Simon de Visscher
Former member
Postdoc in CP3 from October 2015
Current position: Data Analytics Expert @ Gamaya (CH).
Dissertations, status,...
June 2004: Graduate diploma.
Dissertation: Analyse de topologies à un lepton dur lors de processus associés à un Higgs se désintégrant en deux bosons W
September 2005: DEA (master) diploma
Report:Identification et sélection des leptons produits lors de la production associée d'un boson de Higgs et d'une paire de quarks top-antitop dans l'expérience CMS
September 2005 - October 2009
PhD Thesis and as research assistant: work related to the modelling of collision in hadron-hadron colliders, on the BSM phenomenology particularly on 2HDM, and associated discovery potentials in general, in CMS in particular
October 2009 - September 2012
PostDoc at Universität Zürich ( work on CMS pixel commissioning and performance, B-physics, collision modeling,...
October 2012-September 2015
Fellow at CERN in the CMS group. Activities: Studies of SM V+HF process, Higgs search, b-tagging activities
September 2015-...
Chargé de Recherche F.N.R.S. Fields of activity: Standard Model, Higgs search, CMS tracker simulation, hadronic collision modeling,...
I am involved in the following research directions:

CMS Tracker commissioning and performance assessment

The CMS silicon strip tracker is the largest device of its type ever built. There are 24244 single-sided micro-strip sensors covering an active area of 198m2.
Physics performance of the detector are being constantly assessed and optimized as new data comes.
Members of UCL are playing a major role in the understanding of the silicon strip tracker and in the maintenance and development of the local reconstruction code.

External collaborators: CMS tracker collaboration.

Search for Higgs boson(s) in CMS at the LHC in the llbb topology

Search for Higgs boson(s) within the Standard Model and beyond and also withing a minimal extension of the scalar sector (2HDM).

The final state under study is a Z decaying into a lepton pair associated with two b-jets. This topology is sensitive to a light SM Higgs via the associate ZH production, as well as a middle mass range SM Higgs boson via the inclusive Higgs production followed by its decay into ZZ with one Z decaying into a lepton pair and the other into bbar.

It is also very sensitive to the production of a non standard heavy Higgs boson decaying into Z plus A (pseudo scalar Higgs boson).

Similar selection (but outside of the Z window) is also sensitive to H->aa->llbb, with "a" a generic light scalar.

External collaborators: CMS collaboration.

Past projects
Hide past projects.

I am involved in the following research directions:

CMS Tracker commissioning at the Magnet Test Cosmic Challenge

The so called Magnet Test Cosmic Challenge (MTCC) was the first comprehensive operational and functional test of the CMS experiment. the MTCC took place in the first months of 2006 and was a slice test in which a small fraction of all the CMS detection equipment was operated in the 4 T solenoid of the experiment. Cosmic rays detected in the muon chambers were used to trigger the readout of all detectors in the global CMS data acquisition system. Prior to data taking, the detectors and their readout electronics were tuned and synchronized with dedicated software procedures. Local reconstruction was carried out online and offline in all sub-detectors for event selection and monitoring purposes. Global reconstruction, linking different sub-detectors, was performed mainly offline. A number of monitoring and visualization tools were also used for validation purposes and monitoring. One of the main goals of the MTCC was the validation of the hardware alignment system functionality.
At the MTCC, UCL had a leading role in the preparation, operation and offline data analysis related to the silicon strip tracker detector.

Heavy colored particles + jets

QCD radiation in heavy colored particle production at the LHC is studied.

In collaboration with Johan Alwall (SLAC)

Observability of a minimal extension of the scalar sectror: 2HDM at the LHC

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).

Simulation of events with QCD radiation

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.

Publications in CP3
All my publications on Inspire


Particle-flow reconstruction and global event description with the CMS detector
CMS collaboration
[Abstract] [PDF] [Journal] [Full text] Submitted to JINST.
Refereed paper. 21st August.


Search for A/H to Z(ll)+H/A(bb) with 2015 data
CMS collaboration
[Full text] Prepared for Moriond 2016
Public experimental note. 28th April.


Unconventional phenomenology of a minimal two-Higgs-doublet model
Simon de Visscher, Jean-Marc Gerard, Michel Herquet, Vincent Lemaitre, Fabio Maltoni
[Abstract] [PDF] [Journal] Published in JHEP08(2009)042.
Refereed paper. 3rd April.


The CMS experiment at the CERN LHC
The CMS Collaboration
[Journal] [Full text] The CMS Collaboration, "The CMS experiment at the CERN LHC", 2008 JINST 3 S08004, 361pp doi: 10.1088/1748-0221/3/08/S08004.
Refereed paper. 10th December.
The CMS tracker operation and performance at the Magnet Test and Cosmic Challenge
S. Assouak, J.-L. Bonnet, G. Bruno, B. de Callatay, S. de Visscher, D. Favart, B. Florins, E. Forton5, A. Giammanco, G. Gregoire, S. Kalinin, D. Kcira, Th. Keutgen, V. Lemaitre, D. Michotte, O. Militaru, S. Ovyn, K. Piotrzkowski, X. Rouby, D. Teyssier, O. Van der Aa et al. (> 100 authors)
[Journal] [Full text] W. Adam et al., “The CMS tracker operation and performance at the Magnet Test and Cosmic Challenge”, 2008 JINST 3 P07006. doi: 10.1088/1748-0221/3/07/P07006.
G. Bruno co-editor

