Electron triggers are responsible for selecting events resulting of proton-proton collisions at the Large Hadron Collider and their performance is a key ingredient for many physics analyses with the ATLAS detector. This work presents recent studies of Run3 electron trigger efficiencies and the corresponding scale factors, which correct for small differences between data and simulated events....
The ATLAS experiment has published measurement of Higgs trilinear self-coupling with LHC Run 2 + partial Run 3 data, reaching a range of -1.7 < $\kappa_{\lambda}$ < 6.6 ; but the core algorithm for statictical inference is a $m_{\gamma\gamma}$ histogram-based fit, which is not optimal given the $\kappa_{\lambda}$ is non-linear to the signal strength. Motivated by the drawback of histogram...
In high-energy collisions, jets, which are collimated sprays of particles, can originate from various fundamental particles, including W and Z bosons, top quarks, and the Higgs boson. Accurately identifying these jets is crucial for studying Standard Model processes and investigating new physics beyond its framework. This study, conducted within the ATLAS collaboration at the Large Hadron...
The Higgs boson pair production (HH) takes center stage in the LHC physics program. Vector Boson Fusion (VBF), the second largest production mode of HH, represents a probe to the Higgs boson doublet structure in the Standard Model and to physics beyond it. Studying HH via VBF is particularly interesting in the boosted topology which is sensitive to anomalous couplings of two Higgs bosons to...
The upcoming High Luminosity LHC (HL-LHC) era is expected to bring opportunities for studies involving rare processes, including di-Higgs production. Flavour tagging is going to play a crucial role in the analysis of such processes. This talk will explore the challenges we expect to encounter for flavour tagging in the HL-LHC era, with its higher luminosity, increased pile-up and upgraded...
The search for non-resonant Higgs boson pair production provides an important probe to the Higgs self-coupling and thus the electroweak symmetry breaking mechanism. The HH $\rightarrow bb\gamma\gamma$ channel is one of the most sensitive channels in the search for di-Higgs bosons. The search performed with Run2 and partial Run3 data collected by the ATLAS experiment with the unprecedented...
Vector boson scattering processes are precision probes of the electroweak sector and provide strong sensitivity to new physics that affects gauge and Higgs couplings. Although VBS cross sections in the Standard Model are small, these processes have been observed at the Large Hadron Collider by the ATLAS and CMS experiments. The semi leptonic final state, where one boson decays hadronically to...
My thesis subject is the study of the polarisation of electroweak gauge bosons. The longitudinally polarised state is highly correlated to the Goldstone boson, so before the electroweak symmetry breaking, thus allows us to test the limit of the Standard Model prediction. The challenge of this observation of simultaneously produced bosons, called Vector Boson Scattering, is the very low...
This presentation summarises the work I have done so far for my PhD. First, the presentation introduces the audience to the VBS process, why it is important and what is its signature in the detector. Then, it proceeds with the QCD background modelling studies that were performed using the MG5_aMC@NLO MC generator. Moreover, it briefly discusses the work I have been doing for my Qualification...
The CMS collaboration, which analyzes proton-proton collisions at CERN's Large Hadron Collider (LHC), has measured the tau leptons polarization from the decay of Z bosons with LHC Run 2 data from 2016. The polarization (helicity asymmetry) measures the different couplings of the Z boson to left- and right-handed fermions due to its electroweak nature and allows a determination of the effective...
Processes involving Flavor Changing Neutral Currents (FCNC), where a B meson undergoes decay into a pair of oppositely charged leptons, serve as potent avenues in the exploration of physics beyond the Standard Model (SM). Notably, the decay $B \to \mu^+ \mu^-$ has been observed by LHC experiments, and its measured branching fraction (BF) aligns with the SM prediction, thereby imposing rigorous...
The Future Circular Collider (FCC-ee) is a proposed electron-positron collider designed to enable high-energy collisions at unmatched scales. It is expected to produce $O(10^{12})$ $Z \to q\bar{q}$ events, significantly enhancing our ability to perform precision measurements of electroweak observables. So far, LHCb has measured CP violation in $D^0$ decays to charged particles....
The g-2 of the muon is one of the oldest (longstanding) potential anomalies in the standard model, although recent theoretical developements synthesized by the g-2 theory initiative and the most precise measurements carried out at Fermilab contributed to a shift in the field's landscape. However, tensions persist and are still very much unresolved in the data driven approach, with recent...
