List of PhD offers of laboratory.

Atlas
Exploring the low mass regime with the ATLAS detector at the LHC
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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
IC Design for High Energy Physics experiments
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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


Application should be made under:

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


Keywords:
Physique des particules
Code:
Doctorat-2225-AT-01
Search for the associated production of a Higgs boson and a Z boson in the preparation for the detection of di-Higgs production at the LHC
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PhD supervisor:
Emmanuel Monnier - monnier@in2p3.fr
Description:

The last piece of the standard model of particle physics, the Higgs boson, was discovered by the ATLAS and CMS collaborations in 2012. The newly discovered boson provides a unique possibility to search for new unknown physics beyond the Standard Model. The ATLAS group at CPPM have a leading role in detecting and studying the Higgs boson properties in several of its production and decay modes. The group is currently concentrating on the detection of the production of two Higgs bosons or two scalar bosons, a process that was never observed before.


This thesis will concentrate on the study of the production of a Higgs boson and a Z boson decaying to a pair of photons and a pair or b-quarks(ZH->bbyy). This process constitute a first step towards the detection of the production of di-Higgs in the HH->bbyy channel. The detection of ZH->bbyy allows to build and validate the analysis procedure for HH->bbyy with a process that has a higher cross section and thus is easier to detect with the run 3 of the LHC. The HH analysis of the run 3 data is being prepared now by a group of several institutes around the world that collaborate at CERN. Derivations of the analysis where one of the Higgs bosons is replaced by a scalar (SH) or a Z boson (ZH) are also in preparation. The HH and ZH analysis will run hand in hand with common framework, selection techniques and combined results extracted from the data. The CPPM group at Marseille is heavily involved in the SH analysis and want to expend its involvement to the ZH analysis.


The successful candidate will work within this collaboration and will take part of preparing and studying simulation samples that describes this physics process. The candidate will work within a team of three researchers and one PhD student at CPPM. He/She will analyze the kinematic and topological distributions of the signal in order to improve the selection of signal events and separate them from the background. He/She will also work on the estimation of the background and extract the corresponding uncertainties. The last task would be to observe the ZH process, measure its cross section and extrapolate the analysis techniques to the HH and SH analyses in the bbyy final state.


The efficient identification of photons in the ATLAS detector is one of the main ingredient for the analysis described above. This identification relies mostly on the liquid argon (LAr) calorimeter of the ATLAS detector. The ATLAS group at CPPM had a major contribution to the construction of the LAr calorimeter and is currently one of the main players for maintaining and operating this calorimeter. The candidate is expected to contribute to the LAr calorimeter operation and data quality in order to improve the photon identification in ATLAS. The candidate can also contribute to the upgrade of the readout electronics of the LAr calorimeter for the HL-LHC that is being prepared now at CPPM.


Prior knowledge of programming language especially C++/root or python is

an advantage but is not mandatory.


Keywords:
Physique des particules
Code:
Doctorat-2427-AT-02
Search for pair production of Higgs bosons with the ATLAS experiment at the LHC to constrain the Higgs boson self coupling parameter.
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PhD supervisor:
Georges Aad - aad@cern.ch
Sorry, this position is no longer available
Description:

The last piece of the standard model of particle physics, the Higgs boson, was discovered by the ATLAS and CMS collaborations in 2012. The newly discovered boson provides a unique possibility to search for new unknown physics beyond the Standard Model. The ATLAS group at CPPM have a leading role in detecting and studying the Higgs boson properties in several of its production and decay modes. The group is currently concentrating on the detection of the production of two Higgs bosons or two scalar bosons, a process that was never observed before.


This thesis will concentrate on the study of the production of two Higgs bosons decaying to a pair of photons and a pair or b-quarks (HH->bbyy). The detection of such process is a strong proof of the Higgs self coupling and the electroweak symmetry breaking as described by the standard model. The run 3 of the LHC, currently in operation, will provide enough data (in combination with previous data) to improve the discovery potential of such process. The analysis of the run 3 data is being prepared now by a group of several institutes around the world that collaborate at CERN. The analysis will look for the HH production as described by the Standard Model as well as with beyond the Standard Model models where the Higgs self coupling is modified or where new heavy scalar particles exist and decay to a pair of Higgs bosons.