Refereed paper. 10th December.
QCD radiation in the production of heavy colored particles at the LHC
Johan Alwall, Simon de Visscher, Fabio Maltoni
[Abstract] [PDF] [Journal] Published in JHEP02(2009)017.
Refereed paper. 29th October.
New Developments in MadGraph/MadEvent
J. Alwall, P. Artoisenet, S. de Visscher, C. Duhr, R. Frederix, M. Herquet, O. Mattelaer
[Abstract] [PDF] [Journal] SUSY08 Proceedings (plenary talk by Johan Alwall)
Contribution to proceedings. 15th September.
Radiation of Extra-Jets in Inclusive SUSY Samples
Simon de Visscher, Johan Alwall, Fabio Maltoni
[Full text] Proceeding for the talk of S. de Visscher at SUSY08 conference
Contribution to proceedings. 15th September.


MadGraph/MadEvent at Work: From QCD to new physics.
Simon de Visscher
[Journal] [Full text] Prepared for 15th International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2007), Munich, Germany, 16-20 Apr 2007.
Published in *Munich 2007, Deep-inelastic scattering, vol. 2* 1065-1068

Contribution to proceedings. 31st December.
Madgraph/MadEvent v4: The new web generation
Johan Alwall, Pavel Demin, Simon de Visscher, Rikkert Frederix, Michel Herquet, Fabio Maltoni, Tilman Plehn, David Rainwater, Tim Stelzer
[Abstract] [PDF] [Journal] Published in JHEP 0709:028,2007
Refereed paper. 4th June.


Tagging b jets with electrons and muons at CMS
P. Demin, S. de Visscher, A. Bocci, R. Ranieri
[Full text] CERN-CMS-NOTE-2006-043
Public experimental note. 31st December.
Talks outside UCL
23rd September 05:BND Summer school: First look at ttH, H->WW associated productions in CMS
02nd December 05: CERN (Higgs Meeting): search for ttH->WW with two same sign leptons leptons
18th april 2007: Munich (DIS2007): Madgraph/MadEvent at work, from QCD to new physics
25th may 2007: Liege (PHD student day): Study of scalar sector with associated production of Higgs bosons and top quarks.
5th june 2007 : CERN (Top meeting): Production of ttbar + jets samples with MadGraph/MadEvent.
16th july 2007 : CERN (Top meeting): Lastest development of matching in MadGraph/MadEvent.
13th November 2007 : SUSY-GDR workshop: Extra-jet radiations in inclusive SUSY sample and SM backgrounds
February 08: Talks at LCG, Atlas MC meeting: Multi-jet process generation
March 08: CMS generator meeting: status of mas production for CMS

June 08: SUSY08 (Seoul - invited talk): radiation of extra-jet in inclusive SUSY processes
July 08: CERN: radiation of extra-jet in inclusive SUSY processes
December 08: CERN : MadGraph tutorial, running the code and gridpack preparation
March 09: Nikhef; QCD radiation in the production of heavy colored particles at the LHC (th. seminar)
March 10: CEA/Saclay: Unconventional phenomenology of a minimal 2HDM
June 10: IPRD 10 (Siena): Evaluation of the CMS pixel detector performances from the first LHC collisions
June 10: SPG10 (Basel): First results from the CMS experiment
June 11: Pheno11 (Madison): Recent heavy flavour results from the CMS experiment
April 12: LPCC CERN: V+HF studies in CMS
July 12: ICHEP 2012 (Melbourne): Heavy flavor quark production in association (or not) with vector bosons in CMS
November 12: LPCC (CERN): Recent V+HF results in ATLAS and CMS
January 14: HepMC WG (CERN): Future use of HepMC in CMS
October 14: ERC workshop (CERN): ME+PS merging in Madgraph5+Pythia8
Kruger 14 (South Africa): Review of Standard Model studies in CMS
March 15: Collider X-talk (CERN): Joint ATLAS and CMS seminar on V+jets
August 15: Lepton-Photon 2015 (Ljubljana): QCD measurements at high P_{T} (invited, plenary)
Teaching duties
UCL - 2005-2009
PHY 1113 (I):Mechanics (Ex + Labos) 1q
PHY 1113 (II): Hydrodynamics, Electricity, thermodynamics (Ex + Labo)
PHY 1210: Electromagnetism, waves machanics, modern physics (Ex) 2q
PHYS 2362: Data Processing in Physics 1
U.Zürich 2009-2012
Different laboratories for undergraduate students (optics, nuclear physics, electromagnetism,...)
Nuclear and particle physics exercises.
PhD supervision
Oct 2009-Aug 2010
Co-supervisor of PhD student (T.Rommerskirschen) at U. Zürich.
Context : study of multi-jet events for SUSY discovery.
June 2011-Dec 2012
Supervisor of PhD student (C.Favaro) at U.Zürich.
Context : Analysis of the associated production of dilepton final states and heavy-flavour quarks.

[UCLouvain] - [SST] [IRMP] - [SC]
Contact : Jérôme de Favereau
Job opportunities Postdoctoral position: Search for Hidden Sector mediations at NA62 experiment
EOS be.h : 10 PhD positions
Postdoctoral position: Data Analysis and GTK operation for NA62 experiment
Postodoctoral position in precision and BSM Phenomenology
Postdoctoral Position in Precision Computations for the LHC