The Standard Model of Particle Physics explains successfully the fundamental interactions between particles of ordinary matter. However, it is incomplete, as it cannot explain neutrino masses nor cosmological observations such as matter-antimatter asymmetry in the Universe or the origin of dark matter. Physics beyond the Standard Model is either searched for production of new particles via...
The cosmological principle assumes the isotropy of the Universe. The high coverage of the Zwicky Transient Facility survey (ZTF) makes it possible to carry out an unprecedented study of the veracity of this principle by using observation of type Ia supernovae (SNe Ia).
This unique low redshift (z<0.15) survey with more than 3000 SNe Ia in the second data release (ZTF-DR2-SNe Ia) increases...
Développée dans les années 1980, l’astronomie à très haute énergie (THE) a connu un bond lors des deux dernières décennies grâce à l’arrivée de la génération actuelle de télescopes tcherenkov à imagerie atmosphérique (IACTs). Le réseau de télescopes H.E.S.S. (High Energy Stereoscopic System), installé en Namibie, a grandement contribué à cet essor.
Parmi les nombreux phénomènes...
Both the Rubin Observatory and the first telescopes of the CTAO will be collecting data by 2026, marking a new era in optical and gamma-ray astronomy. Compared to predecessors like the ZTF, H.E.S.S., MAGIC, and VERITAS, their enhanced sensitivity will extend extragalactic observations to a redshift of at least $\sim$2.5. This advancement offers fresh insights into non-thermal astrophysical...
The DarkSide20k experiment is a direct Dark Matter detector focused on the search for WIMP dark matter. Its main component is a dual-phase Argon Time Projection Chamber (TPC). Here, particles are detected from collisions with Argon atoms and the subsequent emission of scintillation light as well as ionisation electrons. Since the rate of signal events is expected to be much lower than...
The Cherenkov Telescope Array Observatory (CTAO) is going to consist of more than 60 telescopes in the northern and southern hemispheres, being the largest and most sensitive instrument to gamma rays from 20 GeV to 300 TeV. The arrays will be made of four Large-Sized Telescopes (LSTs) in the Northern Hemisphere, up to 23 Medium-Sized Telescopes (MSTs) distributed over both array sites for its...
Multi-wavelength and multi-messenger astrophysics have experienced remarkable growth over the past decade, aiming to build a comprehensive picture of various cosmic phenomena. Transient sources, in particular, greatly benefit from the complementary information provided by multi-messenger observations, both enhancing follow-up of rapidly fading signals and allowing for a better physical...
The first direct observation of gravitational waves (GW) in 2015 by the LIGO/Virgo/Kagra (LVK) collaboration opened a new era of astronomy. The GW group at IP2I in Lyon contributes to both the analysis of interferometers data and the characterization of the VIRGO detector. Most gravitational-wave online search pipelines rely on matched filtering (MF), a method which compares the data to a...
T2K is a long-baseline experiment measuring neutrino and antineutrino oscillations by observing the disappearance of muon neutrinos, as well as the appearance of electron neutrinos. The ND280 near detector at J-PARC plays a crucial role to minimise the systematic uncertainties related to the neutrino flux and neutrino-nucleus interactions of the un-oscillated neutrino beam. The ND280 detector...
DUNE is a neutrino oscillation experiment expected to take its first data around 2030. A near and a far measurement of a accelerator-produced muon neutrino flux allows for a precise determination of the oscillation parameters, including a first measurement of $\delta_{\mathrm{CP}}$ (CP violation parameter). The far detector is a compound of tens of kilotons liquid argon time projection...
The Deep Underground Neutrino Experiment (DUNE) is a next-generation long baseline neutrino experiment. By using Liquid Argon Time Projection Chamber (LArTPC) detectors to detect GeV-scale neutrinos produced by an accelerator, DUNE's main physics goals are to measure the CP-violating phase ($\delta_{\text{CP}}$), determine the neutrino mass ordering and resolve the $\theta_{23}$ octant....
The ALERT experiment aims to advance our understanding of the nuclear structure in terms of quarks and gluons by precisely measuring the electroproduction of a real photon through the interaction with a nuclear target such as the Helium-4. This process referred as the Deeply Virtual Compton Scattering (DVCS) gives us access to the tomography of quarks inside the nucleus. The achievement of...