The successful candidate will work within this collaboration and will take part of preparing and studying simulation samples that describes this physics process. The candidate will work within a team of three researchers and one PhD student at CPPM. He/She will analyze the kinematic and topological distributions of the signal in order to improve the selection of signal events and separate them from the background. He/She will also work on the estimation of the background and extract the corresponding uncertainties. The last task would be to measure the Higgs boson self coupling and compare it with predictions from the Standard Model.


The efficient identification of photons in the ATLAS detector is one of the main ingredient for the analysis described above. The candidate is expected to work on improving the photon identification in ATLAS in addition to the search for the HH->bbyy signal.


Prior knowledge of programming language especially C++/root or python is an advantage but is not mandatory.


Keywords:
Physique des particules
Code:
Doctorat-2427-AT-01
DarkSide
Direct search for Dark Matter with the DarkSide-20k experiment
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PhD supervisor:
Fabrice Hubaut, Pascal Pralavorio - 0491827251 - hubaut@cppm.in2p3.fr , pralavor@cppm.in2p3.fr
Description:

Dark matter is today one of the main puzzles in fundamental physics. Indeed, its contribution to the total mass of the Universe is 85%, but it cannot be explained in the framework of the Standard Model (SM) of particle physics. Several candidates exist in theories beyond the SM, and the WIMP (Weakly Interacting Massive Particle) is one of the best motivated of these candidates, as it allows to also solve the SM hierarchy problem, directly linked to the stability of the Higgs boson mass.


Experiments searching directly for dark matter thus use our galaxy halo as a potential source of WIMPs. Since 2010, the most sensitive technology is based on the measurement of the scintillation light from the scattering of a WIMP on a liquid noble atom – argon or xenon. In this framework, the DarkSide-20k (DS-20k) experiment, which will be installed 1.4 km underground in the Gran Sasso laboratory in Italy, is the third generation of liquid argon detectors. It will use a time projection chamber of 3.5 m diameter and 3.5 m high filled with 50 tons of purified argon and read out by 200,000 silicon photomultipliers. This will allow to have the world leading discovery potential for WIMPs after few years of data taking. The actual work is dedicated to the construction of the detector. Data taking should start in 2027. The increase of the liquid argon volume, compared to the first and second generation, will allow DS-20k to have the best sensitivity of all the liquid argon detectors after only one month of data.


The goal of this thesis, already financed by the Agence Nationale de la Recherche between October 2024 and September 2027, is to prepare and to participate to the analysis of the first data, for which the CPPM computed the sensitivity to WIMPs of low (<10 GeV) and high mass (>100 GeV). First, the student will participate to the simulation and the installation of the calibration system, designed and validated at CPPM. In parallel, the student will improve data reconstruction algorithms by using artificial intelligence techniques (e.g. neural networks), to optimize the separation between signal and backgrounds. Finally, he (she) will participate to the analysis of calibration data taken by DS-20k, and to the first physics analyses. These activities bring a complete education in particle physics, including instrumental aspects, software and data analysis.


In this framework, the student will have to do stays at Gran Sasso, especially to install the calibration system.


More details about the CPPM Dark Matter team: https://www.cppm.in2p3.fr/web/en/research/particle_physics/#Dark%20Matter


Keywords:
Physique des particules
Code:
Doctorat-2427-DS-01
HESS-CTA
Early science and commissioning preparation with the first telescopes of CTA
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PhD supervisor:
Heide Costantini et Franca Cassol - 0491827257 - costant@cppm.in2p3.fr ; cassol@cppm.in2p3.fr
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 in 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. The last few years have been extremely exciting for the PeVatron search since the large field of view detector LHAASO has detected several ultra high energy gamma-ray sources (E??>100 TeV) proving that PeVatrons exist in our Galaxy [3]-[4]. Nevertheless the nature of these sources is still unknown and CTA, thanks to its excellent angular and energy resolution, will be able to precisely study these PeVatrons and to disclose their hadronic or leptonic nature.

