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in publisher: "SLAC National Accelerator Laboratory"  
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Study of the $\tau^- to 3h^- 2h^+ \nu_\tau$ Decay

Description: The branching fraction of the {tau}{sup -} {yields} 3h{sup -} 2h{sup +} {nu}{sub {tau}} decay (h = {pi}, K) is measured with the BABAR detector to be (8.56 {+-} 0.05 {+-} 0.42) x 10{sup -4}, where the first error is statistical and the second systematic. The observed structure of this decay is significantly different from the phase space prediction, with the {rho} resonance playing a strong role. The decay {tau}{sup -} {yields} f{sub 1}(1285){pi}{sup -}{nu}{sub {tau}}, with the f{sub 1}(1285) m… more
Date: May 4, 2005
Creator: Aubert, Bernard; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
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Partner: UNT Libraries Government Documents Department
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Effect of Centrifugal Transverse Wakefield for Microbunch in Bend

Description: We calculate centrifugal force for a short bunch in vacuum moving in a circular orbit and estimate the emittance growth of the beam in a bend due to this force. Many of the basic features of the coherent synchrotron radiation (CSR) of short bunches and its effect on beam dynamics in accelerators are now well established. The effect is usually described in terms of the longitudinal force, or wakefield, that causes the energy loss in the beam, and also redistributes the energy between the particl… more
Date: March 22, 2006
Creator: Stupakov, G. V.
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Partner: UNT Libraries Government Documents Department
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What Einstein Did Not Know

Description: This public lecture is about 100 years of research on elementary particles and fundamental forces, beginning with the identification of the electron about 1900 and extending to the astonishing discovery of Dark Matter in the late 1900s. The author talks about the elementary particle concept; the discoveries of leptons, quarks and force carrying particles; and some of the experimental technology used. The author tells of his own research, the discovery of the tau lepton, the long, inconclusive s… more
Date: February 2, 2007
Creator: Perl, Martin L.
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Partner: UNT Libraries Government Documents Department
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Dark Matter Searches With GLAST

Description: Indirect detection of particle dark matter relies upon pair annihilation of Weakly Interaction Massive Particles (WIMPs), which is complementary to the well known techniques of direct detection (WIMP-nucleus scattering) and collider production (WIMP pair production). Pair annihilation of WIMPs results in the production of gamma-rays, neutrinos, and anti-matter. Of the various experiments sensitive to indirect detection of dark matter, the Gamma-ray Large Area Space Telescope (GLAST) may play th… more
Date: February 5, 2007
Creator: Wai, Lawrence & Nuss, E.
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Partner: UNT Libraries Government Documents Department
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The Conformal Template and New Perspectives for Quantum Chromodynamics

Description: Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the q… more
Date: March 6, 2007
Creator: Brodsky, Stanley J.
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Partner: UNT Libraries Government Documents Department
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Measurements of the CKM Angle Gamma at BaBar

Description: We present a short review of the measurements of the CKM angle {gamma} performed by the BABAR experiment. We focus on methods using charged B decays, which give a direct access to {gamma} and provide the best constraints so far.
Date: October 2, 2007
Creator: Latour, Emmanuel & Polytechnique, /Ecole
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Partner: UNT Libraries Government Documents Department
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Techniques of the FLASH Thin Target Experiment

Description: The fluorescence yield in air is reported for wavelength and pressure ranges of interest to ultra-high energy cosmic ray detectors. A 28.5 GeV electron beam was used to excite the fluorescence. Central to the approach was the system calibration, using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air, at 304 K the yield is 20.8 {+-} 1.6 photons per MeV.
Date: October 30, 2007
Creator: Field, Clive; Hüntemeyer, Petra & Thomas, Stanton
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Partner: UNT Libraries Government Documents Department
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Searches for the Decays B0 to l+- tau-+ and B+ to l+ nu(L=e,mu) using Hadronic Tag Reconstruction

Description: We present searches for the leptonic decays B{sup +} {yields} {ell}{sup +}{nu} and the lepton flavor violating decays B{sup 0} {yields} {ell}{sup {+-}}{tau}{sup {-+}}, where {ell} = e, {mu}, with data collected by the BABAR experiment at SLAC. This search demonstrates a novel technique in which we fully reconstruct the accompanying {bar B} in {Upsilon}(4S) {yields} B{bar B} events, and look for a monoenergetic lepton from the signal B decay. The signal yield is extracted from a fit to the signa… more
Date: January 30, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prudent, X. et al.
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Partner: UNT Libraries Government Documents Department
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GLAST and Suzaku: Study on Cosmic-Ray Acceleration And Interaction in the Cosmos

