Search for chargino and neutralino associated production at the Tevatron Page: 4 of 5
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Search for chargino and neutralino
with an electron, a tau decaying hadronically, and a third lepton (e+thad+f); final states with a
muon, a tau decaying hadronically and a third lepton (y+thad+f); final states with two electrons
and a third lepton (e+e+f); final states with an electron a muon and a third lepton (e++f); final
states with two muons and a third lepton ( ++f); final states with two like sign muons (LS
[+[). Events are selected with large )T and two isolated leptons satisfying analysis dependent
selection criteria. The analysis containing electrons and muons are described in detail in [6]. DO
has also implemented an analysis focused on the detection of taus decaying hadronically in the
final state. The tau leptons are identified by a neural net algorithm which was developed using
Z->z decays. To maintain the highest possible efficiency the third lepton in all of the six
analyses is reconstructed as an isolated track. The isolation conditions for the third track have
been designed to be efficient for all lepton flavors, including hadronic tau decay. The dominant
SM background sources are dibosons and QCD production.Table I shows the number of events
observed in data and the number of
background events expected from
Monte Carlo for the six analyses. The
number of expected signal events for
the m-SUGRA point
m0 =102GeV/c2, m_ =98GeV/c2
X2 x-
mR =99GeV/c2, tang=3, p>O and
LR
Ao=O is also reported in Table 1. The
analyses use 320 pb-' of data. The MC
has been generated using the CTEQ5L
parton distribution functions [8]. The
values of axBF are calculated with
CTEQ6L1 at leading order and
multiplied with the next to leading
order QCD k-factors taken from
[5].The PDF uncertainty of -3.7% to -
4.2% is taken into account in deriving
limits on the chargino mass.
To avoid double-counting, a
signal selected by more than one
analysis channel is assigned to
one channel and removed from
the other channels in a way which
maximizes the combined
sensitivity. No evidence for SUSY
has been found. The results are
combined to extract limits on the
total cross section using the
likelihood ratio method (LEP CLs
method [7]).Analysis Data Background Expected
Signal
e+e+L 0 0.21 0.11 0.05 3.19 0.14 0.26
e+p+l 0 0.31 0.13 0.03 2.17 0.07 0.17
p+p+/ 2 1.75 0.37 0.4 1.41 0.04 0.18
LS p+p 2 0.64 0.36 0.13 1.03 0.19 0.16
e+tu+L 0 0.58 0.11 0.09 1.02 0.04 0.08
++l 1 0.36 0.12 0.06 0.65 0.02 0.05
SUM 4 3.85 0.57 0.49 9.47 0.50 0.90
Table 1: Number of observed events, SM
background and signal events expected in 320 pb-1
of data for the DO trilepton analyses.a
O.6
0.5
C]
6 %0.4
b0.3
0.2Search for Z1 2 31+X D0, 320 pb
mfsmi-1pwlli~m,"n1MI;JPreliminary-
111t3- 3, p n 0, no slipon mling
- bsredLmiI
-Expected Limit -
...lar e-"...100 10 11 115 12 125 130 13 40
Charging Mass (GeV)
Figure 2: DO combined limit on axBR for pp -> _ "2
3/+ ET as a function of m z for 3 mSUGRA models.
2 i4
Daniela Bortoletto
0.1
i
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Bortoletto, Daniela. Search for chargino and neutralino associated production at the Tevatron, article, December 1, 2005; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc879027/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.