Liste des offres de thèses du laboratoire.

Atlas
Etude des propriétés du boson de Higgs avec le détecteur ATLAS au LHC
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Directeur de thèse :
Emmanuel MONNIER - +33 4 91 82 72 69 - monnier@cppm.in2p3.fr
Description :

English Version: Physics at the Large Hadron Collider (LHC) at CERN (European Organization for Nuclear Research) is the high priority research field of the Particle Physics community worldwide. ATLAS is one of the two general purpose experiments installed at the LHC that discovered a Higgs boson in July 2012, key piece for the understanding of the fundamental interactions and the origin of elementary particle mass. Its physics program extends beyond Higgs property measurements to the search for signs of physics beyond the Standard Model of particle physics.


The ATLAS group of the “Centre de Physique des Particules de Marseille” (CPPM) is deeply involved in this scientific program, in particular linked to its expertise of the electromagnetic calorimeter. The latter is a key component for the identification and energy measurement of electrons and photons, which were at the core of the Higgs boson discovery. It is also at the forefront of this boson studies and of the supersymmetry searches in the ongoing data taking campaign, so called “Run 2”, with major consequences in several analyses with leptons in their final states. Moreover, for the upgrade of the accelerator performances foreseen in 2021, this calorimeter has a major ongoing development program to dramatically upgrade its trigger and readout to which the CPPM group actively contributes.


In the Standard Model, the Higgs boson is highly coupled to the top quark, the known particle with the largest mass. The only way to directly measure this Higgs-top coupling (called top Yukawa coupling) is to observe the associated production of a Higgs boson with top quarks. This will be accessible for the first time with the “Run 2” data that are taken since 2015 and until 2018. This key measurement, and more generally the Higgs properties studies are of high importance since they would allow to confirm that the observed boson is the Standard Model Higgs boson, or could reveal New Physics.


The goal of this thesis is on the one hand to exploit the “Run 2” data set to get the best sensitivity on the Higgs property measurements and in particular the Yukawa coupling. The student will focus on the Higgs property measurement in multilepton final states (electron or muon). The “Run 2” data taking conditions at the LHC (proton-proton collision center of mass energy increased to 13 TeV, high luminosity) are particularly suited for these measurements. The sensitivity to the sub-dominant Higgs production modes – particularly its associated production with top quarks – is increased, allowing for refined measurements of the Higgs boson properties. On the other hand and in parallel, the student will also contribute to the electromagnetic calorimeter upgrade, and in particular, to the study of its upgraded configuration, first exploiting data taken with a prototype installed for the 2018 data taking, then contributing to the installation and commissioning of its final system, and finally to its validation and performances assessment with the first Run 3 data in 2021.


In this framework, the student will have to do frequent stays at CERN and the research work will combine physics analysis on real and simulated data as well as studies and operation of experimental systems.


French Version: La physique auprès du Large Hadron Collider (LHC) du Centre Européen de Recherche Nucléaire (CERN) constitue aujourd'hui l'axe de recherche prioritaire de la communauté mondiale en physique des particules. ATLAS, l'une des deux expériences généralistes installées auprès de cet accélérateur, a découvert un boson de Higgs en juillet 2012, pièce essentielle pour la compréhension des interactions fondamentales et en particulier l'origine de la masse. Son programme de physique est néanmoins plus vaste et s'étend à l'étude des propriétés du boson de Higgs et plus généralement à l'obtention des premiers signes de physique au-delà du Modèle Standard de la physique des particules.


Le groupe ATLAS du Centre de Physique des Particules de Marseille (CPPM) est fortement impliqué dans ce programme scientifique, avec notamment une expertise liée au calorimètre électromagnétique. Ce dernier est un élément clé pour l'identification et la mesure de l'énergie des électrons et des photons, qui ont fait le succès de la découverte du boson de Higgs. Il est également en pointe sur l'étude de ce boson et la recherche de supersymétrie dans la campagne de prise de données actuelle, dite « Run 2 », avec des implications majeures dans plusieurs analyses avec des leptons dans l'état final. De plus, en vue de l'amélioration des performances de l'accélérateur prévue pour 2021, ce calorimètre fait l'objet d'un important programme d'évolution de son système de lecture et de déclenchement auquel participe activement le groupe du CPPM.