Description: The Gamma-Ray Large Area Space Telescope (GLAST) is an international and multiagency mission scheduled for launch in the fall 2007. The Large Area Telescope (LAT), the primary instrument of the mission, will survey the high energy sky found to be very dynamic and surprisingly diverse by its predecessor the Energetic Gamma Ray Experiment Telescope (EGRET). GLAST-LAT will have a much improved sensitivity when compared with EGRET and extend the higher energy coverage to {approx} 300 GeV. The instr… more
Date: May 23, 2008
Creator: Kamae, T. & /KIPAC, Menlo Park /SLAC
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Partner: UNT Libraries Government Documents Department
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Analytical analysis of longitudinal space charge effects for a bunched beam with radial dependence

Description: The longitudinal space-charge (LSC) force can be a major cause of the microbunching instability in the linac for an x-ray free-electron laser. In this paper, the LSC-induced beam modulation is studied using an integral equation approach that takes into account the transverse (radial) variation of the LSC field for both the coasting-beam limit and a bunched beam. Variation of the beam energy and the transverse beam size is also incorporated. We discuss the validity of this approach and compare i… more
Date: June 16, 2008
Creator: Wu, Juhao; Huang, Zhirong & Emma, Paul
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Partner: UNT Libraries Government Documents Department
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Microwave Transmission Measurements of the Electron Cloud Density In The Positron Ring of PEP-II

Description: Clouds of electrons in the vacuum chambers of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We applied a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave which is independently excited and transmitted over a straight se… more
Date: July 3, 2008
Creator: Pivi, M. T. F.; Krasnykh, A. K; Byrd, J.; Santis, S.De; Sonnad, K. G.; Caspers, F. et al.
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Partner: UNT Libraries Government Documents Department
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Secondary Electron Yield Measurements and Groove Chambers Tests in the PEP-II Beam Line Straights Sections

Description: Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders such as ILC and CLIC [1, 2]. In the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed vacuum chambers with rectangular grooves in a straight magnetic-free section to test this promising possible electron cloud mitigation technique. We have also inst… more
Date: July 3, 2008
Creator: Pivi, M. T. F.; King, F.; Kirby, R. E.; Markiewicz, T; Raubenheimer, T. O.; Seeman, J. et al.
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Partner: UNT Libraries Government Documents Department
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An Improved Design for a Super-B Interaction Region

Description: We present an improved design for a Super-B interaction region. The new design attempts to minimize the bending of the two colliding beams which results from shared magnetic elements near the Interaction Point (IP). The total crossing angle at the IP is increased from 34 mrad to 50 mrad and the distance from the IP to the first quadrupole is increased. Although the two beams still travel through this shared magnet, these changes allow for a new magnetic field design with a septum which gives th… more
Date: July 25, 2008
Creator: Sullivan, M. K.; Seeman, J.; Wienands, U.; Bettoni, S.; Biagini, M. E.; Raimondi, P. et al.
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Partner: UNT Libraries Government Documents Department
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Distortion of Crabbed Bunch Due to Electron Cloud and Global Crabbing

Description: Crab cavities may be used improve the luminosity in colliding beam colliders with crab crossing. In a global crab crossing correction, only one crab cavity is installed in each ring and the crab cavities generate a horizontally titled bunch oscillating around the ring. The electron cloud in positively charged rings may distort the crabbed bunch and cause the luminosity drop. This paper briefly estimates the distortion of positron bunch due to the electron cloud with global crab and estimates th… more
Date: August 1, 2008
Creator: Wang, L.; Raubenheimer, T.O. & Cai, Y.
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Partner: UNT Libraries Government Documents Department
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AdS/QCD and Its Holographic Light-Front Partonic Representation

Description: Starting from the Hamiltonian equation of motion in QCD we find a single variable light-front equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space.
Date: November 12, 2008
Creator: de Teramond, Guy F. & Brodsky, Stanley J.
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Partner: UNT Libraries Government Documents Department
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Breakdown Characteristics Study on an 18 Cell X-band Structure

Description: A CLIC designed 18 cells, low group velocity (2.4% to 1.0% c), X-band (11.4 GHz) accelerator structure (denoted T18) was designed at CERN, its cells were built at KEK, and it was assembled and tested at SLAC. An interesting feature of this structure is that the gradient in the last cell is about 50% higher than that in the first cell. This structure has been RF conditioned at SLAC NLCTA for about 1400 hours where it incurred about 2200 breakdowns. This paper presents the characteristics of thes… more
Date: November 12, 2008
Creator: Wang, Faya
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Partner: UNT Libraries Government Documents Department
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