List of PhD offers of laboratory.

Atlas
Search for doubly resonant beyond the Standard Model process with one Higgs boson and one scalar resonance in the final state in the $b\bar{b}\gamma\gamma$ channel in the ATLAS experiment at the LHC
PhD supervisor:
E. Monnier - T. Theveneaux-Pelzer - monnier@cppm.in2p3.fr - tpelzer@cppm.in2p3.fr
Description:

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. The group is also at the forefront of the study of this boson and the search for supersymmetry in the 2015-2018 data taking campaign known as Run 2 and the ongoing one known as Run 3, with major implications in several analyses with electromagnetic particles in the final state. Moreover, for the upgrade of the accelerator performances, high luminosity phase of the LHC (HL-LHC), this calorimeter has a major ongoing development program to dramatically upgrade its trigger and readout to which the CPPM group is actively involved. The LHC Run 3 started in 2022, and is expected to continue until 2025. The data from proton-proton collisions collected during this period by the ATLAS experiment will allow the large particle physics research programme to continue, improving the measurements of the Standard Model (SM) parameters and the limits on new physics phenomena, before the high-luminosity phase of the LHC (HL-LHC) from 2029.

Among the studied processes, the search for pp->HH Higgs boson pair production appears to be a new frontier, as its observation would allow a direct measurement of the self-coupling of this long-predicted scalar particle, discovered in 2012 only. This process predicted by the SM is particularly rare, and analysis of the HL-LHC data should be necessary to observe it. However, beyond-the-SM theories predict the existence of new scalar (S) particles, which could be produced in proton-proton collisions in association with a Higgs boson: pp->SH. The CPPM ATLAS team is involved in the search for the pp->HH process, in particular in the channel with a bottom quark-antiquark pair and two photons in the final state.

The proposed thesis topic aims to search for pp->SH processes with the Run 3 data, in the same decay channel. The student will participate to this analysis, to the necessary detector performance studies related to the team areas of expertise, in particular on aspects related to photon reconstruction and identification, and to the liquid argon calorimeter operation. 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.

Keywords:
Physique des particules
Code:
Doctorat-2326-AT-04
Exploring the low mass regime with the ATLAS detector at the LHC
PhD supervisor:
Lorenzo Feligioni, Aoife Bharucha - +33 6 86 11 58 45, +33 491 26 95 28 - lorenzo@in2p3.fr , aoife.bharucha@cpt.univ-mrs.fr
Description:

The predictivity of the Standard Model (SM) of particle physics remains unchallenged by experimental results. After the tantalizing discovery of the Higgs boson at LHC, the measurements of properties such as its mass, spin, parity and its couplings with other SM particles have confirmed its SM-like nature. This goes hand in hand with the absence of direct signs of TeV physics beyond the SM from current direct searches.

The excellent performance of the LHC in terms of delivered luminosity allowed the ATLAS and CMS experiments to set stringent limits on new particle masses well beyond the EW scale, thus worsening the naturalness problem. If the new physics scale lies well above the present experimentally probed energies, one would be left with the only experimental perspective of searching for deviations within the LHC precision measurements, and with no solid theoretical explanation of why the new physics should be so unnaturally heavy. There is, however, another logical possibility: new physics may be hidden at lower energies although weakly coupled to the SM known particles, so that its signals could be swamped in the SM background.

The possibility of recording low energy signatures rely on the capacity of processing the enormous amount of data provided by the LHC. For this ATLAS uses an advanced two-level trigger, the first level implemented in custom hardware, and High Level Trigger that relies on selections made by algorithms implemented in software. Moreover, a series of detector upgrades have been realized to face the challenges posed by the current Run 3 LHC high luminosity data taking. This allows the implementation of efficient algorithms to trigger low energy thresholds at much harsher LHC collision conditions.

In light of the above-mentioned theoretical scenarios, only little can be predicted in a model-independent way about the couplings of new light resonances to the SM. Therefore, we envisage considering specific models, focusing on particular final states. An example of this low mass resonance is an axion-like particle (ALP), which further acts as a mediator to Dark Matter. We will determine the region of parameter space where all existing collider, astrophysical, cosmology constraints are respected, and the relic density is obtained. We will then study the prospects of producing such an ALP which subsequently decays to b-anti-b pairs at the LHC. This will allow us to pinpoint novel signatures, providing a complementary handle on the models in question, signatures that will be then looked for by the candidate, analyzing ATLAS data recorded during Run 3.

