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Abstract: Measurements of identified single particle distributions in d+Au collisions at at the RHIC collider are described. The dependence of these distributions on the centrality of the collisions, as well as the rapidity of the detected particles are emphasized in this report. [Copyright &y& Elsevier]

The RHIC high energy collision of species ranging from p+p, p(d)+A to A+A provide access to the small-x component of the hadron wave function. The RHIC program has brought renewed interest in that subject with its ability to reach values of the parton momentum fraction smaller than 0.01 with studies of particle production at high rapidity. Furthermore, the use of heavy nuclei in the p(d)+A collisions facilitates the study of saturation effects in the gluonic component of the nuclei because the appropriate scale for that regime grows as . We review the experimental results of the RHIC program that have relevance to small-x emphasizing the physics extracted from d+Au collisions and their comparison to p+p collisions at the same energy. [Copyright &y& Elsevier]

Abstract: A Ring Imaging Cherenkov detector built for the BRAHMS experiment at the Brookhaven RHIC is described. This detector has a high index of refraction gas radiator. Cherenkov light is focused on a photo-multiplier based photon detector with a large spherical mirror. The combination of momentum and ring radius measurement provides particle identification from 2.5 to 35GeV/c for pions and kaons and well above 40GeV/c for protons during runs that had the radiator index of refraction set at . [Copyright &y& Elsevier]

An array of 40 tiles of thin plastic scintillators is used to construct the outer layer of the charged particle multiplicity detector for the BRAHMS experiment at the Relativistic Heavy Ion Collider (RHIC). Each tile is a square with 12 cm long sides and 5 mm thickness. The light from each of the scintillators is collected by wavelength shifting fibers embedded on the periphery. The light collection is uniform within 5% over the tile with the edge effect limited to 4 mm along the edge. The response is found to be linear in the high-multiplicity environment at RHIC with Au+Au beams at √ of sNN of 200 GeV. [Copyright &y& Elsevier]

Abstract: Invariant spectra and rapidity densities covering a large rapidity range () are presented for and mesons from central Au + Au collisions at . The mid-rapidity yields of meson particles relative to their anti-particles are found to be close to unity (, ) while the anti-proton to proton ratio is . The rapidity dependence of the ratio is consistent with a small increase towards forward rapidities while the and ratios show a steep decrease to ∼0.3 for kaons and 0.022 for protons at . It is observed that the kaon production relative to its own anti-particle as well as to pion production in wide rapidity and energy ranges shows an apparent universal behavior consistent with the baryo-chemical potential, as deduced from the ratio, being the driving parameter. [Copyright &y& Elsevier]

Abstract: The proton-to-pion ratios measured in the BRAHMS experiment for and collisions at and 200 GeV are presented as a function of transverse momentum and collision centrality at selected pseudorapidities in the range of 0–3.8. A strong pseudorapidity dependence of these ratios is observed. We also compare the magnitude and -dependence of the ratios measured in collisions at and with the same ratio measured at and . The great similarity found between these ratios throughout the whole range (up to ) is consistent with particle ratios in collisions being described with grand-canonical distributions characterized by the baryo-chemical potential . At the collision energy of 62.4 GeV, we have observed a unique point in pseudorapidity, , where the ratio is independent of the collision system size in a wide -range of . [Copyright &y& Elsevier]

Abstract: Transverse momentum spectra of protons and anti-protons measured in the rapidity range from 0–10% central Au+Au collisions at are presented. The rapidity densities, , of protons, anti-protons and net-protons have been deduced from the spectra over a rapidity range wide enough to observe the expected maximum net-baryon density. From mid-rapidity to the net-proton yield is roughly constant (), but rises to at . The mean rapidity loss is units from beam rapidity. The measured rapidity distributions are compared to model predictions. Systematics of net-baryon distributions and rapidity loss vs. collision energy are discussed. [Copyright &y& Elsevier]

Abstract: We present spectra of charged pions and protons in 0–10% central Au+Au collisions at at mid-rapidity () and forward pseudorapidity () measured with the BRAHMS experiment at RHIC. The spectra are compared to spectra from collisions at the same energy scaled by the number of binary collisions. The resulting nuclear modification factors for central Au+Au collisions at both and exhibit suppression for charged pions but not for (anti-) protons at intermediate . The ratios have been measured up to at the two rapidities and the results indicate that a significant fraction of the charged hadrons produced at intermediate range are (anti-) protons at both mid-rapidity and . [Copyright &y& Elsevier]

