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Accessing Generalized Parton Distributions through 2 to 3 exclusive processes
No full text7 pages, 1 figure, Presented by S. Wallon at the 31st International Workshop on Deep Inelastic Scattering (DIS2024).International audienceWe review our results on a new class of 2 to 3 exclusive processes, as a probe of both chiral-even and chiral-odd quark GPDs. We consider the exclusive photoproduction of a photon-meson pair, in the kinematics where the pair has a large invariant mass, described in the collinear factorization framework. We cover the whole kinematical range from medium energies in fixed target experiments to very large energies of colliders, by considering the experimental conditions of JLab 12-GeV, COMPASS, future EIC and LHC (in ultra-peripheral collisions) cases. Our analysis covers neutral and charged rho-mesons, as well as charged pions. The case of the rho-meson, depending on its polarization, provides access to either chiral-even or chiral-odd GPDs, at leading twist. We find that the order of magnitude of the obtained cross sections are sufficiently large for a dedicated experimental analysis to be performed, especially at JLab. Furthermore, we compute the linear photon beam polarization asymmetry, which we find to be sizeable, in the case of a longitudinally polarized -meson or of a charged pion. These predictions are obtained for both asymptotic distribution amplitude (DA) and holographic DA
PSWF-Radon approach to reconstruction from band-limited Hankel transform
No full textInternational audienceWe give new formulas for reconstructions from band-limited Hankel transform of integer or half-integer order. Our formulas rely on the PSWF-Radon approach to super-resolution in multidimensional Fourier analysis. This approach consists of combining the theory of classical one-dimensional prolate spheroidal wave functions with the Radon transform theory. We also use the relation between Fourier and Hankel transforms and Cormack-type inversion of the Radon transform. Finally, we investigate numerically the capabilities of our approach to super-resolution for band-limited Hankel inversion in relation to varying levels of noise
A note on non-Lorentzian duality symmetries
No full textInternational audienceWe work out non-Lorentzian dual actions for electromagnetism and linearised gravity, both in the Carrollian and Galilean cases. This is done in the same way as for Lorentzian theories, by first constructing a parent action that reduces to a pair of dual actions. In the case of Maxwell theory, each pair of dual actions consists of the known `electric' and `magnetic' limits of the original theories, showing that these limits are related by an off-shell electromagnetic duality. We have obtained dualities between on one hand the non-Lorentzian contractions of linearised gravity in second-order form, and on the other hand the theories one obtains by gauging the corresponding kinematic algebras. In the Carrollian contraction, these dual actions reproduce the known `electric' and `magnetic' Carrollian theories of gravity, and we find a similar result in the Galilean case
Measurement of multidifferential cross sections for dijet production in proton-proton collisions at = 13 TeV
No full textInternational audienceA measurement of the dijet production cross section is reported based on proton-proton collision data collected in 2016 at = 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3 fb. Jets are reconstructed with the anti- algorithm for distance parameters of = 0.4 and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity of the two jets with the highest transverse momenta and their invariant mass , and triple-differentially (3D) as a function of the rapidity separation , the total boost , and either or the average of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the Z boson is investigated, yielding a value of = 0.1179 0.0019
Crediting football players for creating dangerous actions in an unbiased way: the generation of threat (GoT) indices
No full textInternational audienceWe introduce an innovative methodology to identify football players at the origin of threatening actions in a team. In our framework, a threat is defined as entering the opposing team's danger area. We investigate the timing of threat events and ball touches of players, and capture their correlation using Hawkes processes. Our model-based approach allows us to evaluate a player's ability to create danger both directly and through interactions with teammates. We define a new index, called Generation of Threat (GoT), that measures in an unbiased way the contribution of a player to threat generation. For illustration, we present a detailed analysis of Chelsea's 2016-2017 season, with a standout performance from Eden Hazard. We are able to credit each player for his involvement in danger creation and determine the main circuits leading to threat. In the same spirit, we investigate the danger generation process of Stade Rennais in the 2021-2022 season. Furthermore, we establish a comprehensive ranking of Ligue 1 players based on their generated threat in the 2021-2022 season. Our analysis reveals surprising results, with players such as Jason Berthomier, Moses Simon and Frederic Guilbert among the top performers in the GoT rankings. We also present a ranking of Ligue 1 central defenders in terms of generation of threat and confirm the great performance of some center-back pairs, such as Nayef Aguerd and Warmed Omari
Mott Transition and Volume Law Entanglement with Neural Quantum States