Keywords:
Physique des particules
Code:
Doctorat-2326-AT-03
Development of Artificial Intelligence algorithms applied to hardware processing units based on FPGAs for the phase II upgrade of the ATLAS liquid Argon Calorimeter
PhD supervisor:
Description:

The data acquisition and trigger electronics of the ATLAS liquid argon calorimeter will be fully replaced as part of the second phase of upgrade of the ATLAS detector. The new backend electronics will be based on high-end FPGAs that will compute on-the-fly the energy deposited in the calorimeter before sending it to the trigger and data acquisition systems. New state-of-the-art algorithms, based on neural networks, are being developed to compute the energy and improve its resolution in the harsh conditions of the HL-LHC.

The candidate is expected to take a role in the development of data processing algorithms allowing to efficiently compute the energies deposited in the LAr calorimeters in the high pileup conditions expected at the HL-LHC. These algorithms will be based on AI techniques such as recurrent neural networks will be adapted to fit on hardware processing units based on high-end FPGAs. The successful candidate will be responsible of designing the AI algorithms, using python and keras, and assessing their performance. The candidate will also assess the effect of employing such algorithms for electromagnetic object reconstruction (especially at trigger level). She/he will work closely with the engineers designing the electronic cards at CPPM in order to adapt the AI algorithm to the specifics of FPGAs. Candidates with a strong interest for hardware will be encouraged to take part in the design of the firmware to program the FPGAs.

Prior knowledge of keras, python and C++ is desirable but not mandatory.

Keywords:
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Code:
Doctorat-2326-AT-01
IC Design for High Energy Physics experiments
PhD supervisor:
Marlon Barbero - barbero@cppm.in2p3.fr
Description:

The Aix-Marseille University and the ATLAS CPPM group in Marseille have an opening for a PhD (already funded) in the domain of IC design and characterization of depleted CMOS sensors and hybrid pixel electronics for future applications at particle colliders.

The Centre de Physique des Particules de Marseille (CPPM) is a joint research unit of the Centre National de la Recherche Scientifique (CNRS) and the Aix-Marseille University. The CPPM is a leading player in research in Particle Physics, Astroparticle Physics and Observational Cosmology. It is present in the largest physics experiments currently underway or being developed throughout the world.

The CPPM ATLAS group has a long-standing experience on hybrid pixel technologies. It is currently involved in the ATLAS Inner Tracker (ITk) upgrade project, targeting the High Luminosity phase of the Large Hadron Collider (HL-LHC project), and also in developments of technologies for future applications at collider experiments.

We are seeking candidates to join the group and develop CMOS sensors and hybrid pixel electronics in small feature size for particle physics pixel detectors at high intensity and high radiation dose, in the context of several international collaborations and projects.

We are seeking motived candidates that should have skills or strong will to acquire experience in:

- Microelectronics and circuit design.

- Silicon semiconductor process technologies.

- Deep submicron CMOS technologies.

- Design tools, simulation, design and verification.

- Experimental verification, designing test systems, acquisition software.

- Testing complex devices, data processing and data analysis.

Further inquiries can be addressed to: barbero@cppm.in2p3.fr

https://emploi.cnrs.fr/Offres/Doctorant/UMR7346-ANNPOR-077/Default.aspx

Keywords:
Physique des particules
Code:
Doctorat-2225-AT-01
Probing the Higgs boson pair production through Vector Boson Fusion at the LHC in the ATLAS experiment
PhD supervisor:
Thomas Strebler / Arnaud Duperrin - +33 4 91 82 72 52 / +33 4 91 82 76 25 - strebler@cppm.in2p3.fr / duperrin@cppm.in2p3.fr
Sorry, this position is no longer available
Description:

The study of the Higgs boson pair production is generating a growing interest in the particle physics community, in particular in view of the High-Luminosity phase of LHC. In addition to the Higgs self-coupling, the VVHH coupling is also an important parameter to improve our understanding of the electroweak symmetry breaking, which can be probed through the search for di-Higgs events in the VBF production mode.

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 Higgs bosons, such as the di-Higgs production modes. 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 quark and of the Higgs boson for instance.

