14 sujets IRFU/DPhP

Dernière mise à jour : 04-07-2022


• Astroparticles

• Astrophysics

• Health and environment technologies, medical devices

• Particle physics

 

Searches for counterparts to gravitational waves with H.E.S.S. and CTA

SL-DRF-22-0068

Research field : Astroparticles
Location :

Service de Physique des Particules (DPHP)

Groupe Astroparticules (GAP)

Saclay

Contact :

Fabian Schussler

Starting date : 01-10-2022

Contact :

Fabian Schussler
CEA - DRF/IRFU

+33169083020

Thesis supervisor :

Fabian Schussler
CEA - DRF/IRFU

+33169083020

Personal web page : http://irfu.cea.fr/Pisp/fabian.schussler/index.html

Laboratory link : http://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=1025&voir=fm

More : https://astro-colibri.com

Over the last two years the Imaging Air Cherenkov Telescopes (IACTs) H.E.S.S. and MAGIC were able to detect very-high-energy gamma-ray emission from gamma-ray bursts (GRBs). These breakthrough results have triggered renewed discussions of the particle acceleration and emission mechanisms that can be found in these violent explosions [1].



Complementing the detections of GRBs via X-ray satellites, the detection of gravitational waves allows to provide new and complementary insights into the pre-explosion phase, the initial conditions, the geometry of the system, and much more. The proposed thesis project will exploit the exciting possibilities of combining the detection of GWs and the detection of the resulting GRB by VHE gamma-ray observatories in truly multi-messenger observations and analyses.



The core of the proposed project will be H.E.S.S., currently the world’s most sensitive gamma-ray instrument, and CTA, the next generation, global high-energy gamma-ray observatory. We’ll also collaborate closely with partners from around the world including obviously the gravitational wave instrument Advanced VIRGO, the SVOM satellite to detect GRBs, various radio telescopes in Australia and South Africa, optical observatories, and many more. The group at IRFU, CEA Paris-Saclay is leading observations of transient phenomena by both H.E.S.S. and CTA and has long-standing experience with these challenging observations. The group is also driving changes and modernizations of the communication in the astroparticle community (e.g. via the Astro-COLIBRI web/smartphone application, [2]).



The PhD student will first have the opportunity to participate in the development and improvement of the framework that allows to optimize the schedule of follow-up observations of astrophysical transients. Some of the most interesting event are being detected only with large localization uncertainties (i.e. especially GWs, but also GRBs, neutrinos and others). We therefore need specialized tools and algorithms that allow to point the follow-up instruments like H.E.S.S. into the right direction to rapidly catch the associated emission [3]. A crucial observation period by the GW interferometers (called O4) is scheduled to start end of 2022. This timing is perfectly matching the PhD project presented here, as the selected student will have the opportunity to lead the H.E.S.S. and CTA/LST-1 follow-up observations searching for GRBs and other VHE gamma-ray counterparts to the GWs detected by LIGO/VIRGO/KAGRA during that period. A sizeable amount of observation time with both the H.E.S.S. and CTA/SLT-1 IACTs has been reserved for these exciting searches. We’ll thus have ample opportunities to optimize our follow-up procedures, lots of data to analyze, results to present at international conferences, and papers to publish.



The core of the proposed thesis project will be the real-time search for transient high-energy gamma-ray emission linked to the detection of a gravitational wave (and other multi-messenger astrophysical transients like high-energy neutrinos, gamma-ray bursts, fast radio bursts, stellar/nova explosions, etc.). The combined observations will unequivocally prove the existence of a high-energy cosmic ray accelerator related to these violent multi-messenger phenomena and will allow to derive novel insights into the most violent explosion in the universe.



References:

[1] H.E.S.S. Collaboration: “Revealing x-ray and gamma ray temporal and spectral similarities in the GRB 190829A afterglow, Science, Vol. 372 (2021);

[3] P. Reichherzer, F. Schüssler, et al. : “Astro-COLIBRI-The COincidence LIBrary for Real-time Inquiry for Multimessenger Astrophysics”, ApJS 256 (2021);

[2] H. Ashkar, F. Schüssler, et al. : “The H.E.S.S. gravitational wave rapid follow-up program”, JCAP 03 (2021);
Dark matter search and the Galactic Center in very-high-energy gamma rays with H.E.S.S.

