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Swiss National Science Foundation (SNSF)

Wildhainweg 3P.O. Box

CH-3001 Bern

Phone +41 31 308 22 22

English title | Computing multi-particle production processes at LHC |
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Applicant | Gehrmann-De Ridder Aude |

Number | 139192 |

Funding scheme | SNSF Professorships |

Research institution | Institut für Theoretische Physik ETH Zürich |

Institution of higher education | ETH Zurich - ETHZ |

Main discipline | Theoretical Physics |

Start/End | 01.03.2012 - 28.02.2014 |

Approved amount | 669'799.00 |

Particle Physics; LHC; Precision observables; Monte Carlo Methods

Lead |
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Lay summary |

With the CERN LHC a new proton-proton collider has started taking data at the end of 2009. Compared to previous facilities, the LHC will attain collision energies never probed before in a laboratory. With this higher energy reach, the LHC could uncover new physics effects and provide answers to some of the most intriguing questions in fundamental physics. In order to establish experimental signatures of new physics effects, it is mandatory to have a very solid and precise theoretical understanding of known Standard Model processes yielding similar final state signatures. Depending on the final state under consideration, these predictions are obtained either through precision calculations of multi-particle final states in perturbation theory or within the context of parton showers. In either approach, the theory description of collider reactions relies on an accurate knowledge of the Standard Model parameters and of the structure of the colliding protons. Precise determinations of these quantities require accurate measurements of benchmark cross sections, combined with equally precise theoretical predictions, involving higher order quantum field theory corrections. Within the project proposed here, we aim to compute higher order corrections to next-to-next-to-leading order (NNLO) in perturbation theory to the following benchmark cross sections: 1. pp -> 2j: the production of di-jet final states is the most basic 2-> 2 QCD scattering processes at hadron colliders; it allows for precision tests of the theory of strong interactions, i.e. QCD. 2. pp -> V+j: the production of a massive vector boson (W+- or Z0) in association with a hadronic jet. This process has multiple applications both in view of direct and indirect searches for new physics effects, precision determinations of physics parameters (electroweak couplings, parton distributions) and calibration of experimental conditions (jet energy scale, luminosity). 3. pp -> tt: top quark pair production. With the large number of top quark pairs produced at the LHC, the study of the top quark properties will become precision physics. For each of the processes considered, we will develop a parton-level event generator, which is a Monte Carlo program generating events with full kinematical information on all final state particles. This program will contain all partonic channels relevant at a given order and will allow to apply the precise experimental definitions to all observables which can be constructed from a given final state. The calculations are based on the antenna subtraction method, which we developed as a theoretical tool to handle multi-parton final states at higher orders in perturbation theory. A different application of the antenna formalism is the description of multi-particle final states through parton showers. The VINCIA parton-shower event generator program uses antenna functions to obtain a reliable description of single particle emissions, which are then exponentiated to obtain a full event description. Within this project, we aim to contribute to the further development of VINCIA by including particle mass effects, and by developing a matching of this antenna-based parton shower onto fixed order matrix elements including higher-order perturbative corrections. |

Direct link to Lay Summary | Last update: 21.02.2013 |

Name | Institute |
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Publication |
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NNLO QCD corrections to jet production at hadron colliders from gluon scattering |

Double real radiation corrections to $t\bart$ production at the LHC: the all-fermion processes |

Double Virtual corrections for gluon scattering at NNLO |

Second order QCD corrections to jet production at hadron colliders: the all-gluon contribution |

Antenna subtraction at NNLO with hadronic initial states: double real initial-initial configurations |

Antenna subtraction with massive fermions at NNLO: Double real initial-final configurations |

Double real radiation corrections to $t\bart$ production at the LHC: the $gg\rightarrow t\bartq\barq$ channel |

Double real radiation corrections to top-antitop production at the LHC |

Group / person | Country |
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Types of collaboration |
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CERN Theory Group | Switzerland (Europe) |

- in-depth/constructive exchanges on approaches, methods or results - Publication |

Universität Zürich | Switzerland (Europe) |

- in-depth/constructive exchanges on approaches, methods or results - Publication |

University of Durham | Great Britain and Northern Ireland (Europe) |

- in-depth/constructive exchanges on approaches, methods or results - Publication |