Very strong constrains on the VVHH coupling can already be achieved with the LHC Run 3 dataset, in particular combining the low and high m(HH) regions. The corresponding analyses are the focus of a collaborative research effort involving several French laboratories members of the ATLAS Collaboration at CERN. The PhD position would complement this research effort, with a particular focus on the analysis of the bbtautau resolved final state, benefitting from the strong expertise of the ATLAS group at CPPM in b-tagging and di-Higgs studies [1-2].

Applications should include a CV, a letter of motivation, academic records from bachelor to master and contacts of two reference persons willing to provide reference letters.

[1] ATLAS flavour-tagging algorithms for the LHC Run 2 pp collision dataset https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/FTAG-2019-07/

[2] Search for Higgs boson pair production in the final state with two bottom quarks and two photons in pp collisions at ?s = 13 TeV with the ATLAS detector https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2018-34/

Keywords:
Physique des particules
Code:
Doctorat-2326-AT-02
Belle II
Search for lepton flavour violating decays $B \to \tau\ell X$ and $b \to s \tau \tau$ transitions.
PhD supervisor:
Justine Serrano - 0491827280 - serrano@cppm.in2p3.fr , Giampiero Mancinelli - 0491827675 - giampi@cppm.in2p3.fr
Description:

Being forbidden in the Standard Model (SM) of particle physics, lepton flavor violating decays are among the most powerful probes to search for physics beyond the SM. In view of the recent anomalies seen by LHCb on tests of lepton flavor universality in $b\to s \ell \ell$ and $b \to c \ell \nu$ processes, the interest of lepton flavor violating decays involving tau leptons in the initial or final state has been greatly reinforced. In particular, several new physics models predict branching fractions of $\tau \to \phi\mu$ and $B \to K\tau\mu$ decays just below the current experimental limits. This is true as well for the FCNC prosesses $b \to s \tau \tau$ .

The Belle II experiment located at KEK, Japan, started to take data in 2019, aiming at collecting 50 times more data than its predecessor, Belle, by 2031. The goal of this phD is to exploit the Belle II data in order to obtain the best experimental limits on lepton flavor violating decays such as $B \to \tau\ell X$ , where X is a hadronic system and $\ell$ an electron or a muon and on the transitions $b \to s \tau \tau$ , as $B \to K* \tau \tau$ .

Activities:

Data analysis using Machine Learning techniques (in particular Graph Neural Networks), participation to data taking, participation to Belle II service tasks, activities of outreach and dissemination.

Work context:

This phD will take place at CPPM, Marseille (https://www.cppm.in2p3.fr/web/en/index.html). Travels to KEK for collaboration meetings, and longer stay for participation to the data taking, are foreseen.

Applicants must hold a Master degree (or equivalent) in Physics, or expect to hold such a degree by the start of employment.

Application must include a CV, grade records, a motivation statement and contacts of three possible persons to supply letter of recommendation.

References:

https://arxiv.org/abs/2208.14924

Keywords:
Physique des particules
Code:
Doctorat-2326-BE-01
HESS-CTA
Observation of the PeVatron candidate SNR G106.3-2 with the LST1+MAGIC Cherenkov telescopes
PhD supervisor:
Franca Cassol & Heide Costantini - 0491827248 & 0491827257 - cassol@cppm.in2p3.fr & costant@cppm.in2p3.fr
Sorry, this position is no longer available
Description:

The CTA (Cherenkov Telescope Array) is a worldwide project to construct the next generation ground based very high energy gamma ray instrument [1]-[2]. CTA will use tens of Imaging Air Cherenkov Telescopes (IACT) of three different sizes (mirror diameter of 4 m, 12 m and 23 m) deployed on two sites, one on each hemisphere (La Palma on the Canary Islands and Paranal in Chile). The observatory will detect gamma-rays with energy ranging from 20 GeV up to 300 TeV by imaging the Cherenkov light emitted from the charged particle shower produced by the interaction of the primary gamma ray in the upper atmosphere.

The unconventional capabilities of CTA will address, among others, the intriguing question of the origin of the very high energy galactic cosmic rays by the search for galactic sources capable of accelerating cosmic rays up to the PeV energies, called PeVatrons. Recently, the Supernova Remnant (SNR) G106.3-2.7 has been indicated as a highly promising PeVatron candidate [4]. In fact, G106.3-2.7 emits gamma-rays up to 500 TeV from an extended region (~0.2o) well separated from the SNR pulsar (J2229+6114) and in spatial correlation with a local molecular cloud.