SL-DRF-22-0023

Research field : Astroparticles
Location :

Service de Physique des Particules (DPHP)

Groupe Astroparticules (GAP)

Saclay

Contact :

Emmanuel MOULIN

Starting date : 01-10-2022

Contact :

Emmanuel MOULIN
CEA - DRF/IRFU/DPhP/HESS 2

01 69 08 29 60

Thesis supervisor :

Emmanuel MOULIN
CEA - DRF/IRFU/DPhP/HESS 2

01 69 08 29 60

Personal web page : http://irfu.cea.fr/Pisp/emmanuel.moulin/

Laboratory link : http://irfu.cea.fr/dphp/Phocea/Vie_des_labos/Ast/ast_sstheme.php?id_ast=28&id_unit=8

More : https://www.mpi-hd.mpg.de/hfm/HESS/

The PhD thesis will be focused on the analysis and interpretation of the observations carried out in the Galactic Centre region by the H.E.S.S. observatory over more than 15 years. The first part of the work will be devoted to the low-level analysis of the GC data and the study of the systematic uncertainties in the massive GC dataset. In the second part, the PhD student will combine the H.E.S.S.-I GC and H.E.S.S.-II IGS observations in order to search for DM signal using multi-template analysis techniques. The third part of the work will be dedicated to the development of a new analysis method to search for astrophysical signal using Bayesian neural networks and its implementation for the search of dark matter and source variability in the GC region. In addition, the PhD student will be involved in the data taking and data quality selection of H.E.S.S. observations.
Measurement of the small-scale Lyman-alpha forest with the DESI survey: looking for dark matter and neutrinos.

SL-DRF-22-0227

Research field : Astrophysics
Location :

Service de Physique des Particules (DPHP)

Groupe Cosmologie (GCOSMO)

Saclay

Contact :

Eric Armengaud

Guillaume Mention

Starting date : 01-09-2022

Contact :

Eric Armengaud
CEA - DRF/IRFU/DPhP

01 69 08 19 50

Thesis supervisor :

Guillaume Mention
CEA - DRF/IRFU/DPhP

01 69 08 56 32

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=3428

More : https://www.desi.lbl.gov

The matter distribution on cosmological scales can be predicted within the standard cosmological model. It depends among others on the (yet unknown) absolute neutrino mass and on the properties of dark matter, whose nature is a great scientific mystery. The IRFU-DPhP cosmology team, gathering around 10 permanent researchers, is strongly involved in the DESI sky survey (Dark Energy Spectroscopic Instrument). DESI is the first among next-generation projects whose goal is to map large scale structures in the Universe. The DESI telescope, located in Arizona, started its observations in 2021 and will provide in the coming years an unprecedented 3D map of the Universe.



This thesis proposes to analyze and interpret DESI observations of the so-called Lyman-alpha forest, which measures the absorption by the intergalactic medium of light from distant quasars located at redshifts z ~ 2 - 4. Lyman-alpha observations provide the only measurement of the matter distribution both at "small" cosmological scales (~megaparsec), and in the early Universe (10 - 12 billion years ago, just 2 billion years after the Big Bang).

The PhD student will participate in the analysis of the complete DESI-Y1 ("Year-1") to Y3 Lyman-alpha forest data. He/she will improve our understanding of instrumental and astrophysical effects that are crucial for this observation. We propose that the student develops an original method to recover the full 3D statistical power spectrum of matter fluctuations from the 1D Lyman-alpha forest data, using tomographic reconstruction techniques already pioneered by the group.

In a second part of the thesis, the student will interpret the Lyman-alpha data to measure the properties of dark matter and neutrinos. The intensity and slope of the Lyman-alpha power spectrum depend in particular on the sum of neutrino masses. They also depend on other cosmological parameters, so that to break degeneracies, Lyman-alpha data will be combined with Cosmic Microwave Background (CMB) measurements. Currently the CMB+Lyman-alpha already bound the neutrino mass to be less than ~110 milli-eV (the best upper bound), while particle physics tells us it should be 60 milli-eV or more. With improved measurements and data combinations we therefore expect to get closer to a first detection. This work will be based on dedicated sets of cosmological simulations which are run at HPC infrastructures. Depending on his/her affinities, the student may use machine learning algorithms to optimize the exploitation of these simulations in order to infer cosmological parameters from the data.

