Speaker
Description
It is widely known that the quark-gluon plasma (QGP), a state of deconfined quarks and gluons under equilibrium, is generated in relativistic heavy-ion collisions. Compared to the heavy-ion, small colliding systems such as nucleon-induced collisions were regarded as a reference for the heavy-ion collisions. Since around 2010, however, it has been reported that the QGP might be formed even in the small colliding systems according to various experimental data. It is still being discussed whether the signals truly are consequences of the QGP formation. We approach this problem by building a dynamical model which is capable of performing p–p to A–A collisions within a unified manner to acquire comprehensive understandings of the observed data. Motivated by one of the important experimental results, strangeness enhancement reported by the ALICE Collaboration [1], we apply the core–corona picture to a dynamical initialization of hydrodynamic simulations of the QGP. The core–corona is a two-component picture of the thermalized and non-thermalized matter. Under the conventional core–corona picture, high-density regions in which matter reaches thermal equilibrium are referred to as core while low-density regions in which thermalization is not achieved are referred to as corona. In our framework, initially produced partons dynamically generate QGP fluids as they traverse vacuum/medium. Generated fluids are regarded as an initial state of hydrodynamics while surviving partons go through string fragmentation. Due to the dynamical separation of core and corona, our model, the dynamical core-corona initialization (DCCI) [2, 3] is applicable for the entire multiplicity regime from small to large colliding systems. In this talk, I highlight some recent results in proton-proton (pp) and lead-lead (PbPb) collisions from an updated version of our model (DCCI2). I mainly discuss how each contribution from core and corona affects multiplicity-dependent bulk observable in small systems. Also, I discuss the existence of corona possibly affect transverse momentum distribution and anisotropy even in PbPb collisions.
[1] J. Adam et al., Nature Phys., 13:535{539, 2017.
[2] Y. Kanakubo et al., PTEP, 2018(12):121D01, 2018.
[3] Y. Kanakubo et al., Phys. Rev. C, 101(2):024912, 2020.
