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ABSTRACT: Transverse bunch centroid oscillations, induced at operating beam
currents at which transverse wakefields are substantial, and observed at
Beam Position Monitors, are sensitive to the actual magnetic focusing,
energy gain, and RF phase profiles in a linac, and are insensitive to
misalignments and jitter sources. In the `pulse-stealing' set-up
implemented at the SLC, they thus allow the frequent monitoring of the
stability of the in-place emittance growth inhibiting or mitigating
measures-primarily the energy scaled magnetic lattice and the RF phases
necessary for BNS damping-independent of the actual emittance growth as
driven by misalignments and jitter. We have developed a physically based
analysis technique to meaningfully reduce this data. Oscillation
beta-beating is a primary indicator of beam energy errors; shifts in the
`invariant' amplitude reflect differential internal motion along the
longitudinally extended bunch and thus are a sensitive indicator of the
real rf phases in the machine; shifts in betatron phase advance contain
corroborative information sensitive to both effects. Examples from
initial SLC applications illustrate the method. Differential internal
motion due to intra-bunch energy or amplitude spread, or bunch spatial
extension which makes collective or multiparticle interactions possible,
causes striking differences between the behavior of the centroid of a
bunched beam, which is measured by a beam position monitor, and a single
particle. Bunch inhomogeneities that respond differentially to the
beamline environment engender decoherence, and possibly recoherence and
echo phenomena; current dependent collective effects can strongly excite
novel patterns of centroid motion. We first discuss general aspects of
the difference between centroid and single particle mechanics in the
context of developing a general parameterization scheme for the former;
and then move to some more specific features of beam dynamics with
transverse wakefields
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
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ABSTRACT: The distributions of quarks in the pion and nucleon are extracted from measurements of the reaction π-N→μ+μ-X at 253 GeV/c in a naive Drell-Yan analysis, as well as QCD-corrected analyses at leading-log and next-to-leading-log order. As xπ→1 the pion structure function shows a term that varies as 1/mμμ4, which we interpret as a higher-twist effect. Additionally, the angular distribution of the μ+ in the muon-pair rest frame tends towards sin2θ as xπ→1 and as mμμ→0 in a manner consistent with higher-twist effects. When the strongly mass-dependent higher-twist effects are included as part of the pion structure function, the nucleon structure function agrees well with leading-twist results from deeply inelastic lepton-hadron scattering. A significant advance of the present work is the extension of the analysis to low masses by the subtraction of the J/ψ and ψ′ resonances from the continuum. Our analysis covers the kinematic range 0.4<xπ<1.0 and 0.02<xN<0.33 with 3.0<mμμ<8.55 GeV/c2. Cross sections for ψ′ production are presented in an appendix.
Phys. Rev. D. 09/1991; 44(7).
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ABSTRACT: The SLC (SLAC Linear Collider) Ring-to-Linac (RTL) transport lines employ intense bending and strong transverse focusing to produce the momentum compaction needed for bunch length compression prior to S-band acceleration. In the presence of the large RF-induced energy spread needed for compression the consequent chromatic effects (i.e. the variation with energy of residual output dispersion and of the RTL transfer matrix) threaten to destroy the small emittances produced by the damping rings. The tuning methods that have been developed and used to implement the sextupole-based chromatic correction scheme are discussed.< >
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE; 06/1991
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ABSTRACT: In order to maintain a small emittance at the end of the linac, the tolerance on the trajectory deviations become tighter when the beam intensities increase. The existing two-beam trajectory correction method works well when the theoretical model agrees with the real machine lattice. Unknown energy deviations along the linac as well as wake field effects can cause the real lattice to deviate from the model. This makes the trajectory correction difficult. Several automated procedures have been developed to solve these problems. They are: an automated procedure to frequently steer the whole linac by dividing the linac into several small regions, an automated procedure to empirically correct the model to fit the real lattice, and eight trajectory-correcting feedback loops along the linac and steering through the collimator region with restricted corrector strengths and a restricted number of correctors.< >
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE; 06/1991
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A. J. Weir,
S. R. Klein,
G. Abrams, C. E. Adolphsen,
C. Akerlof,
J. P. Alexander,
M. Alvarez,
D. Amidei,
A. R. Baden,
J. Ballam, [......],
P. Voruganti,
S. R. Wagner,
P. Weber,
A. J. Weinstein,
S. Weisz,
S. L. White,
E. Wicklund,
D. R. Wood,
D. Y. Wu,
J. M. Yelton
[show abstract]
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ABSTRACT: Data taken by the Mark II detector at the SLAC e+e- storage ring PEP was used to search for exclusive decays of D± and B± mesons into two charged leptons plus a charged pion or kaon. All possible charge and lepton combinations consistent with charge conservation were considered and no evidence for any signals was found. We obtain upper limits for the various branching ratios ranging from 2.5×10-3 to 9.2×10-3, at a 90% confidence level. Some of these limits can be used to constrain leptoquark masses in various models.
