Symmetric cumulants and event-plane correlations in Pb+Pb collisions

The ALICE Collaboration has recently measured the correlations between amplitudes of anisotropic flow in different Fourier harmonics, referred to as symmetric cumulants. We derive approximate relations between symmetric cumulants involving $v_4$ and $v_5$ and the event-plane correlations measured by ATLAS. The validity of these relations is tested using event-by-event hydrodynamic calculations. The corresponding results are in better agreement with ALICE data than existing hydrodynamic predictions. We make quantitative predictions for three symmetric cumulants which are not yet measured.Comment: 6 pages. Minor revision: error bars in Fig.2 have been correcte

Separating the impact of nuclear skin and nuclear deformation in high-energy isobar collisions

Bulk nuclear structure properties, such as radii and deformations, leave distinct signatures in the final state of relativistic heavy-ion collisions. Isobaric collisions offer an easy route to establish explicit connections between the colliding nuclei's structure and the observable outcomes. Here, we investigate the effects of nuclear skin thickness and nuclear deformations on the elliptic flow ($v_2$) and its fluctuations in high-energy $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions. Our findings reveal that the difference in skin thickness between these isobars only influences the inherent ellipticity of the collision systems, $v_2^{\mathrm{rp}}$. In contrast, differences in nuclear deformations solely impact the fluctuations of $v_2$ around $v_2^{\mathrm{rp}}$. Hence, we have identified a data-driven method to disentangle the effects of nuclear skin and nuclear deformations, marking a significant step toward assessing the consistency of nuclear phenomena across energy scales.Comment: 7 pages, 3 figures plus an appendi

The shape of gold

Having a detailed theoretical knowledge of the low-energy structure of the heavy odd-mass nucleus $^{197}$Au is of prime interest as the structure of this isotope represents an important input to theoretical simulations of collider experiments involving gold ions performed worldwide at relativistic energies. In the present article, therefore, we report on new results on the structure of $^{197}$Au obtained from state-of-the-art multi-reference energy density functional (MR-EDF) calculations. Our MR-EDF calculations were realized using the Skyrme-type pseudo-potential SLyMR1, and include beyond mean-field correlations through the mixing, in the spirit of the Generator Coordinate Method (GCM), of particle-number and angular-momentum projected triaxially deformed Bogoliubov quasi-particle states. Comparison with experimental data shows that the model gives a reasonable description of $^{197}$Au with in particular a good agreement for most of the spectroscopic properties of the $3/2_1^+$ ground state. From the collective wave function of the correlated state, we compute an average deformation $\bar{\beta}(3/2_1^+)=0.13$ and $\bar{\gamma}(3/2_1^+)=40^\circ$ for the ground state. We use this result to construct an intrinsic shape of $^{197}$Au representing a microscopically-motivated input for precision simulations of the associated collider processes. We discuss, in particular, how the triaxiality of this nucleus is expected to impact $^{197}$Au+$^{197}$Au collision experiments at ultrarelativistic energy.Comment: 16 pages, 6 figure

Structure of 128,129,130^{128,129,130}Xe through multi-reference energy density functional calculations

Recently, values for the Kumar quadrupole deformation parameters of the nucleus $^{130}$Xe have been computed from the results of a Coulomb excitation experiment, indicating that this xenon isotope has a prominent triaxial ground state. Within a different context, it was recently argued that the analysis of particle correlations in the final states of ultra-relativistic heavy-ion collisions performed at the Large Hadron Collider (LHC) points to a similar structure for the adjacent isotope, $^{129}$Xe. In the present work, we report on state-of-the-art multi-reference energy density functional calculations that combine projection on proton and neutron number as well as angular momentum with shape mixing for the three isotopes $^{128,129,130}$Xe using the Skyrme-type pseudo-potential SLyMR1. Exploring the triaxial degree of freedom, we demonstrate that the ground states of all three isotopes display a very pronounced triaxial structure. Moreover, comparison with experimental results shows that the calculations reproduce fairly well the low-energy excitation spectrum of the two even-mass isotopes. By contrast, the calculation of $^{129}$Xe reveals some deficiencies of the effective interaction.Comment: 26 pages, 17 figure

Imaging the initial condition of heavy-ion collisions and nuclear structure across the nuclide chart

A major goal of the hot QCD program, the extraction of the properties of the quark gluon plasma (QGP), is currently limited by our poor knowledge of the initial condition of the QGP, in particular how it is shaped from the colliding nuclei. To attack this limitation, we propose to exploit collisions of selected species to precisely assess how the initial condition changes under variations of the structure of the colliding ions. This knowledge, combined with event-by-event measures of particle correlations in the final state of heavy-ion collisions, will provide in turn a new way to probe the collective structure of nuclei, and to confront and exploit the predictions of state-of-the-art ab initio nuclear structure theories. The US nuclear community should capitalize on this interdisciplinary connection by pursuing collisions of well-motivated species at high-energy colliders.Comment: 23 pages, 6 figure

Observing the deformation of nuclei with relativistic nuclear collisions

International audienceI show that particle collider experiments on relativistic nuclear collisions can serve as direct probes of the deformation of the colliding nuclear species. I argue that collision events presenting very large multiplicities of particles and very small values of the average transverse momentum of the emitted hadrons probe collision geometries in which the nuclear ellipsoids fully overlap along their longer side. By looking at these events one selects interaction regions whose elliptic anisotropy is determined by the deformed nuclear shape, which becomes accessible experimentally through the measurement of the elliptic flow of outgoing hadrons

Constraining the quadrupole deformation of atomic nuclei with relativistic nuclear collisions

International audiencePreliminary data by the STAR collaboration at the BNL Relativistic Heavy Ion Collider shows that the elliptic flow, v2, and the average transverse momentum, 〈pt〉, of final-state hadrons produced in high-multiplicity U238+U238 collisions are negatively correlated. This observation brings experimental evidence of a significant prolate deformation, β≈0.3, in the colliding U238 nuclei. I show that a quantitative description of this new phenomenon can be achieved within the hydrodynamic framework of heavy-ion collisions, and that thus such kind of data in the context of high-energy nuclear experiments can help constrain the quadrupole deformation of the colliding species