Generalized Gluon Currents and Applications in QCD

We consider the process containing two quark lines and an arbitrary number of gluons in a spinor helicity framework. A current with two off-shell gluons appears in the amplitude. We first study this modified gluon current using recursion relations. The recursion relation for the modified gluon current is solved for the case of like-helicity gluons. We apply the modified gluon current to compute the amplitude for $q \bar q \rightarrow q \bar q gg \cdots g$ in the like-helicity gluon case.Comment: 80 pages, 2 figures (appended in pictex), CLNS 91/112

Multiphoton Production at High Energies in the Standard Model I

We examine multiphoton production in the electroweak sector of the Standard Model in the high energy limit using the equivalence theorem in combination with spinor helicity techniques. We obtain recursion relations for currents consisting of a charged scalar, spinor, or vector line that radiates $n$ photons. Closed form solutions to these recursion relations for arbitrary $n$ are presented for the cases of like-helicity and one unlike-helicity photon production. We apply the currents singly and in pairs to obtain amplitudes for processes involving the production of $n$ photons with up to two unlike helicities from a pair of charged particles. The replacement of one or more photons by transversely polarized $$Z$-bosons is also discussed.Comment: 75 pages, CLNS 91/111

Weyl-van-der-Waerden formalism for helicity amplitudes of massive particles

The Weyl-van-der-Waerden spinor technique for calculating helicity amplitudes of massive and massless particles is presented in a form that is particularly well suited to a direct implementation in computer algebra. Moreover, we explain how to exploit discrete symmetries and how to avoid unphysical poles in amplitudes in practice. The efficiency of the formalism is demonstrated by giving explicit compact results for the helicity amplitudes of the processes gamma gamma -> f fbar, f fbar -> gamma gamma gamma, mu^- mu^+ -> f fbar gamma.Comment: 24 pages, late

The Analysis of Multijet Events Produced at High Energy Hadron Colliders

We define and discuss a set of (4N - 4) parameters that can be used to analyse events in which N jets have been produced in high energy hadron-hadron collisions. These multijet variables are the multijet mass and (4N - 5) independent dimensionless parameters. To illustrate the use of the variables QCD predictions are presented for events with up to five jets produced at the Fermilab Tevatron Proton-Antiproton Collider. These QCD predictions are compared with the predictions of a model in which multijet events uniformly populate the N-body phase-space

Charge asymmetry in hadroproduction of heavy quarks

A sizeable difference in the differential production cross section of top and antitop quarks, respectively, is predicted for hadronically produced heavy quarks. It is of order $\alpha_s$ and arises from the interference between charge odd and even amplitudes respectively. For the TEVATRON it amounts to approximately 5-10% in the region where the cross section is large and could therefore be measured in the next round of experiments. At the LHC the asymmetry can be studied by selecting appropriately chosen kinematical regions.Comment: LaTeX, 5pp, 5 figures, uses revtex. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/ Final version as published in Phys.Rev.Let

Detection of Neutral MSSM Higgs Bosons at LEP-II and NLC

We study the possibility of detecting the neutral Higgs bosons predicted in the Minimal Supersymmetric Standard Model (h0, H0, A0), with the reactions e+ e- --> b b h0 (H0, A0), using the helicity formalism. We analyze the region of parameter space (m_A0-tan beta) where h0(H0, A0) could be detected in the limit when tan beta is large. The numerical computation is done for the energy which is expected to be available at LEP-II (sqrt{s} = 200 GeV) and for a possible Next Linear e+ e- Collider (sqrt{s}=500 GeV).Comment: To be published in Phys.Rev.

Multiphoton Production at High Energies in the Standard Model II

We examine multiphoton production in the electroweak sector of the Standard Model in the high energy limit using the equivalence theorem in combination with spinor helicity techniques. We utilize currents consisting of a charged scalar, spinor, or vector line that radiates $n$ photons. Only one end of the charged line is off shell in these currents, which are known for the cases of like-helicity and one unlike-helicity photons. We obtain a wide variety of helicity amplitudes for processes involving two pairs of charged particles by considering combinations of four currents. We examine the situation with respect to currents which have both ends of the charged line off-shell, and present solutions for the case of like-helicity photons. These new currents may be combined with two of the original currents to produce additional amplitudes involving Higgs, longitudinal $Z$ or neutrino pairs.Comment: 73 pages, 2 figures (appended in pictex), CLNS 92/115

Amplitudes With Different Helicity Configurations Of Noncommutative QED

The amplitudes of purely photonic and photon{2-fermion processes of non- commutative QED (NCQED) are derived for different helicity configurations of photons. The basic ingredient is the NCQED counterpart of Yang-Mills recursion relations by means of Berends and Giele. The explicit solutions of recursion relations for NCQED photonic processes with special helicity configurations are presented.Comment: 23 pages, 2 figure

Quantum Corrections to the Reissner-Nordstrom and Kerr-Newman Metrics: Spin 1

A previous evaluation of one-photon loop corrections to the energy-momentum tensor has been extended to particles with unit spin and speculations are presented concerning general properties of such forms.Comment: 21 pages, 1 Figur

Special case of sunset: reduction and epsilon-expansion

We consider two loop sunset diagrams with two mass scales m and M at the threshold and pseudotreshold that cannot be treated by earlier published formula. The complete reduction to master integrals is given. The master integrals are evaluated as series in ratio m/M and in epsilon with the help of differential equation method. The rules of asymptotic expansion in the case when q^2 is at the (pseudo)threshold are given.Comment: LaTeX, 13 pages, 1 figur