Matthias Komm
Former member
PhD student in CP3 from April 2013 to September 2017
Current position: Postdoc at Imperial College, London (UK).
I am involved in the following research directions:

Fast Simulation of the CMS experiment

A framework for Fast Simulation of particle interactions in the CMS detector (FastSim) has been developed and implemented in the overall simulation, reconstruction and analysis framework of CMS. It produces data samples in the same format as the one used by the Geant4-based (henceforth Full) Simulation and Reconstruction chain; the output of the Fast Simulation of CMS can therefore be used in the analysis in the same way as data and Full Simulation samples. FastSim is used in several physics analyses in CMS, in particular those requiring a generation of many samples to scan an extended parameter space of the physics model (e.g. SUSY) or for the purpose of estimating systematic uncertainties. It is also used by several groups to design future sub-detectors for the Phase-II CMS upgrades.
Related activities at UCL include the integration with the Full Simulation in the simulation of the electronic read-out ("digitization") and of the pileup of events from other proton-proton collisions, both in-time and out-of-time; the performance monitoring; and the overall maintenance and upgrade of the tracking-related code. Matthias Komm is current L3 convener of Tracking in FastSim, and Andrea Giammanco has been main responsible of the FastSim project from 2011 to 2013.

Single top studies at LHC

The electroweak production cross section of single top quarks is an important measurement for LHC, being a potential window on "new physics" effects.
Past achievements of this group include the very first measurement at 7 TeV (in t channel) with 2010 data, followed by the most precise inclusive cross section measurements of t-channel cross section at 7, 8 and 13 TeV, and the first differential measurements at 13 TeV; the most precise |Vtb| extraction from single top in the world; the first measurement of W-helicity fractions in a single-top topology; the first observation of the tW production mode; the first measurement of single-top polarization in t channel; stringent limits on anomalous tWb, tgu, tgc couplings.

External collaborators: CMS collaboration.

Testing the sign of the coupling of the new H(125) boson to top quarks with the CMS data

During 2012, the CMS and ATLAS collaborations independently reported unambiguous evidence of the existence of a new particle of mass around 125 GeV.
Several analyses are ongoing to challenge the hypothesis that the new particle is the SM Higgs. We focus on the search for its production in association with a single top quark. Due to an effect of quantum interference, this process is strongly suppressed in the Standard Model while it gets enhanced if its couplings to the top quark and to the W boson have opposite sign. An observation of this production mode would therefore be a convincing proof that this new particle does not belong to the Standard Model.
We published the first search for this process using 8 TeV data, and we expect to achieve sensitivity to anomalous values of the top Yukawa phase during the LHC Run-II.

External collaborators: CMS collaboration.

Past projects
Hide past projects.

I am involved in the following research directions:

Advanced Techniques for Fast Simulation and Data Analysis in High Energy Physics (ASAP)

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.

Search for Higgs boson(s) in CMS at the LHC in the llbb+MET 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 lepton pair associated with two b-jets and missing transverse energy. This topology is sensitive to a light SM Higgs via the H(bb)H(WW) production (via loop or Higgs self-coupling diagrams) and via the associated production of ttbar pairs and invisible particles. Requiring additional b jets (thus defining the llbbbb+MET final state) allows also the very interesting studies of a standard model Higgs produced in association with a top quark pair and It is also sensitive to the production of non standard heavy Higgs bosons decaying into ZA or WA, in the WAWA and ZAZA channels.

In particular, we are studying both resonant and non-resonant Higgs-pair production.

External collaborators: CMS collaboration.

Publications in CP3
All my publications on Inspire


The Phase-2 Upgrade of the CMS Tracker
CMS collaboration
[Full text] CERN-LHCC-2017-009 ; CMS-TDR-014
Refereed paper. 13th December.
Object definitions for top quark analyses at the particle level
CMS Collaboration
[Full text] CERN-CMS-NOTE-2017-004
Public experimental note. 6th June.


Cross section measurement of $t$-channel single top quark production in pp collisions at $sqrt s =$ 13 TeV
Sirunyan, Albert M and others
[Abstract] [PDF] [Journal] Most precise measurement of the single-top cross section at 13 TeV.
Refereed paper. Public experimental note. 4th October.
Measurement of the differential cross section for t-channel single-top-quark production at sqrt(s)=13 TeV
CMS Collaboration
[Full text] CMS Physics Analysis Summary CMS-TOP-16-004
Public experimental note. 27th April.


Measurement of top quark polarisation in t-channel single top quark production
Khachatryan, Vardan and others
[Abstract] [PDF] [Journal] JHEP 04 (2016) 073
Refereed paper. 9th November.
Measurement of the t-channel single top-quark cross section at 13 TeV
CMS collaboration
[Full text] Physics Analysis Summary TOP-15-004
Public experimental note. 14th September.
First look at top-quark selections with 13 TeV data
CMS collaboration
[Full text] CMS Detector Performance Note released in occasion of the EPS-HEP 2015 conference
Public experimental note. 24th July.


Update to the measurement of top quark polarization in t-channel single-top production
T. Chwalek, A. Giammanco, M. Kadastik, M. Komm, D. Konstantinov, J. Pata, S. Rocker, A. Tiko, F. Roscher, J. Wagner-Kuhr
Analysis Note AN-2014/001 in support of the paper for CMS-TOP-13-001. Update of AN-2012-448.
Private experimental note. 9th June.
Search for H->bb in association with single top quarks as a test of Higgs boson couplings
A. Anuar, A. Bean, K. Bloom, C. Boeser, T. Chwalek, S. Fink, A. Giammanco, R. Gonzalez Suarez, D. Knowlton, J. Komaragiri, M. Komm, B. Maier, D. Noonan, A. Popov, J. Wagner-Kuhr
[Full text] Analysis Note AN-2013/113 in support of CMS-HIG-14-015
Private experimental note. 7th June.


Measurement of top quark polarization in t-channel single-top production
T. Chwalek, A. Giammanco, A. O. M. Iorio, M. Kadastik, M. Komm, D. Konstantinov, J. Pata, M. Piibeleht, A. Popov, L. Rebane, A. Remm, S. Roecker, A. Tiko, F. Roscher, J. Wagner-Kuhr
[Full text] Supporting note for CMS-TOP-13-001
Private experimental note. 23rd September.
Measurement of top quark polarization in t-channel single-top production
CMS Collaboration
[Full text] Physics Analysis Summary
Public experimental note. 23rd September.

[UCLouvain] - [SST] [IRMP] - [SC]
Contact : Jérôme de Favereau
Job opportunities Postdoctoral Position on advanced analysis techniques applied to the CMS di-Higgs study
Post-doctoral positions in collider phenomenology and particle astrophysics
EOS be.h : 10 PhD positions