Observation of Exclusive Dijet Production at the Fermilab Tevatron p-pbar Collider Page: 22 of 27
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------- Exclusive DPE (DPEMC)
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Idet,2< 2.5
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Jet E-r' (GeV)FIG. 20: Exclusive dijet cross sections for events with two
jets of ETCt > 10 GeV plotted vs. the minimum ET t of the
two jets in the kinematic range denoted in the figures: (a)
total exclusive cross sections compared with ExHuME and
ExcLDPE predictions; (b) exclusive cross sections for events
with Ryy > 0.8 compared with ExHuME (solid curve) and
with the LO analytical calculation from Ref. [40] scaled down
by a factor of three (dashed lines - the shaded area represents
uncertainties in the calculation due to hadronization effects);
and (c) the ratio of total exclusive to inclusive DPE cross
sections.The predicted exclusive qq-dijet suppression offers the
opportunity of searching for an exclusive signal in IDPE
data by comparing the inclusive dijet R4 shape with
that of data containing identified qq dijets. This method,
which avoids the use of a MC simulation, can be used
to corroborate the MC-based extraction of the exclusive
signal. To ensure quark origin, we select jets from heavy
flavor (HF) b- or c-quarks, identified from secondary ver-
tices produced from the decay of intermediate B or D
mesons using the SVX II detector. Both b- and c-quark
jets are used, since the suppression mechanism holds for
all quark flavors.
A. Data sample and event selection
The data used in this analysis were collected at a full
rate (no pre-scaling) with a trigger satisfying the same re-
quirements as the DPE trigger, Jet5+RPS+BSC1P, plus
an additional one designed to enhance the HF jet content.
The latter required the presence of at least one track with
transverse momentum pT > 2 GeV/c displaced from the
IP by a distance d of 0.1 < d < 1.0 mm, where d is the
distance of closest approach of the track to the IP [44].
The total integrated luminosity of this data sample is
200 + 12 pb-1.
Jets are reconstructed using a CDF Run I based iter-
ative cone algorithm [45] with an i-4 cone of radius 0.4.
The SECVTX tagging algorithm is used to search for a
displaced secondary vertex due to a B or D meson de-
cay within a jet cone. This algorithm seeks tracks with
hits in the SVX II within the jet cone, and reconstructs
the secondary vertex from those which are significantly
displaced from the primary vertex. A jet is considered
SECVTX tagged if it has a secondary vertex consisting
of at least two (or three) such tracks with pT > 1 (0.5)
GeV/c. Events are further required to pass the IDPE
selection criteria listed in Eq. (7). This selected "pretag"
event sample contains 34 187 jets with at least two tracks
in the SVX II. Applying the SECVTX tagging algorithm
to the jets in the pretag sample yields 1,118 tagged jets
with ETCt > 10 GeV and tJefl < 1.5.
B. Heavy flavor selection efficiencies
A SECVTX tag in a jet without a HF quark is labeled
as a "mistag." The mistag probability per jet, measured
from inclusive jet data, is parameterized as a function of
the number of tracks, ET, i, and 4 of the jet, and the
sum over the ET values of all jets with EfTt > 10 GeV
and if54t < 2.4 in the event. The mistag background in
tagged jets is estimated by weighting each jet in the pre-
tag sample by the mistag probability and summing up
the weights over all jets in the sample. The total num-
ber of mistag jets, Nmistag, is measured to be 104 + 15.
This number is consistent with a background estimate
obtained from studies of the distribution of the invariant
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Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M. G.; Gonzalez, B.Alvarez; Amerio, S. et al. Observation of Exclusive Dijet Production at the Fermilab Tevatron p-pbar Collider, article, December 1, 2007; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc902230/m1/22/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.