The construction of the CTA observatory has started and a first Large-Sized Telescope (LST-1) is already installed and taking data in La Palma. Three more LST telescopes and one Medium-Sized Telescope (MST) will be installed in the next 1-2 years. The camera of the first MST telescope on La Palma (NectarCAM) is fully equipped and should be installed on the structure in 2025.


The PhD project will be divided in two parts. A first part will be devoted to the preparation of the commissioning of NectarCAM and science verification measurements of the Crab nebula which is the standard calibration source for very high energy gamma-ray observations. To this end the candidate will perform the full simulation of the observation that consists in particle shower and telescope Monte Carlo simulations. A detailed simulation of the camera has been developed in the past and will have to be adapted comparing the simulation results to real data taken in the laboratory and on-sky. For the data analysis of both simulation and on sky data the official dataPipe pipeline of the CTA Observatory will be used. The main goal of this part will be to predict the expected performance of the MST telescope in detecting the Crab and prepare the data analysis of on-sky data.


The second part of the PhD project will be focused on the analysis of the data of the coming observation campaign of LST-1 of PeVatron sources detected by LHAASO. Some of these sources are unidentified with no very high energy counterpart. Even if LST-1 cannot reach enough sensitivity to access energies above 10-50 TeV, it should be able to detect some of them in the 100 GeV-10 TeV energy region for the first time or to provide stringent upper limits contributing significantly to the understanding of these intriguing sources. In the case of detection, thanks to the good angular resolution of the telescope, energy dependent morphology study can be performed. A possible extension of the measurement could be to observe the source at large zenith angle maximizing the detection efficiency at very high energy. The latter would allow to explore the energy region above 10 TeV and to extend to higher energies the study of energy dependent morphology to understand the nature of the source.


The project will include the participation to the LST-1 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 both in the building of the NectarCAM camera for MST and in the building and commissioning of the LST-1 telescope. The group also works on the preparatory studies for the research of galactic PeVatrons with CTA [6] and is leading the observation campaign with LST-1 and MAGIC of SNR G106.3-2, which is one of the PeVatron LHAASO sources.

Candidates should send their CV and motivation letter as well as grades (Bachelor, M1, M2) to costantini@cppm.in2p3.fr and cassol@cppm.in2p3.fr. Applications will be selected on the base of qualifications and an oral interview.


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

[2] https://www.cta-observatory.org/

[3] Z. Cao et al. Nature, 594, 33–36 (2021)

[4] Z. Cao et al. (2023) https://arxiv.org/abs/2305.17030

[5] F. Acero et al., Astroparticle Physics, 2023, 150, pp.102850.


Keywords:
----
Code:
Doctorat-2427-CT-01
Observation of the PeVatron candidate SNR G106.3-2 with the LST1+MAGIC Cherenkov telescopes
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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

[2] https://www.cta-observatory.org/

[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)

[5] https://github.com/cta-observatory/magic-cta-pipe

[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
Multi-messenger astronomy analysis with the KM3NeT neutrino telescope
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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), especially with the SVOM satellite and COLIBRI robotic telescope which will start their observations in Summer 2024. 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-2427-KM-02
Constraining lepton universality from neutrino data taken by the KM3NeT/ORCA detector
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PhD supervisor:
Jürgen Brunner - 04 91 82 72 49 - brunner@cppm.in2p3.fr
Description:

KM3NeT is an international collaboration aiming at the construction and operation of neutrino telescopes in the Mediterranean Sea. Two such devices are currently under construction: ARCA in the Ionian Sea optimised for the detection of neutrinos in the TeV/PeV energy range and ORCA, offshore Toulon, focused on the measurement of GeV/TeV neutrinos.


