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 boosted final state, benefitting from the strong expertise of the ATLAS group at CPPM in b-tagging, boosted object identification 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] Combination of searches for Higgs boson pair production in collisions at sqrt(s)=13 TeV with the ATLAS detector

https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2021-18/

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. A contribution to the search for new physics in the same decay mode is expected. This will involve searching for a heavy particle decaying to two Higgs bosons (X->HH->bbyy) or a Higgs boson and a new scalar boson (X->SH->bbyy). The search, detection and measurement of the Standard Model process ZH->bbyy, which has the same final state products, is important to validate the previous analysis. A contribution to the understanding of ZH->bbyy will be also considered.

The analyses described above with the run 3 LHC data is being prepared now by a group of several ATLAS 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 scalar particles exist and couple to the Higgs boson.

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. This work involves understanding the shower shapes that a photon leave in the Liquid Argon calorimeter as well as developing modern method (based on neural networks) to identify photons and separate them from the background.

The successful candidate will work within this collaboration and will take part of preparing and studying simulation samples that describes the physics processes. The candidate will work within a team of four researchers and two 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 and/or set limits of the production cross section of beyond the Standard Model processes in case additional scale bosons are not discovered.

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

This thesis is expected to start in October 2025 (if funding is obtained).

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.

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

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/

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$B \to D^+ l$ 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.

Dark matter is one of the great enigmas of fundamental physics today. Its contribution to the total mass of the Universe is 85%, but it cannot be explained within the framework of the Standard Model of particle physics (SM). However, several candidates for dark matter exist in theories beyond the SM: this is the case of the axion, one of the best-motivated candidates as it also explains the absence of CP violation in the strong interaction.

The discovery of axions requires the invention of new experimental techniques. Several proposals have emerged in recent years. MADMAX is one of the few that is sensitive to the mass domain around 100 micro-eV, favored by theory. For this reason, it has attracted the attention of the scientific community since 2016, when it was first proposed. Today, MADMAX is a collaboration of 50 scientists from German and French laboratories (including CPPM since 2019) and is part of the DMLab International Research Laboratory, installed at DESY-Hamburg. Based on the innovative concept of dielectric haloscope, MADMAX will consist of a booster made of 80 1-meter-diameter disks that need to be positioned to micrometer precision at a temperature of 4 degrees Kelvin and in a magnetic field of 9 T. In order to realize this detector, which will take data at DESY after 2030, the MADMAX collaboration is in an R&D phase, which will be concluded by the construction and operation of a prototype whose main aim is to demonstrate the feasibility of the dielectric booster concept.

The aim of the thesis is to conduct a search for axions in an uncharted phase space by commissioning and analyzing data from the prototype. The student will contribute to the realization and mechanical characterization of the dielectric disks and their interface with the piezoelectric motors developed at CPPM. The prototype will be assembled in an experimental hall on the DESY campus, then inserted and tested at liquid helium temperature in a cryostat in 2025-2026. After these initial tests, the data from which will be analyzed by the student, the prototype will be sent to CERN for long-term tests between 2027 and 2029, under the supervision of CPPM, in a magnetic field of 1.6 T. The data analysis carried out by the student will allow to search for axions around 100 micro-eV using the innovative concept of the dielectric haloscope, with unprecedented sensitivity to axion-photon coupling.

In this context, the student will be required to make regular visits to DESY and CERN, in particular to take part in detector installation and data acquisition.

Requirements:

1. Education: master in experimental particle physics

2. Programming: knowledge in python or C++

3. Language: fluency in spoken and written English

The application consists of:

1. a motivation letter

2. CV (2 pages maximum) and university grade transcripts (for all degrees)

3. Three reference letters

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

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 $\Lambda$ 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 will publish a first cosmological analysis in 2025 with ~3000 SN1a. We have also been involved in the construction and implementation of LSST for years, preparing for the arrival of the first data this summer.

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) 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. The totality of 30000 SN1a of ZTF will be available to do the final cosmological analysis of this survey. The thesis coincides also with the arrival of the first SN1a catalogs of LSST.

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/

Scientific Context (3012 / 5000)

Euclid is an M-class ESA mission launched in July, 2023. It is one of the major observatories dedicated to cosmology and understanding the nature of dark energy and dark matter. By combining galaxy clustering and weak gravitational lensing observations, Euclid will provide data on an unprecedented scale and accuracy.

Galaxy clustering (the large-scale distribution of galaxies) and weak gravitational lensing are two of the mission's key observables. Galaxy clustering allows the study of galaxy distribution across the Universe, revealing critical insights into the structure of the Universe, its dynamics and the nature of dark energy. On the other hand, weak lensing enables the inference of dark matter distribution by analyzing the deformation of background galaxies by foreground masses.

The 3x2pt method, which combines galaxy clustering, cosmic shear, and galaxy-galaxy lensing, is one of the most promising approaches to leveraging these observations. This method maximizes information on cosmological parameters, particularly those related to dark energy, by using complementary measurements to reduce potential systematic biases. These analyses will play a key role in constraining essential cosmological parameters and refining our understanding of dark energy and dark matter.

The PhD project:

This thesis aims to exploit data from the Euclid mission to conduct an in-depth study of galaxy clustering and to perform a comprehensive 3x2pt analysis. Specifically, the thesis will be structured around several key objectives:

• Study of Galaxy Clustering : Analyze the 3D distribution of galaxies on a large scale, using photometric and spectroscopic data from the Euclid survey.

• 3x2pt Analysis: Conduct a combined 3x2pt analysis, combining galaxy clustering and weak gravitational lensing, to fully exploit the cross-information between these two observables. Optimize methodologies to reduce systematic uncertainties, such as galaxy bias contamination and photometric redshift calibration.

• Cosmological Constraints: Apply these tools and methods to DR1 and DR2 Euclid data to constrain models of dark energy and dark matter. Compare the obtained results with theoretical predictions from various cosmological models (?CDM models and modified gravity extensions).

This thesis lies at the intersection of cosmological observations and advanced analysis techniques. By exploiting Euclid mission data and applying the 3x2pt method, this project aims to provide crucial cosmological constraints while developing essential methodological tools for next-generation surveys. This work will contribute to improving our understanding of the dark Universe and exploring new approaches to studying dark matter and dark energy.

Scientific environment:

The thesis will be carried out at the Centre de Physique des Particules de Marseille, under the supervision of Stephanie Escoffier and William Gillard. The cosmology team at CPPM is involved in large cosmological survey like DESI, Euclid and Rubin.

Required Skills:

The candidate should have a Master (MSc) in Astronomy/Astrophysics, Fundamental Physics or Data science. He/she should have a strong background in observational cosmology and statistics, and an interest in advanced methodological approaches and statistical inference techniques relevant to cosmological surveys. Experience in data analysis and programming (Python, C++), and familiarity with handling large datasets is not required but would be advantageous.

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 2025 and will be fully operational by the end of 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/Subaru data, as well as the first images of LSST.

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