The CTA observatory completion is foreseen in 2025 but the first Large-Sized Telescope (LST1) is already installed and taking data in La Palma. LST1 is placed very close to the two MAGIC telescopes [3], which are one of the presently active IACT experiments. This configuration permits to perform joint observations of the same source with the three telescopes LST1+MAGIC increasing the effective detection area and improving the energy and angular resolution, thanks to the enhanced quality reconstruction of stereoscopic data. While the LST1+MAGIC telescopes cannot reach enough sensitivity to access energies above 100 TeV, they can provide exclusive and unprecedented data for establishing the spectral morphology of this exciting PeVatron candidate in the 100 GeV-100 TeV energy region. A campaign of joint observations of G106.3-2.7 will start in 2022 and will continue in the following years.

The PhD project will be on the analysis of the data of the coming campaign, its ambitious target will be to contribute in disclosing the hadronic or leptonic nature of this promising PeVatron. In order to maximize the effective area at very high energy, G106.3-2.7 will be observed at large zenith angle (LZA), 62o-70o, which represents a challenging detection condition. The project will start with the development and verification of the joint LST1+MAGIC stereo reconstruction chain [5] at LZA, using Monte Carlo (MC) data. This MC study will aim to optimize the data reconstruction and selection in order to reach a high quality Instrument Response Function and sensitivity for this specific source. Real data will be then reconstructed so as to achieve both a morphological and a spectral reconstruction of the source in the 100 GeV-100 TeV energy range. Finally, the high-quality LST1-MAGIC data will be used for a multiwavelength analysis that will compare different emission models and try to disentangle the nature of the source.

The project will include the participation to the LST1+MAGIC observation campaign with stays of four weeks in the Roque de los Muchachos Observatory in La Palma.

The CPPM CTA group works since several years in the building and commissioning of the LST1 telescope and on the preparatory studies for the research of galactic PeVatrons with CTA [6][7].

Candidates should send their CV and motivation letter as well as grades (Licence, M1, M2) to cassol@cppm.in2p3.fr and costant@cppm.in2p3.fr before 10/4/2022. Applications will be selected on the base of qualifications and an oral interview.

References:

[1] Science with the Cherenkov Telescope Array: https://arxiv.org/abs/1709.07997

[3] MAGIC Collaboration, Aleksi?, J. et al. Astropart. Phys. 72 (2016) 7694.

[4] Z. Cao et al. Nature, 594, 3336 (2021); M. Amenomori et al. Nature Astronomy, 5, 460464 (2021)

[6] O. Angüner et al. Cherenkov Telescope Array potential in the search for Galactic PeVatrons, ICRC 2019

[7] G. Verna et al. HAWC J2227+610: a potential PeVatron candidate for the CTA in the northern hemisphere, ICRC 2021

Keywords:
Astroparticules
Code:
Doctorat-2225-CT-01
KM3NeT
PhD supervisor:
Description:
Keywords:
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Code:
Doctorat-2326-KM-02
Multi-messenger analysis with KM3NeT
PhD supervisor:
Damien Dornic - 0491827686 - dornic@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 and path deviation. Nowadays, the sources of very high-energy cosmic rays are still unknown. Doing neutrino astronomy is a long quest for neutrino telescopes. Several observational hints have been detected by ANTARES and IceCube (active galaxy nuclei, tidal disruption events).

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 (1 GeV-10 TeV) and a high energy site ARCA in Italy (1 TeV-10 PeV). Its main goals are to study of neutrino oscillations, with as flagship measurement the determination of the neutrino mass ordering and to perform neutrino astronomy. Both detectors are already collecting data with the first detection units and will soon reach significantly better sensitivities for the detection of cosmic neutrinos surpassing by far the ANTARES one. Thanks to the unprecedented angular resolution, the extended energy range and the full sky coverage, KM3NeT will play an important role in the rapidly evolving multi-messenger field. A good sensitivity over such a large energy coverage can only be obtained by combining the data of the two detectors. KM3NeT will achieve a precision of <0.1 degrees for the muon neutrino tracks at very high energies, and <1.5º for the cascade events (electron, tau charge current + all flavor neutrino neutral current interactions). With KM3NeT, we will be able to perform a very efficient all-flavour neutrino astronomy.

