Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 0707.3342

Automated calculations for multi-leg processes

Stefan Weinzierl
View original source ↗Read source document ↗Export metadata ↓

Abstract

The search for signals of new physics at the forthcoming LHC experiments involves the analysis of final states characterised by a high number of hadronic jets or identified particles. Precise theoretical predictions for these processes require the computation of scattering amplitudes with a large number of external particles and beyond leading order in perturbation theory. The complexity of a calculation grows with the number of internal loops as well as with the number of external legs. Automatisation of at least next-to-leading order calculations for LHC processes is therefore a timely task. I will discuss various approaches.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Stefan Weinzierl. 2007-07-26. Automated calculations for multi-leg processes. https://arxiv.org/abs/0707.3342

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Extra-dimensional Origins of Chemical Potentials at the Cosmological Collider

We study the realization of the chemical potential mechanism in cosmological collider physics in a robust class of inflationary models arising from multiple higher-dimensional gauge fields. The rolling inflaton background corresponds to an electric field in the extra dimension in which charged particles are produced analogously to the Schwinger mechanism, while neutral particles can be produced through non-minimal interactions. We show that particles heavier than the inflationary Hubble scale can be created without Boltzmann suppression in both cases. In particular, charged Kaluza-Klein excitations can be created through minimal gauge interactions. We construct realistic models along these lines consistent with both theoretical and experimental constraints.

hep-ph↗
arXiv2026

A Chiral Nelson-Barr Relaxion

We present the chiral Nelson-Barr relaxion model, an extension of the Nelson-Barr relaxion framework with a gauged chiral $\mathrm{U}(1)$ symmetry. It includes vector-like quarks to cancel gauge anomalies and a scalar whose vacuum expectation value generates their masses. The chiral symmetry forbids the leading operators responsible for the Nelson-Barr and clockwork quality problems. Right-handed neutrinos generate light-neutrino masses through the type-I seesaw mechanism and permit thermal leptogenesis. For the particular coupling considered, relaxion phenomenology gives $f_{\mathrm{max}}^{\mathrm{pheno}}\sim 4\times 10^{11}\ \mathrm{GeV}$, about eight times the corresponding phenomenological ceiling in the original model. The model can accommodate thermal leptogenesis if its right-handed-neutrino masses and reheating history satisfy the required temperature bounds.

hep-ph↗
arXiv2026

Coupled-channel extension of the effective-range expansion with left-hand cut

We generalize the recently proposed effective-range expansion with a left-hand cut [Phys. Rev. Lett. 135, 011903 (2025)] to a coupled-channel framework. By systematically analyzing the singularity structure of the $S$-wave coupled-channel one-particle exchange (OPE) potential under various mass configurations, we derive an analytical parametrization of the coupled-channel scattering amplitude that incorporates the OPE left-hand cut for multiple channels. Taking the two-channel case as an illustration, we benchmark this parametrization against the Lippmann--Schwinger equation (LSE) by comparing the amplitudes and their inverses at different expansion orders. Even at the lowest order, with only six parameters, the coupled-channel parametrization faithfully reproduces the LSE results and enables precise extraction of the coupling constants, demonstrating its reliability for two-body coupled-channel scattering problems involving particle exchange.

hep-ph↗