Dans le Modèle Standard, le boson de Higgs se couple préférentiellement avec le quark top, particule élémentaire la plus massive jamais découverte. Le seul moyen de mesurer directement ce couplage (dit couplage de Yukawa du top) est d'observer la production associée du Higgs avec des quarks top. Cela sera accessible pour la première fois avec les données du « Run 2 » qui sont prises depuis 2015 jusqu'en 2018. Cette mesure et plus généralement, l'étude des propriétés du boson de Higgs sont très importantes, car elles peuvent confirmer que le boson observé est bien le boson de Higgs du Modèle Standard ou pourrait révéler de la nouvelle physique.


Le sujet de cette thèse est d'une part d'exploiter la prise de données du « Run 2 » pour obtenir la meilleure sensibilité sur ces mesures des propriétés du boson de Higgs, en particulier sur la mesure du couplage de Yukawa. L'étudiant(e) axera son travail d'analyse sur la mesure des propriétés du boson de Higgs dans les états finals à plusieurs leptons (électrons ou muons). Les conditions de la prise de données « Run 2 » au LHC (énergie dans le centre de masse des collisions protons-protons accrue à 13 TeV, grande luminosité) sont particulièrement favorables pour ces mesures. En effet, la sensibilité aux productions sous-dominantes du boson de Higgs – notamment en association avec une paire de quarks top - est accrue, permettant des mesures plus fines des propriétés du boson de Higgs. D'autre part et en parallèle, l'étudiant contribuera au programme d'amélioration du calorimètre électromagnétique, et en particulier, étudiera ses performances dans sa configuration optimisée, d'abord en exploitant les données prises avec un prototype installé sur le détecteur pour la prise de données 2018, puis en contribuant à l'installation et à la mise en œuvre du système final et enfin à sa qualification et à l'établissement de ses performances avec les premières données du Run 3 en 2021.


Dans ce cadre l'étudiant sera amené à effectuer de nombreux séjours au CERN, et son travail de recherche combinera des analyses de physique (sur données et simulation) ainsi que l'étude et la mise en œuvre de systèmes expérimentaux.


Mots clefs :
Physique des particules
Code :
Doctorat-1821-AT-01
Unravelling the top-Higgs coupling with the ATLAS experiment at the LHC
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Directeur de thèse :
Thomas Strebler - (+33) 04 91 82 72 52 - strebler@cppm.in2p3.fr / Arnaud Duperrin - (+33) 04 91 82 72 00 - duperrin@cppm.in2p3.fr - - - -
Description :

After the observation of the Higgs boson in 2012 and thanks to the large luminosity collected during the successful LHC Run 2 data-taking, the properties of the Higgs boson can now be studied in more and more details. In particular, the coupling between the Higgs boson and the top quark, the two most massive elementary particles in the Standard Model (SM), is of high phenomenological interest, as it can be very sensitive to deviations from the Standard Model predictions. One of the key channels to study the top-Higgs coupling is the so-called ttH production mode, where the Higgs boson is produced in association with top quarks and which has been recently observed by the ATLAS collaboration [1]. The study of this channel will be the main focus of this thesis.


The ATLAS detector is ideally suited for such studies, with its design optimised to reconstruct and identify most of the decay products of the Standard Model particles produced in rare physics processes involving a Higgs boson, such as the ttH production mode. This thesis will include some work on the optimisation of the algorithms used to identify jets produced in the hadronization of b-quarks for the upgrade of the ATLAS detector planned for the High-Luminosity phase of the LHC. Those algorithms play a major role in all the final states involving b-quarks, produced in the decay of the top quarks and of the Higgs boson for instance.


