12 sujets IRFU/DPhN

Dernière mise à jour :


• Nuclear Physics

• Nuclear physics

• Particle physics

 

MACHINE LEARNING FOR INVERSE PROBLEMS IN HADRON STRUCTURE

SL-DRF-24-0306

Research field : Nuclear Physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire structure du nucléon (LSN) (LSN)

Saclay

Contact :

Valerio Bertone

Hervé Moutarde

Starting date : 01-10-2024

Contact :

Valerio Bertone
CEA - DRF/IRFU/DPhN/LSN


Thesis supervisor :

Hervé Moutarde
CEA - DRF/IRFU/DPhN

33 1 69 08 32 06

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=4189

Characterizing the multidimensional structure of hadrons in terms of quarks and gluons is one of the major objectives of hadronic physics today. This is not only the central theme of many experimental facilities worldwide, but also one of the main reasons for the construction of future colliders in the USA and China. It is also one of the key areas of research for intensive numerical simulations of the strong interaction. However, in both cases, the connection between measured and simulated data on the one hand, and the multidimensional structure of hadrons on the other, is not direct. The data are linked to the hadron structure via mathematically ill-posed multidimensional inverse problems. It has been shown that these inverse problems lead to a significant increase in uncertainties, to the point of becoming the dominant source of uncertainty in some cases. The aim of this thesis is to use machine learning tools to assess, reduce and correctly propagate uncertainties from experimental or simulation data to the multidimensional structure of hadrons. The strategy for achieving this is to develop an original neural network architecture capable of taking into account the full range of theoretical properties arising from quantum chromodynamics, and then to adapt it to inverse problems linking experimental and simulation data to the 3D structure of hadrons.
Variety of nuclear shapes in 96Zr studied with AGATA and GRIFFIN gamma-ray spectrometers

SL-DRF-24-0294

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Magdalena Zielinska

Starting date : 01-10-2024

Contact :

Magdalena Zielinska
CEA - DRF/IRFU/DPhN/LENA

01 69 08 74 86

Thesis supervisor :

Magdalena Zielinska
CEA - DRF/IRFU/DPhN/LENA

01 69 08 74 86

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=483

More : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=790

The thesis will focus on the experimental study of the nuulear properties of the heaviest stable zirconium isotope (96Zr).
Recently, observation of a low-lying deformed state in this magic nucleus has been explained by a reorganization of nuclear shells in function of their occupation by protons and neutrons. These sophisticated nuclear-structure calculations predict a variety of shapes, both ellipsoidal and pear-like, to appear at low excitation energy in the 96Zr nucleus. We will investigate them using the powerful Coulomb-excitation technique, which is the most direct method to determine the shapes of nuclei in their excited states. The experiment will be performed using AGATA, a new-generation gamma-ray spectrometer, consisting of a large number of finely segmented germanium crystals, which allows us to identify each point where a gamma ray interacts with the detector material and then, using the so-called “gamma-ray tracking” concept, to reconstruct the energies of all emitted gamma rays and their angles of emission with highest precision. A complementary measurement will be performed at TRIUMF (Vancouver, Canada) using the world’s leading setup for beta-decay measurements called GRIFFIN. This project is a part of an extensive experimental program on shape coexistence and evolution of nuclear shapes undertaken by our group.
INVESTIGATION OF THE NUCLEAR TWO-PHOTON DECAY IN SWIFT FULLY STRIPPED HEAVY IONS

SL-DRF-24-0289

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Wolfram KORTEN

Starting date : 01-10-2024

Contact :

Wolfram KORTEN
CEA - DRF/IRFU/DPhN/LENA

+33169084272

Thesis supervisor :

Wolfram KORTEN
CEA - DRF/IRFU/DPhN/LENA

+33169084272

Personal web page : https://www.researchgate.net/profile/Wolfram_Korten

Laboratory link : http://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_sstheme.php?id_ast=293

More : https://www.gsi.de/en/work/research/appamml/atomic_physics/experimental_facilities/esr.htm

