Download or read book Correlations Relative to the Reaction Plane at the Relativistic Heavy Ion Collider Based on Transverse Deflection of Spectator Neutrons written by Gang Wang and published by . This book was released on 2006 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern physics is challenged by the puzzle of quark confinement in a strongly interacting system. High-energy heavy-ion collisions can experimentally provide the high energy density required to generate Quark-Gluon Plasma (QGP), a deconfined state of quark matter. For this purpose, the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has been constructed and is currently taking data. Anisotropic flow, an anisotropy of the azimuthal distribution of particles with respect to the reaction plane, sheds light on the early partonic system and is not distorted by the post-partonic stages of the collision. Non-flow effects (azimuthal correlations not related to the reaction plane orientation) are difficult to remove from the analysis, and can lead us astray from the true interpretation of anisotropic flow. To reduce the sensitivity of our analysis to non-flow effects, we aim to reconstruct the reaction plane from the sideward deflection of spectator neutrons detected by the Zero Degree Calorimeter (ZDC). It can be shown that the large rapidity gap between the spectator neutrons used to establish the reaction plane and the rapidity region of physics interest eliminates all of the known sources of non-flow correlations. In this project, we upgrade the ZDC to make it position-sensitive in the transverse plane, and utilize the spatial distribution of neutral fragments of the incident beams to determine the reaction plane. The 2004 and 2005 runs of RHIC have provided sufficient statistics to carry out a systematic analysis of azimuthal anisotropies as a function of observables like collision system (Au+Au and Cu+Cu), beam energy (62 GeV and 200GeV), impact parameter (centrality), particle type, etc. Directed flow is quantified by the first harmonic (v1) in the Fourier expansion of the particle's azimuthal distribution with respect to the reaction plane, and elliptic flow, by the second harmonic (v2). They carry information on the very early stages of the collision. For example, the variation of directed flow with rapidity in the central rapidity region is of special interest because it might reveal a signature of a possible QGP phase. This flow study using the 1st-order reaction plane (the reaction plane determined by directed flow) reconstructed using the ZDC-SMD has minimal, if any, influence from non-flow effects or effects from flow fluctuations. The experimental results can be compared with different theoretical model predictions such as AMPT, RQMD, UrQMD and hydrodynamic models. We can also use our flow results to test the hypothesis of limiting fragmentation - the effect whereby particle emission as a function of rapidity in the vicinity of beam rapidity appears unchanged over a wide range of beam energy.