Study of quasar clustering at all scales in DESI

SL-DRF-22-0122

Research field : Astrophysics
Location :

Service de Physique des Particules (DPHP)

Groupe Cosmologie (GCOSMO)

Saclay

Contact :

Christophe YECHE

Starting date : 01-10-2022

Contact :

Christophe YECHE
CEA - DRF/IRFU/SPP/Bao

01-69-08-70-50

Thesis supervisor :

Christophe YECHE
CEA - DRF/IRFU/SPP/Bao

01-69-08-70-50

Laboratory link : http://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=3428

More : https://www.desi.lbl.gov

The Large Scale Structures (LSS) of the Universe come from the growth, under the effect of gravitation, of small primordial fluctuations of density created by inflation. The measurement of the statistical properties of LSS allow us to study the inflation at very large scales (~Gpc), the Dark Energy at smaller scales (~100 Mpc) with Baryonic Acoustic Oscillations (BAO) and the gravity at even smaller scales (~tens of Mpc) with Redshift Space Distortions (RSD).



Our strategy for studying the LSS is to use a spectroscopic survey, DESI that will observe tens of millions of galaxies and quasars. The observations take place at the 4-meter Mayall telescope in Arizona .Since spring 2021, the project has started an uninterrupted observation period that will last 5 years and that will cover a quarter of the sky.



For this PhD, LSS are measured with a single tracer of the matter: the quasars, very distant and very luminous objects. This tracer allows us to cover a wide redshift range from 0.9 to 3.5 and to the Universe clustering at all scales, from a few tens of Mpc to Gpc.



During the first year, the PhD student will participate in the analysis of the first observation year (from spring 2021 to spring 2022). The PhD student will be able to devote to a global measurement of the cosmological parameters which will simultaneously cover all the scales. The thesis will end with the study of the first three years of observation of DESI.
Impact of the density of galaxies in the analysis of the large spectroscopic survey DESI

SL-DRF-22-0278

Research field : Astrophysics
Location :

Service de Physique des Particules (DPHP)

Groupe Cosmologie (GCOSMO)

Saclay

Contact :

Etienne Burtin

Vanina RUHLMANN-KLEIDER

Starting date : 01-10-2022

Contact :

Etienne Burtin
CEA - DRF/IRFU/DPHP/GCOSMO

01 69 08 53 58

Thesis supervisor :

Vanina RUHLMANN-KLEIDER
CEA - DRF/IRFU/DPHP/GCOSMO

01 69 08 61 57

Over the last 30 years, the study of the Universe has led to the emergence of a standard model of cosmology based on general relativity. In this model, the Universe is made of ordinary matter, dark matter and a mysterious component called "dark energy", responsible for the recent acceleration of the expansion of the Universe. The large spectroscopic survey DESI, which has just started its 5-year observation campaign in the United States, aims to map the distribution of galaxies in the Universe 10 times more accurately than existing surveys. The scientific community is organizing itself to define the methods of data analysis in order to extract the maximum of information from these surveys and to enter the era of precision cosmology, in particular on the measurement of the growth rate of structures. This thesis proposes the original approach of using the large-scale matter density to significantly improve the precision of this measurement, in order to strengthen the tests of general relativity.

This thesis will take place at the Research Institute for the Fundamental Laws of the Universe at CEA-Saclay. The future PhD student will be integrated in the cosmology group of Irfu/DPhP, composed of 10 physicists and 4 PhD students. Present and driving force in the DESI experiment, the group also participates in Euclid and had in the past a strong contribution in SNLS, Planck and SDSS (BOSS and eBOSS), all experiments organized in international collaborations. The future PhD student will be integrated in the DESI collaboration and will analyze the data, benefiting from all the expertise of the group already acquired on BOSS and eBOSS.

Forward modelling of the galaxy density field in the DESI spectroscopic survey

SL-DRF-22-0364

Research field : Astrophysics
Location :

Service de Physique des Particules (DPHP)

Groupe Cosmologie (GCOSMO)

Saclay

Contact :

Arnaud de Mattia

Vanina RUHLMANN-KLEIDER

Starting date : 01-10-2022

Contact :

Arnaud de Mattia
CEA - DRF/IRFU/DPHP/GCOSMO

01 69 08 62 34

Thesis supervisor :

Vanina RUHLMANN-KLEIDER
CEA - DRF/IRFU/DPHP/GCOSMO

01 69 08 61 57

The goal of this PhD project is to develop a novel analysis pipeline to extract cosmological information from the wide galaxy redshift survey DESI (Dark Energy Spectroscopic Instrument), using numerical simulations and state-of-the-art machine learning and statistical inference techniques to overcome limitations of standard analyses.



