Multijet events in the k_T-factorisation scheme
A Markovian Monte Carlo algorithm for multi-parton production in the high-energy limit is proposed and the matching with unintegrated parton densities is discussed.
hep-ph↗
arXiv subjects
Frank Krauss
Publications and source records attributed to Frank Krauss.
From multileg loops to trees (by-passing Feynman's Tree Theorem)
We illustrate a duality relation between one-loop integrals and single-cut phase-space integrals. The duality relation is realised by a modification of the customary +i0 prescription of the Feynman propagators. The new prescription regularizing the propagators, which we write in a Lorentz covariant form, compensates for the absence of multiple-cut contributions that appear in the Feynman Tree Theorem. The duality relation can be extended to generic one-loop quantities, such as Green's functions, in any relativistic, local and unitary field theories.
hep-th↗
Initial-state showering based on colour dipoles connected to incoming parton lines
A parton-shower model for hadronic collisions based on the emission properties of QCD dipoles is proposed. This proposal therefore extends the well-known radiation pattern of pure final-state colour dipoles to QCD initial-state radiation, both of which are treated perturbatively. Corresponding dipole splitting functions are derived and the kinematics of all dipole splittings is discussed. Application to hadron production in electron-positron annihilation, to Drell-Yan lepton-pair and QCD jet production yields encouraging results.
hep-ph↗
Automating dipole subtraction for QCD NLO calculations
In this publication the construction of an automatic algorithm to subtract infrared divergences in real QCD corrections through the Catani-Seymour dipole subtraction method [arXiv:hep-ph/9605323] is reported. The resulting computer code has been implemented in the matrix element generator AMEGIC++ [arXiv:hep-ph/0109036]. This will allow for the automatic generation of dipole subtraction terms and their integrals over the one-parton emission phase space for any given process. If the virtual matrix element is provided as well, this then directly leads to an NLO QCD parton level event generator.
hep-ph↗
A parton shower algorithm based on Catani-Seymour dipole factorisation
In this publication the implementation of a new parton shower model based on the Catani-Seymour dipole factorisation, as first suggested by Z. Nagy and D. E. Soper, is discussed. First results obtained with the new algorithm are compared with experimental data.
hep-ph↗
New trends in modern event generators
Some features of modern simulation tools for high-energy physics are reviewed.
hep-ph↗
Matching Parton Showers and Matrix Elements
We compare different procedures for combining fixed-order tree-level matrix element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW scheme and one based on the so-called MLM scheme using different matrix element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.
hep-ph↗
Implementing the ME+PS merging algorithm
The method to merge matrix elements for multi particle production and parton showers in electron-positron annihilations and hadronic collisions and its implementation into the new event generator SHERPA is described in detail. Examples highlighting different aspects of it are thoroughly discussed, some results for various cases are presented. In addition, a way to extend this method to general electroweak interactions is presented.
hep-ph↗
Simulating W/Z+jets production at the CERN LHC
The merging procedure of tree-level matrix elements and the subsequent parton shower as implemented in the new event generator SHERPA will be validated for the example of single gauge boson production at the LHC. The validation includes consistency checks and comparisons to results obtained from other event generators. In particular, comparisons with full next-to-leading order QCD calculations prove SHERPA's ability to correctly account for additional hard QCD radiation present in these processes.
hep-ph↗
Simulating W/Z+jets production at the Tevatron
The merging procedure of tree-level matrix elements and the subsequent parton shower as implemented in the new event generator SHERPA will be validated for the example of W/Z+jets production at the Tevatron. Comparisons with results obtained from other approaches and programs and with experimental results clearly show that the merging procedure yields relevant and correct results at both the hadron and parton levels.
hep-ph↗
A modified cluster-hadronization model
A new phenomenological cluster-hadronization model is presented. Its specific features are the incorporation of soft colour reconnection, a more general treatment of diquarks including their spin and giving rise to clusters with baryonic quantum numbers, and a dynamic separation of the regimes of clusters and hadrons according to their masses and flavours. The distinction between the two regions automatically leads to different cluster decay and transformation modes. Additionally, these aspects require an extension of individual cluster-decay channels that were available in previous versions of such models.
hep-ph↗
Resummed jet rates for $e^+e^-$ annihilation into massive quarks
Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates for up to four jets in $e^+e^-$ annihilation. The coefficients of leading and next-to-leading logarithmic corrections, mandatory for a combination with higher order matrix elements, are evaluated up to second order in $α_s$.
hep-ph↗
Resummed jet rates with heavy quarks in electron-positron collisions
Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates in electron-positron annihilation. Predictions are given for production of bottom quarks at LEP and top quarks at the Linear Collider.
hep-ph↗
Resummed jet rates for heavy quark production in electron-positron annihilation
Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates in electron-positron annihilation. Predictions are given for production of bottom quarks at LEP and top quarks at the Linear Collider.
hep-ph↗
Lepton-flavor-violating decays L->l gamma gamma as a new probe of supersymmetry with broken R-parity
Lepton-flavor-violating decays of the type L->l gamma gamma (mu->e gamma gamma, tau->e gamma gamma, and tau->mu gamma gamma) are proposed as new probes of R-parity-violating supersymmetry. Non-penguin diagrams with a sneutrino that decays into two photons via a triangle graph might trigger such decays even in the absence of the corresponding radiative decays into one photon only, e.g. mu->e gamma. Thus, processes of the type L->l gamma gamma may provide an independent probe of new flavor physics.
hep-ph↗
Determining the quantum numbers of excited heavy mesons
We discuss the decays X^* -> Xe^+e^- (``Dalitz decays'') of excited heavy mesons into their ground states and an electron-positron pair. We argue that the measurement of the invariant mass spectrum of the lepton pair gives clear indication on the quantum numbers of the excited meson and thus provides an experimental test of the quark model predictions.
hep-ph↗