Measurement of the Double Differential Diject Mass Cross Section in Pp(bar) Collisions at Sqrt(s)
Measurement of the Double Differential Diject Mass Cross Section in Pp(bar) Collisions at Sqrt(s)

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Published: 2009

Total Pages: 176

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This thesis presents the analysis of the double differential dijet mass cross section, measured at the D0 detector in Batavia, IL, using p{bar p} collisions at a center of mass energy of (square root)s = 1.96 TeV. The dijet mass was calculated using the two highest p{sub T} jets in the event, with approximately 0.7 fb−1 of data collected between 2004 and 2005. The analysis was presented in bins of dijet mass (M{sub JJ}) and rapidity (y), and extends the measurement farther in M{sub JJ} and y than any previous measurement. Corrections due to detector effects were calculated using a Monte Carlo simulation and applied to data. The errors on the measurement consist of statistical and systematic errors, of which the Jet Energy Scale was the largest. The final result was compared to next-to-leading order theory and good agreement was found. These results may be used in the determination of the proton parton distribution functions and to set limits on new physics.

Measurement of Double-differential Cross Sections for Top Quark Pair Production in Pp Collisions at $\sqrt{s}$
Measurement of Double-differential Cross Sections for Top Quark Pair Production in Pp Collisions at $\sqrt{s}$

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Published: 2017

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Normalized double-differential cross sections for top quark pair (ttbar) production are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7 inverse femtobarns. The measurement is performed in the dilepton e+/- mu-/+ final state. The ttbar cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and ttbar system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured ttbar cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution.