With the 2012 discovery of the Higgs boson at the Large Hadron Collider, LHC, the Standard Model of particle physics has been completed, emerging as a most successful description of matter at the smallest distance scales. But as is always the case, the observation of this particle has also heralded the dawn of a new era in the field: particle physics is now turning to the mysteries posed by the presence of dark matter in the universe, as well as the very existence of the Higgs. The upcoming run of the LHC at 13 TeV will probe possible answers to both issues, providing detailed measurements of the properties of the Higgs and extending significantly the sensitivity to new phenomena.
Since the LHC is the only accelerator currently exploring the energy frontier, it is imperative that the analyses of the collected data use the most powerful possible techniques. In recent years several analyses have utilized multi-variate analysis techniques, obtaining higher sensitivity; yet there is ample room for further improvement. With our program we will import and specialize the most powerful advanced statistical learning techniques to data analyses at the LHC, with the objective of maximizing the chance of new physics discoveries.
We are part of a network of European institutions whose goal is to foster the development and exploitation of Advanced Multi-Variate Analysis (AMVA) for New Physics searches. The network offers extensive training in both physics and advanced analysis techniques to graduate students, focusing on providing them with the know-how and the experience to boost their career prospects in and outside academia. The network develops ties with non-academic partners for the creation of interdisciplinary software tools, allowing a successful knowledge transfer in both directions. The network studies innovative techniques and identifies their suitability to problems encountered in searches for new physics at the LHC and detailed studies of the Higgs boson sector.
External collaborators: University of Oxford, INFN, University of Padova, Université Blaise Pascal, LIP, IASA, CERN, UCI, EPFL, B12 Consulting, SDG Consulting, Yandex, MathWorks.
Study of the complementarity between dark matter relic abundance, direct detection, indirect detection and collider searches applied to the dark matter simplified models. These models consider a dark matter candidate communicating to the quark (especially top) sector of the standard model via a bosonic or vectorial mediator.
External collaborators: Eric Conte (GPRHE), Benjamin Fuks (LPTHE), Jun Guo (Chinese Academy of Science), Jan Heisig (RWTH), Kentarou Mawatari (LPSC Grenoble), Michael Kraemer (RWTH), Mathieu Pellen (University of Wuerzburg).
Implementation of the SMEFT at NLO in QCD in the Feynrules MadGraph5_aM
External collaborators: Cen Zhang, Celine Degrande.
Automation of the calculation of NLO Electroweak corrections and phenomenological studies of their impact on Standard-Model and Beyond-the-Standard-Model processes at colliders.
An automated framework for BSM phenomenology that allows one to compute Feynman rules from a Lagrangian.
External collaborators: Céline Degrande (CERN)
Benjamin Fuks (Jussieu).
We study the Vector Boson Fusion production channel for the Higgs boson and other particles at the LHC, mainly focusing on the role of QCD corrections.
Automation within MadGraph5_aM
Monte Carlo development.
External collaborators: Benjamin Fuks, Kentarou Mawatari, Kaoru Hagiwara, Tim Stelzer, Stefano Frixione, Marco Zaro, Rikkert Frederix, Valentin Hirschi, Paolo Torrielli, Johan Alwall, Hua-Sheng Shao, Mihailo Backovic,...
The discovery of a Higgs boson (H) by the ATLAS and CMS experiments fixes the value of the self-coupling λ in the scalar potential whose form is determined by the symmetries of the Standard Model and the requirement of renormalisability. Higgs boson pair production is sensitive to the self-coupling and will play a major role in investigating the scalar potential structure.
This project consists in a search for nonresonant Higgs boson pair production via gluon fusion in the final state with two leptons, two b jets and missing transvere energy – gg → H(bb) H(WW) asking for the leptonic decay of the W's. The analysis is conducted in close collaboration with phenomenologists to ensure the approach is theoretically sound and future-proof.
The difference between predictions obtained with a massive scheme, where a heavy quark is treated as a finale massive state and the massless scheme, where the heavy quark is viewed as an initial parton may be extremely sizable. The aim of the project is to gain a better understanding of the size of the collinear logarithms arising when a heavy quark is treated as a final massive state and to investigate its kinematical origin.
External collaborators: Maria Ubiali, Giovanni Ridolfi.
The discovery of the 125GeV Higgs boson by the LHC experiments has finally opened a new era in the exploration of the TeV scale. The physics programs of CMS and ATLAS aim far beyond the simple discovery, and vigorously pursue the full characterization of the newly discovered state and the full exploration of the TeV scale in search of new phenomena. A key lesson drawn from first two years of LHC running is that most probably first discoveries and then identification of new states/interactions will not be easy. On the one hand, model-independent searches in simple topologies such as single/multi lepton at high transverse momenta have not shown any hint of new physics so far. On the other, topologies with jets and/or missing transverse energies, much more challenging experimentally, do strongly depend on the underlying theoretical models so that efficiently identifying signal enhanced regions of the phase space is quite involved. In this context, multi-variate techniques have become more and more central in the analysis of data from hadron collider experiments, to maximally exploit the information available on the signal and on the backgrounds. Amongst the most advanced techniques and certainly the most powerful one from the theoretical point of view, the so called matrix element method stands out. The main goal of this proposal is to advance the use and the scope of the matrix-element method so to significantly extend the range of physics applications at the LHC to the search of new physics. First we aim at providing the experimental HEP community with complete and automatic simulation tools, such as MadWeight/MoMEMta and Delphes, that overcome the technical limitations of the method. Second we propose to test and apply the new tools to current analyses in signatures that involve final state leptons and b-jets. Finally, we explore new and original applications of the method to both model-dependent or model-independent searches of new physics at the LHC.