Thanks to the large branching fraction of the Higgs boson into b-quarks, the ttH(bb) channel offers the advantage of a relatively large signal acceptance in comparison to the other decay channels. It is possible to exploit this in particular to measure some of the Higgs boson kinematics properties, which can be used to constrain for instance the CP structure of the top-Higgs coupling. Those constraints may shed some light on one of the current biggest unanswered questions of physics, namely why our Universe is nowadays dominated by matter instead of antimatter. This thesis will focus on the detailed study of that channel, benefitting from the very strong expertise of the ATLAS group at CPPM in this area and will involve regular stays at CERN.


[1] Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2018-13/


Mots clefs :
Physique des particules
Code :
Doctorat-1922-AT-01
KM3NeT
Study of Neutrino Mass Ordering with data of the KM3NeT/ORCA deep sea Neutrino Detector
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Directeur de thèse :
Paschal COYLE - office: 0491827253, portable: 0675713799 - coyle@cppm.in2p3.fr
Description :

KM3NeT/ORCA (Oscillation Research with Cosmics in the Abyss) is a deep sea neutrino telescope currently under construction at a depth of 2500m in the Mediterranean Sea off the coast of Toulon. ORCA is optimised for the detection of low energy (3-100 GeV) atmospheric neutrinos and will allow precision studies of neutrino properties including the neutrino mass ordering. ORCA is part of the multisite KM3NeT research infrastructure, which also incorporates a second telescope array (in Sicily) optimised for the detection of high-energy cosmic neutrinos. The first ORCA detection strings have recently been deployed and are providing high quality data.


During this thesis, at the Centre de Physique des Particules de Marseille, the student will develop the analysis methods for a preliminary estimation of the neutrino mass ordering with the first years of ORCA data.


There is also the possibility of a related M2 stage on this project.


Links: http://antares.in2p3.fr http://www.km3net.org http://www.cppm.in2p3.fr/rubrique.php3?id_rubrique=259


Mots clefs :
----
Code :
Doctorat-1821-KM-01
Measurement of atmospheric neutrino oscillations with early KM3NeT/ORCA data
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Directeur de thèse :
Jürgen Brunner - 0491827249 - brunner@cppm.in2p3.fr
Description :

KM3NeT/ORCA (Oscillation Research with Cosmics in the Abyss) is a deep sea neutrino telescope currently under construction at a depth of 2500m in the Mediterranean Sea off the coast of Toulon. ORCA is optimised for the detection of low energy (3-100 GeV) atmospheric neutrinos and will allow precision studies of neutrino properties. The first ORCA detection strings will be deployed late 2018 or early 2019.


The student will actively participate in the data taking of the ORCA detector and analyse those data. The goal of the thesis is to extract a clean signal of upgoing atmospheric neutrinos, to demonstrate that these data are affected by the phenomenon of neutrino oscillations and to measure the relevant oscillation parameters. Links: http://antares.in2p3.fr http://www.km3net.org http://www.cppm.in2p3.fr/rubrique.php3?id_rubrique=259


Mots clefs :
Physique des particules
Code :
Doctorat-1922-KM-02
Real-time multi-messenger analysis with KM3NeT
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Directeur de thèse :
Damien Dornic, Vincent Bertin - 04 91 82 72 86 - dornic@cppm.in2p3.fr , bertin@cppm.in2p3.fr
Description :

Neutrinos are unique messengers to study the high-energy Universe as they are neutral and stable, interact weakly and therefore travel directly from their point of creation to the Earth without absorption. Nowadays, the sources of very high-energy cosmic rays are still unknown. The detection of a neutrino signal is a direct evidence of the sources and the proof of the hadronic mechanism that produced the cosmic rays.


KM3NeT is the second-generation neutrino detector in the Mediterranean Sea. It will be distributed in two sites: a low energy site ORCA in France (5 GeV-10 TeV) and a high energy site ARCA in Italy (1 TeV-10 PeV). Both detectors will have a sensitivity largely improved compared to ANTARES at low and high energies. The French site is located at 2500 m depth in the Mediterranean Sea, 40 km off Toulon close-by ANTARES. The infrastructure is already deployed in both sites and the first lines should be deployed by the end of 2018. The completion of the KM3NeT is expected to be achieved around 2023. High-energy neutrino physics is a young and an almost unexplored field, which owns much discovery potentials. IceCube, a complementary neutrino detector in the South Pole has already discovered the first cosmic neutrinos. This guaranties to have neutrino signal detections in KM3NeT.


