Measurements of top quark decay properties Page: 4 of 9
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f+ jets Dilepton
0 tags 1 tag 2 tags 0 tags 1 tag 2 tags
ExpectedSS+B 80.4 5.2 21.5 4.1 5.0 1.4 6.1 0.4 4.0 0.2 0.9 0.2
Observed 79 23 5 5 4 2
Table 1: Distribution of tagged events in 160pb-1 of CDF data.
for possible BR combinations
CDF Run II mH=120 GeV/c 2 J L dt = 192 pb-
00 0.1 0.2 0.3
Figure 2: 95% C.L. upper limits on BR(t
H+b) under various assumed H+ decay modes for a 120
to be 1.03+'1(stat. + syst.). Both values are consistent with standard model expectations, and
using a Bayesian method the lower limit on R is found to be 0.64 at 95% C.L.
Further details on the CDF measurement are available in Ref. , and the DO measurement is
described in Ref. .
In addition to the measurement of R, it is also important to search for evidence of t -> H+b,
which is allowed if there is a charged Higgs boson with mass less than that of the top quark. The
standard model does not require a charged Higgs boson, so observing such a decay would indicate
new physics. This is of particular interest because supersymmetry requires the existence of at least
one charged Higgs boson.
The existence of the H+b decay mode would alter the distribution of tt modes, typically sup-
pressing final states with electrons and or muons, and enhanching those with taus. Therefore sen-
sitivity to H+b decays requires the identification of 2 leptons, which appear in the detector as a
narrow jet of particles with a low multiplicity (typically one or three) of charged tracks.
The distribution of tt candidates in 192 pb-1 of CDF data is consistent with standard model
expectations, so there is no evidence of t -> H+b. The upper limit that this implies for the branch-
ing ratio to H + b depends upon both the H+ mass and decay branching ratios, which are model
dependent. The limits obtained for a range of H+ decay models for a 120 GeV H+ are presented
Measurements of top quark decay properties
Erich W. Varnes
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Varnes, Erich W. & U., /Arizona. Measurements of top quark decay properties, article, April 1, 2006; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc883225/m1/4/: accessed April 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.