External collaborators: CMS collaboration.
Create a code to create automatically HELAS routine in various format from the Feynman Rules.
Madweight is a algorithm to automatically reweight experimental events with the squared matrix element, and therefore provides the required computation techniques for a practical application of the matrix element method.
We also study the usefullness of MadWeight to estimate differential cross-section via the marginal distributions of the the experimental weights .
External collaborators: Pierre Artoisenet (Ohio state university).
Study of the potential effects (such as black hole production) of a low scale gravity at the LHC.
We construct a supersymmetric grand unified model where the leptogenesis under the gravitino constraint is successfully implemented after determining the parameters of the dominated double seesaw mechanism by fitting the available data on neutrino masses and mixings.
External collaborators: M. K. Parida (NISER), Amitava Raychaudhuri (HRI).
We are mainly concentrated here on the electroweak scalars and vector bosons production in the higher dimensional model.
External collaborators: Gautam Bhattacharyy (SINP), Anindya Datta (CU) and Amitava Raychaudhuri (HRI).
To study graviton production through multi-jet final state processes at hadron colliders taking into account the following models: ADD, RS and a massless graviton model.
External collaborators: Qiang Li (Paul Scherrer Institut - PSI, Switzerland) and prof. Kaoru Hagiwara (KEK Theory Center and Sokendai, Japan).
QCD radiation in heavy colored particle production at the LHC is studied.
In collaboration with Johan Alwall (SLAC)
Herwig++ will be one of two or three, work-horse, multi-purpose event generators used in the analysis of LHC data.
In collaboration with Prof. Bryan Webber (Cambridge), Prof. Mike Seymour (CERN), Dr. Peter Richardson (Durham), Dr. Stefan Gieseke (Karlsruhe), Dr. David Grellscheid (Durham).
We study a general approach to make predictions in terms of event generator of production processes induced by loops, such as gg>H.
Non UCL collaborators: Rikkert Frederix (ETH-Zurich), Valentin Hirschi (EPL-Lausanne), Stefano Frixione (CERN).
Keywords: Monte Carlo simulations, LHC, Higgs
Automatizing the Catani-Seymour dipole subtraction formalism for NLO in QCD calculations within the MadGraph/MadEvent framework. Both for the subtraction terms for the real and the virtual contributions.
External collaborators: Thomas Gehrmann and Nicolas Greiner.
We study modifications of the Higgs sector which involve Higgs bosons with anomalous scaling dimensions and/or hidden sectors.
The goal of this work is to explore the phenomenology of a two Higgs doublet model with a custodial symmetry. It provides topologies that are unusual in the models usually considered in the literature. Notably, it opens the possibility of having an inverted mass spectrum with respect to MSSM with the lightest Higges being a pseudo-scalar and an heavier triplet of charged and neutral higgses.
External collaborators: Simon de Visscher (Zurich university).
We study the renormalization of the Planck mass including quantum gravity effects and study potential experimental tests.
The POWHEG formalism of Prof. Paolo Nason allows the consistent combination of NLO calculations and parton shower simulations. We aim to exploit and realise this method for processes occuring in the LHC. Implementation of the method for various processes is a key part of the work. We are also interested in a general formulation of the method for automating 2->2 processes. Extensions of the method to NNLO, including realisations, are also to be addressed.
In collaboration with Prof. P.Nason (Milan), Dr. P.Richardson (Durham), J.Tully (Durham)
The new approach from twistor spaces is applied to the study of the properties of multiparton amplitudes.
Production and decay of bound states of heavy quarks. Phenomenology and MC tools (MadOnia).
P. Artoisenet (Ohio), T. Stelzer (UIUC), J.P. Lansberg (Univ. Friburg, Germany), J. Campbell (Glasgow, UK), F. Tramontano (Univ. Napoli, Italy),...
We are interested here to extract some new features of the neutrino physics with the use of renormalisation group equations.
External collaborators: Rathin Adhikari (CTP, JMI), Anindya Datta (CU).
The aim of this project is to quantify the impact of using jet matching techniques in the context of the production of multi-jets processes, in the Standard Model and beyond. Such methods mix the PS simulation and the matrix-element calculation, leading notably to a strong reduction of the sensitivity to parton shower parameterization.
Top pair and single-top production is investigated, both for SM measurements and BSM searches.
J. Campbell (Glasgow, UK), F. Tramontano (Univ. Napoli, Italy),
+ E. Laenen (NIKHEF), S. Frixione (CERN), C. White (NIKHEF)
+ EXP group at CP3 (A. Giammanco, V. Lemaitre,...)
We study the phenomenology the top quark at colliders as well as at low energy via loops.
External collaborators: Christophe Grojean, Geraldine Servant, Scott Willenbrock, Benjamin Fuks.
Various SM backgrounds to new physics or SM measurements are considered.
* Z+heavy quarks + jets @ NLO
* W+heavy quarks + jets @ NLO
Collaborators: J. Campbell (Glasgow, UK), R.K. Ellis (Fermilab, US), S. Willenbrock (UIUC, US),
+ M.L. Mangano (CERN, Switzerland), F. Tramontano (Univ. Napoli, Italy),...
Study of vector boson (very peculiar) phenomenology at the LHC.
In collaboration with Francesco Tramontano (Univ. Napoli,IT) and Valentin Hirschi (EPL, CH)