High Rapidity Physics with the BRAHMS Experiment

We report the measurement of charged hadron production at different pseudo-rapidity values in deuteron+gold as well as proton+proton collisions at $sqrt{s_{NN}}$ = 200GeV at RHIC. The nuclear modification factors $R_{dAu}$ and $R_{cp}$ are used to investigate new behaviors in the deuteron+gold system as function of rapidity and the centrality of the collisions respectively.

The nuclear modification factor $R_{AA}$ for $\pi_0$ production in Au+Au collisions at $\sqrt{s}=200$ AGeV is calculated, and studied at high transverse momenta $p_T$. The soft thermalized nuclear medium is described within the framework of relativistic ideal three-dimensional hydrodynamics. The energy loss of partonic jets is evaluated in the context of gluon bremsstrahlung in the thermalized partonic matter. We provide a systematic analysis of the azimuthal asymmetry of $\p...

The BRAHMS experiment at RHIC has measured the transverse momentum spectra of charged pions, kaons and (anti-)protons over a wide range of rapidity in d+Au and p+p collisions at $\sqrt{s_{NN}}=200 $GeV. The nuclear modification factor $R_{dAu}$ at forward rapidities shows a clear suppression for $\pi^{+}$. The measured net-proton yields in p+p collisions are compared to PYTHIA and HIJING/B and seem to be better described by the latter.

Transverse momentum spectra of charged hadrons with ${p_{T} <}$ 6 GeV/c have been measured near mid-rapidity (0.2 $< \eta <$ 1.4) by the PHOBOS experiment at RHIC in Au + Au and d + Au collisions at ${\sqrt{s_{_{NN}}} = \rm {200 GeV}}$. The spectra for different collision centralities are compared to ${p + \bar{p}}$ collisions at the same energy. The resulting nuclear modification factor for central Au + Au collisions shows evidence of strong suppression of charged hadrons in...

We report on a study of the transverse momentum dependence of nuclear modification factors $R_{dAu}$ for charged hadrons produced in deuteron + gold collisions at $\sqrt{s_{NN}}= 200$GeV, as a function of collision centrality and of the pseudorapidity ($\eta = 0,1,2.2,3.2$) of the produced hadrons. We find significant and systematic decrease of $R_{dAu}$ with increasing rapidity. The midrapidity enhancement and the forward rapidity suppression are more pronounced in central c...

We report on measurements of identified particle yields from Au-Au collisions at $\sqrt{s_{NN}} = 62.4$ GeV made with the BRAHMS spectrometer. Here we will concentrate on the charged $K/\pi$ ratios as function of rapidity and baryo-chemical potential. We find that the $K/\pi$ ratios measured at different rapidities in the analysed dataset have a common dependence with the same ratios measured in mid-rapidity at SPS energies when plotted as function of the $\bar{p}/p$ ratio. T...

We have measured the rapidity distributions dN/dy of pi+/-, K+/- and p,pbar in central Au+Au collisions at sqrt(s_nn) = 200 GeV. The average rapidity loss per participant nucleon is 2.0 +/- 0.2 units of rapidity. The strange to non--strange meson ratios K/pi are found to track variations of the baryo--chemical potential in energy and rapidity.

A brief review of BRAHMS measurements of bulk particle production in RHIC Au+Au collisions at $\sqrt{s_{NN}}=200GeV$ is presented, together with some discussion of baryon number transport. Intermediate $p_{T}$ measurements in different collision systems (Au+Au, d+Au and p+p) are also discussed in the context of jet quenching and saturation of the gluon density in Au ions at RHIC energies. This report also includes preliminary results for identified particles at forward rapidi...

The proton-to-pion ratios measured in the BRAHMS experiment for Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV are presented as a function of transverse momentum and collision centrality at selected pseudorapidities in the range of 0 to 3.8. A strong pseudorapidity dependence of these ratios is observed. We also compare the magnitude and p_T-dependence of the p/pi ratios measured in Au+Au collisions at \rootsnn{200} and $\eta \approx 2.2$ with the same ratio m...

Transverse momentum spectra and rapidity densities, dN/dy, of protons, anti-protons, and net--protons (p-pbar) from central (0-5%) Au+Au collisions at sqrt(sNN) = 200 GeV were measured with the BRAHMS experiment within the rapidity range 0 < y < 3. The proton and anti-proton dN/dy decrease from mid-rapidity to y=3. The net-proton yield is roughly constant for y<1 at dN/dy~7, and increases to dN/dy~12 at y~3. The data show that collisions at this energy exhibit a high degree o...