The goal of the thesis is to analyse atmospheric neutrinos which have been measured by the KM3NeT/ORCA detector. The detector takes data with a growing number of detection lines. The candidate will participate in the calibration process of newly assembled lines and assist the shore station team during the sea operations to deploy additional detection lines. Further he/she will help processing the data which have been taken and confront them with simulations. A particle identification procedure needs to be developed to identify on a statistical level the tau neutrino component in the event sample. This will ultimately allow to derive unitarity constraints in the lepton sector.


https://www.km3net.org/


Keywords:
Physique des particules
Code:
Doctorat-2427-KM-01
Multi-messenger analysis with KM3NeT
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PhD supervisor:
Damien Dornic - 0491827686 - dornic@cppm.in2p3.fr
Sorry, this position is no longer available
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
Neutrino Oscillation Studies with KM3NeT/ORCA
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PhD supervisor:
Sorry, this position is no longer available
Description:

Context and Subject

The Centre de Physique des Particules de Marseille (CPPM) in collaboration with the University of Toulon is opening a doctoral position (3 years), funded by the Aix Marseille University (AMU). The successful candidate will integrate CPPM to carry out research on neutrino oscillations with the ORCA detector and its possible upgrades.~

ORCA is a megaton scale natural water Cerenkov neutrino detector being constructed by the KM3NeT collaboration on the sea bed at 40 km offshore Toulon and at a depth of 2400 m. The primary purpose of the detector is to study neutrino oscillations using atmospheric neutrinos. While the detector construction should be over by 2027, the first detection units deployed since 2018 are fully operational, and the data collected have already allowed to observe the neutrino oscillations phenomena. The detector is now reaching a size that allows to probe unexplored physics territories. The Ph.D. student will participate in these data analyses, in particular, to the study of the appearance of tauic neutrinos in the atmospheric neutrino flux.

In addition to the atmospheric neutrinos studies, the Ph.D. student will also participate in a team work to develop of a novel technique for accelerator-based experiments called neutrino tagging. The very large size of the natural water Cerenkov detectors such as ORCA (few megatons) allows to perform experiments with neutrino beams of modest intensity for which the beam line can be instrumented. These instruments allow to get first-hand information (energy, direction, flavour, chirality) on each of the produced neutrinos. Ongoing studies indicate that such experiments would offer an unprecedented precision on the leptonic CP violating phase. The Ph.D. will take part to this pioneering design phase of a tagged neutrino experiment (e.g. sensitivity estimate, tracker R\\&D etc...).

The research activities will be conducted in tight collaboration with the Signal and Tracking group at University of Toulon, but also with the CERN Physics Beyond Colliders (PBC) study group (for the tagging part).

Candidate Profile

We are seeking for a highly motivated person who would ideally have:

  • knowledge of experimental particle physics,
  • skills in applied statistics for data analysis,
  • experience in c/c++, ROOT, or python,
  • oral and written proficiency in English and French (optional).

Application Procedure


The student interested in applying for the internship must provide:

  • CV
  • Motivation letter
  • Grades from M1 and M2
  • Two reference letters or reference contacts

This information should be sent to -tln.fr?subject=">-tln.fr?subject=[PhD-2326-KM-04]>mathieu.perrin-terrin@cern.ch and antoine.roueff@univ-tln.fr by July 31st.


References


Keywords:
Astroparticules
Code:
Doctorat-2326-KM-04
Measurement of neutrino oscillations with the KM3NeT/ORCA detector.
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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.


Links:

http://www.km3net.org

https://arxiv.org/abs/1601.07459

https://arxiv.org/abs/2103.09885


Keywords:
Physique des particules
Code:
Doctorat-2326-KM-03
PhD supervisor:
Sorry, this position is no longer available
Description:
Keywords:
Physique des particules
Code:
Doctorat-2326-KM-02
LHCb
Study of semileptonic B meson decays at LHCb
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PhD supervisor:
Dorothea vom Bruch - +33 4 91 82 72 76 - dorothea.vom.bruch@cern.ch
Description:

The LHCb group of the Centre de Physique des Particules de Marseille (CPPM) invites applications for a PhD position on semileptonic B meson decays at LHCb and LHCb's heterogeneous real-time selection software.