No full textInternational audienceThe interplay between delocalisation and repulsive interactions can cause electronic systems to undergo a Mott transition between a metal and an insulator. Here we use neural network hidden fermion determinantal states (HFDS) to uncover this transition in the disordered, fully-connected Hubbard model. Whilst dynamical mean-field theory (DMFT) provides exact solutions to physical observables of the model in the thermodynamic limit, our method allows us to directly access the wavefunction for finite system sizes well beyond the reach of exact diagonalisation. We directly benchmark our results against state-of-the-art calculations obtained using a Matrix Product State (MPS) ansatz. We demonstrate how HFDS is able to obtain more accurate results in the metallic regime and in the vicinity of the transition, with the volume law of entanglement exhibited by the system being prohibitive to the MPS ansatz. We use the HFDS method to calculate the amplitudes of the wavefunction, the energy and double occupancy, the quasi-particle weight and the energy gap, hence providing novel insights into this model and the nature of the transition. Our work paves the way for the study of strongly correlated electron systems with neural quantum states
Ergodic control of a heterogeneous population and application to electricity pricing
No full textThe present version (v3) is an extended version of an article originally published in the Proceedings of CDC 2022International audienceWe consider a control problem for a heterogeneous population composed of agents able to switch at any time between different options. The controller aims to maximize an average gain per time unit, supposing that the population is of infinite size. This leads to an ergodic control problem for a “mean-field” Markov Decision Process in which the state space is a product of simplices, and the population evolves according to controlled linear dynamics. By exploiting contraction properties of the dynamics in Hilbert’s projective metric, we prove that the infinite-dimensional ergodic eigenproblem admits a solution and show that the latter is in general non unique.This allows us to obtain optimal strategies, and to quantify the gap between steady-state strategies and optimal ones. In particular, we prove in the one-dimensional case that there exist cyclic policies – alternating between discount and profit taking stages – which secure a greater gain than constant-price policies. On numerical aspects, we develop a policy iteration algorithm with “on-the-fly” generated transitions, specifically adapted to decomposable models, leading to substantial memory savings.We finally apply our results on realistic instances coming from an electricity pricing problem encountered in the retail markets, and numerically observe the emergence of cyclic promotions for sufficient inertia in the customer behavior
Fractons on curved spacetime in dimensions
No full textInternational audienceWe study dipole Chern-Simons theory with and without a cosmological constant in dimensions. We write the theory in a second order formulation and show that this leads to a fracton gauge theory coupled to Aristotelian geometry which can also be coupled to matter. This coupling exhibits the remarkable property of generalizing dipole gauge invariance to curved spacetimes, without placing any limitations on the possible geometries. We also use the second order formulation to construct a higher dimensional generalization of the action. Finally, for the -dimensional Chern-Simons theory we find solutions and interpret these as electric monopoles, analyze their charges and argue that the asymptotic symmetries are infinite-dimensional
Numerical study of Darcy's law of yield stress fluids on a deep tree-like network
No full textInternational audienceUnderstanding the flow dynamics of yield stress fluids in porous media presents a substantial challenge. Both experiments and extensive numerical simulations frequently show a non-linear relationship between the flow rate and the pressure gradient, deviating from the traditional Darcy law. In this article, we consider a tree-like porous structure and utilize an exact mapping with the directed polymer (DP) with disordered bond energies on the Cayley tree. Specifically, we adapt an algorithm recently introduced by Brunet et al. [Europhys. Lett. 131, 40002 (2020)] to simulate exactly the tip region of branching random walks with the help of a spinal decomposition, to accurately compute the flow on extensive trees with several thousand generations. Our results confirm the asymptotic predictions proposed by Schimmenti et al. [Phys. Rev. E 108, L023102 (2023)], tested therein only for moderate trees of about 20 generations
Long-lived particle reconstruction downstream of the LHCb magnet
No full textInternational audienceCharged-particle trajectories are usually reconstructed with the LHCb detector using combined information from the tracking devices placed upstream and downstream of the 4 T m dipole magnet. Trajectories reconstructed using only information from the tracker downstream of the dipole magnet, which are referred to as T tracks, have not been used for physics analysis to date due to their limited momentum resolution. The challenges of the reconstruction of long-lived particles using T tracks for use in physics analyses are discussed and solutions are proposed. The feasibility and the tracking performance are studied using samples of long-lived and hadrons decaying between 6.0 and 7.6 metres downstream of the proton-proton collision point, thereby traversing most of the magnetic field region and providing maximal sensitivity to magnetic and electric dipole moments. The reconstruction can be expanded below this range for use in direct searches of exotic long-lived particles. The data used in this analysis have been recorded between 2015 and 2018 and correspond to an integrated luminosity of 6 fb. The results obtained demonstrate the possibility to further extend the fiducial volume and the physics reach of the LHCb experiment