Direct Proof Of Tree-Level Recursion Relation In Yang-Mills Theory

Recently, by using the known structure of one-loop scattering amplitudes for gluons in Yang-Mills theory, a recursion relation for tree-level scattering amplitudes has been deduced. Here, we give a short and direct proof of this recursion relation based on properties of tree-level amplitudes only.Comment: 10 pp. Added section 4: Proof of MHV Recursion Relation

Helicity Amplitudes for Charmonium Production in Hadron-Hadron and Photon-Hadron Collisions

We present the gluon-gluon and photon-gluon helicity amplitudes for color singlet and octet charmonium production in polarized and unpolarized hadron-hadron and photon-hadron collisions.Comment: 11 pages amstex no figure

Closed-Form Decomposition of One-Loop Massive Amplitudes

We present formulas for the coefficients of 2-, 3-, 4- and 5-point master integrals for one-loop massive amplitudes. The coefficients are derived from unitarity cuts in D dimensions. The input parameters can be read off from any unitarity-cut integrand, as assembled from tree-level expressions, after simple algebraic manipulations. The formulas presented here are suitable for analytical as well as numerical evaluation. Their validity is confirmed in two known cases of helicity amplitudes contributing to gg -> gg and gg -> gH, where the masses of the Higgs and the fermion circulating in the loop are kept as free parameters.Comment: 37 page

Singular terms of helicity amplitudes at one-loop in QCD and the soft limit of the cross sections of multi-parton processes

We describe a general method that enables us to obtain all the singular terms of helicity amplitudes of n-parton processes at one loop. The algorithm uses helicity amplitudes at tree level and simple color algebra. We illustrate the method by calculating the singular part of the one loop helicity amplitudes of all $2\to 3$ parton subprocesses. The results are used to derive the soft gluon limit of the cross sections of all $2\to 4$ parton scattering subprocesses which provide a useful initial condition for the angular ordering approximation to coherent multiple soft gluon emission, incorporated in existing Monte Carlo simulation programs.Comment: Latex,13 pages, ETH-TH/94-

Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation

We propose measurements of the deeply virtual Compton amplitude (DVCS), gamma* to H H-bar gamma, in the timelike t = (p_{H} + p_{H-bar})^2 > 0 kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process e+ e- to H H-bar gamma. These processes allow the measurement of timelike deeply virtual Compton scattering for a variety of H H-bar hadron pairs such as pi+ pi-, K+ K-, and D D-bar as well as p p-bar. As in the conventional spacelike DVCS, there are interfering coherent amplitudes contributing to the timelike processes involving C= - form factors. The interference between the amplitudes measures the phase of the C=+ timelike DVCS amplitude relative to the phase of the timelike form factors and can be isolated by considering the forward-backward e+ \leftrightarrow e- asymmetry. The J=0 fixed pole contribution which arises from the local coupling of the two photons to the quark current plays a special role. As an example we present a simple model.Comment: 9 pages, 8 figures; v2 has improved kinematic discussio

Sphinx: Monte Carlo Program for Polarised Nucleon-Nucleon Collisions

This program can be used to simulate polarised nucleon - nucleon collisions at high energies. Spins of colliding particles are taken into account. The program allows to calculate cross sections for various processes.Comment: 33pp, LaTe

Higgs production at the large hadron collider: Phenomenological model and theoretical predictions

Using the results from relativistic gauge field theory, a phenomenological model is developed for the production of an isolated Higgs particle H. The specific process is p+p → A+H +B, where the group of particles A (B) mostly goes down one (the other) beam pipe. The theory and the phenomenology apply when the center-of-mass energy √s ≫ M ≫ m, with M and m the masses of the Higgs particle and the proton respectively. Thus, there are two large parameters, namely √s/M and M/m. That M ≫ m plays a central role. This phenomenological model is applied to the Large Hadron Collider (LHC) to predict the differential production cross sections. With high probability, this isolated Higgs particle is produced with a small transverse momentum of the order of 1 GeV/c. Because of this fact and the relatively small number of observed particles in such events, the method of data analysis is different from those developed so far for Higgs detection. These events can be described as due to Pomeron-Pomeron annihilation, and are ‘clean’ in the sense that those from TeV linear colliders are called ‘clean’. The LHC, with its center-of-mass design energy of 14 TeV and its design luminosity of 1034 cm−2s−1, can function exceptionally well as a Pomeron collider.Physic

Generalized gauge transformations: SU(2) Yang-Mills case

We consider generalized gauge transformations for SU(2) Yang-Mills theory involving products of field operators at different space-time points. The infinitesimal gauge transformations are explicitly constructed to third order in the coupling constant. Also the case of an SU(2) doublet in interaction with the Yang-Mills fields is worked out to third order