Phys. Rev. D. 02/1990; 41(5).
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S. Bethke,
G. Abrams, C. E. Adolphsen,
C. Akerlof,
J. P. Alexander,
M. Alvarez,
A. R. Baden,
J. Ballam,
B. C. Barish,
T. Barklow, [......],
P. Voruganti,
S. R. Wagner,
P. Weber,
A. J. Weinstein,
A. J. Weir,
S. Weisz,
S. L. White,
E. Wicklund,
D. R. Wood,
D. Y. Wu
[show abstract]
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ABSTRACT: Production rates of multijet hadronic final states are studied ine
+
e
– annihilation at 29 GeV center of mass energy. QCD shower model calculations with exact first order matrix element weighting at the first gluon vertex are capable of reproducing the observed multijet event rates over a large range of jet pair masses. The method used to reconstruct jets is well suited for directly comparing experimental jet rates with parton rates calculated in perturbative QCD. Evidence for the energy dependene of
s
is obtained by comparing the observed production rates of 3-jet events with results of similar studies performed at higher center of mass energies.
Zeitschrift für Physik C 08/1989; 43(3):325-330.
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ABSTRACT: It is pointed out that misalignments of quadrupole magnets and
beam position monitors (BPMs) in the linac of the SLAC (Stanford Linear
Accelerator Center) Linear Collider (SLC) cause the electron and
positron beams to be steered off-center in the disk-loaded waveguide
accelerator structures. Off-center beams produce wakefields which limit
the SLC performance at high beam intensities by causing emittance
growth. A general method is presented for simultaneously determining
quadrupole magnet and BPM offsets using beam trajectory measurements.
Results from the application of the method to the SLC linac are
described. The alignment precision achieved is approximately 100 μm,
which is significantly better than that obtained using optical surveying
techniques
Particle Accelerator Conference, 1989. Accelerator Science and Technology., Proceedings of the 1989 IEEE; 04/1989
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ABSTRACT: Misalignments of magnetic quadrupoles and biases in beam position monitors (BPMs) in the Stanford Linear Collider (SLC) linac can lead to a situation in which the beam is off-center in the disk-loaded waveguide accelerator structure. The off-center beam produces wakefields which can limit SLC performance by causing unacceptably large emittance growth. We present a general method for determining quadrupole misalignments and BPM biases in the SLC linac by using beam trajectory measurements. The method utilizes both electron and positron beams on opposite rf cycles in the same linac lattice to determine simultaneously magnetic quadrupole misalignments and BPM biases. The two-beam trajectory data may be acquired without interrupting SLC colliding beam operations. 2 refs., 5 figs.
08/1988
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ABSTRACT: A model-based beam orbit simulation program has been used successfully to analyze the beam energy errors at the two-mile linear accelerator during commissioning of the SLC system. This simulation program has also been used to develop a nondestructive beam energy error monitoring system. The method of analysis, the simulation program, and a beam energy analysis and monitoring system using expert systems techniques will be described.
01/1988
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A. Petersen,
G. Abrams, C. E. Adolphsen,
C. Akerlof,
J. P. Alexander,
M. Alvarez,
D. Amidei,
A. R. Baden,
J. Ballam,
B. C. Barish, [......],
S. R. Wagner,
P. Weber,
A. J. Weinstein,
A. Weir,
S. Weisz,
S. L. White,
E. Wicklund,
D. R. Wood,
D. Y. Wu,
J. M. Yelton
[show abstract]
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ABSTRACT: Multihadronic e+e- annihilation events at a center-of-mass energy of 29 GeV have been studied with both the original (PEP 5) Mark II and the upgraded Mark II detectors. Detector-corrected distributions from global shape analyses such as aplanarity, Q2-Q1, sphericity, thrust, minor value, oblateness, and jet masses, and inclusive charged-particle distributions including x, rapidity, p⊥, and particle flow are presented. These distributions are compared with predictions from various multihadron event models which use leading-logarithmic shower evolution or QCD matrix elements at the parton level and string or cluster fragmentation for hadronization. The new generation of parton-shower models gives, on the average, a better description of the data than the previous parton-shower models. The energy behavior of these models is compared to existing e+e- data. The predictions of the models at a center-of-mass energy of 93 GeV, roughly the expected mass of the Z0, are also presented.
Phys. Rev. D. 12/1987; 37(1).
