recently above threshold. The recent experimental observations made them interested in it again. This note is a progress report of their work.
Date: December 1, 1996
Creator: Heifets, S. & Chao, A.
Partner: UNT Libraries Government Documents Department

On wakefields with two-dimensional planar geometry

Description: In order to reach higher acceleration gradients in linear accelerators, it is advantageous to use a higher accelerating RF frequency, which in turn requires smaller accelerating structures. As the structure size becomes smaller, rectangular structures become increasingly interesting because they are easier to construct than cylindrically symmetric ones. One drawback of small structures, however, is that the wakefields generated by the beam in such structures tend to be strong. Recently, it has been suggested that one way of ameliorating this problem is to use rectangular structures that are very flat and to use flat beams. In the limiting case of a very flat planar geometry, the problem resembles a purely two-dimensional (2-D) problem, the wakefields of which have been studied.
Date: October 1, 1996
Creator: Chao, A.W. & Bane, K.L.F.
Partner: UNT Libraries Government Documents Department

Towards a next-to-leading logarithmic result in B {r_arrow} X{sub s}{gamma}

Description: The calculation of the O ({alpha}{sub s}) virtual corrections to the matrix element of the inclusive decay b {r_arrow} s{gamma} is reported. These contributions drastically reduce the large renormalization scale dependence of the leading logarithmic calculation. Combining these results with the preliminary result for the Wilson coefficient C{sub {gamma}} (m{sub b}) calculated recently by Chetyrkin, Misiak, and Muenz, we estimate the branching ratio to be BR(B {r_arrow} X{sub s} {gamma}) = (3.25 {plus_minus} 0.50) x 10{sup {minus}4}.
Date: August 1, 1996
Creator: Greub, C. & Hurth, T.
Partner: UNT Libraries Government Documents Department

Cold test results of a standing wave muffin-tin structure at X-band

Description: A muffin-tin structure is chosen to study high gradient acceleration in the millimeter wavelength range. In order to understand the electromagnetic field characteristics, a standing wave structure operating at a frequency around 11.4 GHz was built. Cold test measurements were performed and results are presented. Comparisons with theoretical predictions based on computer simulation are shown.
Date: November 1, 1996
Creator: Chou, P.J.; Hanna, S.M.; Henke, H.; Menegat, A.; Siemann, R.H. & Whittum, D.
Partner: UNT Libraries Government Documents Department

CP violation in K decays and rare decays

Description: The present status of CP violation in decays of neutral kaons is reviewed. In addition selected rare decays of both K and B mesons are discussed. The emphasis is in particular on observables that can be reliably calculated and thus offer the possibility of clean tests of standard model flavor physics. 105 refs.
Date: December 1, 1996
Creator: Buchalla, G.
Partner: UNT Libraries Government Documents Department

Zeroth-order design report for the next linear collider. Volume 2

Description: This Zeroth-Order Design Report (ZDR) for the Next Linear Collider (NLC) has been completed as a feasibility study for a TeV-scale linear collider that incorporates a room-temperature accelerator powered by rf microwaves at 11.424 GHz--similar to that presently used in the SLC, but at four times the rf frequency. The purpose of this study is to examine the complete systems of such a collider, to understand how the parts fit together, and to make certain that every required piece has been included. The ``design`` presented here is not fully engineered in any sense, but to be assured that the NLC can be built, attention has been given to a number of critical components and issues that present special challenges. More engineering and development of a number of mechanical and electrical systems remain to be done, but the conclusion of this study is that indeed the NLC is technically feasible and can be expected to reach the performance levels required to perform research at the TeV energy scale. Volume II covers the following: collimation systems; IP switch and big bend; final focus; the interaction region; multiple bunch issues; control systems; instrumentation; machine protection systems; NLC reliability considerations; NLC conventional facilities. Also included are four appendices on the following topics: An RF power source upgrade to the NLC; a second interaction region for gamma-gamma, gamma-electron; ground motion: theory and measurement; and beam-based feedback: theory and implementation.
Date: May 1, 1996
Creator: Raubenheimer, T.O.
Partner: UNT Libraries Government Documents Department

Spectral analysis of reltivistic bunched beams

Description: Particles in a storage ring are oscillating in the longitudinal and transverse dimensions, and therefore, the frequency domain is natural for analyzing many beam generated signals. Information ranging from oscillation frequencies to beam phase space distributions can be extracted from the spectral content of these signals. The spectrum of a single particle is like a Green`s function, and it is the key to understanding the spectrum produced by a beam. Three separate cases are consider in an order of increasing complexity: (1) constant revolution frequency, (2) Frequency Modulation introduced by synchrotron oscillations, and (3) Amplitude Modulation introduced by betatron oscillations.
Date: May 1, 1996
Creator: Siemann, R.H.
Partner: UNT Libraries Government Documents Department

Are partons confined tachyons?

