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Title	A search for B_S0 oscillations at the Tevatron collider experiment D0
Creator/Author	Krop, Dan N. ; /Indiana U.
Publication Date	2007 Apr 01
OSTI Identifier	OSTI ID: 918719
Report Number(s)	FERMILAB-THESIS-2007-23
DOE Contract Number	AC02-76CH03000
Other Number(s)	TRN: US200819%%424
Resource Type	Thesis/Dissertation
Research Org	Fermi National Accelerator Laboratory (FNAL), Batavia, IL
Sponsoring Org	USDOE
Subject	72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; B MESONS; CERN; DECAY; EFFICIENCY; FERMILAB TEVATRON; HADRONS; MESONS; OSCILLATIONS; PERFORMANCE; PRODUCTION; SENSITIVITY
Related Subject	Experiment-HEP
Description/Abstract	We present a search for B{sub S}{sup 0} oscillations using semileptonic B{sub S} {yields} D{sub s}{mu}X (D{sub S} {yields} K{sub S}{sup 0}K). The data were collected using the D0 detector from events produced in {radical}s = 1.96 TeV proton-antiproton collisions at the Fermilab Tevatron. The Tevatron is currently the only place in the world that produces B{sub S}{sup 0} mesons and will be until early 2008 when the Large Hadron Collider begins operating at CERN. One of the vital ingredients for the search for B s oscillations is the determination of the flavor of the B{sub S}{sup 0} candidate (B{sub S}{sup 0} or {bar B}{sub S}{sup 0} ) at the time of its production, called initial state flavor tagging. We develop an likelihood based initial state flavor tagger that uses objects on the side of the event opposite to the reconstructed B meson candidate. To improve the performance of this flavor tagger, we have made it multidimensional so that it takes correlations between discriminants into account. This tagging is then certified by applying it to sample of semimuonic B{sup (0,+)} decays and measuring the well-known oscillation frequency {delta}m{sub d}. We obtain {delta}m{sub d} = 0.486 {+-} 0.021 ps{sup -1}, consistent with the world average. The tagging performance is characterized by the effective efficiency, {epsilon}D{sup 2} = (1.90 {+-} 0.41)%. We then turn to the search for B{sub S}{sup 0} oscillations in the above-named channel. A special two-dimensional mass fitting procedure is developed to separate kinematic reflections from signal events. Using this mass fitting procedure in an unbinned likelihood framework, we obtain a 95% C.L. of {Delta}m{sub s} > 1.10 ps{sup -1} and a sensitivity of 1.92 ps-1. This result is combined with other analyzed B{sub S}{sup 0} decay channels at D0 to obtain a combined 95% C.L. of {Delta}m{sub s} > 14.9 ps-1 and a sensitivity of 16.5 ps-1. The corresponding log likelihood scan has a preferred value of {Delta}m{sub s} = 19 ps-1 with a 90% confidence level interval of 17 < {Delta}ms < 21 ps-1, assuming Gaussian uncertainties. A comparison of the change in the likelihood between {Delta}m{sub s}s = 19 ps-1 and {Delta}m{sub s} = {infinity} yields an 8% expectation for a background fluctuation.
Country of Publication	United States
Language	English
Format	Size: 227 pages
System Entry Date	2008 Oct 06
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