DESI is a multi-object spectrograph mounted on the Mayall telescope at Kitt Peak, Arizona, which will enable redshift measurements of 35 millions of galaxies and quasars between 0.05 < z < 3.0, yielding a tenfold increase in statistics compared to previous spectroscopic surveys (e.g. BOSS, eBOSS). By the start of the PhD, the first year of DESI data taking, corresponding to one fifth of the total statistics will be completed, thereby constituting the largest spectroscopic dataset ever assembled. A threefold increase of this dataset is expected by the end of the PhD.



In this PhD we propose to develop a theoretically lossless approach to extracting cosmological information from galaxy surveys, in particular DESI, which consists in reproducing the observed galaxy density with simulations. Namely, an initial random dark matter density field is generated in a cubic box and evolved forward in time following the equations of gravity. The galaxy density field is then modelled on top of the simulated dark matter field and survey selection effects are applied. The likelihood of the observed galaxy density field given the simulated one is computed, and its value is used to iterate over, or to sample, initial conditions of the density field and cosmological parameters. This project, which may result in the first cosmological contraints from the galaxy forward modelling approach applied on real data, will lead to one or two first-author publications. It will also benefit greatly to the DESI standard analyses.
Optimization of the ClearMind detection module for the high resolution PET imaging

SL-DRF-22-0257

Research field : Health and environment technologies, medical devices
Location :

Service de Physique des Particules (DPHP)

Groupe Santé et Energie (GSE)

Saclay

Contact :

Dominique YVON

Viatcheslav SHARYY

Starting date : 01-10-2022

Contact :

Dominique YVON
CEA - DRF/IRFU/DPHP

01 6908 3625

Thesis supervisor :

Viatcheslav SHARYY
CEA - DRF/IRFU

0169086129

Personal web page : https://irfu.cea.fr/Pisp/viatcheslav.sharyy/

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=3730

Positron emission tomography (PET) is a nuclear imaging technique widely used in oncology and neurobiology research. The decay of the radioactive tracer emits positrons, which annihilate into two photons of 511 keV. Using time-of-flight technology, they can be used to reconstruct the point of annihilation and the distribution of tracer activity in the patient's body.

In this thesis, we propose to contribute to the development of the cutting-edge patented technology ClearMind. The first prototype is currently being tested in the laboratory. The proposed detector uses a monolithic lead tungsten crystal in which Cherenkov and scintillation photons are produced. Those photons are converted to electrons by the photo-electric layer and multiplied in the microchannel plate. The induced electrical signals are amplified by gigahertz amplifiers and digitized by the fast acquisition modules SAMPIC. The time and coordinates of the gamma-conversion in the crystal are reconstructed using machine-learning techniques.

The candidate will work on characterization and optimization of the ClearMind detection module. This includes the measurement with pulsed laser and radioactive 22Na source, data analysis using ROOT/C++ software, reconstruction with machine-learning algorithms and interpretation with the help of Geant4 simulation.

The foreseen detector optimization will boost the TRL1 of the ClearMind technology from the level 2 to the level 5/6. It consists in improving the detection module design and thus in increasing the detection efficiency, in optimizing the high-speed read-out, and in improving the integration of the detection module with the digitizing electronics.

BINGO: Bi-Isotope 0nBB Next Generation Observatory

SL-DRF-22-0338

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Sources et Réacteurs (GNSR)

Saclay

Contact :

Claudia Nones

Starting date : 01-10-2022

Contact :

Claudia Nones
CEA - DRF/IRFU/DPHP/GNSR

0169083520

Thesis supervisor :

Claudia Nones
CEA - DRF/IRFU/DPHP/GNSR

0169083520

More : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast.php?t=fait_marquant&id_ast=4713

BINGO is a new project funded with an ERC grant. It will set the grounds for a large-scale bolometric experiment searching for neutrinoless double beta decay with a background index of about 10-5 counts/(keV kg y) and with very high energy resolution in the region of interest. These features will enable a search for lepton number violation with unprecedented sensitivity. BINGO is based on luminescent bolometers for the rejection of the dominant alpha surface background. It will focus on two extremely promising isotopes – 100Mo and 130Te – that have complementary merits and deserve to be both considered for future large-scale searches.

The project will bring three original ingredients to the well-established technology of hybrid heat-light bolometers: i) the light-detector sensitivity will be increased by an order of magnitude thanks to Neganov-Luke amplification; (ii) a revolutionary detector assembly will reduce the total surface radioactivity contribution by at least one order of magnitude; (iii) for the first time in an array of macrobolometers, an internal active shield, based on ultrapure ZnWO4 scintillators with bolometric light readout, will suppress the external gamma background.