Description: The author notes that if hadrons are gravitationally stabilized ``black holes``, as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v{sup 2} > c{sup 2}, without conflict with the observational fact that neither quarks nor tachyons have appeared as ``free particles``. Some consequences of this model are explored.
Date: March 1, 1996
Creator: Noyes, H.P.
Partner: UNT Libraries Government Documents Department

Measurement of subpicosecond electron pulse length

Description: A new frequency-resolved bunch-length measuring system has been developed at the Stanford SUNSHINE facility to characterize subpicosecond electron pulses. Using a far-infrared Michelson interferometer, this method measures the spectrum of coherent transition radiation emitted from electron bunches through optical autocorrelation. The electron bunch length is obtained from the measurement with a simple and systematic analysis which includes interference effects caused by the beam splitter. This method demonstrates subpicosecond resolving power that cannot be achieved by existing time-resolved methods. The principle of this method and experimental results are discussed.
Date: April 1, 1996
Creator: Lihn, Hung chi
Partner: UNT Libraries Government Documents Department

Beam-beam disruption and the case for a plasma lens in e{sup {minus}}e{sup {minus}} collisions

Description: In an e{sup {minus}}e{sup {minus}} collider, the mutual disruption of the beams will significantly decrease the luminosity, different from the case of e{sup +}e{sup {minus}} colliders, where the mutual attraction of the oppositely-charged beams leads to a self-focusing effect. In this paper the authors estimate the beam disruption at SLC and NLC energies using ABEL simulations. They then give estimates of how a plasma lens might improve the luminosity in e{sup {minus}}e{sup {minus}} collisions.
Date: March 1, 1996
Creator: Chen, P.; Spitkovsky, A. & Weidemann, A.W.
Partner: UNT Libraries Government Documents Department

Preliminary measurements of production of {pi}{sup {plus_minus}}, K{sup {plus_minus}}, p, K{sup 0} and {Lambda}{sup 0} in hadronic Z{sup 0} decays

Description: We have measured production of {pi}{sup {+-}}, {Kappa}{sup {+-}}, {ital p}/{ital {bar p}}, {Kappa}{sup 0} and {Lambda}{sup 0}/{bar {Lambda}}{sup 0} as a function of momentum in inclusive hadronic {ital Z}{sup 0} decay events and separately in events containing primary light-({ital uds}) and {ital b}-quarks. The SLD Cherenkov Ring Imaging Detector was used to identify charged pions, kaons, and protons over most of the available momentum range 0.8{lt}{ital p}{lt}33 GeV/c. The neutral {Kappa}{sup 0}{sub s} and {Lambda}{sup 0} were reconstructed using the {pi}{sup +}{pi}{sup -} and {ital p}{pi}{sup -} decay modes, respectively. We present the first comparisons of momentum of charged tracks measured in the SLD Vertex Detector. Substantial differences are observed, consistent with the kinematics of {ital B}-hadron production in Z{sup 0} decays and the properties of {ital B}-hadron decays as measured at lower energies.
Date: June 1, 1996
Creator: Collaboration, The SLD
Partner: UNT Libraries Government Documents Department

Preliminary measurement of D*/D production and D* spin alignment at the Z{sup 0} resonance

Description: Using hadronic Z{sup 0} decays recorded by the SLD experiment at SLAC, we have measured the vector/(vector+pseudoscalar) production ratio, V/(V+P), for the prompt charmed mesons, D{sup *+} and D{sup +}. Using the channels D{sup *+}{r_arrow}D{sup 0}{pi}{sup +}{sub s}, D{sup 0}{r_arrow} K{sup -}{pi}{sup +}, and D{sup 0}{r_arrow} K{sup - }{pi}{sup +}{pi}{sup -}{pi}{sup +}, as well as D{sup +}{r_arrow} K{sup -}{pi}{sup +}{pi}{sup -}, we find V/(V+P) = 0.57 {+-} 0.07 ({ital stat}){+-} 0.02({ital BR}), which disfavors the expectations of 0.75 from naive spin counting. We have also measured the degree of D{sup *+} spin alignment along the flight direction and find it to be consistent with the zero for D{sup *+} fractional momenta {chi} {triple_bond} E{sub D{sup *}}/D{sub {ital beam}} {gt} 0.2. We compare these results with QCD model predictions.
Date: June 1, 1996
Creator: Collaboration, The SLD
Partner: UNT Libraries Government Documents Department

The virtual library in action: Collaborative international control of high-energy physics pre-print

Description: This paper will discuss how control of the grey literature in high-energy physics pre-prints developed through a collaborative effort of librarians and physicists. It will highlight the critical steps in the development process and describe one model of a rapidly evolving virtual library for high-energy physics information. In conclusion, this paper will extend this physics model to other areas of grey literature management.
Date: February 1, 1996
Creator: Kreitz, P.A.; Addis, L.; Galic, H. & Johnson, T.
Partner: UNT Libraries Government Documents Department