Recent results from the BRAHMS experiment

We present recent results obtained by the BRAHMS experiment at the Relativistic Heavy Ion Collider (RHIC) for the systems of Au+Au and Cu+Cu at and at 62.4 GeV, and p+p at . BRAHMS explores reaction dynamics and properties of the hot and high energy density matter produced in ultra-relativistic heavy-ion collisions versus its longitudinal expansion. Overall charged-particle production and particle spectra over a large rapidity interval and pT range are presented. Nuclear modification factors for Au+Au and Cu+Cu collisions are discussed. The observed number of charged particles produced per unit of rapidity in the central rapidity region indicates that a high energy density system is produced at the initial stage of the Au+Au reaction. Analysis of anti-particle to particle ratios as a function of rapidity and collision energy reveal that particle populations at the chemical freeze-out stage for heavy-ion reactions at and above SPS energies are controlled by the baryon chemical potential. From the particle spectra we deduce significant radial expansion (β≈0.75), as expected for systems created with a large initial energy density. We also measure the elliptic flow parameter v2 versus rapidity and pT. A weak dependence on rapidity of the pT differential v2 is observed. We present rapidity dependent p/π ratios within 0