N.B.: Last modification on 2024-10-14.

Webpage Editor: F. NORTIER

Theory

Manager: Dimitrios TSIMPIS

The research activities of the theoretical physics teams at IP2I Lyon cover a very wide array of subjects, ranging from the infinitely small to the infinitely large: from the properties of the smallest constituents of matter, to questions pertaining to the large-scale structure of the universe. The ultimate goal is to provide theoretical models to explain the experimental observations, or make theoretical predictions that may be tested experimentally. Our activities are separated into 3 teams, with frequent collaborations:

• Particles, Fields & Strings
• Nuclear & Hadronic Physics
• Astro & Gravitational Waves

Group picture in Spring 2024.

N.B.: Last modification on 2024-10-06.

Webpage Editor: F. NORTIER

Particles, Fields & Strings

Manager: Aldo DEANDREA

From particles to strings.

Members

Scientific Staff

• Aldo DEANDREA (PR)
• François GIERES (PR)
• Stefan HOHENEGGER  (MCF, on detachment at Naples U.)
• Farvah Nazila MAHMOUDI (PR)
• Florian NORTIER (CR)
• Dimitrios TSIMPIS (PR)

Emeriti

Visitors

Postdoctoral Fellows

• Dayanand Kishan Kumar MISHRA
• Siavash NESHATPOUR

PhD Students

• Timothé ALEZRAA (1/2)
• Alfred BOVON (1/2)
• Niels FARDEAU
• Baptiste FILOCHE
• Wanda ISNARD (1/2)
• Yann MONCEAUX
• Théo REYMERMIER (1/2)
• Christian VEROLLET (1/4)

Research Topics

• Particle Physics
  • Higgs Boson Physics
  • Flavor Physics
  • Collider Phenomenology
  • Physics Beyond the Standard Model
  • Astroparticles, Cosmology, Black Holes
• Field & String Theories
  • Superspace, Higher-Order Corrections & Fermionic Condensates
  • Flux Compactification, NATD & Consistent Truncations
  • Little Strings & U-Duality
  • Monodromies in One-Loop String Amplitudes
  • Field Theoretical Models in Ordinary & Non-Commutative Spaces
  • Non-Localizable Field Theories

Research Activities

Particle Physics

High-energy physics is devoted to the study of fundamental interactions between elementary particles. The currently accepted theory of fundamental interactions – the Standard Model (SM) – has proven to be extremely accurate in describing the ultimate constituents of matter that can be measured experimentally. However, there are serious reasons to believe that it cannot represent a complete theory of the laws of nature and we devote part of our research to the study of different theories going beyond the SM, whose aim is to describe this New Physics (NP).

Table of elementary particles.

Higgs Boson Physics

Contacts: A. DEANDREA, F.N. MAHMOUDI & F. NORTIER

The Higgs field is the origin of the mass of the elementary particles in the SM. The discovery of its main signature, the Higgs boson, has given us new tools to study the physics of spontaneous electroweak symmetry breaking.

Left: “Sombrero” potential of the Higgs field. Right: Feynman diagrams of the Higgs boson production modes at the LHC, and pie chart of the branching ratios (BRs) of its main decay channels.

The team proposed a new parameterization of the Higgs boson couplings, which allows to directly extract the loop contributions of New Physics (NP). We extended our studies by including a second Higgs boson, and we collaborate with CMS for the interpretation of the low-mass results. We are working on the characterization of the supersymmetric and composite Higgs sector, as well as on the prospects for future colliders such as the FCC.

Flavor Physics

Contact: F.N. MAHMOUDI

Flavor physics is at the heart of many unanswered mysteries in the SM and is intimately linked to the Higgs sector via Yukawa couplings. Therefore, solving the flavor puzzle involves seeking to elucidate the origin(s) of: the replication in generations of fermions, their mass hierarchy, the mass of neutrinos, the particular textures of quark and neutrino mixing matrices, and the matter-antimatter asymmetry via CP violation.

Left: Legend has it that Murray Gell-Mann and his student Harald Fritzsch came up with the idea of ​​distinguishing quarks by their “flavor” and “color” in 1971, while testing different flavors of ice cream. Center and right: Examples of Feynman diagrams, known as “penguin diagrams,” in flavor physics in the SM (center) and in a supersymmetric model (right).

Flavor physics has become an emerging field to probe new phenomena, mainly due to the emergence of several deviations from SM predictions in B-meson semi-leptonic decays. The team is working on precision calculations of these observables, and more precisely the calculation of local and non-local hadronic effects. This constitutes an important challenge in the field, and a necessary step to unambiguously distinguish SM hadronic effects from potential NP phenomena. We have recently proposed a new method for calculating local form factors to reduce systematic theoretical uncertainties. We are also working on the theoretical interpretation of these anomalies in an NP context. For this, we will consider effective field theory approaches, with multidimensional fits of observables, as well as specific UV-models (supersymmetric models, extended scalar sector, etc). Finally, we are working on the development of numerical codes that will allow studying the phenomenological implications of experimental data. Our goal is in particular to automate the calculation of flavor observables in any NP model. Therefore, the public code SuperIso, for the calculation of flavor physics observables, has been considerably improved in recent years.