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. The unprecedented data sample to be collected until 2025 will be the basis of this PhD project.


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 characterize B ? D* l ? decays with electrons in the final state.


You will perform studies of kinematic distributions of the decay products and asymmetries in these decays, which are sensitive to New Physics effects.

To this end, you will study the multidimensional distributions of the kinematic parameters that characterise the internal degrees of freedom of semileptonic multibody decays. You will employ a multidimentional fit, modeling background processes with templates and including detector resolution effects. The project will require the usage of modern computing techniques and machine learning approaches.


In addition to the physics analysis, you will perform studies for extending the existing real-time analysis software running reconstruction and selection algorithms on graphics processing units (GPUs). This is in preparation of LHCb's next Upgrade, where a data rate five times larger than in Run 3 will have to be processed. Therefore, you will gain experience in developing within a heterogeneous software framework.


The LHCb group at CPPM consists of five 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 data acquisition system.


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.


Application details and deadlines:

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-122/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 2024.


Keywords:
Physique des particules
Code:
Doctorat-2427-LH-01
Renoir
Cosmological tests of dark energy and general relativity with surveys of galaxy positions and velocities in the local Universe
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PhD supervisor:
Julian Bautista - bautista@cppm.in2p3.fr
Description:

The context: More than twenty years after the discovery of the accelerated nature of the Universe's expansion, there is still no definitive explanation for its physical origin. Several types of dark energy or even alternatives/extensions to general relativity have been proposed in the literature attempting to explain the acceleration of the expansion. By accurately measuring of both the expansion rate of the Universe as well as the growth rate of structures as a function of cosmic time, we can learn more about this cosmological mystery. Particularly at low redshift when the expansion is accelerated and dark energy dominates the expansion, we are interested in obtaining the best constraints on the growth rate of structures. These measurements can be achieved by combining galaxy positions and their velocities. The statistical properties of the density and velocity field are tightly connected to the underlying cosmological model.


Experiments: Measurements of the expansion and growth rates of the Universe are the main scientific goal of current and future experiments such as the Dark Energy Spectroscopic Instrument (DESI), the Zwicky Transient Facility (ZTF), Euclid and the Vera Rubin Observatory Legacy Survey of Space and Time (Rubin-LSST).

DESI is currently measuring the 40 million galaxy positions (with their redshift) and their lower redshift sample will be the most complete to date.

The ZTF survey will discover more than 6000 type-Ia supernovae, from which we can derive galaxy velocities. Rubin-LSST will increase this number to the hundreds of thousands.


Goal of thesis: The selected candidate will work towards the joint analysis of DESI and ZTF datasets, which contain millions of galaxies and thousands of type-Ia supernovae. The candidate will get familiarised with the physics and the statistics of galaxy clustering, will code their own analysis pipeline, test it on state-of-the-art simulations, and hopefully apply it on real data.


Profile required: The candidate has to have large interest by cosmology, statistics, data analysis and programming (we use mostly python). English proficiency and team work skills are also required.


Keywords:
Cosmologie observationnelle
Code:
Doctorat-2427-RE-01
Commissioning of the Rubin/LSST observatory and analysis of the first supernova observations
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PhD supervisor:
Dominique Fouchez - fouchez@cppm.in2p3.fr
Description:

Twenty years after the discovery of the accelerating expansion of the universe through supernova measurements, the supernova probe remains one of the most accurate means of measuring the cosmological parameters of this recent period in the history of our universe, dominated by the so-called dark energy.


The Rubin Observatory with the Large Survey of Space and Time (Rubin/LSST) will be commissioned in 2024 and will be fully operational by mid-2025. It is an 8.4-m 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 track the variation over 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 impose strong constraints on the nature of dark energy. The LSST project aims to discover up to half a million supernovae. This improvement of two to three statistical orders of magnitude over the current data set will enable precise testing of the parameters of dark energy, test general relativity and also impose new constraints on the isotropy of the universe.


During the thesis, we propose to prepare and then participate in the analysis of the first LSST supernova data. The preparation will be done using existing HSC/Subsaru data.

