6,219 research outputs found
Top quark pair production at small transverse momentum in hadronic collisions
We investigate the transverse momentum resummation for top quark pair
production at hadron colliders using the soft-collinear effective theory and
the heavy-quark effective theory. We derive the factorization formula for
production at small pair transverse momentum, and show in detail the
procedure for calculating the key ingredient of the factorization formula: the
next-to-leading order soft functions. We compare our numerical results with
experimental data and find that they are consistent within theoretical and
experimental uncertainties. To verify the correctness of our resummation
formula, we expand it to the next-to-leading order and the
next-to-next-to-leading order, and compare those expressions with the exact
fixed-order results numerically. Finally, using the results of transverse
momentum resummation, we discuss the transverse-momentum-dependent
forward-backward asymmetry at the Tevatron.Comment: 39 pages, 7 figures, 1 table; final version in PR
Efficient and convenient synthesis of symmetrical carboxylic anhydrides from carboxylic acids with sulfated zirconia by phase transfer catalysis
An efficient and convenient procedure for the synthesis of symmetrical carboxylic anhydrides from carboxylic acids with sulfated zirconia by PEG-1000 phase transfer catalysis has been developed. The reactions proceeded under mild and solvent-free conditions to provide the carboxylic anhydrides in good to excellent yields. The product can be isolated by a simple extraction with organic solvent, and the catalyst system can be recycled or reused without any significant loss of catalytic activity.KEY WORDS: Carboxylic anhydrides, Carboxylic acids, SO42-/ZrO2, Phase transfer catalysis Bull. Chem. Soc. Ethiop. 2011, 25(2), 255-262
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