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Measurement of Upsilon (1S) Production at BaBar

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Title: Measurement of Upsilon (1S) Production at BaBar
Author: So, Rocky Yat Cheung
Subject Keywords Upsilon 1S;Upsilon 4S;Bottomonium;anti-bottom quark;anti-B meson;B meson;quarkonia;muon;Monte Carlo;muon pairs
Issue Date: 2008-05
Publicly Available in cIRcle 2008-05-21
Citation: So, Rocky Yat Cheung. 2008. Measurement of Upsilon (1S) Production at BABAR - Inclusive Measurement at the Upsilon (4S). Undergraduate Honours Thesis. Department of Physics and Astronomy. University of British Columbia.
Series/Report no. Undergraduate Honours Theses
Abstract: BABAR is a particle physics experiment at the Stanford Linear Accelerator Center (SLAC). The purpose of BABAR is to study matter-antimatter asymmetry in the bottom quark system. At SLAC, electons and positrons collide, which annihilate and decay into a variety of daughters. An Upsilon(4S) meson is one of the possible daughters. An Upsilon(4S) decays into a B meson and an anti-B meson more than 96% of the time. A B meson has an anti-bottom quark and an anti-B meson has a bottom quark. The purpose of this thesis is to measure how many Upsilon(1S) originated from Upsilon(4S) in the entire BABAR data set. This thesis compares on-peak data and off-peak data. On-peak data was taken at center of mass energy 10.58GeV. One of the possible interactions is e+e− -> Upsilon(4S) since the mass of Upsilon(4S) is 10.58GeV/c^2. On-peak data, taken at center of mass energy 10.54GeV, is not enough to have any BB pairs because 10.54GeV is less than the mass of an Upsilon(4S). This thesis can be useful for BABAR physicist because it helps set an upper limit on how many BB pairs there are in the entire BABAR data set. In other words, it sets an upper limit on how much more than 96% does Upsilon(4S) decay to BB. Measurement of the decay of Upsilon(4S) -> Upsilon(1S) + X give evidence for non-BB decays of the Upsilon(4S). The final results of this study show that there were (110 +- 3) × 10^5 Upsilon(1S) on-peak, of which (10 +- 9) × 10^5 originated from an Upsilon(4S). Increasing the centre of mass energy from 10.54GeV to 10.58GeV increases the Upsilon(1S) production by (10 +- 8)%.
Affiliation: Physics and Astronomy, Dept of
URI: http://hdl.handle.net/2429/840
Peer Review Status:

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