The dijet mass spectrum with the D0 detector Page: 3 of 5
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The Dijet Mass Spectrum with the DO Detector
for the DO Collaboration
Seoul National University
151-742 Seoul, Korea
We present preliminary results from an analysis of dijet data collected
during the 1994-1995 Tevatron Collider run with an integrated luminos-
ity of 91 pb-. Measurements of dijet mass spectrum distributions in
pp collisions at f/ = 1.8 TeV are compared with next-to-leading order
Predictions for the inclusive jet cross section and hence the inclusive dijet cross
section have been made using next-to-leading order (NLO) QCD 3,2,3. These
O(a's3) calculations, which include the possibility of a third radiated parton,
reduce theoretical uncertainties to 10-20%. We measure the inclusive dijet
mass spectrum in the DO detector at the Fermilab Tevatron Collider at fi =
1.8 TeV. Such a measurement, when compared to NLO, constitutes a rigorous
test of QCD.
The data sample was collected during the 1994-95 data taking period
and corresponds to a luminosity of 91 pb-1. A complete description of the
data selection can be found elsewhere 4. For each event the dijet mass can be
calculated (assuming massless jets): M? = 2- ET - ET . (cosh(Aq) - cos(AO)),
where E and Ej are the transverse energies of the two leading Er jets,
7= - log(tan 6/2), where 6 is the angle from the direction of proton beam at
the vertex and 4 is the azimuthal angle. Cone size of R=0.7 is used. Each
event is weighted by the efficiency of the quality cuts applied to the data. The
data were collected using four triggers with ET thresholds of 30, 50, 85 and 115
GeV with integrated luminosities of 0.36, 4.6, 52 and 91 pb-1. These trigger
samples were used to measure the dijet mass spectrum above mass thresholds
of 200, 270, 370 and 500 GeV where each of the triggers is 100% efficient. The
relative normalizations of the four trigger sets is established by requiring equal
cross sections in the regions where two trigger sets overlap and are efficient.
The inclusive dijet mass cross sections are computed for two partially over-
lapping pseudorapidity ranges: I1I1,2 < 1.0, Ai < 1.6 (I1I,2 < 0.5). The final
observed cross section corrected for jet and event selection efficiency is shown
in Fig. 1. The combined systematic errors are also shown in Fig 1, ranging from
-13% at 200 GeV to -55% at 950 GeV. The systematic error is dominated
by the uncertainty due to the energy scale with smaller contributions due to
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Choi, S. The dijet mass spectrum with the D0 detector, report, September 1, 1996; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc679162/m1/3/: accessed December 11, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.