5,023 research outputs found
An automated focal point positioning and emittance measurement procedure for the interaction point of the SLC
To achieve maximum luminosity at the SLC, both the electron and positron beams must reach their minimum transverse size within 1 mm of the longitudinal location where the two bunches collide. This paper describes an automated procedure for positioning the focal point of each beam at this collision point. The technique is based on measurements of the beam size utilizing either secondary emission or bremsstrahlung signals from carbon fibers a few microns in diameter. We have achieved simultaneous and reproducible measurements of the angular spread (~ 200 [mu] rad) and of the optimum beam spot size ~ [omega]m), which when combined yield measurements of the beam emittance consistent with those obtained using conventional profile monitor techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28674/1/0000491.pd
Machine-Related Backgrounds in the SiD Detector at ILC
With a multi-stage collimation system and magnetic iron spoilers in the
tunnel, the background particle fluxes on the ILC detector can be substantially
reduced. At the same time, beam-halo interactions with collimators and
protective masks in the beam delivery system create fluxes of muons and other
secondary particles which can still exceed the tolerable levels for some of the
ILC sub-detectors. Results of modeling of such backgrounds in comparison to
those from the e+ e- interactions are presented in this paper for the SiD
detector.Comment: 29 pages, 34 figures, 7 table
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Maintaining micron-size beams in collision at the interaction point of the Stanford Linear Collider
In order to maintain collisions between two micron-size beams at the interaction point of the SLC, we take advantage of the mutual electromagnetic deflection induced by one beam on the other as they cross with a nonzero relative impact parameter. We determine simultaneously the incoming and outgoing trajectory parameters of each beam on a pulse-by-pulse basis, using beam position monitors located near the IP. Comparing incoming and outgoing angles for a given beam yields the magnitude of the deflection the beam experienced during the collision from which the distance currently separating the two beams can be extracted. A simple proportional control is applied to calculate the change in upstream corrector settings to null out this distance. 3 refs., 6 figs
Comparison of the TESLA, NLC and CLIC Beam Collimation Systems Performance
This note describes studies performed in the framework of the Collimation task Force organized to support work of the International Linear Collider Technical Review Committee aiming in comparison of performance of the post-linac beam collimation systems in TESLA, JLC/NLC and CLIC linear collider designs. Collimation of the beam halo and synchrotron radiation collimation have been compared for all projects using the same computer code and same assumptions. It is shown that though the performance of the presently designed systems differ, and not always correspond to expected performance, achieving required performance in the future collider is feasible. Furthe, post-TRC plans of the Collimation task Force are discussed as well
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Beam-beam deflection as a beam tuning tool at the SLAC linear collider
To achieve maximum integrated luminosity at the SLAC Linear Collider, a method of noninvasive beam tuning is required. Traditional luminosity monitors based on Bhabha scattering are inadequate because of low instantaneous counting rates. Coherent deflections of one beam by the electromagnetic field of the other are sensitive not only to the relative steering of the two bunches but also to their spot sizes. A brief description of beam-beam deflection theory forms the basis for a discussion of this phenomenon as a tool for single-beam tuning and for luminosity optimization at the interaction point of the SLC.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28771/1/0000603.pd
A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in
neutral B meson decays collected with the BABAR detector at the PEP-II
asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data
sample consists of 29.7 recorded at the
resonance and 3.9 off-resonance. One of the neutral B mesons,
which are produced in pairs at the , is fully reconstructed in
the CP decay modes , , , () and , or in flavor-eigenstate
modes involving and (). The flavor of the other neutral B meson is tagged at the time of
its decay, mainly with the charge of identified leptons and kaons. The proper
time elapsed between the decays is determined by measuring the distance between
the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample
finds . The value of the asymmetry amplitude is determined from
a simultaneous maximum-likelihood fit to the time-difference distribution of
the flavor-eigenstate sample and about 642 tagged decays in the
CP-eigenstate modes. We find , demonstrating that CP violation exists in the neutral B meson
system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
Measurement of the Branching Fraction for B- --> D0 K*-
We present a measurement of the branching fraction for the decay B- --> D0
K*- using a sample of approximately 86 million BBbar pairs collected by the
BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is
detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the
K*- through its decay to K0S pi-. We measure the branching fraction to be
B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid
Communications
Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays
We present measurements of the branching fractions for the three-body decays
B0 -> D(*)-/+ K0 pi^+/-B0 -> D(*)-/+ K*+/- using
a sample of approximately 88 million BBbar pairs collected by the BABAR
detector at the PEP-II asymmetric energy storage ring.
We measure:
B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4}
B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4}
B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4}
B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4}
From these measurements we determine the fractions of resonant events to be :
f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) =
0.72 +/- 0.14(stat) +/- 0.05(syst)Comment: 7 pages, 3 figures submitted to Phys. Rev. Let
Evidence for the Rare Decay B -> K*ll and Measurement of the B -> Kll Branching Fraction
We present evidence for the flavor-changing neutral current decay and a measurement of the branching fraction for the related
process , where is either an or
pair. These decays are highly suppressed in the Standard Model,
and they are sensitive to contributions from new particles in the intermediate
state. The data sample comprises
decays collected with the Babar detector at the PEP-II storage ring.
Averaging over isospin and lepton flavor, we obtain the branching
fractions and , where the
uncertainties are statistical and systematic, respectively. The significance of
the signal is over , while for it is .Comment: 7 pages, 2 postscript figues, submitted to Phys. Rev. Let
Measurement of the quasi-elastic axial vector mass in neutrino-oxygen interactions
The weak nucleon axial-vector form factor for quasi-elastic interactions is
determined using neutrino interaction data from the K2K Scintillating Fiber
detector in the neutrino beam at KEK. More than 12,000 events are analyzed, of
which half are charged-current quasi-elastic interactions nu-mu n to mu- p
occurring primarily in oxygen nuclei. We use a relativistic Fermi gas model for
oxygen and assume the form factor is approximately a dipole with one parameter,
the axial vector mass M_A, and fit to the shape of the distribution of the
square of the momentum transfer from the nucleon to the nucleus. Our best fit
result for M_A = 1.20 \pm 0.12 GeV. Furthermore, this analysis includes updated
vector form factors from recent electron scattering experiments and a
discussion of the effects of the nucleon momentum on the shape of the fitted
distributions.Comment: 14 pages, 10 figures, 6 table
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