In this PhD thesis, the student will contribute to the assembly and installation of the MINI-BINGO demonstrator in a new cryostat at the Underground Laboratory of Modane. He/she will participate to the data taking and data analysis. He/she will estimate the final background rejection made possible by the performance of the final detector configuration.



ANTIHYDROGEN IONS: MEASUREMENT OF THE PRODUCTION CROSS SECTIONS AND FIRST DETECTION

SL-DRF-22-0784

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Antimatière et gravitation (GAG)

Saclay

Contact :

Pauline Comini

Patrice Pérez

Starting date : 01-10-2022

Contact :

Pauline Comini
CEA - DRF/IRFU/DPhP

+41227663573

Thesis supervisor :

Patrice Pérez
CEA - DRF/IRFU/DPhP

0612573587

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=784

More : https://gbar.web.cern.ch/

The GBAR experiment at CERN aims at measuring the gravitational acceleration of antimatter on Earth using ultra-cold antihydrogen atoms. In order to obtain these ultra-cold anti-atoms, the key is to first produce positive antihydrogen ions (two positrons and one antiproton, equivalent to H-), using positronium (bound state of an electron and a positron) for that purpose.

The PhD topic is dedicated to the study of the charge exchange reaction between an antihydrogen atom and a positronium atom, producing a positive antihydrogen ion. The first objective is to measure the cross sections for this reaction, for which only theoretical values exist, using hydrogen instead of antihydrogen and producing H-. The second objective is to observe the production of antihydrogen ions and optimise it. An experimental measurement of the cross sections will provide a test for several low-energy atomic collision models that currently provide disagreeing theoretical values. The first ever detection of an antihydrogen ion will be a major milestone for GBAR but it will also open new opportunities for future antimatter experiments.

From 2022 to 2024, GBAR will receive beams of antiprotons and H- and the experimental program of this thesis will be carried out during this period at CERN. 2025 will mainly be dedicated to data analysis and PhD dissertation writing.
LHC luminosity measurement with the ATLAS Liquid Argon Calorimeter and search for long lived massive particles

SL-DRF-22-0296

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Atlas (ATLAS)

Saclay

Contact :

Philippe Schwemling

Starting date : 01-10-2022

Contact :

Philippe Schwemling
CEA - DRF/IRFU

33 1 69 08 85 85

Thesis supervisor :

Philippe Schwemling
CEA - DRF/IRFU

33 1 69 08 85 85

Since the discovery of the Higgs boson efforts are focused on the search for new phenomena, beyond the Standard Model.

One of the important aspects of the comparison between experimental measurements and theory is the need to normalize as

precisely as possible experimental results to theory. This means in practice being able to measure as precisely as

possible the luminosity of the LHC. The goal is to reach a precision better than 1% within the next few years,

a factor two or three better than the precision that has been reached up to now.



After the LHC restart, foreseen in 2022, it is planned to increase the luminosity by a factor of about two. To make

the best out of this luminosity increase, the calorimeter trigger system is being significantly modified and upgraded.

The upgraded trigger system is based on real time analysis of the digitized detector signals.



An essential feature of the upgraded trigger system is its ability to measure the energy deposited in the calorimeter

bunch crossing by bunch crossing. Combined with the stability, excellent linearity and response uniformity of the ATLAS

Liquid Argon calorimeter, the upgraded trigger system offers the potential to measure the luminosity with excellent

linearity and stability performances. A very promising analysis technique would be to use a neural net to process the data.



An other feature of the upgraded trigger system is its ability to keep track of all the interactions taken place in the

detector over a much longer period of time than the main readout. The main readout system is able to keep in memory only

up to four or five consecutive interactions. The trigger system has the capability to keep track of each individual bunch

crossing over a period of time corresponding to several tens of consecutive bunch crossings.

