Z. Bern

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  • Z Bern, L Dixon, D C Dunbar, M Perelstein, J S Rozowsky
  • 1998
String theory implies that field theories containing gravity are in a certain sense 'products' of gauge theories. We make this product structure explicit up to two loops for the relatively simple case of N = 8 supergravity four-point amplitudes, demonstrating that they are 'squares' of N = 4 super-Yang-Mills amplitudes. This is accomplished by obtaining an(More)
We show, for previously uncalculated examples containing a uniform mass in the loop, that it is possible to obtain complete massive one-loop gauge theory amplitudes solely from unitarity and known ultraviolet or infrared mass singularities. In particular, we calculate four-gluon scattering via massive quark loops in QCD. The contribution of a heavy quark to(More)
  • Z Bern, J S Rozowsky, B Yan
  • 1997
Using cutting techniques we obtain the two-loop N = 4 super-Yang-Mills helicity amplitudes for four-gluon scattering in terms of scalar integral functions. The N = 4 amplitudes are considerably simpler than corresponding QCD amplitudes and therefore provide a testing ground for exploring two-loop amplitudes. The amplitudes are constructed directly in terms(More)
We present the two-loop pure gauge contribution to the gluon-gluon scattering amplitude with maximal helicity violation. Our construction of the amplitude does not rely directly on Feynman diagrams, but instead uses its analytic properties in 4 − 2ǫ dimensions. We evaluate the loop integrals appearing in the amplitude through O(ǫ 0) in terms of(More)
  • Z Bern, L Dixon, A Ghinculov
  • 2000
We present the two-loop virtual QED corrections to e + e − → µ + µ − and Bhabha scattering in dimensional regularization. The results are expressed in terms of polylogarithms. The form of the infrared divergences agrees with previous expectations. These results are a crucial ingredient in the complete next-to-next-to-leading order QED corrections to these(More)
We present a definition of the four-dimensional helicity (FDH) regularization scheme valid for two or more loops. This scheme was previously defined and utilized at one loop. It amounts to a variation on the standard 't Hooft-Veltman scheme and is designed to be compatible with the use of helicity states for " observed " particles. It is similar to(More)
  • Z Bern, L Dixon, M Perelstein, J S Rozowsky
  • 1998
By exploiting relations between gravity and gauge theories, we present t w o innite sequences of one-loop n-graviton scattering amplitudes: thèmaximally helicity-violating' amplitudes in N = 8 supergravity, and thèall-plus' helicity amplitudes in gravity with any minimally coupled massless matter content. The all-plus amplitudes correspond to self-dual eld(More)
We present the next-to-leading order (NLO) QCD results for W+4-jet production at hadron colliders. This is the first hadron-collider process with five final-state objects to be computed at NLO. It represents an important background to many searches for new physics at the energy frontier. Total cross sections, as well as distributions in the jet transverse(More)
We review how (dimensionally regulated) scattering amplitudes in N = 4 super-Yang-Mills theory provide a useful testing ground for perturbative QCD calculations relevant to collider physics, as well as another avenue for investigating the AdS/CFT correspondence. We describe the iterative relation for two-loop scattering amplitudes in N = 4 super-Yang-Mills(More)
The anti-de Sitter/conformal field theory duality conjecture raises the question of how the perturbative expansion in the conformal field theory can resum to a simple function. We exhibit a relation between the one-loop and two-loop amplitudes whose generalization to higher-point and higher-loop amplitudes would answer this question. We also provide(More)