Collider Phenomenology

Contacts: A. DEANDREA & F.N. MAHMOUDI

High-energy proton collisions continue to provide new high-precision results in previously unexplored energy regions. These results can be used to test theories beyond the SM.

Simulation of the showers of subatomic particles produced in the CMS detector, during the collision of proton-proton beams at the CERN LHC.

The team has developed world-class expertise in the phenomenology of heavy vectorlike quarks, composite Higgs, supersymmetry, and has developed several numerical tools for the detection of such particles at the LHC. We implemented vectorlike quarks with generic couplings in Monte Carlo tools such as MadGraph, allowing model-independent studies. NLO effects in QCD are also included, and our tools are regularly used by experimental collaborations, such as CMS, for the production of Monte Carlo data. We continue to develop the public code MARTY, which aims to perform automatic calculations of amplitudes, cross sections and Wilson coefficients in any NP model. The team is involved in the scientific preparation of future colliders, including the electron-positron and proton-proton FCCs, and is eagerly awaiting the start-up of the HL-LHC.

Physics Beyond the Standard Model

Contacts: A. DEANDREA, F.N. MAHMOUDI, F. NORTIER & D. TSIMPIS

Beyond the flavor puzzle, there are several motivations to build extensions of the SM, such as dark matter, the electroweak hierarchy problem, the strong CP problem, gauge coupling unification, quantum gravity, etc.

Artistic illustration of various physics topics beyond the SM, represented by islands separated by seas of unknowns.

The team has developed expertise in different classes of models: extra dimensions, composite models, supersymmetry, extended scalar sectors, dark matter. The recruitment of F. NORTIER has allowed us to acquire new expertise on weakly non-local models with UV/IR mixing. Concerning models with extra dimensions, we have proposed new models for dark matter candidates arising from geometric symmetries. We studied “gauge-Higgs unification” models, and shown the possibility of a unification of gauge and Yukawa couplings. Currently, we are building phenomenological models with compactifications on hyperbolic geometries, such as nilmanifolds and their implications for gauge-Higgs unification scenarios. In parallel, we are developing asymptotic grand unification models, with dark matter candidates called “Indalos”. As for composite Higgs models, we study the phenomenology of new resonances predicted by these models, and we developed UV-completions with fermionic fundamental constituents. In addition, we studied flavor constraints on composite models or with extra dimensions. Finally, we participate in the development of the GAMBIT code, whose goal is to perform global fits for generic NP scenarios.

Astroparticles, Cosmology & Black Holes

Contacts: A. DEANDREA, F.N. MAHMOUDI, S. HOHENEGGER & D. TSIMPIS

Connections with astroparticle physics and cosmology are of great importance for understanding the properties of physics beyond the SM, particularly through its relationship to dark matter and dark energy, which constitute the majority of the total energy composition of the current observable Universe.

Left: Schematic view of the expansion of the Universe during its cosmological history. Right: Pie chart of the current energy composition of the Universe.

The team activities on dark matter focus on the search for new particles by direct or indirect detection, the relic density of dark matter and the links with collider physics. The SuperIso Relic code was developed to provide a computational tool for different observables related to dark matter and particle physics. Initially dedicated to supersymmetry (SuperIso), the code is currently being developed to allow a flexible and generic implementation of all types of physics scenarios beyond the SM. In addition, we have studied the links with primordial cosmology, and shown that the discovery of new particles will provide information on the content of the Universe before primordial nucleosynthesis, despite the fact that this era is currently unobservable. In 2022, the DarkPACK code was published: interfaced with MARTY and SuperIso Relic, it automatically generates a numerical library of scattering amplitudes in a given model to calculate dark matter observables, such as the relic density. In cosmology, we recently realized a composite model of inflation, using a construction similar to that of composite Higgs models, and we are studying string theory realizations of dark energy models, such as quintessence. In black hole physics, we developed an effective theory approach to include quantum corrections to classical Schwarzschild geometry, and we have studied the theoretical impact of extra dimensions and the weak gravity conjecture on quasi-normal modes of black holes.

Field & String Theories

N.B.: Sections marked with an asterisk require updating.

The problem of a UV-completion to quantum gravity motivated the development of string theory. The search for a non-perturbative formulation, the so-called “M-Theory”, is still an active field of research nowadays. However, recent applications of string theory has gone far beyond its original purpose. They are at the origin of many formal results in field theory, that have allowed important breakthroughs in understanding strongly coupled interactions in supersymmetric “toy” theories, such as with the AdS/CFT correspondence or the electric-magnetic duality. String theory has also stimulated the study of non-local and/or non-commutative field theories.

