Non-perturbative Models for the Simulation of Hadronic Collisions at the LHC

Nicht-störungstheoretische Modelle sind ein wesentlicher Bestandteil der Simulation von hadronischen Hochenergie-Kollisionen. In dieser Arbeit untersuchen, implementieren und verbessern wir mehrere nicht-störungstheoretische Modelle des Monte-Carlo-Ereignisgenerators Herwig 7. Wir entwickeln zunächst ein neues Modell für die Farbwiederverbindung, welches die Bildung von baryonischen Clustern ermöglicht und die Beschreibung von Daten mit minimalen Detektionskriterien, insbesondere in Regionen hoher Teilchenvielzahl und in Bezug auf die beobachtbare Teilchenart verbessert. Anschließend untersuchen wir die Struktur der Farbwiederverbindung unter störungstheoretischen Gesichtspunkten indem wir den Austausch weicher Gluonen studieren. Wir entwickeln ein Monte-Carlo Programm, welches uns erlaubt die Farbstruktur von Systemen, die aus bis zu fünf Clustern bestehen, zu entwickeln und die resultierenden Farbstrukturen numerisch zu untersuchen. Als nächstes studieren wir den Produktionsmechanismus seltsamer Quarks des Hadronisierungsmodells von Herwig 7. Um den Prozess dynamischer und kollektiver zu gestalten, führen wir an verschiedenen Stellen der Hadronisierung einen neuartigen Mechanismus für die Produktion seltsamer Quarks ein, der von der unmittelbaren Umgebung abhängig ist. Abschließend verbessern wir das Mehrteilcheninteraktionsmodell von Herwig 7. Wir bestimmen die freien Parameter des Modells anhand verfügbarer Daten aus Messungen mit minimalen Detektionskriterien und Messungen der hintergrundartigen Ereignisse, welche eine Massenschwerpunktsenergie von 200 GeV bis 13 TeV umfassen und stellen fest, dass es uns möglich ist alle betrachteten Observablen mit nur einem Satz von Parametern zu beschreiben

Baryon production from cluster hadronization

We present an extension to the colour reconnection model in the Monte-Carlo event generator Herwig to account for the production of baryons and compare it to a series of observables for soft physics. The new model is able to improve the description of charged-particle mutliplicities and hadron flavour observables in pp collisionsComment: 13 pages; v3: updated to match journal versio

Colour Reconnection from Soft Gluon Evolution

We consider soft gluon evolution at the amplitude level to expose the structure of colour reconnection from a perturbative point of view. Considering the cluster hadronization model and an universal Ansatz for the soft anomalous dimension we find strong support for geometric models considered earlier. We also show how reconnection into baryonic systems arises, and how larger cluster systems evolve. Our results provide the dynamic basis for a new class of colour reconnection models for cluster hadronization.Comment: 24 pages, 15 figure

Improving the description of multiple interactions in Herwig

The modeling of multiple parton interactions in Monte Carlo event generators is a crucial part not only for the dressing of signal processes but also to describe data with a minimum bias on the event selection. Much work has and will be put into the theoretical framework and the numerical implementation of these models. In this contribution, we document various improvements of the multiple parton interaction model of Herwig 7 (Bellm et al. in Eur Phys J C76(4):196, 2016), that lead to an improved description of minimum bias and underlying event data

Kinematic strangeness production in cluster hadronization

We present a modification to the non-perturbative strangeness production mechanisms in the Monte-Carlo event generator Herwig in order to make the processes more dynamic and collective. We compare the model to a series of observables for soft physics at both LEP and LHC

Baryon production from cluster hadronisation

We present an extension to the colour reconnection model in the Monte Carlo event generator Herwig to account for the production of baryons and compare it to a series of observables for soft physics. The new model is able to improve the description of charged-particle multiplicities and hadron flavour observables in pp collisions

Soft QCD Effects in VBS/VBF Topologies

We consider the impact of multi-parton interactions, colour reconnection and hadronization on the modeling of vector boson fusion and vector boson scattering (VBS) final states at the Large Hadron Collider (LHC). We investigate how the variation of the model parameters, compatible with a reasonable spread of predictions around typical tuning observables, extrapolates into the VBS phase space. We study the implications of this variation on the total uncertainty budget attached to realistic simulation of the final states in current event generator predictions. We find that the variations have a non-trivial phase space dependence and become comparable in size to the perturbative uncertainties once next-to-leading order predictions are combined with parton shower evolution.Comment: 9 pages, 5 figures. Additional figures can be found at: https://cern.ch/apapaefs/VBSQCD

Herwig 7.1 Release Note

A new release of the Monte Carlo event generator Herwig (version 7.1) is now available. This version introduces a number of improvements, notably: multi-jet merging with the dipole shower at LO and NLO QCD; a new model for soft interactions and diffraction; improvements to mass effects and top decays in the dipole shower, as well as a new tune of the hadronisation parameters.Comment: 7 pages, 7 figures. Herwig is available from https://herwig.hepforge.org

Confronting experimental data with heavy-ion models: Rivet for heavy ions

The Rivet library is an important toolkit in particle physics, and serves as a repository for analysis data and code. It allows for comparisons between data and theoretical calculations of the final state of collision events. This paper outlines several recent additions and improvements to the framework to include support for analysis of heavy ion collision simulated data. The paper also presents examples of these recent developments and their applicability in implementing concrete physics analyses