Rapidity Dependence of High-pt Suppresion

The rapidity dependence of the nuclear modification factor in d-Au collaisions at sqrt(s) = 200 GeV at RHIC is discussed.Comment: To appear in the proceedings of the XIII International Workshop on Deep Inelastic Scattering (DIS 2005), Madison. 4 pages 4 figure

Stopping in Relativistic Heavy Ion Reactions - From SIS to RHIC

The status of stopping in heavy ion reactions is reviewed by comparing available data in pp, pA and AA systems over the energy regime sqrt(s_NN) ~ 2.5 - 130 GeV/c. The data consist of average rapidity losses, anti-proton over proton ratios, and net-baryon values at mid-rapidity. The overall features of nuclear stopping are reasonbly well described by simple extrapolations of pp, and pA collisions to AAComment: 10 pages incl. 8 figures. Proceedings of the 17th winter workshop on Nuclear Dynamics, Park City,Utah 200

The ring imaging Cherenkov detector for the BRAHMS experiment at RHIC

A ring imaging Cherenkov counter, to be read out by four 100-channel PMTs, is a key element of the BRAHMS experiment. We report here the most recent results obtained tested at the BNL AGS using several radiator gases, including the heavy fluorocarbon C4F10. Ring radii were measured for different particles (pions, muons, and electrons) for momenta ranging from 2 to 12 GeV/c employing pure C4F10 as radiator.Comment: 3 pages 3 figure

Proton stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c

The shape of proton rapidity distributions is analysed in terms of their Gaussian components, and the average rapidity loss is determined in order to estimate the amount of stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c. Three Gaussians correspond to the nuclear transparency and describe well all peripheral and also C+C central collisions. Two-component shape is obtained in case of d+C and C+Ta central collisions. Finally one Gaussian, found in d+Ta central collisions, corresponds to the full stopping. The calculated values of the average rapidity loss support the qualitative relationship between the number of Gaussian components and the corresponding stopping power. It is also observed, in central collisions, that the average rapidity loss increases with the ratio of the number of target and the number of projectile participants.Comment: 9 pages REVTeX, 1 PS figure replaced, to be published in Phys.Rev.

The BRAHMS experiment at RHIC

The BRAHMS experiment is designed to measure semi-inclusive spectra of charged hadrons over a wide range of rapidity. It will yield information on particle production, both at central rapidity and in the baryon rich fragmentation region. Examples of measurements for soft as well as for hard physics are presented

Single-Transverse Spin Asymmetry in Dijet Correlations at Hadron Colliders

We present a phenomenological study of the single-transverse spin asymmetry in azimuthal correlations of two jets produced nearly "back-to-back" in pp collisions at RHIC. We properly take into account the initial- and final-state interactions of partons that can generate this asymmetry in QCD hard-scattering. Using distribution functions fitted to the existing single-spin data, we make predictions for various weighted single-spin asymmetries in dijet correlations that are now readily testable at RHIC.Comment: 14 pages, 2 figure

The Spectator Electromagnetic Effect on Charged Pion Spectra in Peripheral Ultrarelativistic Heavy-Ion Collisions

We estimate the electromagnetic effect of the spectator charge on the momentum spectra of $\pi^+$ and $\pi^-$ produced in peripheral Pb+Pb collisions at SPS energies. We find that the effect is large and results in strongly varying structures in the $x_F$ dependence of the $\pi^+/\pi^-$ ratio, especially at low transverse momenta where a deep valley in the above ratio is predicted at $x_F \sim$ 0.15 -- 0.20. It appears that the effect depends on initial conditions. Thus, it provides new information on the space and time evolution of the non-perturbative pion creation process.Comment: 20 pages and 8 figure

RESULTS FROM PP AT 62.4 AND 200 GeV WITH THE BRAHMS EXPERIMENTATION.

Measurements of elementary pp collisions are essential for understanding heavy ion collisions. R.esu1ts for pp collisions at 200 and 62.4 GeV are presented. At both energies NLO pQCD describes pion production well. The measured pion transverse single spin asymmetries are very large at 62.4 GeV and are reasonably well described by models relying on pQCD at transverse momenta larger than 1 GeV/c