Superspace, Higher-Order Corrections & Fermionic Condensates*

Contact: D. TSIMPIS

The effective action of string/M-theory admits an infinite tower of derivative corrections, playing a crucial role in areas such as black holes, cosmology and the AdS/CFT duality. We have applied superspace methods to constrain the form of M-theory invariants. The tools developed were used in order to determine the quartic fermion terms of IIA supergravity and their impact on the search for de Sitter solutions.

Flux Compactification, NATD & Consistent Truncations*

Contact: D. TSIMPIS

Flux compactification (FC) refers to the most general setup in which the various tensor fields of string theory are turned on, thus resolving the “problem of moduli”. We used Generalized geometry and G-structures to uncover certain general periodicities and features of FC backgrounds. These tools were also used to shed light on non-abelian T-duality, and in constructing consistent truncations admitting de Sitter solutions.

Little Strings & U-Duality*

Contact: S. HOHENEGGER

Little string theories are a class of interacting, non-local, ultraviolet complete quantum theories in six dimensions (or lower). A large class of such theories lack a Lagrangian description and are therefore notoriously difficult to describe with purely field theoretic methods alone. However, their connection to string theory provides us with many new approaches and tools which allow to analyze non-perturbative aspects of these theories. In a series of works, we have shown that various incarnations of string U-duality lead to remarkable dualities and symmetries among these gauge theories, which are intrinsically non-perturbative in nature. These symmetries allow us a better understanding of the gauge theories, as well as the construction of new theories. We will continue this approach, focusing in particular on non-perturbative dualities among theories with different matter and gauge content.

Monodromies in One-Loop String Amplitudes*

Contact: S. HOHENEGGER

N-point tree-level scattering amplitudes in open string theory are described as correlation functions on the world-sheet disk. Monodromy relations can be established which have been instrumental in the study (and solution) of tree level string scattering amplitudes. A generalization of these relations to 1-loop amplitudes has been performed, giving new relations among one-loop string scattering amplitudes.

Toroidally compactifying supergravity theories to lower dimensions reveals the presence of exceptional symmetries, which cannot be explained by Riemannian geometry of the internal manifold alone (or any other “conventional’’ symmetries within SUGRA itself). They are remnants of the U-duality of string (or M-) theory, hinting at more complex structures at higher energy scales. Since these exceptional symmetries are difficult to explain within the framework of standard SUGRA theories, it has been attempted to extend the higher dimensional versions of the latter in such a way as to make the appearance of the exceptional symmetries manifest upon compactification. The resulting theories are called exceptional field theories. The basic idea behind these constructions is an extended space-time, which allows for a geometric realization of the U-duality group. We are exploring various possibilities to formulate the (3,1) and (4,0) supergravity theories within the framework of exceptional field theories.

Field Theoretical Models in Ordinary & Non-Commutative Spaces*

Contacts: F. GIERES & S. HOHENEGGER

We gave an improvement procedure to construct a gauge-invariant, symmetric energy-momentum tensor. We generalized Wong’s equations to non-commutative space and determined the properties of the energy-momentum tensor of gauge fields coupled to matter. We studied field theoretical models on deformed spaces and obtained local conservation laws as well as balance equations for interacting fields on these spaces.

Non-Localizable Field Theories

Contact: F. NORTIER

Non-localizable field theories have enjoyed renewed activity in the last 15 years, notably to solve the UV-completion problem of gravity or the electroweak hierarchy problem. When non-locality is introduced via form factors in the classical Lagrangian, an infinite tower of Ostrogradsky ghosts usually appears when a symmetry is spontaneously broken. We have recently developed a new formalism where form factors are introduced via a covariant star product between the fields that avoids this pitfall. We are currently working on linking these theories to UV-completions by classicalization, exhibiting UV/IR mixing via the Vainshtein screening phenomenon.

N.B.: Page under construction.

Webpage Editors: M. BENDER & F. NORTIER

Nuclear & Hadronic Physics

Manager: Michael BENDER

Members

Scientific Staff

• Michael BENDER (DR)
• Karim BENNACEUR (MCF)
• Dany DAVESNE (PR)

Emeriti

• Jacques MEYER (PR)
• Jean-Marc RICHARD (PR)

Visitors

• Xavier ARTRU

Postdoctoral Fellows

PhD Students

• Clémentine AZAM (1/2)
• Damien BLONDEAU-PATISSIER (1/2)
• Valentin GUILLON

Research Activities

N.B.: To be updated.

Nuclear and hadronic physics is the study of the properties of the nuclei and their constituents, the quarks and the gluons. Some of the phenomena we address occur at low energies, while others arise at extreme conditions, e.g. in the interior of very hot and dense stars.

