| Paper |
Title |
Page |
| TPAT076 |
Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e± Bunch-Length Determination
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3973 |
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- B.F. Viaud
Montreal University, Montreal, Quebec
- W. Kozanecki
CEA/DSM/DAPNIA, Gif-sur-Yvette
- I.V. Narsky
CALTECH, Pasadena, California
- C. O'Grady, A. Perazzo
SLAC, Menlo Park, California
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The three-dimensional luminosity distribution at the interaction point (IP) of the SLAC B-Factory is measured continuously, using e+e- –> e+e- and e+e –> mu+mu- events reconstructed online in the silicon tracker of the BaBar detector. The centroid of the transverse luminosity profile provides a very precise and reliable monitor of medium- and long-term orbit drifts at the IP. The longitudinal centroid is sensitive to variations in the relative RF phase of the colliding beams, both over time and differentially along the bunch train. The measured horizontal r.m.s. width of the distribution is consistent with a sizeable dynamic-beta effect; it is also useful as a benchmark of strong-strong beam-beam simulations. The longitudinal luminosity distribution depends on the e± bunch lengths and vertical IP beta-functions, which can be different in the high- and low-energy rings. Using independent estimates of the beta-functions, we analyze the longitudinal shape of the luminosity distribution in the presence of controlled variations in accelerating RF voltage and/or beam current, to extract separate measurements of the e+ and e- bunch lengths.
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| TPPP024 |
Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider
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1874 |
| |
- W. Kozanecki
CEA/DSM/DAPNIA, Gif-sur-Yvette
- Y. Cai, J. Seeman, M.K. Sullivan
SLAC, Menlo Park, California
- I.V. Narsky
CALTECH, Pasadena, California
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In a series of dedicated accelerator experiments, we have measured the dependence of the PEP-II luminosity performance on small horizontal crossing angles and on the horizontal separation at the first parasitic crossing. The experiment was carried out by varying the IP angle of one of the beams in two different bunch patterns, one with and one without parasitic crossings. The experimental measurements show satisfactory agreement with three-dimensional beam-beam simulations.
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