This long term memory feature gives the possibility to compensate real time the effect of charge space accumulation,

which will be crucial for data taken after 2025, at very high luminosity. More importantly, this also opens up the

possibility to detect particles reaching the detector long (several tens or even hundreds of ns, to be compared to the

25 ns between two consecutive bunch crossings) after their production. Such particles are slow and very heavy, and can be

detected almost up to the kinematic limit of 7 TeV. This is significantly higher than the limits reachable by more

classic techniques. Such particles typically appear in many classes of supersymmetric models.
PROCESSING/ANALYSIS OF NUCLEUS AND CRAB EXPERIMENTAL DATA FOR THE MEASUREMENT OF COHERENT SCATTERING OF REACTOR NEUTRINOS

SL-DRF-22-0270

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Sources et Réacteurs (GNSR)

Saclay

Contact :

Thierry Lasserre

Edoardo MAZZUCATO

Starting date : 01-10-2022

Contact :

Thierry Lasserre
CEA - Liste des pôles/Liste des départements/Liste des services/Double Chooz

0169083649

Thesis supervisor :

Edoardo MAZZUCATO
CEA - DRF/IRFU/DPHP

+33169084476

Personal web page : http://irfu.cea.fr/Pisp/thierry.lasserre/

Laboratory link : https://irfu.cea.fr/en/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=2260

The NUCLEUS experiment aims for the detection of coherent elastic neutrino-nucleus scattering (CEvNS) at the Chooz nuclear power station using ultra-low threshold gram-scale cryogenic detectors. This technology will enable the miniaturization of neutrino detectors and has the potential to probe physics beyond the Standard Model of particle physics in a second kilogram-scale phase. The complete understanding of the NUCLEUS data will be accomplished by a dedicated calibration experiment, called CRAB, which will take place next to the Triga research reactor in Vienna.



The Ph.D. concerns the analysis of data from the first phase of the NUCLEUS experiment by integrating the results of the calibration of the CRAB experiment into the NUCLEUS analysis. The analysis will be carried out according to the following experimental phases: analysis of the commissioning data (TUM, 2022), analysis of the NUCLEUS blank assembly data (TUM, 2023), analysis of the NUCLEUS neutrino data (Chooz, 2024-25) and CRAB data (Munich and Vienna, 2023-25). The work first involves the development of a dedicated analysis chain, based on existing CRESST software packages, to eventually integrate the analysis of NUCLEUS and CRAB data into a common framework. The first step in the analysis typically entails large-scale processing of the raw data on computer clusters, including triggering and energy reconstruction. After this phase, the reconstructed data need to be processed to isolate the expected signals from the various backgrounds. In parallel, calibration data (from radioactive sources, light-emitting diode systems, and CRAB results) and their uncertainties need to be incorporated. Altogether, novel analysis methods have to be developed to exploit the NUCLEUS 4pi-vetoing strategy to suppress backgrounds. Connections to state-of-the-art machine learning techniques to improve analysis performance will be also explored and eventually implemented.

T2K Near Detector performance and CP violation measurement in the neutrino’s oscillations

SL-DRF-22-0275

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Neutrinos Accélérateurs (GNA)

Saclay

Contact :

Jean-Francois Laporte

Samira Hassani

Starting date : 01-10-2022

Contact :

Jean-Francois Laporte
CEA - DRF/IRFU/SPP/Atlas

01 69 08 37 49

Thesis supervisor :

Samira Hassani
CEA - DRF/IRFU/DPHP/TK2

0169087226

The neutrino masses and flavor mixing are a direct evidence of new physics Beyond the Standard Model (BSM): the study of neutrino oscillations is thus a royal road to the search of new, unexpected phenomena. In particular, the analysis of neutrino and antineutrino oscillations at T2K and NOVA are providing first exciting hints of CP violation in the leptonic sector. This would be a major discovery related with one of the most fundamental questions in High Energy Physics: why there is an asymmetry between matter and antimatter in the Universe?



T2K is a neutrino experiment designed to investigate how neutrinos change from one flavour to another as they travel (neutrino oscillations). An intense beam of muon neutrinos is generated at the J-PARC nuclear physics site on the East coast of Japan and directed across the country to the Super-Kamiokande neutrino detector in the mountains of western Japan. The beam is measured once before it leaves the J-PARC site, using the near detector ND280, and again at Super-Kamiokande: the change in the measured intensity and composition of the beam is used to provide information on the properties of neutrinos.



The work of the proposed thesis will concentrate on the installation, commissioning and scientific exploitation of the High-Angle Time Projection Chamber (High-Angle TPC). The goal of this new detector is to improve the Near Detector performance, to measure the neutrino interaction rate and to constrain the neutrino interaction cross-sections so that the uncertainty in the number of predicted events at Super-Kamiokande is reduced to about 4% (from about 8% as of today). This will allow improving the physics reach of the T2K-II project. This goal is achieved by modifying the upstream part of the detector, adding a new highly granular scintillator detector (Super-FGD), two new TPCs and six Time Of Flight planes.