Nuclear EDF methods

The activities in nuclear structure physics address the description of low-energy phenomena with energy density functionals (EDFs). During the past few years, we focused on three aspects of these methods: the construction of generalized forms of the EDF and the set-up of advanced fit protocols for the adjustment of their parameters; the construction of numerical tools to describe ground- and low-lying states of complex nuclei, and to characterize the effective interaction; the application of the available parametrizations and codes to questions of experimental interest.

There are several motivations, both phenomenological and formal, to investigate more general forms of the EDF. Several directions are presently explored. In order to improve the performance of contact interactions of Skyrme type, their generalization including terms with four (N2LO) and six (N3LO) gradients is considered. To overcome certain formal problems, a new type of non-local EDF based on finite-range generators has been proposed. New formal and numerical developments and exploratory fits have been achieved.

A second major axis of this activity is the development of tools to study properties of complex finite nuclei. One of these is a new Cartesian 3D coordinate-space code for self-consistent mean-field calculations. The code supersedes codes we developed in the past, and offers several major improvements, including numerical accuracy, a major reduction of computational time, together with a decrease of the need for fine-tuning numerical parameters. The second tool that is also constantly maintained and improved is a code for generator-coordinate-method calculations based on angular-momentum and particle-number projected mean-field states.

Another activity in our group is related to the development of relativistic effective Lagrangians. The first finite temperature Relativistic Hartree-Fock-Bogoliubov calculation has been performed by our group and applied to understand pairing properties in finite nuclei, such as pairing persistence or pairing re-entrance, predicted in 48Ni and 48Si drip-line nuclei. The latter was also predicted to be a doubly closed-shell and doubly bubble nucleus.

Neutrino-nucleus interaction and hadronuclear physics

One recognized expertise of our group concerns the interface between the nuclear many-body problem and the physics of its constituents. Our nuclear model for the neutrino-nucleus interaction, incorporates the n particle-n hole interactions. This proposal is now recognized as a decisive breakthrough. We compared our results to those of the “Continuum Random Phase Approximation” (CRPA), and successfully tested our model on the MiniBooNE or T2K data.

We have solved another outstanding problem concerning the determination, in a given event, of the true neutrino energy from the information provided by the characteristics of the emitted lepton: its energy and its emission angle. We have introduced the distribution of the true energy around this reconstituted value and shown the existence of a low-energy shift induced by the multi-nucleon excitations.

Another subject concerns the coupling between the strong interaction many-body problem and the nucleon structure. In a chiral approach including the response of the nucleon to the nuclear vector and scalar fields, an EDF has been constructed, with parameters constrained by non-perturbative QCD and hadron phenomenology.

Hadronic matter and quark-gluon plasma

The study of the hot and dense phases of QCD and the search for a chiral critical point is one of the main goals of current research, together with the formal understanding of deconfinement. Our approach is based on effective quark models of QCD. We have developed statistical tools to examine the parameterization of effective models and their predictive power. We develop improved effective potentials for Polyakov loop effective models, and we quantitatively assess the predictive power of the models.

We are developing a diagrammatic approach facilitating the computation of correlation coefficients used in the analysis of elliptic flow, and we are contributing to the calculation of four-body combinatorial background. We also work on the parallelization of the GNU Scientific Library (GSL) quadrature routines.

Multiquarks

We analyzed the spectroscopy of string-inspired models, and studied new flavor configurations for tetraquarks, pentaquarks and di-baryons with heavy quarks. We are currently working on heavy quark correlations.

Few-body systems

We have shown that certain hyperon-nucleon and hyperon-hyperon interaction models allow for the existence of novel light hypernuclei with S=−2 strangeness. Our recent work includes the first study of a three-body exotic atom, and a review of Hall-Post inequalities with new developments and applications.

We performed the first hypernuclear charts in three-dimension (N,Z,S) based on a new density functional approach, and studied the strangeness composition of these hypernuclei.

Oscillations neutron-antineutron

The neutron-antineutron oscillations in 40Ar were revisited, in connection with members of the DUNE collaboration. The spatial distribution of the antineutron cloud around the 39Ar core and its subsequent annihilation was estimated, and used in Monte-Carlo simulations for the DUNE experiment.

Quark polarimetry and Electromagnetism

We are developing a recursive model for Monte Carlo simulation of the fragmentation of a polarized quark, reproducing the Collins effect. A simplified version, where only pseudoscalar mesons are emitted, has been implemented in a Monte Carlo program interfaced with PYTHIA. The simulations are in qualitative agreement with data from COMPASS and BELLE. In a stand-alone program, vector mesons have been included. We found an analogue of the Collins effect in atomic physics.

We studied the light created in an optical fiber when a charged particle passes through or near the fiber. We pointed out the common properties of synchrotron radiation and light leaking from a bent optical fiber. We participate in the research on positron sources assisted by channeling radiation.

