Sleuth at CDF: A Quasi-model-independent search for new electroweak scale physics Page: 3 of 4
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points within the MSSM and several flavors of Z', are
partitioned into SLEUTH final states according to the
objects reconstructed in these events, and are added
to pseudo data drawn from the Standard Model pre-
diction. SLEUTH is run "blind" on the resulting mix of
pseudo data and trace amounts of pseudo signal, not
knowing anything about the pseudo signal that has
been added. The amount of pseudo signal is gradually
increased until SLEUTH identifies a region of interest
corresponding to P < 0.001.
The models tested require a cross section of roughly
a few picobarns to reach SLEUTH's discovery threshold
in 927 pb-- of data. SLEUTH's sensitivity is found to
be comparable to that of targeted searches for models
that sufficiently satisfy the three assumptions on which
SLEUTH is based. SLEUTH's sensitivity to unspecified
new physics is in general significantly greater than any
specific targeted search, due to SLEUTH's noticeably
Specific Standard Model processes are also used to
examine SLEUTH's sensitivity. If the top quark were
unknown, its production at the Tevatron would have
been caught using SLEUTH. Observation of tt produc-
tion in 927 pb-- is shown in Fig. 1. An integrated
luminosity of roughly 80 pb-- would be required to
reach the SLEUTH discovery threshold, as shown in
Fig. 2. Standard Model WW production is also easily
observed. SLEUTH has more difficulty with single top
quark and Higgs boson production, which only par-
tially satisfy SLEUTH'S assumption that new physics
will appear at large Z PT relative to (other) Standard
In 927 pb-- of CDF Run II data, the most interest-
ing region is observed in the bb final state, shown in
Fig. 3. The fraction of pseudo experiments in this final
state alone that would produce a region more interest-
ing than the one observed is P 0.0055. Taking into
account the many final states considered, the fraction
of hypothetical similar CDF experiments that would
observe a final state with P < 0.0055 is P 0.46.
Unfortunately, with = 0.46 0.001, SLEUTH
has not indentified any final state containing a region
at large Z pT with a significant excess of data above
Standard Model prediction.
These proceedings have described SLEUTH, a quasi-
model-independent search algorithm designed to iden-
tify an excess of data above Standard Model predic-
tion at large summed scalar transverse momentum in
1 When comparing to the 67 pb-1 needed for discovery
in CDF Run I , differences such as the improved CDF II
detector should be kept in mind.
CDF Run II Preliminary (927 pb
S CDF RinhlIdata l0d
SPytdia 1 (SM,d)=(9540,9900)
u1 3500 0Pytnia b :18%
- Pytniayj:02% 10
mj 3000 Other
z 2500 10,
10 600 800 1000 1200
0400 500 600 700 800 900 1000 1100 1200 1300
469 - YP (GeV)
Fig. 3. The most interesting SLEUTH final state (bb). Filled
circles (black) show CDF Run II data; the (red) histogram
shows the standard model prediction, with jj standing for
two non-b generated partons, and bj for at least one gener-
ated b-quark. The horizontal axis shows the summed scalar
transverse momentum of all objects in each event in the his-
togram, with the number of events per 20 GeV bin shown
on the vertical axis. The region SLEUTH determines to be
most interesting is shown with the (blue) arrow to be the
region corresponding to -_PT > 469 GeV. A magnified
view of this region in logarithmic scale is shown in the in-
set, together with the number of events predicted (SM) and
the number of events observed (d). Taking into account the
trials factor associated with looking at many different re-
gions, SLEUTH determines the fraction of hypothetical sim-
ilar experiments that would produce something in this final
state as interesting as the region shown to be P = 0.0055
(number at upper right).
any final state. A specific definition of regions con-
sidered allows SLEUTH to rigorously calculate the tri-
als factor associated with looking in many different
places. Sensitivity tests performed indicate SLEUTH is
broadly comparable to targeted searches for specific
models adequately satisfying the three assumptions on
which it is based. SLEUTH is expected to be signifi-
cantly more sensitive to unspecified new physics than
any particular targeted search, due to SLEUTH'S no-
ticeably broader scope. Application of SLEUTH in as-
sociation with VISTA  to the first 927 pb-- of CDF
II data has unfortunately revealed no indication of new
physics. This analysis represents one of the most en-
compassing searches so far conducted for new physics
at the energy frontier.
This result does not prove that no new physics is
hiding in Tevatron data; merely that this particular
global analysis strategy has not yet revealed a discrep-
ancy on which a discovery claim can be based in the
927 pb so far analyzed. A global analysis of more
recently collected CDF data is in progress.
1. G. Choudalakis, companion (SUSY 07) proceedings.
2. DO collaboration, Phys. Rev. Lett. 86 (2001) 3712.
Sleuth at CDF
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Choudalakis, Georgios & /MIT, LNS. Sleuth at CDF: A Quasi-model-independent search for new electroweak scale physics, article, October 1, 2007; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc884223/m1/3/: accessed June 17, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.