Transverse Energy Measurement and Fluctuation Studies in Ultra-Relativistic Heavy Ion Collisions

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Transverse energy (Eₜ) has been measured with both of it's components, namely hadronic (Eₜhad) and electromagnetic (Eₜem) at mid-rapidity, for 62.4 GeV Au+Au collisions by the STAR experiment. In the common phase space of TPC and BEMC (0 < η< 1 and full ϕ), we have obtained Eₜhad from the TPC reconstructed tracks and Eₜem from the BEMC tower hits after correcting for the hadronic contaminations in the calorimeter. The centrality behavior of <dEₜ/dη>/(0.5 Npart) and the excitation function of <dEₜ/dy>/(0.5 Npart) has been compared with the final state gluon saturation model (EKRT) along with similar measurements from SPS to RHIC. The most striking feature is the observation of a nearly constant value of Eₜ/Nch 0.8 GeV from AGS, SPS to RHIC. The Eₜ and Nch production has been observed to follow a logarithmic behavior. The initial energy density estimated by the boost-invariant Bjorken hydrodynamic model, is well above the lattice QCD value for a deconfined matter of Quarks and Gluons. Taking similar colliding species i.e. Au+Au, the εBj.τ has been predicted for LHC, based on the measurements at RHIC. We have also made predictions for (dEₜ/dη)/(0.5 Npart) and (dNch/dη)/(0.5 Npart) for the LHC energy. Furthermore, we have studied the event-by event fluctuations in Eₜ and in the ratio of it's components using σ/μ as the fluctuation observable.