arXiv subjects

Marek Schonherr

Publications and source records attributed to Marek Schonherr.

23 records · Page 2Linked to original sources

arXiv2011

NLO matrix elements and truncated showers

In this publication, an algorithm is presented that combines the ME+PS approach to merge sequences of tree-level matrix elements into inclusive event samples with the POWHEG method, which combines exact next-to-leading order matrix element results with the parton shower. It was developed in parallel to the MENLOPS technique and has been implemented in the event generator Sherpa. The benefits of this approach are exemplified by some first predictions for a number of processes, namely the production of jets in e+ e- annihilation, in deep-inelastic ep scattering, in association with single W, Z or Higgs bosons, and with vector boson pairs at hadron colliders.

hep-ph↗

arXiv2011

Automating the POWHEG method in Sherpa

A new implementation of the POWHEG method into the Monte-Carlo event generator Sherpa is presented, focusing on processes with a simple colour structure. Results for a variety of processes, namely e+e- to hadrons, deep-inelastic lepton-nucleon scattering, hadroproduction of single vector bosons and of vector boson pairs as well as the production of Higgs bosons in gluon fusion serve as test cases for the successful realisation. The algorithm is fully automated such that for further processes only virtual matrix elements need to be included.

hep-ph↗

arXiv2010

Multi-jet merging with NLO matrix elements

In the algorithm presented here, the ME+PS approach to merge samples of tree-level matrix elements into inclusive event samples is combined with the POWHEG method, which includes exact next-to-leading order matrix elements in the parton shower. The advantages of the method are discussed and the quality of its implementation in Sherpa is exemplified by results for e+e- annihilation into hadrons at LEP, for deep-inelastic lepton-nucleon scattering at HERA, for Drell-Yan lepton-pair production at the Tevatron and for W+W- production at LHC energies.

hep-ph↗

arXiv2010

Comparing different ansatzes to describe electroweak radiative corrections to exclusive semileptonic B meson decays into (pseudo)scalar final state mesons using Monte-Carlo techniques

In this publication electroweak next-to-leading order corrections to semileptonic B-meson decays into (pseudo)scalar final states are presented. To this end, these corrections of O(alpha G_F) have been calculated in the QED-enhanced phenomenological model, incorporating the bound-state mesons as its degrees of freedom, and matched to a similar calculation on the level of constituent partons in the full Standard Model. Consequently, the effects arising due to corrections of the partial decay widths on the extraction of the CKM matrix elements |V_cb| and |V_ub| are detailed. Further, the results of two independent Monte-Carlo implementations are presented: One is the dedicated, strict fixed-order generator BLOR, and the other is embedded into the generic Yennie-Frautschi-Suura-type resummation of Photons++, which is part of the multi-purpose event generator Sherpa. The resulting distributions are compared against the standard tool used in many experimental analyses, PHOTOS, showing improvements on the shapes of kinematic distributions of both the lepton and the final state meson.

hep-ph↗

arXiv2010

Next-to-leading order matrix elements and truncated showers

An algorithm is presented that combines the ME+PS approach to merge sequences of tree-level matrix elements into inclusive event samples with the POWHEG method, which combines exact next-to-leading order matrix elements with parton showers. The quality of the approach and its implementation in Sherpa are exemplified by results for e+e- annihilation into hadrons at LEP, for Drell-Yan lepton-pair production at the Tevatron and for Higgs-boson and W+W- production at LHC energies.

hep-ph↗