CEA Saclay, Physique Theorique | France (Europe) |

- in-depth/constructive exchanges on approaches, methods or results - Publication |

RWTH Aachen | Germany (Europe) |

- in-depth/constructive exchanges on approaches, methods or results - Publication - Exchange of personnel |

ETH Institute for Particle Physics | Switzerland (Europe) |

- in-depth/constructive exchanges on approaches, methods or results |

Max-Planck-Institut München | Germany (Europe) |

- in-depth/constructive exchanges on approaches, methods or results |

Title | Type of contribution | Title of article or contribution | Date | Place | Persons involved |
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Santa Barbara Workshop: Exploring TeV Scale New Physics with LHC data, | Individual talk | blackboard seminar on: Antenna subtraction | 08.07.2013 | Kavli Institute, UCSB, Santa Barbara , United States of America | Gehrmann-De Ridder Aude; |

Brookhaven Forum | Talk given at a conference | Review talk on Perturbative QCD | 01.05.2013 | Brookhaven National Laboratory , United States of America | Gehrmann-De Ridder Aude; |

HP2 Workshop | Talk given at a conference | Towards jet cross sections at NNLO | 03.09.2012 | Munich, Germany, Germany | Gehrmann-De Ridder Aude; |

LoopFest X1 | Talk given at a conference | Towards jet cross sections at NNLO for the LHC | 07.05.2012 | Pittsburgh,USA, United States of America | Gehrmann-De Ridder Aude; |

Title | Date | Place |
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Topical workshop ZPW13 | 07.01.2013 | Zurich, Switzerland |

Number | Title | Start | Funding scheme |
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141847 | Particle Physics with high-quality data from the CERN LHC | 01.10.2012 | Sinergia |

118864 | Computing multi-particle production processes at LHC | 01.03.2008 | SNSF Professorships |

With the CERN LHC a new proton-proton collider has started taking data at the end of 2009. Compared to previous facilities, the LHC will attain collision energies never probed before in a laboratory. With this higher energy reach, the LHC could uncover new physics effects and provide answers to some of the most intriguing questions in fundamental physics. In order to establish experimental signatures of new physics effects, it is mandatory to have a very solid and precise theoretical understanding of known Standard Model processes yielding similar final state signatures. Depending on the final state under consideration, these predictions are obtained either through precision calculations of multi-particle final states in perturbation theory or within the context of parton showers. In either approach, the theory description of collider reactions relies on an accurate knowledge of the Standard Model parameters and of the structure of the colliding protons. Precise determinations of these quantities require accurate measurements of benchmark cross sections, combined with equally precise theoretical predictions, involving higher order quantum field theory corrections. Within the project proposed here, we aim to compute higher order corrections to next-to-next-to-leading order (NNLO) in perturbation theory to the following benchmark cross sections:1. pp -> 2j: the production of di-jet final states is the most basic 2-> 2 QCD scattering processes at hadron colliders; it allows for precision tests of the theory of strong interactions, i.e. QCD. 2. pp -> V+j: the production of a massive vector boson (W+- or Z0) in association with a hadronic jet. This process has multiple applications both in view of direct and indirect searches for new physics effects, precision determinations of physics parameters (electroweak couplings, parton distributions) and calibration of experimental conditions (jet energy scale, luminosity). 3. pp -> tt: top quark pair production. With the large number of top quark pairs produced at the LHC, the study of the top quark properties will become precision physics. For each of the processes considered, we will develop a parton-level event generator, which is a Monte Carlo program generating events with full kinematical information on all final state particles. This program will contain all partonic channels relevant at a given order and will allow to apply the precise experimental definitions to all observables which can be constructed from a given final state. The calculations are based on the antenna subtraction method, which we developed as a theoretical tool to handle multi-parton final states at higher orders in perturbation theory.A different application of the antenna formalism is the description of multi-particle final states through parton showers. The VINCIA parton-shower event generator program uses antenna functions to obtain a reliable description of single particle emissions, which are then exponentiated to obtain a full event description. Within this project, we aim to contribute to the further development of VINCIA by including particle mass effects, and by developing a matching of this antenna-based parton shower onto fixed order matrix elements including higher-order perturbative corrections.

Swiss National Science Foundation (SNSF)

Wildhainweg 3P.O. Box

CH-3001 Bern

Phone +41 31 308 22 22

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