On-going activities

The development, implementation, adjustment and validation of generalized nuclear energy density functionals for nuclear structure studies will be continued, with the long-term goal of widening their range of applicability at the mean-field (and possibly beyond mean-field) level and enhancing their predictive power. One particular focus will be the improvement of the description of properties of very heavy and super heavy nuclei, which most notably requires better control over the single-particle spectra in deformed nuclei. Calculations of charge radii, electromagnetic moments, characteristics of rotational bands, and other observables will be used in the evaluation of future experiments to be performed at ISOLDE/CERN, GANIL, and elsewhere.

Our group is investigating the links between bare nuclear interactions, such as the Bonn-type one-boson exchange potential, and relativistic effective Lagrangians developed for finite nuclei and uniform matter. Our project aims at improving the boson exchange potential and establishing a bridge from the bare nuclear potential to the effective approaches used in finite-nuclei. The ultimate goal of our project is to determine whether a novel meson exchange Lagrangian, adjusted on nucleon-nucleon scattering and complemented with off-shell interaction couplings, could bridge the gap between few-body and many-nucleon systems. Applications of this new model to the physics of the neutron star crust will also be considered. This approach can be extended to the strange sector including hyperon interactions.

We shall pursue and refine the construction of generalized Nambu-Jona-Lasinio models incorporating simultaneously chiral symmetry breaking and confinement, using either the Field Correlator Method or the Coulomb gauge in QCD. One aim is to improve the calculation of the condensates using an RPA-like method, but the main aim will be to derive an effective theory for nuclear physics or neutron star matter generating microscopically the nuclear vector and scalar fields, and the in-medium nucleon polarization, starting from pure QCD parameters (string tension and correlation length).

Other on-going activities include the work on light hypernuclei so as to include charmed baryons; the systematic study of the weak decays of stable tetraquarks, in order to predict their lifetime and provide hints for the discovery channels; simulation models of jets of polarized quarks and their polarimetry: the search of efficient estimators of quark polarization, and the simulation of “spin entanglement” of two jets in e+e- annihilation.

N.B.: Page under construction.

Webpage Editors: L. DARMÉ & F. NORTIER

Astro & Gravitational Waves

Manager: Hubert HANSEN

Members

Scientific Staff

• Alexandre ARBEY (MCF)
• Luc DARMÉ (MCF)
• Sacha DAVIDSON (DR)
• Hubert HANSEN (MCF)
• Jérôme MARGUERON (DR, on detachment at IRL NPA)

Emeriti

• Guy CHANFRAY (PR)
• Magda ERICSON (PR)

Visitors

• Samuel FRIOT (MCF, Paris-Saclay U. & IJCLab)

Postdoctoral Fellows

• Alexis BOUDON (1/2)
• Marco PALMIOTTO

PhD Students

Research Activities

N.B.: To be updated.

Astroparticles

Our activities focus on searches for new particles by direct or indirect detection, relic density of dark matter, and the links with collider physics. The code SuperIso Relic was developed in order to provide a calculational tool for different observables in connection with dark matter and particle physics. Until recently devoted to supersymmetry, the code is currently being developed to allow a flexible and generic implementation of all types of scenarios of BSM physics. Moreover, we have studied the links with primordial cosmology and shown that the discovery of new particles will allow to obtain information on the content of the universe before primordial nucleosynthesis, despite the fact that this era is currently unobservable.

Black holes, Big-Bang nucleosynthesis, gravitational waves

Our research includes the development of the public code AlterBBN, devoted to the study of alternative cosmological models. Our studies cover two directions: the consequences of the presence of cosmological scalars, and the existence of primordial black holes during primordial nucleosynthesis. The latter subject requires the study of Hawking radiation of Schwarzschild and Kerr black holes, and a calculational code of primary and secondary spectra has been developed, and will soon become public. It is a code with unique functionalities. Black holes are also studied in the context of gravitational waves and the possibility of particular gravitational signatures in certain exotic models (e.g. boson stars) or alternative gravity theories (LQG, tensor-scalar theories, etc).

Compact stars properties: equation of state, thermal emissivity, neutrino scattering

The inner core of neutron stars can reach high densities where a phase transition to deconfined quarks may occur. We have started an ambitious research program aiming at confronting observations to a large set of nuclear equations of state, setting-up a meta-modeling for nuclear matter inspired by the EDF approach.

Neutrino diffusion in neutron stars is crucially linked to the neutrino spectrum observed on Earth. We have analyzed the neutrino coherent scattering in non-uniform matter, in order to clarify if a coherent effect could enhance the scattering, thereby reducing the neutrino mean free path.

The detection of gravitational waves provided the first firm observational constraint on the radius of neutron stars, through the tidal deformability measured during the last orbits of the inspiral merger phase. We have found that modern nuclear-physics-based calculations of the equation of state of dense neutron-rich matter predict radii that are compatible but more restrictive than the one from GW170817. We have also determined how improved constraints from future observations can provide new insights into dense matter and possible phase transitions in the neutron-star core.