The main goal of the thesis is to develop multi-messenger analyses in the two KM3NeT detectors. With the early data, we have performed a lot of studies to understand the behaviour of the detectors by setting the calibration procedures and by implementing very detailed Monte Carlo simulations that reproduce quite well the data taking. It has also permitted to start the development of the online analysis framework. Most of the elements are in operation (online reconstruction, neutrino classifier, reception of external transient triggers, alert sending). At the beginning of the PhD, the student will have to develop and implement efficient all-flavour neutrino selection over the atmospheric backgrounds. These selections will be performed using advanced analysis methods such as machine learning algorithms, that will be used to classify the nature of all the KM3NeT events between neutrino tracks (charged current muon neutrinos), neutrino cascades (all others neutrino flavours) and background events (atmospheric muons and neutrinos). The second step of the PhD will be to use these neutrino streams to look for time and space correlation with external triggers from electromagnetic transients, gravitational waves and high-energy neutrinos. This correlation analysis will be developed in two steps, starting with the implementation of a simple counting analysis that looks for a signal excess in a pre-optimized region of interest and in a given time window. For the most interesting neutrinos, the PhD student will also participate to the development of the alert sending system and the multi-wavelength follow-ups (radio, visible, X-ray and VHE). The student will have to develop the neutrino filters based on the false alarm rates of those alerts, their energies and angular resolutions Real-time multi-messenger campaigns are crucial in unveiling the sources of the most energetic particles and the acceleration mechanisms at work. The student will also participate to set the multi-wavelength follow-up of the KM3NeT alerts.

The candidate should have a good background in astroparticle physics and astrophysics. The interest in the data analysis is expected together with knowledge of statistics. The analyses will be performed using C++, Python and Root on Linux platforms.

KM3NeT: http://www.km3net.org

Keywords:
Astroparticules
Code:
Doctorat-2326-KM-01
Measurement of neutrino oscillations with the KM3NeT/ORCA detector.
PhD supervisor:
Jürgen Brunner - 0491827249 - brunner@cppm.in2p3.fr
Sorry, this position is no longer available
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. KM3NeT/ORCA is optimised for the detection of low energy (3-100 GeV) atmospheric neutrinos and will allow precision studies of neutrino properties. Currently the detector takes data with 15 detection strings which instrument a volume of about 1Mton - much larger than underground detectors with a similar science program. Several years of data are available, waiting to be analysed.

The task of the student is to participate in data taking, construction and calibration of the KM3NeT/ORCA detector and to analyse several Mton-years of neutrino data. This will allow for a cutting edge measurement of the atmospheric neutrino oscillation parameters and a first estimation of the neutrino mass ordering.

https://arxiv.org/abs/2103.09885

Keywords:
Physique des particules
Code:
Doctorat-2326-KM-03
LHCb
Test of lepton flavor universality in semileptonic B meson decays at LHCb
PhD supervisor:
Dorothea vom Bruch, Olivier Leroy - dorothea.vom.bruch@cern.ch , Olivier.Leroy@in2p3.fr
Description:

Mission

The LHCb group of the Centre de Physique des Particules de Marseille (CPPM) invites applications for a PhD position testing lepton flavor universality in semileptonic B meson decays.

The LHCb experiment at the LHC proton-proton collider at CERN is dedicated to studies of heavy flavour physics, with the major goal to find deviations from the Standard Model of particle physics in decays of heavy hadrons. After a major upgrade, LHCb restarted data taking in 2022 with Run 3 of the LHC. Over the next years, it will collect unprecedented data samples bringing the measurements to a new level of precision.

As successful candidate, you will play an active role in analysing decays of beauty mesons into final states with an excited charm meson, a lepton and a neutrino using Run 3 data. The aim of these studies is to measure electron-tau universality in the ratio of branching fractions BF(B ? D* ? ?) / BF(B ? D* e ?) for the first time at LHCb.

Activities

By employing a multidimentional fit you will separate the signal decays from the various background processes to determine the yields of the B ? D* ? ? and B ? D* e ? decays. For this, you will produce templates representing the signal and background processes in different kinematic variables. Both these templates and the efficiencies are obtained primarily from simulation, so you will correct the simulation to best match the data. The project will require the usage of modern computing techniques and machine learning approaches.

