Intrinsic coupling between transverse spherocity and elliptic flow in heavy-ion collisions

Abstract

Transverse spherocity ($S_0$) is an event-shape observable widely used to classify collision events according to their topology, particularly to distinguish jet-like from isotropic events. Low-spherocity events are generally interpreted as being associated with enhanced jet activity. This event classification has also been applied to heavy-ion collisions to investigate the influence of event topology on several observables, including elliptic flow and constituent-quark-number scaling. In this work, we demonstrate that such an interpretation requires careful reconsideration. Using toy Monte Carlo simulations, A Multiphase Transport (AMPT) model calculations, and an analytical formulation of the spherocity observable, we show that transverse spherocity is intrinsically related to the elliptic flow coefficient, $v_2$. This connection arises because the axis that minimizes the spherocity aligns with the event symmetry plane, causing events with larger elliptic anisotropy to naturally exhibit smaller spherocity values even in the absence of genuine jet-like topologies. We further show that this intrinsic relation gives rise to an inherent anti-correlation between transverse spherocity and $v_2$, implying that several characteristics previously attributed to the enhanced jet-like nature of low-spherocity events in heavy-ion collisions can instead be understood as consequences of collective anisotropic flow. Our results indicate that, in heavy-ion collisions, transverse spherocity should be interpreted primarily as a probe of the collective momentum-space anisotropy rather than as a direct measure of jetty event topology. Consequently, physics conclusions drawn from spherocity-selected events should explicitly account for its intrinsic correlation with elliptic flow.

References in corpus (24)

• A Multi-Phase Transport Model for Relativistic Heavy Ion Collisions
• Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV
• Measurement of the azimuthal anisotropy for charged particle production in sqrt(s_NN) = 2.76 TeV lead-lead collisions with the ATLAS detector
• Measurements of Higher-Order Flow Harmonics in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• Topology studies of hydrodynamics using two particle correlation analysis
• Phenomenology of event shapes at hadron colliders
• Event shapes in e+e- annihilation and deep inelastic scattering
• Ultra-relativistic nuclear collisions: event shape engineering
• Measurement of the correlation between flow harmonics of different order in lead-lead collisions at $\sqrt{s_{NN}}$=2.76 TeV with the ATLAS detector
• Evidence of sub-nucleonic degrees of freedom in J/$\psi$ photoproduction in ultraperipheral collisions at the CERN Large Hadron Collider
• Measurement of event shape distributions and moments in e+e- -> hadrons at 91-209 GeV and a determination of alpha_s
• Charged-particle production as a function of multiplicity and transverse spherocity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV
• Measurement of longitudinal flow de-correlations in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ and 5.02 TeV with the ATLAS detector
• Determination of the Strong Coupling \boldmath{\as} from hadronic Event Shapes and NNLO QCD predictions using JADE Data
• A Study of Event Shapes and Determinations of alpha_s using data of e^+e^- Annihilations at sqrt{s} = 22 to 44 GeV
• Longitudinal Decorrelation of Anisotropic Flows in Heavy-ion Collisions at the CERN Large Hadron Collider
• Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at $\sqrt{s}=0.9$, 2.76 and 7 TeV
• Mid-rapidity charged hadron transverse spherocity in pp collisions simulated with Pythia
• Determination of αS using OPAL hadronic event shapes at sqrt(s) = 91 - 209 GeV and resummed NNLO calculations
• Event shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at $\sqrt{s_\rm{NN}}=2.76$ TeV
• Study of Transverse Spherocity and Azimuthal Anisotropy in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV using A Multi-Phase Transport Model
• Event topology and global observables in heavy-ion collisions at the Large Hadron Collider
• Probing initial geometrical anisotropy and final azimuthal anisotropy in heavy-ion collisions at Large Hadron Collider energies through event-shape engineering
• Event topology and constituent-quark scaling of elliptic flow in heavy-ion collisions at the Large Hadron Collider using a multiphase transport model