9 research outputs found
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Long-range wakefields and split-tune lattice at the SLC
At the SLC, a train consisting of one positron bunch followed by two electron bunches is accelerated in the linac, each separated by about 60 ns. Long-range transverse wakefields from the leading bunch were found to cause up to a factor of three increase in beam jitter for the trailing bunches. Incoming jitter is efficiently damped by BNS damping, but excitations in the middle of the linac from sources such as long-range wakefields can grow in amplitude. To measure the wake function, the time difference between the positron and electron bunches was changed, determining the frequency and strength of the dominant mode contributing to the dipole Wakefield. By splitting the horizontal and vertical phase advance, or {open_quote}tune{close_quote}, of the magnetic lattice, it was possible to decrease the resonant excitation from these wakefields and thereby reduce the jitter of the electron beam by a factor of two
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Measurement of the b{ovr b} Fraction in Hadronic Z{sup 0} Decays with Precision Vertex Detectors
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Search for Nonminimal Neutral Bosons from Z-Boson Decays
Using the Mark II detector at the SLAC Linear Collider, we search for decays of the Z boson to a pair of nonminimal Higgs bosons (ZHs0Hp0), where one of them is relatively light (10 GeV). We find no evidence for these decays and we obtain limits on the ZHs0Hp0 coupling as a function of the Higgs-boson masses. © 1990 The American Physical Society
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Measurement of the charged multiplicity of events containing bottom hadrons at Ec.m.=91 GeV.
Using an impact-parameter tag to select an enriched sample of Z0bb» events, we have measured the difference between the average charged multiplicity of bb» and all hadronic Z0 decays to be 2.11.8(stat) 0.6(syst) tracks per event. The resulting total (nonleading) charged multiplicity for Z0 bb» events is 23.1(12.0)1.8 0.6 tracks. A comparison of this nonleading multiplicity to hadronic multiplicity data in the range of 10 to 60 GeV supports the hypothesis of flavor-independent hadronic fragmentation, and yields a measurement of the average energy fraction of bottom hadrons in Z0 decays of xEb=0.620.100.04. © 1992 The American Physical Society
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A Search for Decays of the Z to Unstable Neutral Leptons with Mass between 2.5 and 22 GeV
Using the sample of neutral vector bosons (Z's) produced at the SLAC Linear Collider and detected with the Mark II detector, we search for the decay of the Z to a pair of particles, one of which decays to two charged particles. The observed number of Z decays with this signature excludes, at a confidence level greater than 95%, the decay of the Z to a pair of fourth-generation Dirac neutrinos with mass between 2.5 and 22 GeV, a decay length less than about 1 cm, and coupling to any of the first three generations of charged leptons. This is the first time the existence of such a lepton coupling to the ± has been excluded by a direct search. © 1990 The American Physical Society