The student will participate in the commissioning of Rubin/LSST. He/she will be in charge of pursuing developments in deep learning methods for supernova identification, and applying them to the first observations.

He/she will then take part in the first analyses using the supernovae he/she has helped to identify.


The LSST group at CPPM is already involved in precision photometry for LSST, with direct involvement in the validation of algorithms within DESC/LSST [1][2][3], and has proposed a new deep learning method to improve photometric identification of supernovae [4] and photometric redshifts [5].


[1] https://www.lsst.org/content/lsst-science-drivers-reference-design-and-anticipated-data-products


[2] https://arxiv.org/abs/1211.0310


[3] https://www.lsst.org/about/dm


[4] https://arxiv.org/abs/1901.01298


[5] https://arxiv.org/abs/1806.06607


[6] https://arxiv.org/abs/1401.4064


Keywords:
Cosmologie observationnelle
Code:
Doctorat-2427-RE-02
Cosmology with type 1a Supernovae from ZTF and LSST
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PhD supervisor:
Benjamin Racine - racine@cppm.in2p3.fr
Description:

In the late 90s, measurements of the distance of Supernovae and the redshift of their host galaxies revealed that the expansion of the Universe was accelerating. More than 20 years after this discovery, the nature of the dark energy at the origin of this phenomenon remains unknown.


The Λ \Lambda CDM concordance model describes a homogeneous, isotropic Universe on large scales, subject to the laws of general relativity (GR). In this model, most of the Universe's energy content comes from cold dark matter and dark energy, introduced as a cosmological constant. The latter behaves like a perfect fluid with negative pressure p, equation of state p = - rho, where rho is the energy density.

Some alternative models (see [1] for a review) introduce scalar fields (quintessence) whose evolution is responsible for the accelerated expansion. These scalar fields can vary in time and space. They can therefore have a time-dependent equation of state and generate anisotropic expansion.

Other models propose to modify the law of gravitation on large scales, mimicking the role of dark energy.

Supernovae remain one of the most accurate probes of the Universe's expansion and homogeneity. In addition, part of the redshift of galaxies is due to a Doppler effect caused by their particular velocities. We can then use supernovae to reconstruct the velocity field on large scales, and measure the growth rate of cosmic structures. This will enable us to test the law of gravitation.

An anisotropy of expansion on large scales, a modification of GR, or an evolution of the equation of state for Dark Energy, would all be revolutionary observations that would challenge our current model.

Until now, supernova surveys have gathered data from multiple telescopes, complicating their statistical analysis. Surveys by the Zwicky Tansient Facility (ZTF: https://www.ztf.caltech.edu/) and the Vera Rubin/LSST Observatory (https://www.lsst.org/) will change all that. They cover the entire sky and accurately measure the distance to tens (hundreds) of thousands of nearby (distant) supernovae.

The CPPM has been working on ZTF data since 2021 and has been involved in the construction and implementation of LSST for years, preparing for the arrival of data in 2025.

Within the group, we are working on the photometric calibration of the ZTF survey, essential for the measurement precision we need (see ubercalibration [2,3]). A recent PhD student has developed a pipeline to simulate ZTF and measure the growth rate of structures ([4]), and a current PhD student is adapting this exercise to LSST. In addition, a post-doc has just joined the group to work on ZTF, and a Chair of Excellence (DARKUNI, see Julian Bautista's internship/thesis) is extending this work by combining these data with spectroscopic data from DESI.


The aim of the thesis is to develop and perfect this analysis pipeline for measuring the growth rate of structures with real ZTF data, and to prepare the analysis of LSST data.

Other aspects may be added to the thesis, such as the study of the homogeneity of the expansion, the photometric calibration of the data, and so on.

This is an observational cosmology thesis, for a candidate interested in cosmology and data analysis.


