Open Access
Multijet event shape variables for Mueller-Navelet jet topologies
(American Physical Society, 2024-12-18) Baldenegro, Cristian ; Chachamis, Grigorios; Kampshoff, Mats ; Klasen, Michael; Milhano, José Guilherme; Royon, Christophe; Sabio Vera, Agustín; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
This paper presents a new set of multijet event shape variables introduced to further understand the Mueller-Navelet jet topology. This topology consists of having at least one pair of jets with a very large rapidity separation between them, treating additional jet activity inclusively. This multijet topology is expected to shed light on the radiation pattern that is expected in the high-energy limit of the strong interaction. The paper relies on a Monte Carlo event generator analysis. One set of predictions uses the bfklex event generator, which is based on Balitsky-Fadin-Kuraev-Lipatov (BFKL) perturbative quantum chromodynamics (pQCD) evolution with a resummation of large logarithms of energy at leading-logarithmic accuracy. The bfklex predictions are compared with a fixed-order next-to-leading order pQCD calculation using powheg matched to the parton shower of pythia8 (NLO+PS), which is the standard for NLO generator predictions at the LHC. We find that both approaches lead to compatible results at current LHC energies, assuming the current experimental constraints for the reconstruction of low transverse momentum jets in ATLAS and CMS. This shows the reliability of the BFKL approach at describing the behavior of the strong interaction in the preasymptotic limit of high center-of-mass energies. Differences between the NLO+PS and the BFKL-based approaches are found when the jet multiplicity is increased or when the minimum transverse momentum of the jets is decreased.
Open Access
Von Neumann entropy and Lindblad decoherence in the high-energy limit of strong interactions
(American Physical Society, 2024) Chachamis, Grigorios; Hentschinski, Martin; Sabio Vera, Agustín; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Quantum properties of the state associated to the gluon Green's function in the Balitsky-Fadin-Kuraev-Lipatov approach are studied using a discretization in virtuality space. Considering the coupling constant as imaginary, its density matrix corresponds to a pure state for any energy. Nonlinear corrections due to high gluon densities are modeled through a suppression of infrared modes in the Hamiltonian making it no longer Hermitian. This introduces quantum decoherence into the evolution equation. When the coupling is real this leads to unbounded normalization of states which becomes bounded for sufficient saturation of infrared modes. Physical quantum properties, such as a purity smaller than one or a positive von Neumann entropy, hence are recovered when the infrared/ultraviolet original symmetry of the formalism is broken. Similarly to the work of Armesto, Domínguez, Kovner, Lublinsky and Skokov in [J. High Energy Phys. 05 (2019) 025JHEPFG1029-847910.1007/JHEP05(2019)025], an evolution equation of Lindblad type for the normalized density matrix describing the open system is obtained.
Open Access
Dynamics of particle-particle correlations and the ridge effect in proton-proton collisions
(American Physical Society, 2024-10-08) Calé, G.; Chachamis, Grigorios; Sabio Vera, Agustín; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
In high-energy particle physics, the study of particle-particle correlations in proton-proton and heavy-ion collisions constitutes a pivotal frontier in the effort to understand the fundamental dynamics of the strong force. To the best of our knowledge, we employ for the first time the Balitsky-Fadin-Kuraev-Lipatov dynamics implemented in a Monte Carlo code in momentum space to compute final-state correlations in proton-proton collisions. Our present work aims to investigate whether the particular dynamics of the high-energy limit of QCD can contribute to the long-range rapidity correlations and the enigmatic ridge effect in proton-proton collisions.

Chachamis, Grigorios

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