Group Theory Factors for Feynman Diagrams

ScienceDirectNuclear Physics B 915 (2017) We observe that fermions charged under large groups acquire much bigger dynamical masses, all things being equal at a high e.g. GUT scale, than ordinary quarks. Should such multicharged fermions exist, they are too heavy to be observed today and have either decayed early on (if they couple to the rest of the Standard Model) or become reliquial dark matter (if they don't).The result follows from strong antiscreening of the running coupling for those larger groups (with an appropriately small number of flavors) together with scaling properties of the Dyson-Schwinger equation for the fermion mass.

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“…There are two classical groups for each odd N c and three classical ones for each even N c [39,38]. Fig.…”

Section: Appendix a Color Factorsmentioning

confidence: 99%

Spontaneous mass generation and the small dimensions of the Standard Model gauge groups U(1),SU(2) and SU(3)

Llanes-Estrada¹,

Fernández²,

Rojas³

2018

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2017)

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“…Johannes Blümlein below we used the codes QGRAF [30], Form and tform [31], and color [32]. For the check of individual moments of the expressions derived we also used MATAD [33].…”

Section: Three-loop Contributions To the Gluonic Massive Omesmentioning

confidence: 99%

Three-Loop Contributions to the Gluonic Massive Operator Matrix Elements at General Values of N

Bluemlein¹

2013

Proceedings of “Loops and Legs in Quantum Field Theory ” 11th DESY Workshop on Elementary Particle Physics — PoS(LL2012)

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“…These factors depend on data from the gauge group G, and we will give them as general as possible in the lines of [265,266].…”

Section: The Group Theoretic Backgroundmentioning

confidence: 99%

“…, g n ) from different multiplets clearly goes beyond SUSY. Based on spinor helicity methods [316,317,318] and color factor technology [265,266], we compute full fledged cross sections for parton collisions in superstring theory up to the five point level and cast the result into a form suitable for LHC data analysis.…”

Section: Chapter 14 Epiloguementioning

confidence: 99%

Scattering amplitudes in open superstring theory

Schlotterer

2011

Fortschritte der Physik

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This review is concerned with scattering amplitudes in open superstring theories. In particular, we introduce two different formalisms to compute tree level amplitudes – the Ramond Neveu Schwarz‐ (RNS‐) and the Pure Spinor (PS‐) formalism. The RNS approach proves to be flexible in describing compactifications from ten to four flat spacetime dimensions. We solve the technical problems due to the underlying interacting conformal field theory on the worldsheet. This is exploited to extract phenomenologically relevant scattering amplitudes of gluons and quarks as well as production‐ and decay rates of massive vibration modes which have already been identified as virtual exchange particles at the massless level. In case of a TeV string scale, string specific signatures in parton collisions might be observed at the LHC experiment in the near future and constitute the first experimental evidence for string theory. These statements apply to a wide class of string vacua and therefore bypass the so‐called landscape problem of string theory. The PS formalism allows for a manifestly supersymmetric treatment of scattering amplitudes in ten spacetime dimensions with sixteen supercharges. We introduce a family of superfields which arises in tree amplitudes of massless open string states and can be naturally identified with diagrams made of cubic vertices. We firstly achieve a compact superspace representation of multiparticle field theory amplitudes and moreover express the complete n point superstring amplitude as a minimal linear combination of partial field theory amplitudes and hypergeometric functions. The latter carry the stringy effects and are analyzed from different perspectives.

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Group Theory Factors for Feynman Diagrams

Cited by 416 publications

References 32 publications

Spontaneous mass generation and the small dimensions of the Standard Model gauge groups U(1),SU(2) and SU(3)

Spontaneous mass generation and the small dimensions of the Standard Model gauge groups U(1),SU(2) and SU(3)

Three-Loop Contributions to the Gluonic Massive Operator Matrix Elements at General Values of N

Scattering amplitudes in open superstring theory

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