On-going activities

The links with astroparticle physics and cosmology are of great importance to understand the properties of physics beyond the SM, in particular through its relation with dark matter. A new extension of SuperIso Relic, which will allow for a flexible new physics implementation, is currently under development, and will provide an automatic calculation of dark matter observables in any new physics scenarios. In case of discovery of new physics at colliders or in astroparticle experiments, it will allow us to be at the forefront of characterization of new physics scenarios, and to derive constraints on the cosmological properties of the early Universe.

The BlackHawk code, which is the first program allowing an automatic calculation of the Hawking radiation of Schwarzschild and Kerr black holes, will be made public in the near future. It will allow us to pursue studies in the domain of cosmology, in particular for primordial black holes, and of astroparticle physics, with the design of new analysis to observe the Hawking radiation with astroparticle physics experiments. Combined with the AlterBBN code, it will also allow us to study the impact of primordial black holes or cosmological scalar fields on Big-Bang nucleosynthesis.

Our group is investigating the links between bare nuclear interactions, such as the Bonn-type one-boson exchange potential, and relativistic effective Lagrangians developed for finite nuclei and uniform matter. Our project aims at improving the boson exchange potential and establishing a bridge from the bare nuclear potential to the effective approaches used in finite-nuclei. The ultimate goal of our project is to determine whether a novel meson exchange Lagrangian, adjusted on nucleon-nucleon scattering and complemented with off-shell interaction couplings, could bridge the gap between few-body and many-nucleon systems. Applications of this new model to the physics of the neutron star crust will also be considered. This approach can be extended to the strange sector including hyperon interactions.

We shall pursue and refine the construction of generalized Nambu-Jona-Lasinio models incorporating simultaneously chiral symmetry breaking and confinement, using either the Field Correlator Method or the Coulomb gauge in QCD. One aim is to improve the calculation of the condensates using an RPA-like method, but the main aim will be to derive an effective theory for nuclear physics or neutron star matter generating microscopically the nuclear vector and scalar fields, and the in-medium nucleon polarization, starting from pure QCD parameters (string tension and correlation length).

A better characterization of the properties of the merging stars can be translated into an improved knowledge of the equation of state of dense matter, with potential hints concerning phase transitions, as well as for the conditions for heavy element nucleosynthesis. We plan to implement the state-of-the-art microphysics into a global simulation for neutron star mergers, initially provided by D. Radice.

Within the next five years we plan to produce kilonovae simulations with state-of-the-art nuclear input. This will allow us to investigate the multi-messenger signals emitted by kilonovae, such as GW. We will also have a new tool to investigate continuous GW emission from neutron stars. Such calculations provide a perfect framework for a close collaboration with the Virgo and observational cosmology groups at IP2I. The modeling of the r-process nucleosynthesis existing in the ejected matter offers a possibility to link with the expertise of the nuclear theoreticians and the nuclear experimentalists of IP2I. The questions related to dense matter also allow a cross-fertilization between nuclear and hadron physics. More globally, the modeling of kilonovae and, possibly in the future, of core-collapse supernovae, could animate an active research program in the laboratory, including also astro-particle physics and cosmology.

N.B.: Last modification on 2024-10-06.

Webpage Editor: F. NORTIER

Computer Tools

Contacts: Alexandre ARBEY & Farvah Nazila MAHMOUDI

Computer tools are nowadays essential to the community of physics of the 2 infinities. The theoretical physics teams at IP2I Lyon are particularly involved in the development of public codes for phenomenology, with international recognition in the field.

SuperIso (2007)

Link : http://superiso.in2p3.fr

Author: F.N. MAHMOUDI

Description: Public code intended for the computation of observables in flavor physics in the Standard Model and in new physics models.

SuperIso Relic (2009)

Link: http://superiso.in2p3.fr/relic

Authors: F.N. MAHMOUDI, A. ARBEY & G. ROBBINS

Description: SuperIso Relic is a SuperIso extension for the computation of dark matter relic density and observables in direct and indirect detection of dark matter. A particularity of SuperIso Relic is that, in addition to the Standard Model of cosmology, it allows the computation of the relic density in alternative cosmological scenarios, allowing the influence of cosmological hypotheses to be tested.

AlterBBN (2012)

Link: https://alterbbn.hepforge.org/

Authors: A. ARBEY, J. AUFFINGER, K. HICKERSON & E. JENSSEN

Description: AlterBBN is a C program which computes the abundances of the elements predicted by Big-Bang nucleosynthesis (BBN). Different cosmological scenarios are implemented in AlterBBN, which can alter the BBN predictions. Also, AlterBBN is included in the SuperIso Relic package so that the alternative models can be tested using BBN constraints.

GAMBIT (2017)

Link: https://gambitbsm.org/

Collaboration: The GAMBIT collaboration is made up of more than 70 international experts. F.N. MAHMOUDI is the coordinator of the part on flavor physics (FlavBit) and a member of the collaboration board.