In addition to the physics analysis, you will have the opportunity to study and improve the newly installed data selection system implemented entirely in software on GPUs and CPUs. Therefore, you will gain experience in developing within a heterogeneous software framework.

Work environment

Situated at the heart of the Callanques National Park, on Luminy campus, CPPM is a joint research laboratory between CNRS and Aix-Marseille University with a staff of around 180 researchers, engineers and PhD students. The laboratory studies topics ranging from particle physics, astroparticle physics and cosmology, with a strong technological force in electronics, mechanics, instrumentation and IT, enabling the design and construction of state-of-the-art detector systems, often required to operate under extreme conditions: deep under the sea, in space or underground. Most of our research is carried out within leading international scientific collaborations and our contributions are recognized worldwide. CPPM is committed to ethical reserach and to diversity and inclusion in the workplace, and provides administrative and logistics support for newcomers, in particular for PhD students. (more details here: https://www.cppm.in2p3.fr/web/en/index.html)

The LHCb group at CPPM consists of seven permanent researchers, four engineers, two postdoctoral researchers and three PhD students. We have been actively involved in studies of semileptonic and rare B decays, as well as in the development of the new data acquisition system installed in 2022.

The position is funded by the ERC Starting Grant ALPaCA for exactly three years. As successful candidate you will be part of the doctoral school Physics and Sciences of Matter of Aix Marseille University, and travel to CERN regularly.

Requirements:

Applicants must hold, or are about to obtain, a Master's degree in physics. Good knowledge of particle physics, mathematical methods of data analysis, and computer programming are required.

Applications should include a statement of interest (1 page), a CV (max 2 pages), two reference letters and if already available the (preliminary) grades of the Master's degree. The statement of interest, CV and grades should be uploaded in the CNRS portal: https://emploi.cnrs.fr/Offres/Doctorant/UMR7346-ANNPOR-098/Default.aspx?lang=EN. Please arrange for the letters of reference to be sent to Dorothea vom Bruch (dorothea.vom.bruch@cern.ch) by the application deadline. The appointment will start on October 1st 2023.

Keywords:
Physique des particules
Code:
Doctorat-2326-LH-01
Renoir
Testing general relativity with measurements of the growth rate of structures using Rubin/LSST supernova observations
PhD supervisor:
Benjamin Racine - racine@cppm.in2p3.fr
Description:

Twenty years after the discovery of the acceleration of the universe's expansion using supernova measurements, the supernova probe remains the most accurate way to measure the parameters of this recent period of our universe's history dominated by the so-called dark energy.

The precision measurements that can be made with the supernova probe will be a crucial element that, in combination with other probes (LSS, weak lensing, CMB, etc.), will allow to establish strong constraints on the nature of dark energy and to explore possible deviations from general relativity. This will be made possible by the exceptional supernova observations that LSST will provide, with a combination of huge statistics and extreme calibration accuracy.

The Vera Rubin Observatory will complete its construction in 2023 and will be commissioned in 2024. The Large Survey of Space and Time (LSST) will start full speed in early 2025, with its 8.4-meter telescope equipped with a 3.2 billion-pixel camera, the most powerful ever built.

This telescope will take a picture of half the sky every three nights for ten years. This survey will make it possible to measure billions of galaxies with great precision and to follow the variation in time of all transient objects. Together with many other astrophysical studies, it will be a very powerful machine for determining cosmological parameters using many different probes and, in particular, will place strong constraints on the nature of dark energy. The LSST project aims at discovering up to half a million supernovae, many of which can be used to probe cosmology. With an improvement of two orders of magnitude in statistics over the current data set, this will allow precise tests of the parameters of dark energy, new tests of general relativity, and will also impose new constraints on the isotropy of the universe.

In this thesis, we propose to prepare and participate in the first analysis of LSST supernova data with a focus on measuring the growth rate of structures. The preparation will be done by working on the accurate photometric measurement and photometric selection of Type Ia supernovae and their link to the properties of their host galaxy. These two points and the selection effects are among the most important sources of systematic errors and any work to reduce and mitigate these sources of errors will have a significant impact on the final measurement. Such a study has already started for the Zwicky Transient Facility (ZTF), which has been observing since 2018. It will serve as a basis for the development of the LSST analysis and a possible LSST/ZTF combination.