The nuclear two-photon, or double-gamma decay is a rare decay mode in atomic nuclei whereby a nucleus in an excited state emits two gamma rays simultaneously. Even-even nuclei with a first excited 0+ state are favorable cases to search for a double-gamma decay branch, since the emission of a single gamma ray is strictly forbidden for 0+ ? 0+ transitions by angular momentum conservation. The double-gamma decay still remains a very small decay branch (<1E-4) competing with the dominant (first-order) decay modes of atomic internal-conversion electrons (ICE) or internal positron-electron (e+-e-) pair creation (IPC). Therefore we will make use of a new technique to search for the double-gamma decay in bare (fully-stripped) ions, which are available at the GSI facility in Darmstadt, Germany. The basic idea of our experiment is to produce, select and store exotic nuclei in their excited 0+ state in the GSI storage ring (ESR). For neutral atoms the excited 0+ state is a rather short-lived isomeric state with a lifetime of the order of a few tens to hundreds of nanoseconds. At relativistic energies available at GSI, however, all ions are fully stripped of their atomic electrons and decay by ICE emission is hence not possible. If the state of interest is located below the pair creation threshold the IPC process is not possible either. Consequently, bare nuclei are trapped in a long-lived isomeric state, which can only decay by double-gamma emission to the ground state. The decay of the isomers would be identified by so-called time-resolved Schottky Mass Spectroscopy. This method allows to distinguish the isomer and the ground state state by their (very slightly) different revolution time in the ESR, and to observe the disappearance of the isomer peak in the mass spectrum with a characteristic decay time. After a first successful experiment establishing the double-gamma decay in 72Ge a new experiment has been accepted by the GSI Programme Committee and its realization is planned for 2024.
Study of pear-shaped nuclei using the new detector SEASON

SL-DRF-24-0312

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire études du noyau atomique (LENA) (LENA)

Saclay

Contact :

Damien THISSE

Marine VANDEBROUCK

Starting date : 01-10-2024

Contact :

Damien THISSE
CEA - DRF/IRFU/DPhN


Thesis supervisor :

Marine VANDEBROUCK
CEA - DRF/IRFU/DPhN


Understanding the limits of existence of the nucleus, especially concerning its mass limit, is one of the major fields of research in contemporary nuclear physics. In the region of heavy nuclei, neutron-deficient actinides are of particular interest. Indeed, pronounced octupole (pear-shaped) deformations are predicted and have even been observed in some nuclei. The aim of this thesis is to study these octupole deformed nuclei using the new-generation detector SEASON, whose detection efficiency and energy resolution are unprecedented for this type of experiment. The thesis work will focus on the installation, testing, experimental data-taking and analysis from an experiment to be carried out in 2025 at the University of Jyväskylä. In this experiment, the proton-induced fusion-evaporation reaction 232Th(p,X)Y will be used to populate neutron-deficient actinide isotopes, whose decay products will be analyzed using SEASON. The thesis will be in cotutelle with the University of Jyväskylä and divided into two parts:
i) a 1-year period at the University of Jyväskylä, during which the experiment will take place
ii) the following two years at CEA Saclay will be devoted to data analysis and preparation of the experimental program with SEASON at the new facility S3-LEB at GANIL-SPIRAL2.
MODELLING LIGHT ANTI-ION REACTIONS ON ATOMIC NUCLEI

SL-DRF-24-0347

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire etudes et applications des reactions nucleaires (LEARN) (LEARN)

Saclay

Contact :

Jean-Christophe DAVID

Starting date : 01-10-2024

Contact :

Jean-Christophe DAVID
CEA - DRF/IRFU/DPhN/LEARN

0169087277

Thesis supervisor :

Jean-Christophe DAVID
CEA - DRF/IRFU/DPhN/LEARN

0169087277

Laboratory link : https://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=2105

The anti-(p, n, d, t, 3He, 4He)-nucleus reactions are both instructive and complicated to study. In addition to knowledge of the products of the antinuclon-nucleon reaction, they require the- nuclear environment to be taken into account, in particular the interactions in the final state.
Antiproton-nucleon reactions are/will be used/studied in particular at Cern's antiproton decelerator (AD) ring and at the FAIR facility in Germany to understand the behaviour oft antimatter. Reactions with light anti-ions (dbar, 3He-bar, for example) are of more recent interest, in particular with the GAPS (General AntiParticle Spectrometer) experiment, which aims to measure the fluxes of these particles in cosmic rays. The idea is to identify dark maJer, of which these particles are decay products, and whose measured quantities could 'easily' emerge from the cosmic background noise.
Recently, antiproton-nucleus reactions have been added to the INCL (IntraNuclear Cascade Liège) nuclear reaction code developed at the CEA (Irfu/DPhN) and this code is currently being implemented in the Geant4 transport code. The aim of the proposed thesis is to now include the reactions anti-(d, t, 3He, 4He)-nucleus in the INCL code.
Uncertainty propagation in a Monte-Carlo transport code

