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Question de forme : observer la déformation des noyaux atomiques aux collisionneurs des hautes énergies

Abstract : Collider experiments conducted atthe BNL RHIC and at the CERN LHC show thatthe the emission of particles following the interactionof two nuclei at relativistic energy is highlyanisotropic in azimuthal angle. This observationis compatible with a hydrodynamic paradigm, accordingto which the final-state hadrons are emittedfollowing the expansion of a fluidlike systemcreated in the interaction region. Withinthis paradigm, anisotropy in the emission of particlesis enhanced whenever the colliding nucleihave deformed ground states. By meansof high-quality comparisons between the predictionsof hydrodynamic models and particle colliderdata, I study the phenomenological manifestationsof the quadrupole deformation of atomicnuclei in relativistic ¹⁹⁷Au+¹⁹⁷Au, ²³⁸U+²³⁸U,and ¹²⁹Xe+¹²⁹Xe collisions. This analysis demonstratesthat a deep understanding of the structureof the colliding ions is required for the interpretationof data in high-energy experiments. RHICdata confirms in particular the well-known factthat the geometry of ²³⁸U nuclei is that of a welldeformedellipsoid, while indicating that ¹⁹⁷Au nuclei are nearly spherical, a result which is atodds with the estimates of mean-field and empiricalnuclear models. LHC data brings instead evidenceof quadrupole deformation in the groundstate of ¹²⁹Xe nuclei, ascribable to the first visiblemanifestation of shape coexistence phenomena inhigh-energy nuclear experiments. I introduce asimple method to isolate collision configurationsthat maximally break azimuthal symmetry dueto the orientation of the deformed nuclei. Thisallows me to define observables with an unprecedentedsensitivity to the deformation of the collidingspecies, thus paving the way for quantitativestudies of nuclear structure at high energy.
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Submitted on : Tuesday, March 30, 2021 - 10:20:09 AM
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Giuliano Giacalone. Question de forme : observer la déformation des noyaux atomiques aux collisionneurs des hautes énergies. High Energy Physics - Phenomenology [hep-ph]. Université Paris-Saclay, 2020. English. ⟨NNT : 2020UPASP072⟩. ⟨tel-03185076⟩

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