The LSST group at CPPM is already involved in precision photometry work for LSST and ZTF with direct involvement in the validation of algorithms within DESC/LSST. The PhD student will work within this framework using a comprehensive analysis pipeline built with these tools, which he will help improve, and apply it to ZTF data and then to LSST data to participate in the first DESC analysis.

Keywords:
Cosmologie observationnelle
Code:
Doctorat-2326-RE-02
Probing modified gravity using cosmic voids
PhD supervisor:
S. Escoffier / P. Vielzeuf - 04 91 82 76 64 - escoffier@cppm.in2p3.fr / vielzeuf@cppm.in2p3.fr
Description:

Although the universe is well described by the concordance model ?CDM, the nature of its components, dark matter and dark energy, remains a major puzzle of modern cosmology. While historically most attention has been paid to the overdense regions, the underdense regions account for about 80 per cent of the total volume of the observable Universe and strongly influence the growth of large-scale structure. As voids are nearly devoid of matter, they have proved to be very promising objects for exploring the imprint of possible modifications of General Relativity (GR) such as f(R) gravity or extended gravity theories.

The RENOIR cosmology team at CPPM focuses on the understanding of the history and composition of our Universe, particularly on its dark components. The team is particularly involved in large spectroscopic surveys Dark Energy Spectroscopic Instrument at Mayall, US and the European space mission Euclid, that will provide the observation of 40 million of galaxies, the largest 3D map of the Universe ever made.

A promising way to probe modified gravity models is to constrain the growth of structure of the Universe using information from Redshift Space Distortions around cosmic voids. The aim of the PhD thesis is on the extraction of cosmological constraints using Alcock-Paczynski deformation information and RSD information around voids, with DESI data which started its observations in June 2021 for 5 years, and the Euclid mission that will be launched in July 2023.

Keywords:
Cosmologie observationnelle
Code:
Doctorat-2326-RE-01
Testing dark energy with the ISW effect in the Euclid mission
PhD supervisor:
Stéphanie Escoffier - 04 91 82 76 64 - escoffier@cppm.in2p3.fr
Sorry, this position is no longer available
Description:

The various observations of the Universe have been indicating for twenty years now that the expansion of the Universe is accelerating. The standard model of cosmology, known as the LCDM model, describes the Universe as composed of 27% dark matter and 68% dark energy. Understanding the nature of these two energy components remains one of the greatest challenges in contemporary physics. Next-generation galaxy surveys, such as Euclid or DESI, will make it possible to measure several tens of millions of galaxy spectra in the coming decade and tighten constraints on the cosmological model, or probe its alternatives like modified gravity models.

The most promising tools to constrain dark energy and gravity properties are based on the observation of large structures in the Universe. The structure of the Universe also reveals the presence of large under-dense regions, enclosed by filaments of matter. These cosmic voids, which occupy nearly 80% of the volume of the Universe, contain very few matter, and are therefore an ideal laboratory for testing dark energy scenarios.

The subject of the thesis is to extract the integrated Sachs-Wolfe (ISW) signal by cross-correlating cosmic voids with Cosmic Microwave Background (CMB). Indeed the time evolution of gravitational potentials imprints secondary anisotropies in the CMB, in addition to the primordial CMB anisotropies generated near the last scattering surface. These additional anisotropies are caused by gravitational interactions of CMB photons with the growing cosmic large-scale structure. The ISW signal is challenging to measure since it is very weak compared to primordial CMB photons. However the signature of the ISW

effect can be observed as a non-zero signal in the cross-correlation between the distribution of foreground tracers of dark matter (such as galaxies) and the temperature of CMB, providing a direct probe of the late-time expansion of the Universe. Recent work (Kovacs 2021) has shown that the ISW signal amplitude exhibits an excess over the expectations of the standard LCDM model, at the 3 sigma level, especially when the study is applied to superstructures such as supervoids.

The thesis project focuses on the ISW effect and the cross-correlation between the CMB and cosmic voids. The work of the student will consist in building the void catalogs from galaxy catalogs, developing estimators and likelihoods associated with the ISW effect and quantifying how the ISW effect impacts onto dark energy and modified gravity parameters.