Abstract: We review the main results obtained by the BRAHMS Collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so-called quark–gluon plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e., the proposed color glass condensate. [Copyright &y& Elsevier]

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]

The BRAHMS experiment at RHIC has measured pions, kaons and protons and their antiparticles over a wide range of rapidity and transverse momenta. Au+Au collisions, d+Au and p+p interactions have been studied. From the net-proton rapidity distribution a stopping power of 73% can be deduced for central Au+Au collisions. The rapidity distributions of produced particles exhibit Gaussian shapes. At midrapidity the nuclear modification factor for central Au+Au collisions shows a strong pion suppression at intermediate transverse momenta; a suppression which is even stronger at forward rapidities. The nuclear modification factor for d+Au changes from a Cronin-like enhancement of charged hadrons at midrapidity to a suppression at forward rapidities. [Copyright &y& Elsevier]

Abstract: We present a measurement of , and from collisions at over the rapidity range . For we see no significant transverse momentum dependence of the ratios. All three ratios are independent of rapidity for and then steadily decline from to . The ratio is below unity for . The ratio is very similar for and 20% central Au+Au collisions at all rapidities. In the fragmentation region the three ratios seem to be independent of beam energy when viewed from the rest frame of one of the protons. Theoretical models based on quark–diquark breaking mechanisms overestimate the ratio up to . Including additional mechanisms for baryon number transport such as baryon junctions leads to a better description of the data. [Copyright &y& Elsevier]

Heavy ion collisions at RHIC energies (Au + Au collisions at √SNN = 200 GeV) exhibit significant new features as compared to earlier experiments at lower energies. The reaction is characterized by a high degree of transparency of the collision partners leading to the formation of a baryon-poor central region. In this zone, particle production occurs mainly from the stretching of the color field. The initial energy density is well above the one considered necessary for the formation of the Quark Gluon Plasma, QGP. The production of charged particles of various masses is consistent with chemical and thermal equilibrium. Recently, a suppression of the high transverse momentum component of hadron spectra has been observed in central Au + Au collisions. This can be explained by the energy loss experienced by leading partons in a medium with a high density of unscreened color charges. In contrast, such high pt jets are not suppressed in d + Au collisions suggesting that the high pt suppression is not due to initial state effects in the ultrarelativistic colliding nuclei. [Copyright &y& Elsevier]

The BRAHMS experiment at RHIC was conceived to pursue the understanding of nuclear matter under extreme conditions by detailed measurements of charged hadrons over the widest possible range of rapidity and transverse momentum. The experiment consists of two spectrometers with complementary charged hadron detection capabilities as well as a series of global detectors for event characterization. A series of tracking detectors, time-of-flight arms and Cherenkov detectors enables momentum determination and particle identification over a wide range of rapidity and transverse momentum. Technical details and performance results are presented for the various detector subsystems. The performance of the entire system working together is shown to meet the goals of the experiment. [Copyright &y& Elsevier]

This report describes a multi plane drift chamber that was designed and constructed to function as a topological detector for the BNL AGS E896 rare particle experiment. The chamber was optimized for good spatial resolution, two track separation, and a high uniform efficiency while operating in a 1.6 T magnetic field and subjected to long term exposure from a 11.6 GeV/nucleon beam of 106 Au ions per second. [Copyright &y& Elsevier]

The BRAHMS collaboration has measured identified particle spectra from Au+Au collisions at √sNN = 200 GeV. Rapidity densities are deduced from fits to the pion and kaon spectra. dN/dy is plotted as a function of rapidity and 4&pai; yields and ratios are calculated. The signed K/&pai; ratios are compared to values obtained at lower energies. We find that K-/&pai;- increases monotonically from the AGS and SPS regimes, while K+/&pai;+ is similar to what was found at the highest √sNN at SPS. [ABSTRACT FROM AUTHOR]

We present transverse momentum spectra of unidentified charged hadrons at two pseudorapidities (η = 0, 2.2) as well as the first results on identified negatively charged pions at rapidity 2.2 from Au+Au collisions at &√sNN = 200 GeV. The high pT yields of charged hadrons in the most central collisions show a strong suppression when compared to expected binary-scaled yields from nucleon-nucleon collisions or semi-peripheral collisions. The &pai;- spectra at forward rapidity (y = 2.2) also indicate a clear suppression of high pT &pai;- yields in central collisions. [ABSTRACT FROM AUTHOR]