Description: GAMBIT is a global fitting code for generic Beyond the Standard Model theories, designed to allow fast and easy definition of new models, observables, likelihoods, and scanners, and to easily backend new physics codes.

BlackHawk (2019)

Link: https://blackhawk.hepforge.org/

Authors: A. ARBEY & J. AUFFINGER

Description: BlackHawk is a public C program for calculating the Hawking evaporation spectra of any black hole distribution. This program enables the users to compute the primary and secondary spectra of stable or long-lived particles generated by Hawking radiation of the distribution of black holes, and to study their evolution in time.

MARTY (2020)

Link: https://marty.in2p3.fr

Authors: G. UHLRICH, F.N. MAHMOUDI & A. ARBEY

Description: The purpose of MARTY is to perform automatic computations of amplitudes, cross-sections and Wilson coefficients in any new physics model. Some of its advantages are that MARTY is written entirely in C++, does not rely on a private code such as Wolfram Mathematica, and contains its own symbolic calculus module (CSL), which can be used separately.

DarkPACK (2022)

Link: https://gitlab.in2p3.fr/darkpack/darkpack-public

Authors: M. PALMIOTTO, A. ARBEY & F.N. MAHMOUDI

Description: DarkPACK automatically generates a digital library of scattering amplitudes in a given model to compute dark matter observables, such as the relic density. DarkPACK is currently interfaced with MARTY and SuperIso Relic.

N.B.: Last modification on 2024-10-06.

Webpage Editor: F. NORTIER

ANR Fundings

RELANSE (2024)

Full Title: Relativistic Lagrangians for finite nuclei and dense matter

Coordinator: Jérôme MARGUERON

Duration: 48 months

Link: https://anr.fr/Project-ANR-23-CE31-0027

Description:

This ANR project RELANSE explores matter properties in a regime where the theory of the strong interaction, the quantum chromo-dynamics (QCD), could not be applied directly because of its non-perturbative nature at low-energy. This theory predicts however the onset of a chiral field emerging spontaneously at low-energy as well as the color confinement. These two properties imply that nucleons and mesons are the important degrees of freedom at low-energy. In this project, we develop an innovative, effective and relativistic approach describing chiral, nucleon and meson fields, and we contribute to consolidate the unified description of finite nuclei and neutron stars. The uniqueness of our project lies in the fact that we consistently analyze model predictions based on Hartree and Hartree-Fock approaches, which are adjusted to the same data. In particular, we address the question of the relativistic description of dense matter, where the sound speed, for instance, becomes comparable to the speed of light.

The originality of our project is to anchor the relativistic approaches employed in finite nuclei to the phenomenology of the quark substructure, e.g. results from Lattice QCD, the nucleon polarizability, VDM and quark model. In this way, the in-medium effects appear in our model in a very simple and traceable way compared to currently employed ones and our approach provides a robust guide to predict the properties of dense matter existing in neutron stars. We employ Bayesian statistics to compare the different scenarios to nuclear and astrophysical data, e.g., gravitational waves, x-ray emission from neutron stars. In this framework the theoretical, experimental and astrophysical uncertainties are employed in order to estimate the goodness of our new models.

For finite nuclei, we investigate the impact of the new models on ground state properties, e.g. energies, radii, neutron skin, as well as deformation, clustering, alpha decay and their experimental consequences. The novelty of our model is to possibly reduce the computing time of the present approaches, which employ density-dependent coupling constants. We estimate that our models can be as accurate as the present ones, and our project is instrumental to demonstrate it. We use all existing data to further constraint our models, we investigate the question of the understanding of the parity violating electron scattering puzzle from PREX and CREX experiments, and we address the description of exotic nuclei.

For neutron stars, we complement our relativistic models considering different scenarios for dense matter. Our methodology consists in exploring all various equations of state, which explore the current theoretical uncertainties in the existence of new phases of matter at high density, e.g. quark matter, hyperonic matter, quarkyonic matter. We then compare the predictions of these various scenarios to astrophysical data and we investigate to what extent these data indicate a preference for one of the scenarios describing the core of neutron stars.
The development of new effective Lagrangians helps us to address fundamental questions related to the strong force in dense matter and the Bayesian approach establishes the link between these fundamental properties and the existing data in finite nuclei and in neutron stars. We want to understand how the gaps between first principle, finite nuclei and neutron stars could be bridged and which effective properties of QCD are crucial in dense matter and low-energy. In addition, we will explore dense and finite temperature phases and produce new tables suitable for astrophysical simulations of core-collapse supenovae and kilonovae from neutron star mergers.

In addition, all data and codes from our project will be made publicly available (open-access) and a user-friendly interface in python will be provided to the community.