[1] https://arxiv.org/abs/1601.06133

[2] https://arxiv.org/abs/astro-ph/0703454v2

[3] https://arxiv.org/abs/1201.2208v2

[4] https://arxiv.org/abs/2303.01198 https://snsim.readthedocs.io/


Keywords:
Physique des particules
Code:
Doctorat-2427-RE-03
Uncorrelated and unbiased pixel response of Euclid and SVOM NIR detectors
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PhD supervisor:
Aurélia Secroun - 04 91 82 72 15 - secroun@cppm.in2p3.fr
Description:

In the last decade, infrared has become increasingly prevalent in both space and ground missions which tend to systematically include an IR (infrared) instrument or channel of photo- or spectrometry as it allows to observe objects with larger redshifts. One key component of these instruments is the NIR~ (near-IR) detector whose performance has recently reached levels close to that of visible detectors.~ CPPM is currently involved in two important missions including NIR detectors: SVOM/Colibri with its unique ground IR channel and the ALFA detector of the CAGIRE camera, and Euclid with its NISP IR spectrophotometer and its 16 H2RG focal plane array, the largest flying IR focal plane ever. A fundamental objective of any such mission involving NIR hybrid pixel detectors is to obtain accurate and unbiased, per-pixel estimation of the flux, defined as the slope of the signal from a non-destructive acquisition. For these two missions, although they have radically different scientific objectives and observation strategies (for one high-energy gamma-ray burst recognition vs. for the other mapping of very low flux galaxies), the issues related to the detectors overlap. The evaluation of flux is both critical and delicate because it is directly influenced by the intrinsic properties of the detectors and associated parameters such as the conversion gain, IPC (inter-pixel capacitance), non-linearity, or persistence.

In a recent PhD work, at CPPM, on the Euclid mission, the importance of considering spatial variations was demonstrated and performance parameters were derived at the pixel level rather than the array level, otherwise inducing biasing in fundamental physical parameters determination. Also the need to decorrelate the effects induced by IPC and non-linearity in the detector response led to adapting existing methods to determine a conversion gain per super-pixel (16*16 pixels) and proposing original methods to decorrelate IPC and non-linearity, thereby correcting the biases they introduce in conversion gain determination and, consequently, flux determination.

Clearly, the observed correlations of different performance parameters require a comprehensive approach and modelisation to determine them at the pixel level, taking into account both spatial and temporal variations and correlations. Only under these conditions will it be possible to extract the unbiased performance maps required for flux calibration.

~

The objective of this new work is to push further decorrelation in a global approach, potentially developing new methods and using the new strategies offered by machine learning. ~ Several aspects of this subject involve a novel approach with undeniable benefits for present and future missions and the processing of data from NIR detectors: pixel-level analysis and consideration of correlations are both essential for a mission like Euclid and computationally intensive, necessitating optimization of calculation algorithms and programming; furthermore, a machine learning approach could improve both calculation times and resulting accuracy (e.g., obtaining a per-pixel conversion gain rather than per super-pixel); the analyses will be based on a substantial amount of data from two types of hybrid detectors calibrated at CPPM, the Lynred ALFA detector and the Teledyne H2RG detector, both based on similar MCT-sensitive layer technologies but showing clearly different behaviors already observed in initial tests. Comparing the two detectors will refine the analyses and models and allow for better account of subtle behaviors.


Candidates should have a strong background in instrumentation, statistics, data analysis and coding in python. PhD will be funded by CNES and CNRS.


Keywords:
Instrumentation
Code:
Doctorat-2427-RE-04
Testing gravity using RSD on cosmic voids with DESI data
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PhD supervisor:
S. Escoffier / P. Vielzeuf - 04 91 82 76 64 - escoffier@cppm.in2p3.fr
Description:

Although the universe is well described by the concordance model LCDM, 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 2021 for 5 years.


Please send your application to Dr. S. Escoffier and P. Vielzeuf (escoffier@cppm.in2P3.fr and vielzeuf@cppm.in2p3.fr), including:



- A motivation letter (maximum two pages).


