A bstract In the limit where partons become collinear to each other, scattering amplitudes factorize into a product of universal, process-independent building blocks and involving fewer partons. We compute these universal — known as splitting for two QCD up third loop order in QCD. Our results describe arbitrary time-like processes. Due violation strict factorization space-like processes, we specifically present three-parton at order. To achieve our results, perform expansion three-loop...

A bstract The method of regions is an approach for developing asymptotic expansions Feynman Integrals. We focus on in Euclidean signature, where the can also be formulated as expansion by subgraph. show that such valid around small/large masses and momenta graph combinatorial operations terms what we call Hopf algebra. This algebra closely related to motic underlying R ∗ operation, extension Bogoliubov’s subtract both IR UV divergences integrals Euclidean. mostly leading power, which...

A bstract Parametric representations of Feynman integrals have a key property: many, frequently all, the Landau singularities appear as endpoint divergences. This leads to geometric interpretation faces Newton polytopes, which facilitates algorithmic evaluation by sector decomposition and asymptotic expansion method regions. Here we identify cases where some instead pinches in parametric space for general kinematics, then extend applicability regions algorithms such integrals, dissecting...

A bstract Parton evolution equations in QCD are controlled by the anomalous dimensions of gauge-invariant twist-two spin- N quark and gluon operators. Under renormalization, these mix with gauge-variant operators same quantum numbers, referred to as alien Our work addresses systematic study at arbitrary spin , using generalized BRST symmetry relations derive their couplings Feynman rules all values . We observe how all- structure (anti-)BRST constraints relates n + 1 gluons those gluons....

A bstract We present an efficient graphical approach to construct projectors for the tensor reduction of multi-loop Feynman integrals with both Lorentz and spinor indices in D dimensions. An ansatz is constructed making use its symmetry properties via orbit partition formula. The allows identify enumerate orbits each case. For case without we find a 1 correspondence between integer partitions describing cycle structure certain bi-chord graphs. This leads compact combinatorial formulae...

(i) Large-transverse-momentum $\stackrel{-}{p}p$ events at $\sqrt{s}=540$ GeV are dominated by two-jet production; the cross section is compatible with predictions of perturbative QCD. (ii) Large-${p}_{T}$ jets rich in charm particles. We investigate implications these experimental observations. find a source heavy quarks and associated prompt leptons which could totally dominate yields conventionally computed from QCD which, more importantly, leads to different event characteristics. For...

We study the polarization amplitudes for production of a weak boson ($W$) and photon from quark-antiquark annihilation in standard model minimally extended by giving $W$ an arbitrary anomalous magnetic moment $\ensuremath{\kappa}$. find that c.m. frame amplitude where is longitudinal transverse to scattering plane shows unique behavior: When we neglect $W$-boson width this vanishes identically all angles if $\ensuremath{\kappa}$ put equal its gauge-theory value, $\ensuremath{\kappa}=1$, but...