Longitudinal Fluctuations in Ultra-Relativistic Heavy-Ion Collisions

Abstract

In this thesis we focus on understanding the longitudinal fluctuations in the initial state of relativistic nuclear collisions when Quark-Gluon Plasma is formed. Hydrodynamic evolution of the QGP state is performed using the three-dimensional viscous hydrodynamic code MUSIC with fluctuating initial density profiles generated using TRENT o 3D of Pb+Pb collisions at √sNN = 5.02 TeV in the centrality range 0 to 1%. The initial state fluctuations leave their signature on the emitted particles as flow coefficients. Anisotropic flows of the emitted particles are analyzed in order to study the fluctuations in the system. Two-particle correlation matrices corresponding to the multiplicity fluctuation, elliptic and triangular flow are constructed and analyzed through the statistical technique called principal component analysis. This method reveals the leading and the sub-leading modes of the fluctuations in the longitudinal direction. The non-flow effects in the flow coefficients are reduced by introducing gaps in the pseudorapidity bins while constructing the two-particle correlation matrix. Longitudinal decorrelations in terms of flow vector, flow magnitude and flow orientation are also explored. Sub-leading modes in pseudorapidity are clearly visible and measurable even after imposing a sizable gap.