My PhD thesis is the measurement of beauty production in
proton-proton and Pb-Pb collisions with the ALICE experiment at the CERN LHC and my talk will focus on a crucial part in the study of b-jet production: b-jet tagging.
I will compare two methods for b-jet tagging: the Track Counting method which relies on impact parameter significance, and Boosted Decision Trees (a machine learning...
Deeply Virtual Compton Scattering (DVCS) is a powerful tool to investigate the internal structure of hadrons in terms of Generalized Parton Distributions (GPDs). The Sullivan process, involving the exchange of a virtual pion from the proton’s meson cloud, offers a unique opportunity to access the three-dimensional structure of the pion at high energies. Since the pion plays a central role in...
The Quark–Gluon Plasma (QGP) is a deconfined state of matter consisting of quarks and gluons, theorized to have existed during the earliest moments after the Big Bang. Hadronisation refers to the process by which quarks combine to form composite particles known as hadrons. Studying how hadronisation occurs within the QGP provides valuable insights into how the first particles in our Universe...
The quark-gluon plasma (QGP) is a state of matter at high temperatures and/or high baryon density where quarks and gluons are asymptotically free and not confined in hadrons anymore. Experimentally, it can be produced
during heavy ion collisions using large accelerator facilities such as the LHC. The ALICE experiment focuses on characterizing the QGP properties using
the aforementioned...
The freeze-in mechanism is an alternative mechanism for dark matter production to standard thermal freeze-out. Freeze-in computations are typically performed assuming a very high initial ("reheating") temperature. However, this temperature is poorly constrained and can take relatively small values. I will discuss dark matter freeze-in in such a scenario and highlight how dark matter production...
We update constraints on a simple model of self-interacting neutrinos involving a heavy scalar mediator with universal flavor coupling. According to past literature, such a model is allowed by Cosmic Microwave Background (CMB) data, with some CMB and large-scale structure data even favoring a strongly-interacting neutrino (SI$\nu$) scenario over $\Lambda$CDM. In this work, we re-evaluate the...
The search for resonant mass bumps in invariant-mass distributions remains a cornerstone strategy for uncovering Beyond the Standard Model (BSM) physics at the Large Hadron Collider (LHC). Traditional methods often rely on predefined functional forms and exhaustive computational and human resources, limiting the scope of tested final states and selections.
This poster presents BumpNet, a...
The Standard Model (SM) of particle physics successfully describes most observed phenomena, yet it fails to explain the matter-antimatter asymmetry in the Universe. This discrepancy suggests the existence of new sources of CP violation beyond those present in the SM. The neutron Electric Dipole Moment (nEDM) is a powerful observable for searching for new physics, as it is highly sensitive to...
The upcoming High-Luminosity phase of the Large Hadron Collider (HL-LHC) will deliver unprecedented luminosities, posing significant challenges for particle reconstruction and pile-up mitigation. To preserve excellent tracking and vertexing performance under these conditions, the ATLAS experiment is developing the High Granularity Timing Detector (HGTD), a precision timing layer capable of...
The X-ArT (Xenon-Argon Technology) collaboration has studied the scintillation mechanisms in pure and Xe-doped liquid argon (LAr) using silicon photomultipliers sensitive to different wavelength ranges. Thanks to our measurements we identified a long-lived (>10μs) component attributed to extreme ultraviolet (EUV) photons emitted by the metastable levels of atomic argon. Based on this...
I am starting my second year thesis at Paris-Saclay university / CEA, within the ERC G-LEAD project, on the development of innovative electronics for a radiometer aimed at QCD axion dark matter searches.
My thesis focuses on developing a radiometer covering a frequency band from 10 GHz to 40 GHz, corresponding to a axion mass range of $50\mu$eV to $150\mu$eV.
This detector is designed to...
Dans le cadre des projets de collisionneurs leptoniques futurs, un prototype de calorimètre hadronique ultra granulaire, le SDHCAL, a été réalisé à l’IP2I.
Pour les projets de collisionneurs leptoniques circulaires comme le FCC et le CEPC, il est proposé d’adjoindre au SDHCAL une capacité de mesures précises du temps pour former un calorimètre ultra granulaire en temps et espace. Cette...