The CPPM is involved in the two projects DESI and Euclid, both dedicated to the measurement of cosmological parameters to constrain dark energy and test modified gravity models.

DESI is a galaxy survey that started in 2021 for 6 years and will observe nearly 40 million spectra of galaxies up to a redshift of 3.5. Euclid was selected by the European Space Agency (ESA) in 2011 and will be launched in 2023 to probe the Universe over a 6 year-period. These data will revolutionize our ability to map the Universe and better understand the nature of dark energy or put Einstein's General Relativity (GR) in default.

Application should be done via the CNES website:

https://recrutement.cnes.fr/fr/annonce/1498789-175-testing-dark-energy-with-the-isw-effect-in-the-euclid-mission-13009-marseille

A CNES/CNRS funding can be obtained for this thesis.

Keywords:
Cosmologie observationnelle
Code:
Doctorat-2225-RE-01
imXgam
Simulation of photocounting Multi-Energy Detector Response.
PhD supervisor:
Yannick Boursier - +33 (0)4 91 82 76 41 - boursier@cppm.in2p3.fr
Description:

This PhD is granted by the Detection Technology (DT) company under a CIFRE contract.

Detection Technology Company description

With us you do WORK THAT MATTERS

We are the most trusted partner imaging the unknown by creating foresight capabilities quicker to discover and prevent threats. Our solutions contribute to the improvement of people's health and safety daily. With us you do work that truly matters.

We are a global provider of off-the-shelf and customized X-ray imaging solutions for medical, security and industrial applications. Our product portfolio ranges from photodiodes to complete detector systems with ASICs, electronics, mechanics and software.

Our net sales totaled EUR 94 million in 2018. With 30% compound annual growth rate (CAGR) of net sales we have exceeded the market growth for over five years. We have 240 active customers in over 40 countries.

Detection Technology employs over 500 people in Finland, China, France and the USA. The company's shares are listed on the Nasdaq First North Finland market place.

We are looking for a skilled master degrees students in data science, physics to join our global R\&D team in Moirans (Isère - 38), France as PhD in algorithm and simulation tools development. DT is international company, and R\&D team is shared between Finland and France offices. Potentially, the PhDs could spend some limited time in Helsinki office, Finland.

Project description

We develop the Multi-Energy high flux photon counting detectors for NDT, security, medical applications. The detector is one of the elements of radiographic detection chain composed of X-rays tubes, filters, cooling and data acquisition system.

It was demonstrated that the spectroscopic counting detectors bring more information than the standard dual energy scintillator detectors, and consequently, allow a better material discrimination.

The optimized radiographic chain is of big importance for the system performances and for investments (commercial). As for the detection system, all detectors are characterized by their performances conditioned by a set of compromises made in development. Obviously, the detector has to be adapted for an application and the detector simulations are critical.

The target of the project consists to develop a simulation tool allowing the modeling of the CdTe detector response in different geometrical and electronic configurations.

The Multi-Energy detector response (DR) simulation would be the time consuming and difficult task, as many Physical \& Electronics contributions have to be considered. This task would demand a PhD full time with strong mathematics and physics background.

At first step, the target of the PhD student would be to understand different physical \& electronics contributions to be considered for CdTe detector response modeling. The second step consists to simulate in very realistic way the Multi-Energy detectors developed at DT (several geometry and compositions of CdTe crystals, different pixels sizes, and various electronics). Monte-Carlo simulations and Machine Learning approaches will be used to model the detector response. The quality of the simulated results will be approved by comparison with the experimental data from different internal detectors and suppliers.

The work will be carried out in the Center de Physique des Particules de Marseille (CPPM) with close collaboration with the Detection Technology company based in Moirans (Isère). The PhD student will be based in Marseille and will release short and regular missions in Moirans within the company. Detection Technology will pay the PhD student 1800 to 2000 euros.

Skills

We are looking for the motivated person with a good level in programming and in physics or material sciences.

Master degree in applied Physics, material sciences, applied mathematics with strong interest to physics

- skills and facility in programming (Python, C, Matlab, Monte Carlo, Geant4, C++)

- background in X-ray and semiconductor physics

- background in electronics is a plus

Keywords:
Imagerie médicale
Code:
Doctorat-2225-IM-02