Search

We present the results obtained by the BRAHMS experiment at the Relativistic Heavy Ion Collider (RHIC) for three colliding systems, namely: Au + Au, d + Au and p + p at $\sqrt{s_{NN}} = 200~{\rm GeV}$. The main focus here is to give an overview of the main results on the reaction dynamics and on the properties of hot and high energy density matter produced in utra-relativistic heavy ion collisions. Measurement of particle production, particle spectra over a large rapidity interval as well as high pt measurements related to nuclear modification in Au + Au and d + Au collision are discussed. The observed number of charged particles produced per unit of rapidity at the central rapidity region indicates that a high energy density (> 5 GeV/fm3) system is created at the initial stage of the Au + Au reaction. From the particle spectra we deduced significant radial expansion (β ≈ 0.75) which is consistent with the large initial energy density. For Au + Au at η = 0 we observe the suppression of the high pT particles as compared to the elementary collisions, whereas for the d + Au reaction the Cronin type enhancement is observed. We also discuss to what extent these results can be taken as evidence for the quark gluon plasma (QGP). Finally, we present the nuclear modification effects in d + Au reaction as a function of rapidity and consider whether the observed suppression at forward rapidities constitutes sufficient evidence for a possible precursor state to the QGP, i.e. the Color Glass Condensate (CGC). [ABSTRACT FROM AUTHOR]