SL-DRF-24-0367

Research field : Nuclear physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire etudes et applications des reactions nucleaires (LEARN) (LEARN)

Saclay

Contact :

Jean-Christophe DAVID

Starting date : 01-10-2024

Contact :

Jean-Christophe DAVID
CEA - DRF/IRFU/DPhN/LEARN

0169087277

Thesis supervisor :

Jean-Christophe DAVID
CEA - DRF/IRFU/DPhN/LEARN

0169087277

Laboratory link : https://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=2105

Nuclear reaction modeling has been continuously being improved for many decades now. That's especially the case for our nuclear cascade code INCL. An ANR project has been funded for the next four years (2024-2027) to work on the issue of uncertainty and error estimate. Since this code is implemented in the particle transport code Geant4, the next step is to propagate these uncertainties from INCL to Geant4. There was a recent study on uncertainty propagation, called Transport Monte Carlo (TMC). However, this study only addresses the propagation of uncertainties related to model parameters, there was no propagation of model biases (related to hypotheses) and their uncertainties, which are both outside the physical model. Therefore, the propagation of biases and their uncertainties, which are coming from Monte Carlo collision models, is unexplored territory. The aim of the proposed PhD project is then to develop methods for this kind of propagation and to study the functioning and features of the developed methods in schematic scenarios. The full implementation of the developed methods into a transport code, such as GEANT4, however, is not within the core scope of the thesis, but it might be possible if time permits.
Drell-Yan production measurement in proton-proton collisions and preequilibrium dilepton production in heavy-ion collisions with the LHCb experiment at the LHC

SL-DRF-24-0277

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire plasma de quarks et gluons (LQGP) (LQGP)

Saclay

Contact :

Michael Winn

Starting date : 01-10-2024

Contact :

Michael Winn
CEA - DRF/IRFU/DPhN/ALICE

+33 1 69 08 55 86

Thesis supervisor :

Michael Winn
CEA - DRF/IRFU/DPhN/ALICE

+33 1 69 08 55 86

At the Large Hadron Collider (LHC) at Geneva, collisions of lead nuclei are used to create a thermodynamic system described by fluid dynamics under extreme conditions. The temperature of the short-lived system is sufficiently large in order to release the building blocks of matter at a subnucleonic scale, quarks and gluons. This state of matter is commonly called Quark Gluon Plasma (QGP). The space-time evolution of heavy-ion collisions at the LHC is described by close-to-ideal hydrodynamics after a short lapse of time. However, key features of the early stages of these collisions are largely unknown. These characteristics are crucial to understand the applicability limits of hydrodynamics and to understand thermalisation of a strongly interacting system.
In recent publications, it was pointed out that the dilepton production in the intermediate mass scale between 1.5 and 5 GeV/c² is highly sensitive to the ´thermalisation´ time scale towards the equilibrium QGP.

In addition, the LHC provides highly energetic proton and heavy-ion beams. They allow us to access the hadronic structure of the projectiles at very small fractional longitudinal momenta and at the same time still relatively large four momentum transfers. This configuration enables hence for perturbative calculations allowing the extraction of hadron structure information at very small fractional longitudinal momenta.
The theoretically best understood process in hadronic collisions is the production of dilepton pairs, the so-called Drell-Yan process. However, so far, no measurement down to 3 GeV/c² at a hadron collider has been published despite its theoretical motivation to test the lowest fractional momenta. In fact, at masses below around 30 GeV/c², semileptonic decays from heavy-flavour hadron decays start to dominate the dilepton production. This process has obscured any attempt to extract dilepton production in this kinematic domain.