- A curriculum vitae


- A brief description of research interest and past achievements


- Two reference letters (Head of the Master's program, supervisor of the Master internship) to be sent directly to eric.kajfasz@univ-amu.fr


- A transcript of all university records (Bachelor and Master)


- A copy of the master's diploma


Keywords:
Cosmologie observationnelle
Code:
Doctorat-2427-RE-05
Cosmological constraints using photometric and spectroscopic galaxy clustering with DR1 Euclid data
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PhD supervisor:
S. Escoffier / W. Gillard - 04 91 82 76 64 - escoffier@cppm.in2p3.fr / gillard@cppm.in2p3.fr
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 CDM 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.


The future Euclid space mission is dedicated to the study of dark energy and dark matter in the Universe and to test gravity on cosmological scales. Euclid was selected by the European Space Agency (ESA) in 2011 and has been launched 1st July, 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.


Two instruments are embarked on board Euclid, the Near Infrared Spectrometer and Photometer (NISP) and the visible imager (VIS). The spectroscopic survey with the NISP instrument will target 40 millions of galaxies in the redshift range 0.9 < z < 1.8, while the photometric survey will get the image and photometric redshift of two billions of galaxies covering the redshift range 0 < z < 2.5.


The subject of the thesis is to measure the galaxy clustering from the Euclid photometric and spectroscopic catalogs, and studied combined analysis, including 3x2pt analysis.


Please send your application to Dr. S. Escoffier and W. Gillard (escoffier@cppm.in2P3.fr and gillard@cppm.in2p3.fr), including:



- A motivation letter (maximum two pages).


- A curriculum vitae


- A brief description of research interest and past achievements


- Two reference letters (Head of the Master's program, supervisor of the Master internship) to be sent directly to eric.kajfasz@univ-amu.fr


- A transcript of all university records (Bachelor and Master)


- A copy of the master's diploma


Keywords:
Cosmologie observationnelle
Code:
Doctorat-2427-RE-06
Constraining cosmology with voids from large-scale structure surveys
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PhD supervisor:
Description:

Modern surveys provide access to high-quality measurements on large areas of the sky, sampling the galaxy distribution in detail also in the emptiest regions, voids. Void cosmology is becoming an increasingly active sector of galaxy clustering analysis: by measuring void properties, such as density profiles or void number counts, it is possible to constrain cosmological parameters.


Cosmic voids are particularly sensitive to the properties of dark energy and neutrinos. Studying voids provides a novel perspective to unravel the unsolved mysteries of our Universe. The Centre de Physique des Particules de Marseille (CPPM) is involved in the Dark Energy Spectroscopic Instrument, in the Euclid mission and the Vera C. Rubin Observatory. The research activity will focus on constraining cosmology with cosmic voids with data from current and upcoming large-scale structure surveys (Euclid, DESI, Rubin). Among other work, this PhD Thesis will contribute to the measurements of the void-galaxy cross-correlation function and the void size function from modern surveys to constrain cosmological parameters. The position is funded by the Aix-Marseille A*Midex initiative. The selected candidate is expected to start in the Fall of 2024. Applications are currently being accepted, and will be accepted until the position is filled. The CPPM features a strong cosmology group, the RENOIR group, with expertise on large-scale structure, cosmic voids and type-Ia supernovae cosmology, and strongly involved in the Euclid mission, the Dark Energy Spectroscopic Instrument (DESI), the Vera Rubin Observatory Legacy Survey of Space and Time (Rubin-LSST) and the Zwicky Transient Facility (ZTF).


The position comes with maternity/paternity leave, family supplement for children, French national medical/dental insurance, participation to public transport fees, pension contributions. For all children above three years old school is free in France. We value diversity and are committed to equality of opportunity, we encourage candidates of all backgrounds to apply.


Please send your application to Dr. A. Pisani (pisani@cppm.in2p3.fr). The application should include a CV, a research statement (maximum 3 pages), a transcript of all university records (Bachelor and Master) and three letters of recommendation (to be sent directly by the writers to pisani@cppm.in2p3.fr). A one page cover letter is optional.


Keywords:
Cosmologie observationnelle
Code:
Doctorat-2427-RE-08
Testing dark energy with the ISW effect in the Euclid mission
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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