FlavBSM (2021)

Full Title: Flavoured path Beyond the Standard Model of Particle Physics

Coordinator: Farvah Nazila MAHMOUDI

Duration: 60 months

Link: https://anr.fr/Project-ANR-21-CE31-0002

Description:

Despite its tremendous success, the shortcomings of the Standard Model (SM) of particle physics are well-known, and it is now commonly accepted in the particle physics community that going beyond the SM is a necessity. Search for physics beyond the SM started in the 1970’s, and no new physics signal has been discovered so far.

Recently, experimental results in flavour physics have exhibited a series of deviations from the SM predictions. These deviations in B meson decays, referred to as “flavour anomalies”, have been growing with time both in terms of statistical significance and in terms of internal consistency. We may therefore be on the verge of the discovery of New Physics (NP).

The FlavBSM proposal aims at understanding the origin of the discrepancies, and determining the underlying new physics model. This objective can be achieved by following three complementary research axes.

The first axis concerns precise calculations of the exclusive semileptonic B decays, and more specifically the calculation of the nonlocal hadronic effects. This constitutes an important challenge in the field, and a necessary step in order to unambiguously distinguish between SM hadronic effects and NP phenomena.
The second axis concerns the design and study of NP models. For this, we will consider not only effective field theory approaches, but also simplified models, based on which we will finally design and study well-motivated “complete” NP models, extending the validity range of the models far beyond the previous effective descriptions.

The third axis consists in software development to study the phenomenological implications of the flavour data. We aim in particular at an automatic calculation of the flavour observables in any NP model, and we will create new tools and techniques to perform statistical analyses and exploration of the parameter spaces of NP models, using simultaneously the constraints from the different sectors of particle physics. The first steps in this direction have already been successfully taken by the coordinator.

This project proposes therefore a full program to address the question of flavour anomalies in its generality. Understanding the origin of flavour anomalies is extremely important for a deeper understanding of fundamental interactions. The determination of the underlying new physics theory will constitute a major step in particle physics, providing directions towards the discovery of new particles. In addition, the project will provide new techniques, calculations and public computing tools to the community which will remain useful independently of the flavour anomalies.

NEWFUN (2019)

Full Title: New energy functional for heavy nuclei

Coordinator: Michael BENDER

Duration: 36 months

Link: https://anr.fr/Project-ANR-19-CE31-0015

Description:

The project aims at the improved theoretical modelling and consistent interpretation of experimental data on very heavy and superheavy atomic nuclei with charge numbers Z greater than 82 and neutron numbers N beyond 126. These finite self-bound systems, many of which owe their very existence to quantal shell effects, exhibit a rich phenomenology of excitation and decay modes that are governed by the competition between the strong nuclear interaction, Coulomb repulsion, surface effects, and quantal shell structure of single-particle states. The available experimental data begin to reveal a consistent picture of their structure in terms of deformed shapes and shells, which at present, however, is not yet satisfactorily described by purely microscopic models. The main deficiency that has been clearly identified, and which is common to all presently available types of effective interactions, concerns the distance between single-particle levels near the Fermi energy. While global trends of observables are unaffected, the description of individual features of specific nuclei is in many cases lacking.

The goal of our project is to arrive at an unprecedented level of accuracy for the theoretical description of very heavy and superheavy nuclei through the adjustment of an effective interaction containing qualitatively new and hitherto unused higher-order terms. The fit of its parameters will take into account information about relevant properties of states of heavy nuclei and be accompanied by an analysis of statistical errors. The resulting interactions will subsequently be employed in systematic symmetry-unrestricted self-consistent mean-field calculations of a wide spectrum of observables of interest addressed in in-beam gamma-ray and conversion-electron spectroscopy, implanted-ion decay spectroscopy, and laser spectroscopy. The results then can be used for the planning and evaluation of experiments at existing and future heavy-ion-beam facilities.

We expect this project to make a decisive contribution to the progress in the theoretical description of the heaviest elements that will expand our understanding of these systems.

N.B.: Last modification on 2024-10-06.

Webpage Editor: F. NORTIER

Prizes & Honours

CNRS Medals

Silver

2021: Michael BENDER

Institut Universitaire de France (IUF)

Senior Members

2023: Farvah Nazila MAHMOUDI

2013: Aldo DEANDREA

Junior Members

2016: Alexandre ARBEY

2014: Farvah Nazila MAHMOUDI

Other Prizes & Honours

Prix Joliot Curie (Société Française de Physique, 2022): Jérôme MARGUERON

Chevalière de la Légion d’honneur (2015): Magda ERICSON

Prix Thibaud (Académie des sciences, belles lettres et arts de Lyon, 1993): Guy CHANFRAY

Prix Gay-Lussac Humboldt (1992): Magda ERICSON

Prix Paul Marguerite de la Charlonie (Académie des sciences française, 1987): Magda ERICSON

Chevalière de l’ordre des Palmes académiques (1978): Magda ERICSON

N.B.: See the tabs of each group for a distribution of the members into groups.