The first goal of the thesis is the first measurement of Drell-Yan dimuons at low invariant masses at the LHC in proton-proton collisions that will be taken in 2024. This measurement will be based on novel background rejection techniques exploiting the forward geometry of LHCb. In a second part, the feasibility of the measurement in heavy-ion collisions will be investigated in the present and the future LHCb set-up. Depending on the outcome of the studies, a measurement in heavy-ion collisions will be conducted.
Study of the first Xenon-136 double-beta decay events of the PandaX-III experiment with neural network techniques

SL-DRF-24-0392

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire structure du nucléon (LSN) (LSN)

Saclay

Contact :

Damien NEYRET

Starting date : 01-10-2024

Contact :

Damien NEYRET
CEA - DRF/IRFU/DPhN/LSN

01 69 08 75 52

Thesis supervisor :

Damien NEYRET
CEA - DRF/IRFU/DPhN/LSN

01 69 08 75 52

More : https://pandax.sjtu.edu.cn/

The PandaX-III collaboration proposes to determine whether the neutrino is a Majorana particle, i.e. its own antiparticle. In this purpose this international collaboration, in which the Research Institute on Fundamental laws of the Universe (IRFU) of CEA Saclay participates, aims to observe neutrinoless double-beta decays of the Xenon-136, where the emission of the two electrons is not compensated by the simultaneous emission of two anti-neutrinos. Such an observation would violate the principle of conservation of leptonic number, in opposition with the predictions of the standard model of particle physics. The search of such rare events requires an enormous quantity of Xenon-136 atoms, a deep underground laboratory protected from cosmic rays and with low radioactive levels, like the Jinping underground laboratory (CJPL, Sichuan province, China), and a very effective particle detector.

The first phase of the experiment aims to construct a first TPC module (Time Projection Chamber) of 145kg of Xenon-136, which will be followed in a second stage by four other 200kg modules. The TPC will be equipped with detectors able to measure the energy of the two beta electrons with an excellent accuracy. The first TPC module will be commissioned end of 2024. The trajectory of the two electrons emitted by the double-beta decay will be reconstructed to measure the initial energy of those electrons, and to recognize the topology of their trajectories to differentiate them from gamma backgrounds which emit only one electron. That module will be equipped with gaseous Micromegas detectors which have a good energy resolution and a very good radio-purity which limits the amount of gamma backgrounds coming from radioactive contamination.

The PandaX-III collaboration is working on the construction of the first TPC module. It will be installed at CJPL during the year 2024. Reconstruction algorithms of detector data using neural networks are being developed, in order to complete the analytical methods already implemented in the REST environment of data reconstruction and analysis, to optimize double-beta events versus gamma backgrounds discrimination, and to improve the quality of the electron energy reconstruction. These algorithms are trained and evaluated on simulated Monte-Carlo events. Data from reduced-size TPC prototype will be also used to test these algorithms in real conditions. As soon as the first module will be installed end of 2024 these algorithms will be used for detector calibrations and for being implemented in real data analysis. They will be then used to extract the first physics results on double-beta events.

The main task of the PhD student will be to contribute on the development of data reconstruction algorithms based on neural networks, in particular by taking into account the defects of the detectors (dead channels, performance inhomogeneity, gas impurities, etc...) and by implementing in REST the data correction methods needed to compensate these defects. That work will include studies of data from prototype TPC chambers, as well as Monte-Carlo simulations. Moreover, as soon as the data from the first TPC module will be available the student will participate to the data analysis and the extraction of the physics results. These studies will be presented in conferences and published in scientific journals. The student will also participate to an R&D to optimize Micromegas detectors in order to improve their energy resolution as well as their general performance in high pressure gaseous Xenon.

A Master internship of 4 to 6 months would be also possible in the IRFU/DPhN PandaX-III group before the start of the PhD thesis.
Lambda hyperon polarization measurement in exclusive deeply virtual meson production processes

SL-DRF-24-0386

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire structure du nucléon (LSN) (LSN)

Saclay

Contact :

Francesco BOSSU

Starting date : 01-10-2024

Contact :

Francesco BOSSU
CEA - DRF/IRFU/SPhN


Thesis supervisor :

