Results for the Summer 2000 conferences

XXXth International Conference on High Energy Physics, July 27 - August 2, 2000, Osaka, Japan (ICHEP 2000)


The following material is available publicly:

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Summary of b-hadron fractions and oscillation averages

The fractions below are for an unbiased sample of weakly decaying b-hadrons produced at high energy. These fractions are assumed to be the same in Z decays or in proton-antiproton collisions at sqrt(s)=1.8 TeV. They have been obtained by combining direct rate measurements from LEP and CDF with all available mixing measurements from ALEPH, CDF, DELPHI, L3, OPAL, SLD as well as from ARGUS and CLEO. The B+ and B0 mesons are assumed to be produced in equal amount, the Bc production is neglected and the sum of the fractions is constrained to unity.

b hadron species fraction correlation with f(Bs) correlation with f(b-baryon)
Bs f(Bs) = 0.097 +- 0.012
b baryons f(b-baryon) = 0.104 +- 0.017 +0.006
B0 or B+ f(Bd) = f(Bu) = 0.400 +- 0.010 -0.583 -0.816


Combined result on B0 mixing, obtained separately from time-dependent measurements of the oscillation frequency dmd at high energy colliders and from time-integrated measurements of the mixing probability chid at Upsilon(4S) machines:

dmd = 0.486 +- 0.015 ps-1 from time-dependent measurements at ALEPH, CDF, DELPHI, L3, OPAL, SLD
chid = 0.182 +- 0.015 from time-integrated measurements at ARGUS and CLEO


Assuming no CP violation in the mixing and no width difference in the B0 system, all above measurements can be combined to yield the following world averages:

dmd = 0.487 +- 0.014 ps-1 from all ALEPH, CDF, DELPHI, L3, OPAL, SLD, ARGUS and CLEO measurements
chid = 0.181 +- 0.007 from all ALEPH, CDF, DELPHI, L3, OPAL, SLD, ARGUS and CLEO measurements


Combined results on Bs oscillations:

dms > 14.9 ps-1 at 95% CL from all ALEPH, CDF, DELPHI, OPAL and SLD studies with a combined 95% CL sensitivity of 17.9 ps-1


The above limit corresponds to xs > 21.1 at 95% CL. Assuming no CP violation in the mixing and no width difference in the Bs system, this also corresponds to chis > 0.49888 at 95% CL.

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Plot of dmd measurements and their averages


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Same without average including Upsilon(4S) data:
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Only LEP measurements and average:
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Plot of dmd averages per experiment


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Plot of combined Bs oscillation amplitude vs dms


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Same, but using only LEP data:
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Plot of Bs oscillation amplitude measurements and their average


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Same, but at a different value of dms:
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Author: OS
Latest mod. 24-Jun-2000