Bootstrapping multiparton loop amplitudes in QCD

We present a new method for computing complete one-loop amplitudes, including their rational parts, in nonsupersymmetric gauge theory. This method merges the unitarity method with on-shell recursion relations. It systematizes a unitarity-factorization bootstrap approach previously applied by the authors to the one-loop amplitudes required for next-to-leading order QCD corrections to the processes e^+e^-, ^*4 jets and pp+2 jets. We illustrate the method by reproducing the one-loop color-ordered five-gluon helicity amplitudes in QCD that interfere with the tree amplitude, namely A₅;₁ (1^-, 2^-, 3^+, 4^+, 5^+) and A₅;₁ (1^-, 2^+, 3^-, 4^+, 5^+). Then we describe the construction of the six- and seven-gluon amplitudes with two adjacent negative-helicity gluons, A₆;₁ (1^-, 2^-, 3^+, 4^+, 5^+, 6^+) and A₇;₁ (1^-, 2^-, 3^+, 4^+, 5^+, 6^+, 7^+), which uses the previously-computed logarithmic parts of the amplitudes as input. We present a compact expression for the six-gluon amplitude. No loop integrals are required to obtain the rational parts.