Francesco BOSSU
CEA - DRF/IRFU/SPhN


This thesis focuses on measuring the polarization of Lambda hyperons in exclusive deeply virtual meson production processes. The study is rooted in a surprising discovery from the 1970s: in proton-Beryllium collisions, ? hyperons exhibited transverse polarization, challenging the predictions of perturbative Quantum Chromodynamics. Similar polarizations have since been observed in various collision systems.
The proposed research topic leverages deeply virtual exclusive reactions in electron-proton scattering, providing precise control over final states and initial particle polarizations. Specifically, the reaction e+p->e+Lambda+K+ is explored to shed light on the Lambda hyperon's polarization. This process is also sensitive to the poorly known transversity Generalized Parton Distributions (GPDs) of the nucleon, offering valuable insights into nucleon properties.
The thesis aims to analyze data collected with the CLAS12 experiment at the Jefferson Laboratory (JLab) in US, with a focus on e-p collisions with a longitudinally polarized NH3 target. Machine learning algorithms and simulations will be employed to enhance data reconstruction and event candidate selection. The candidate will also contribute to simulation studies for future detectors and their reconstruction algorithms for the EIC.
The research will be conducted within the Laboratory of Nucleon Structure at CEA/Irfu. A background in particle physics, computer science (C++, Python), and knowledge of particle detectors is beneficial for active participation in data analysis.
The student will have the opportunity to collaborate with local and international researchers, to participate in the CLAS collaboration, to join the EIC user group with frequent trips to the USA for data collection and workshops, and present research findings at international conferences.
Bc meson production in the Pb-Pb collisions at 5.36 TeV of the LHC Run 3

SL-DRF-24-0364

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire plasma de quarks et gluons (LQGP) (LQGP)

Saclay

Contact :

Javier CASTILLO

Starting date : 01-10-2024

Contact :

Javier CASTILLO
CEA - DRF/IRFU/DPhN/LQGP

+33 169087255

Thesis supervisor :

Javier CASTILLO
CEA - DRF/IRFU/DPhN/LQGP

+33 169087255

Laboratory link : http://irfu.cea.fr/dphn/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=500

More : https://alice-collaboration.web.cern.ch

A few micro-seconds after the Big Bang, the Universe was in a quark gluon plasma (QGP) state. Such state is predicted by Quantum Chromodynamics, which is the theory of strong interactions, and should be reached at very high temperature or energy density. Such conditions are reproduced in ultra-relativistic heavy ion collisions at the LHC at CERN.
Among the various QGP observables, the study of hadrons with heavy-flavour quarks (charm c or beauty b) and quarkonia (c-cbar or b-bbar bound states) is particularly important to understand the properties of the QGP. Indeed, heavy quarks are produced by hard scatterings between partons of the incoming nuclei in the early stage of the collision, and thus experience the full dynamics of the collision.
Thanks to the measurements of J/psi (c-cbar) production in Pb-Pb collisions of Runs 1 and 2 of the LHC, the ALICE collaboration showed the existence of the regeneration mechanism: when the initial number of produced quark/anti-quark pairs is large and if heavy quarks do thermalise in the QGP, then new quarkonia could be produced in the QGP by recombination of heavy quarks. Other mechanisms, such as colour screening, could affect the production of quarkonia. Bc mesons are composed of a b quark and an antiquark c. Their production is therefore strongly disfavored in proton-proton collisions. In Pb-Pb collisions, instead, their production could be largely increased due to the regeneration mechanism.
We propose to study the production of Bc mesons in Pb-Pb collisions at a center-of-mass energy per nucleon pair (sqrt(sNN)) of 5.36 TeV at the LHC with the data of Run 3 (2022-2025). The ALICE apparatus was upgraded in view of LHC Runs 3 and 4 with, in particular, the addition of a silicon pixel tracker (MFT) that complements the ALICE forward spectrometer as well as new readout electronics for the latter. These upgrades will allow us to: Profit from the planned increase in luminosity of the LHC, thus tripling in one year the data collected in the full LHC Run 2 (2015-2018); Measure with high precision secondary vertices of b-hadron decays. The Bc mesons will be measured at forward rapidity by reconstructing three secondary muons with the muon spectrometer and the MFT of ALICE.
The student will first contribute to the optimization and characterization of the muon spectrometer and MFT matching algorithm and the secondary vertex reconstruction. Secondly, the student will study the production of Bc mesons in Pb-Pb collisions. Finally, the results will be compared with other experimental results as well as various theory calculations.
During this work the student will become familiar with the grid computing tools and the simulation, reconstruction and data analysis software of the ALICE Collaboration.
High-precision measurements of nuclear recoil on the 100 eV scale for cryogenic detectors

SL-DRF-24-0274

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire etudes et applications des reactions nucleaires (LEARN) (LEARN)

