Arnaud Pin
Former member
PhD student in CP3 from September 2008 to September 2013
Research statement
I'm interested in the devellopment and application of the Matrix Element method for physics analysis at CMS experiment. I'm working, especially, wich process with two leptons and two b-jets in the final states, in particular top quark pair production in fully-leptonic channel. These method can be applied for top quark mass measurement, differential cross section estimation or to discriminate process with a same final state (as ttbar and Zbb).
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.

Automatic Matrix Element method and associated analyses techniques

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 Formula: 0 via the marginal distributions of the the experimental weights Formula: 1.

External collaborators: Pierre Artoisenet (Ohio state university).

Early observation of top quark pairs in the dileptonic final state

The top quark is the heaviest elementary particle discovered so far, and many properties related to this quark are still to be understood.
Its observation and mass measurement at Tevatron highlighted the uncommon nature of this quark. The fact that its electroweak decay is faster than the hadronization time scale implies that the top quark exists only as a free quark, so that the effects from new physics should show up very clearly by comparing measurements with the precise Standard Model preditions.
Its "re-discovery" at LHC will be a major milestone for the experiments, since the complexity of the final state demands a fairly good knowledge of the experimental apparatus and a certain degree of control of the backgrounds. Its expected large coupling to Higgs bosons will also be relevaant for the searches for higgs sectors beyond the Standard Model.

External collaborators: CMS collaboration.

Measurement of the b(b)Z process at LHC

At LHC, the Z boson can be produced in association with one or two b-quarks, which is here refereed as b(b)Z production. This process has been seen for the first time at LHC, and measurement of it is an important test of QCD calculations.

For the first time, we observed the Z+b final state and measured of the Z+b/Z+j cross-section ratio in 35.9/pb of pp collisions at 7 TeV, using particle flow jets and simple secondary vertex b-tagging algorithm in the definition of the signal.Emphasis is put on kinematic properties of the jets. With more luminosity, we are working on the measurement of the cross-section for the b(b)Z process, with the identification of one or two b-jets.

External collaborators: A.Gilbert, A.-M.Magnan, A.Nikitenko (Imperial College London); N.Heracleous, A.Perieanu (RWTH Aachen); M.Musich, E.Migliore (University of Torino), and CMS Collaboration.

Validation of a fully automatic matrix element technique for CMS data analyses

The matrix element reweighting method attempts to compute the full likelihood of an observed event given a theoretical model. The method therefore measures the degree of compatibility of the event with the given model using as much information as available. MadWeight is a tool that fully automatize the computation of the event likelihood for any model implemented in MadGraph, by performing phase-space integration and providing a framework for taking into account the experimental resolution on the observed final state objects.
This project aims at validating the matrix element reweighting technique implemented in MadWeight on a number of benchmark searches. In some cases, the final goal is the efficient identification of background events. The final states that are being considered are: Zbb, single top, ttbar resonances and dimuon resonances.

Publications in CP3
All my publications on Inspire


Measurement of the production cross sections for a Z boson and one or more b jets in pp collisions at $sqrt{s}$ = 7 TeV
Chatrchyan, Serguei and others
[Abstract] [PDF] [Journal] [Full text] Published in JHEP 1406 (2014) 120
Refereed paper. 10th February.


Matrix Element method applied for ttbar estimation in Z(ll)bb analysis.
A. Pin V. Lemaitre C. Beluffi J. Vizan
[Full text] Supporting document for SMP-13-004
Private experimental note. 26th August.
Measurement of the production cross sections of a Z boson in association with b jets in pp collisions at sqrt(s) = 7 TeV
The CMS Collaboration
[Full text] First presented at DIS 2013
Public experimental note. 26th August.
Search for Z(ll)H(bb) using Matrix Element method
A.Pin, T. du Pree, R. Castello, J. Vizan C. Beluffi, A. Caudron, C. Delaere, V. Lemaitre
[Full text] Internal CMS analysis note
Private experimental note. 26th August.


Determination of differential cross sections from ttbar fully leptonic, using the matrix element method
A. Pin and O. Mattelaer
[Journal] [Full text] Published in Il Nuovo Cimento C, Top 2011 Conference Proceedings
Contribution to proceedings. 6th June.
Measurement of the Z(ll)+bb cross section at CMS
R. Castello, L. Ceard, C. Delaere, A. Pin, and T.A. du Pree
[Full text] CMS internal document supporting CMS-SMP-12-003
Private experimental note. 23rd May.
Measurement of the Z/gamma*+b-jet cross section in pp collisions at 7 TeV
Chatrchyan, SergueiProg. Part. Nucl. Phys. and others
[Abstract] [PDF] [Journal] [Full text] Published in the Journal of High Energy Physics
Refereed paper. 10th April.


Studies of Tracker Material
The CMS Collaboration
[Full text]
Public experimental note. 8th February.
Search for Heavy Stable Charged Particles in pp collisions at sqrt(s) = 7 TeV
The CMS Collaboration
[Abstract] [PDF] [Journal] Published in JHEP
Refereed paper. 8th February.


Measurement of the ttbar cross section in the dileptonic channels with track-jets at 7 TeV
J. Caudron, A. Giammanco, A. Pin, V. Lemaitre
[Full text] Analysis Note 2010/195
Private experimental note. 31st December.
First Measurement of the Cross Section for Top-Quark Pair Production in Proton-Proton Collisions at sqrt(s)=7 TeV
CMS collaboration
[Abstract] [PDF] [Journal] Published in Physics Letters B
Refereed paper. 31st December.
Selection of Top-Like Events in the Dilepton and Lepton-plus-Jets Channels in Early 7 TeV Data
CMS collaboration
[Full text] CMS Physics Analysis Summary
Public experimental note. 31st December.
CMS Tracking Performance Results from early LHC Operation
CMS collaboration
[Abstract] [PDF] [Journal] [Full text] Published in Eur.Phys.J.C70:1165-1192,2010.
Refereed paper. 21st December.


Commissioning of the CMS Experiment and the Cosmic Run at Four Tesla
CMS Collaboration
[Abstract] [PDF] [Journal] [Full text] Published in JINST
Refereed paper. 21st December.
CMS Data Processing Workflows during an Extended Cosmic Ray Run
CMS Collaboration
[Abstract] [PDF] [Journal] [Full text] Published in JINST
Refereed paper. 21st December.
Commissioning and Performance of the CMS Silicon Strip Tracker with Cosmic Ray Muons
CMS Collaboration
[Abstract] [PDF] [Journal] [Full text] Published in JINST
Refereed paper. 21st December.

[UCLouvain] - [SST] [IRMP] - [SC]
Contact : Jérôme de Favereau
Job opportunities Postdoctoral Position on the CMS tracker upgrade for HL-LHC
EOS be.h : 10 PhD positions