The main goal of the thesis is to develop the real-time multi-messenger analysis in the two KM3NeT detectors to look for transient sources such as flares of blazar, gamma-ray bursts, fast radio bursts, supernovae… To achieve this goal, the student will work in the development of the real-time analysis framework. The student will have to implement efficient selection of neutrinos over the atmospheric backgrounds. These neutrino streams can then be used to look for time and space correlation with external triggers from electromagnetic transients, gravitational waves and high-energy neutrinos. For the most interesting neutrinos, the student will also participate to the development of the alert sending system and the multi-wavelength follow-ups (radio, visible, X-ray and VHE). With this method, one neutrino could lead to a major discovery. In addition to the track event topology resulting from muon neutrino events, already exploited by ANTARES, KM3NeT event reconstructions will allow using cascade events (electron and tau neutrinos) with a quite good angular precision. As CPPM is the host lab of KM3NeT, the student will participate to the installation during sea campaigns, the calibration and the data analysis of the first lines. The candidate should therefore have a good background in astroparticle physics and astrophysics and interest in the data analysis. The analyses will be performed using C++, python and Root on Linux platforms.


[1] KM3NeT: http://www.km3net.org [2] https://www.cppm.in2p3.fr/web/fr/recherche/astroparticules/


Mots clefs :
Astroparticules
Code :
Doctorat-1922-KM-01
LHCb
Search for the rare B decays with τ \tau leptons in the final state
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Directeur de thèse :
Giampiero Mancinelli and Julien Cogan - 0491827675 - giampi@cppm.in2p3.fr , cogan@cppm.in2p3.fr
Description :

Over the past few years, several measurements related to flavor-changing neutral current transitions have shown deviations from the Standard Model (SM) expectations. These deviations build up a tension at the 4-5σ \sigma level with respect to the Standard Model (SM) and they are currently the only indications of new physics coming from the CERN Large Hadron Collider (LHC) [1,2]. The consistent picture which is forming points towards violation of Lepton Flavour Universality (LFU), one of the building blocks of the SM. LFU violation is hence becoming an extremely hot topic on which LHCb should be able to shed light in the forthcoming years. The very rare decays of B(s) B_(s) mesons into leptons are key channels to indirectly constraint the new physics phase space. The muonic final states have been widely studied by different experiments but the decays into tau leptons are still very unconstrained, because of the difficulty in reconstructing taus.


The LHCb experiment, one of the 4 large experiments operating at the LHC, is dedicated to heavy flavor physics. During the LHC Run I (2011-2012), it has collected about 3 fb1 ^{-1} of proton-proton interactions, gathering the largest sample of B mesons ever recorded, and thus it is a unique place to look for rare or forbidden decays.


After taking a leading role in the first observation of the Bs0μ+μ B^0_s \to \mu^+ \mu^- decay, after a 20 years search (published in Nature in 2015 [3]), the LHCb team has published the first limit on Bs0τ+τ B^0_s \to \tau^+ \tau^- in 2017 [4] with the Run I data. The goal of this thesis project is to exploit the full LHCb data-set (currently including 3fb1 ^{-1} of Run II data as well) to carry-out searches for several $B$ decay modes with taus in the final state : B0K0τ+ tau B^0 \to K^{*0} \tau^+\ tau^- , B(s)0τ+ tau B^0_{(s)} \to \tau^+\ tau^- and B(s)0τμ B^0_{(s)} \to \tau \mu . The development and optimization of new reconstruction algorithms and analysis techniques are envisaged, as well as frequent trips to CERN.


References: (1)arXiv:1704.05340 (2)Eur. Phys. J. C (2017) 77: 377 (3)arXiv:1411.4413 (4)arXiv:1703.02508


Mots clefs :
Physique des particules
Code :
Doctorat-1821-LH-01