The new 3γ imaging technique, based on the use of the radionuclide 44Sc, enables the direct three-dimensional reconstruction of a radioactive source from the simultaneous detection of three gamma photons. This approach has the potential to reduce both acquisition time and injected activity compared to conventional nuclear imaging methods. To investigate this concept, a liquid xenon Compton...
Abstract: The C70XP cyclotron at ARRONAX, located in Saint Herblain [1], is capable of delivering different types of particle beams: Protons and alpha particles up to 70 MeV & deuterons up to 35 MeV. At the cyclotron level, in standard mode, bunches of ions can be delivered with a duration of 3ns separated by 33ns each, and beam intensities ranging from very low (< 1 pA) to very high (up to...
The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) is scheduled to begin colliding protons in 2028. This increase of luminosity will induce a larger number of collisions per beam crossing (around 200). This phenomenon is called the pile-up (μ). A High Granularity Timing Detector (HGTD) has been proposed for the ATLAS experiment to address this new challenges. This new ATLAS...
With the High Luminosity LHC (HL-LHC) upgrade scheduled for 2030, a major upgrade of the LHCb experiment is planned to adapt to the expected harsh environment. At the Upstream (UP) and MightyTracker (MT) tracking stations, Monolithic Active Pixel Sensors (MAPS) have been chosen for their high resistivity to radiation and their small pixel sizes. This high granularity and the higher pile-up at...
Coherent elastic neutrino nucleus scattering (CEvNS) was first measured experimentally by the COHERENT experiment in 2017 and is currently being studied by many experiments all around the world. In this context, the Ricochet international collaboration aims to detect the CEvNS process in order to search for new physics. The detectors used are germanium crystals operated at cryogenic...
Timing measurements are critical for the detectors at the future HL-LHC, to resolve reconstruction ambiguity when the number of simultaneous interactions reaches up to 200 per bunch crossing. The ATLAS collaboration therefore builds a new High-Granularity Timing detector for the forward region. A customized ASIC, called ALTIROC, has been developed, to read out fast signals from low-gain...
The Large Hadron Collider (LHC) collides protons at nearly the speed of light, producing new particles observed by the ATLAS detector. In 2026, the LHC will undergo a major upgrade to the High-Luminosity LHC (HL-LHC), increasing luminosity by a factor of 5–7 and delivering up to 200 simultaneous collisions. To cope with the resulting data rates, ATLAS will replace the readout electronics of...
Nucleosynthesis is the branch of physics that studies the creation sites and mechanisms of the elements present in our universe. The synthesis of the proton-rich stable isotopes heavier than iron, known as the p-nuclei, remains one of the open questions in nuclear astrophysics. Their production in high-temperature stellar environments critically depends on reaction rates involving...
Présentation de l'intérêt de rajouter une mesure de temps de vol suite a une mesure en spectrométrie pour l'étude de la fission. Présentation du fonctionnement d'une ligne de temps de vol, et de quelques résultats obtenus au laboratoire et à l’ILL.
La composante nucléaire de la transition énergétique en France soulève de nombreuses questions. La prolongation du parc nucléaire historique, la question de la construction de nouveaux réacteurs et la gestion avancée des combustibles usés sont autant de facteurs d’incertitudes, en particulier via leur impact économique sur le coût de la production électrique.
La recherche académique est...
Thorium-based molten salt reactors have recently attracted increasing interest as one of the promising Generation-IV reactor concepts and as a potentially safer alternative to Uranium-fuelled systems. However, the fission properties of Thorium are still insufficiently understood, particularly due to the limited availability of experimental fission yield data. In this work, we analyze γ-ray...
The nature of dark matter, whose existence is firmly established by astrophysical and cosmological observations, remains one of the most compelling open questions in physics. Among the proposed candidates, Weakly Interacting Massive Particles (WIMPs) are one of the most promising models. They are theoretically motivated by the so-called “WIMP miracle”: a weakly interacting, stable particle...
In high-energy collisions, jets, which are collimated sprays of particles, can originate from various fundamental particles, including W and Z bosons, top quarks, and the Higgs boson. Accurately identifying these jets is crucial for studying Standard Model processes and investigating new physics beyond its framework. This study, conducted within the ATLAS collaboration at the Large Hadron...