The new TPCs will be read out by resistive Micromegas detectors and instrumented with a compact and light field cage. The TPC will measure charge; momentum and directions of tracks produced by charged particles and will provide particle identification through dE/dx measurement with excellent efficiency and precision. Detector prototypes of the new TPCs have been successfully tested in Summer 2018, 2019 and 2021 at CERN and DESY test beams validating the detector technologies and their performance.

The IRFU group is heavily involved in the TPC project, especially in Micromegas detectors production and tests. The detector construction is on going for an installation in Japan in 2022.



The first part of the thesis will be devoted to TPC data analyses. The student will contribute to the commissioning and first beam data taking and analyses foreseen in 2023. The work will focus on the characterization of the resistive Micromegas detector. This is an innovative detector, which will exploit for the first time the resistive technology to improve the resolution on track reconstruction in the TPC. The IRFU group has been initiator of both the original Micromegas technology and of its resistive implementation.

A cutting-edge R&D conducted at IRFU has brought today to the deployment of such technology in a real detector. A seminal, unprecedented work of quantitative understanding and simulation of the charge spread in the resistive detector is on going.



New and sophisticated reconstruction algorithm must be developed to fully profit of the new detector capabilities. In particular, the timing information related with the resistive phenomena and encoded in the signal waveforms should be exploited. Indeed the resistive technology brings improved performances but also new challenges: the charge spread over multiple pads, induced by the resistive phenomena, will highly increase the multiplicity of signals to be analyzed.



Machine Learning (ML) methods will be explored to perform background-rejection and particle ID purposes at the pre-selection stage as well as evaluate them for the pattern recognition stage of track reconstruction. ML are known to have improved performance of many experiments in neutrino Physics (SNO, NEXT, NOvA, KamLAND-Zen, EXO-200, MINERvA). Producing images like structures from detectors data allows to benefit of the pattern recognition capabilities of these tools and enhancing useful features of the data, they can improve not only events but also particles classification tasks.



We propose as a first step to apply ML techniques to treat TPC information. The arrival time on the resistive anode plane gives the z coordinate perpendicular to that (x,y) plane. An event in the TPC is represented by two images projecting on (x,y) and (y,z) planes with the color scale being the pad charge to incorporate dE/dx information. This will allow treating the TPC information as images and to use the powerful ML algorithms used in image analysis. We plan to use implementations relying on Convolutional Neural Network (CNN) (for some, adapting the GoogLeNet CNN architecture) originally designed to image recognition. To significantly reduce training time, Graphical Processing Units (GPUs) will be used, which enable to perform computing operations in parallel. At the TPC level, we aim to use such techniques for Particle identification (PID) and possibly for pattern recognition.



Next we plan to use ML techniques combining TPC and the central SFGD for particle identification (muon from pion and from proton) as well as for event classification task. In the ND280, the beam of muon neutrinos interacts predominantly via the Charged Current Quasi Elastic interaction. For the purposes of the oscillation analysis, data are separated by event topology into one of three categories based on number of final state pions (no pions, one charged pion or any number of pions). A repository will be prepared, which will contain the images in a format suitable for the training of different ML algorithms. The samples defined above can be selected by using available data, collected by T2K. Other charged current event will fall in background sample.

A framework will be developed to allow the testing of various algorithms for object detection and classification.



The second part of the thesis will be dedicated to the analysis of the first T2K neutrino beam data, collected with the ND280 Upgrade detector, in order to extract a new, most precise, measurement of neutrino oscillations. Thanks to the increased statistics and the improved control of systematic uncertainties with ND280 upgrade, the project has the potential to achieve the best worldwide constrains on CP violation in the leptonic sector. The work will focus on the definition of the selection of the new ND280 samples, the evaluation of the corresponding experimental systematic uncertainties and the modification of the analysis framework for the fit to the neutrino oscillation parameters. The extraction of near detector constraints must be deeply modified to include the information of outgoing detected protons and neutrons coming from neutrino interactions and nuclei, which are completely missing in the present analysis. In parallel, the theoretical systematic uncertainties will need to be reevaluated on the basis of the new exclusive models of neutrino-nucleus interactions.