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ABSTRACT: The current profile along the 126 ns, multi-bunch beam pulse in the Next Linear Collider Test Accelerator (NLCTA) is monitored with fast toroids (rise time ~1 ns). Inserted at several positions along the beam line, they allow us to track current transmission as a function of position along the bunch train. Various measurements, such as rise time, current, width, and slope, are made on the digitized signals, which can be corrected in software by means of stored frequency response files. The design and implementation of these devices is described.
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S Kuhlman, C E Adolphsen,
R Aiello,
M. Akemoto,
R. Alley,
R W Assmann,
Howard W Baer,
C Baltay,
Karl Leopold Freitag Bane,
B Barakat, [......],
M Woods,
J. Wudka,
J S Wurtele,
M Xie,
Y.T. Yan,
A D Yeremian,
K. Yokoya,
S S Yu,
A.A. Zholents,
Frank Zimmermann
[show abstract]
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ABSTRACT: We present the current expectations for the design and physics program of an e+e- linear collider of center of mass energy 500 GeV -- 1 TeV. We review the experiments that would be carried out at this facility and demonstrate its key role in exploring physics beyond the Standard Model over the full range of theoretical possibilities. We then show the feasibility of constructing this machine, by reviewing the current status of linear collider technology and by presenting a precis of our `zeroth- order' design.
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Frank Zimmermann, C E Adolphsen,
R W Assmann,
Karl Leopold Freitag Bane,
D Burke,
Franz Josef Decker,
P. Emma,
R. Helm,
L. Hendrickson,
S S Hertzbach, [......],
Michiko G Minty,
N Phinney,
Pantaleo Raimondi,
M Ross,
J. Spencer,
H Tang,
P G Tenenbaum,
K. Thompson,
D. Walz,
A D Yeremian
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R W Assmann,
J B Jeanneret,
A Verdier,
L Vos,
E Wildner,
Frank Zimmermann,
R Brinkmann,
C Montag,
I Reyzl,
N. Walker, C E Adolphsen,
J Frisch,
N Phinney,
T O Raubenheimer,
Andrei Seryi,
P G Tenenbaum
[show abstract]
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ABSTRACT: The final focus systems for the future linear colliders need to focus beams to nm-range spot sizes at the collision point. The design spot size varies from several nm for 500 GeV to the one nm range for 3 TeV. In order to keep the beams in collision and to maintain the luminosity stringent stability optimization must be applied. We discuss different sources of beam perturbations and estimate the expected beamline stability based on previous experimental observations. Possible measures for beam stabilization are discussed and plans of further collaborative efforts are outlined.
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ABSTRACT: The Mark II detector has been upgraded in preparation for its role as the first detector to take data at the Stanford Linear Collider. The new detector components include the central drift chamber, the time-of-flight system, the coil, the endcap electromagnetic calorimeters and the beam energy and luminosity measuring devices. There have also been improvements in detector hermeticity. All of the major components were installed for a test run at the PEP storage ring ([radical sign]s = 29 GeV) in 1985. This paper describes the upgraded detector, including its trigger and data acquisition systems, and gives performance figures for its components. Future improvements are also discussed. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/27802/3/0000202.pdf
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ABSTRACT: Data taken by the Mark II detector at the PEP storage ring was used to measure the rate of dilepton production in multihadronic events produced by e+e- annihilation at [radical sign]s=29 GeV. We determine the probability that a hadron initially containing a b (b) quark decays to a positive (negative) lepton to be 0.17-0.08+0.15, with 90% confidence level limits of 0.06 and 0.38. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/28616/3/0000428.pdf
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ABSTRACT: We use data from the Mark II experiment at PEP to search for the process B-->h0X for mh0 between 50 and 210 MeV/c2. No evidence for the Higgs boson is seen in this mass range. The limit obtained rules out the standard Higgs boson for masses between 70 and 210 MeV/c2 and significantly constrains extensions of the Higgs sector. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/27719/1/0000107.pdf
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A. Snyder,
W.N. Murray,
G. Abrams, C.E. Adolphsen,
C. Akerlof,
J.P. Alexander,
M. Alvarez,
D. Amidel,
A.R. Baden,
B.C. Barish, [......],
S.R. Wagner,
P. Weber,
A.J. Weinstein,
S. Weisz,
S.L. White,
E. Wicklund,
A.J. Weir,
D.R. Wood,
D.Y. Wu,
J.M. Yelton
[show abstract]
[hide abstract]
ABSTRACT: We use data from the Mark II experiment at PEP to search for the process B→h0X for mh0 between 50 and 210 MeV/c2. No evidence for the Higgs boson is seen in this mass range. The limit obtained rules out the standard Higgs boson for masses between 70 and 210 MeV/c2 and significantly constrains extensions of the Higgs sector.
Physics Letters B.