Saclay

Contact :

Loïc THULLIEZ

David LHUILLIER

Starting date : 01-10-2024

Contact :

Loïc THULLIEZ
CEA - DRF/IRFU/DPhN/LEARN

0169087453

Thesis supervisor :

David LHUILLIER
CEA - DRF/IRFU/DPHN/LEARN

01 69 08 94 97

The CRAB method aims to provide an absolute calibration of cryogenic detectors used in dark matter and coherent neutrino scattering experiments. These experiments have in common the fact that the signal they are looking for is a very low-energy nuclear recoil (around 100 eV), requiring detectors with a resolution of a few eV and a threshold of O(10eV). Until now, however, it has been very difficult to produce nuclear recoils of known energy to characterize the response of these detectors. The main idea of the CRAB method, detailed here [1, 2], is to induce a nuclear capture reaction with thermal neutrons (25 meV energy) on the nuclei constituent the cryogenic detector. The resulting compound nucleus has a well-known excitation energy, the neutron separation energy, being between 5 and 8 MeV, depending on the isotope. If it de-excites by emitting a single gamma ray, the nucleus will recoil with an energy that is perfectly known, given by the two-body kinematics. A calibration peak, in the desired range of some 100 eV, then appears in the energy spectrum of the cryogenic detector. A first measurement performed in 2022 with a CaWO4 cryogenic detector from the NUCLEUS experiment (a coherent neutrino scattering experiment supported by TU-Munich, in which CEA is heavily involved) has validated the method [3].

This thesis comes within the scope of the second phase of the project, which involves high precision measurements using a thermal neutron beam from the TRIGA-Mark-II reactor in Vienna (TU-Wien, Austria). Two complementary approaches will be used simultaneously to achieve a high precision: 1/ the configuration of the cryogenic detector will be optimized for very good energy resolution, 2/ large crystals of BaF2 and BGO will be placed around the cryostat for a coincident detection of the nuclear recoil in the cryogenic detector and the gamma ray that induced this recoil. This coincidence method will significantly reduce the background noise and will enable the CRAB method to be extended to a wider energy range and to the constituent materials of most cryogenic detectors. We expect these measurements to provide a unique characterization of the response of cryogenic detectors, in an energy range of interest for the search for light dark matter and coherent neutrino scattering. High precision will also open up a window of sensitivity to fine effects coupling nuclear physics (nucleus de-excitation time) and solid-state physics (nucleus recoil time in matter, creation of crystal defects during nucleus recoil) [4].

The PhD student will be heavily involved in all aspects of the experiment: simulation, on-site installation, analysis and interpretation of the results.
Accessing the 3D structure of pions with CLAS12

SL-DRF-24-0328

Research field : Particle physics
Location :

Service de Physique Nucléaire (DPhN)

Laboratoire structure du nucléon (LSN) (LSN)

Saclay

Contact :

Maxime DEFURNE

Damien NEYRET

Starting date : 01-10-2024

Contact :

Maxime DEFURNE
CEA - DRF/IRFU/DPhN/LSN

01 69 08 32 37

Thesis supervisor :

Damien NEYRET
CEA - DRF/IRFU/DPhN/LSN

01 69 08 75 52

Laboratory link : https://irfu.cea.fr/dphn/

In collaboration with the Thomas Jefferson Laboratory (JLab) in the USA, the researchers in the laboratory of nucleon structure at Irfu want to understand how quarks and gluons interact to form hadrons such protons, neutrons and pions. At JLab, a 11-GeV electron beam is impinged on a proton target. The protos are constituted of three quarks surrounded by a cloud of quark/antiquark pairs whose quantum numbers are similar to pions. The electrons of the beam will interact with these pairs with a structure analogous to a pion. More specifically, we are interested in the deeply virtual Compton scattering (DVCS) giving correlations between longitudinal momentum and transverse position of quarks in a pion. In other words, we are going to perform the very first 3D study of the pion structure. The PhD student will analyze data already available to isolate the DVCS events. A digital twins of the Monte-Carlo simulation/reconstruction chain will be produced with a conditional Generative Adversarial Network in order to caracterize faster and more accurately the background and, in the end, subtract it. The PhD student will travel two to three times a year to JLab, participating to the data taking as well as attending the collaboration meeting. The results will be presented in international conferences and published in peer-reviewed journals.

 

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