Thin fast photo-detector for time-of-flight and high resolution PET imaging with SiPM

SL-DRF-22-0252

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Santé et Energie (GSE)

Saclay

Contact :

Viatcheslav SHARYY

Dominique YVON

Starting date : 01-09-2021

Contact :

Viatcheslav SHARYY
CEA - DRF/IRFU

0169086129

Thesis supervisor :

Dominique YVON
CEA - DRF/IRFU/DPHP

01 6908 3625

Personal web page : https://irfu.cea.fr/Pisp/dominique.yvon/

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=3730&voir=3944

Positron emission tomography (PET) is a nuclear imaging technique widely used in oncology and neurobiology research. The decay of the radioactive tracer emits positrons, which annihilate into two photons of 511 keV. Using time-of-flight technology, they can be used to reconstruct the point of annihilation and the distribution of tracer activity in the patient's body.

In this thesis, we propose to contribute to an ambitious and patented detector based on Cherenkov/Scintillant crystals. The first prototype is currently being tested in the laboratory.

The instrument uses advanced technologies for fast particle detection: a dense scintillator crystal, a microchannel plate photomultiplier for the first side of the crystal, gigahertz amplifiers and fast acquisition modules (WaveCatcher, SAMPIC).

The PhD student will work on the choice of technologies and on the realization of a thin photodetector, with a high temporal resolution (a few tens of ps) intended to instrument the second side of the crystal. The preferred technology today would be a fast SiPM array.

You will test the available SiPM technologies, participate in the design of the photodetector assembly. You will run measurements on test benches and prototypes, and analyze the measured data in order to optimize the temporal, spatial resolution and efficiency of the detector. This will involve a wide range of instrumentation skills: photo-detection, fast electronics (analog and digital, to picosecond accuracy), detector simulations using GEANT4 and GATE software.

Supervision

The successful candidate will work in the IRFU Department of Particle Physics in close collaboration with the Department of Detectors, Electronics and Computing for Physics. The CaLIPSO group includes two physicists and two students and two post-docs. We collaborate closely with the CNRS-IJC-labs on fast readout electronics, with the CPPM of Marseille and the CEA-SHFJ, on medical imaging devices, with the CEA-DES on image reconstruction algorithms, and with the University of Munster (Germany).

Requirements

Knowledge of general physics, physics of particle-matter interaction, radioactivity and particle detector principles, as well as a vocation for instrumental work and data analysis are mandatory. Programming skills, Gate/Geant4 simulation and C++ training will be an asset.

Acquired Skills

You will acquire skills in particle detector instrumentation, radiation detector simulation, photo-detection, implementation and operation of fast scanning electronics and data analysis.
Towards the discovery of Charge-Parity violation in the neutrino oscillations

SL-DRF-22-0316

Research field : Particle physics
Location :

Service de Physique des Particules (DPHP)

Groupe Neutrinos Accélérateurs (GNA)

Saclay

Contact :

Georges VASSEUR

Sara Bolognesi

Starting date : 01-10-2022

Contact :

Georges VASSEUR
CEA - DSM/IRFU/SPP

0169081461

Thesis supervisor :

Sara Bolognesi
CEA - DRF/IRFU/SPP/TK2

0169081461

The study of neutrino oscillations entered the precision era with present experiments based on accelerator beams, like T2K. In these experiments, neutrino oscillations are measured by comparing the neutrino rate and spectra at near detectors, placed nearby the accelerator source, and at far detectors, placed hundreds of kilometers away. T2K published in 2020 on the Nature cover first exciting hints of Charge-Parity violation in the lepton sector.

The work proposed for this thesis consists in the analysis of the new data which will be collected by T2K with an upgraded near detector requiring to put in place a new analysis strategy. In particular, for the first time, the measurement of protons and neutrons produced by neutrino interactions will be exploited. New models of neutrino-nucleus interactions will be needed to cope with such additional information: the group proposing this thesis has a deep expertise on the field.

Another item to be addressed in the thesis is the extrapolation of the obtained results to long-term high-statistics measurements and multi-experiment combinations. The study of the most relevant systematic uncertainties will have a direct impact on the design of the next-generation experiments, to which the group is also participating.

The student is expected to participate to the installation and commissioning of new Time Projection Chambers in the Japanese site of the JPARC laboratory end of 2022 and early 2023. This will be a great opportunity for highly-formative hardware experience.

In summary, this thesis will allow to acquire expertise on neutrino oscillations, a highly promising topic for the future of HEP, to develop cutting-edge analysis techniques, to participate to the installation of an innovative detector and to interact with a wide community of nuclear physicists and phenomenologists. The results of the proposed analysis of T2K data will provide worldwide best measurements on neutrino oscillation parameters, notably on the possible first source of Charge-Parity violation in the lepton sector.

 

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