Charged particle multiplicities from Cu+Cu, Au+Au and d+Au collisions at RHIC Richard S Hollis University of Illinois at Chicago detailed distribution: extended longitudinal scaling global view: shape versus energy detailed distribution: scaling in mid-rapidityconclusion: PHOBOS has a comprehensive pseudorapidity density dataset covering a factor of ten in collision energy (√s = 19.6 to 200 GeV) and a broad range in centrality (from 2 to 360 participants). The data distributions exhibit the global features: oIncrease in width with energy (see extended longitudinal scaling). oIncrease of maximum height with collision energy and centrality (see mid-rapidity). New Cu+Cu data exhibits the same systematic trends as Au+Au. oA comparison with the same fractional cross-section: scaled pseudorapidity densities are smaller in Cu+Cu than in Au+Au due to fewer multiple interactions in the smaller system. oA comparison with the same : Cu+Cu is very similar to Au+Au PHOBOS measurements of the pseudorapidity density in d+Au collisions have been found to scale approximately as the equivalent p+p data times the number of participants. oThe figures to the right illustrate the approximate scaling of total charge. oBoth the deuteron and gold limiting slopes (illustrated by the green line) are found to be consistent with the p+p limiting slope. Limiting slopes in Au+Au and Cu+Cu collisions are found to be peculiar to each centrality bin and systematically different than the measured p+p/d+Au slopes. Glauber monte-carlo calculations can be used for inspiration as to how the pseudorapidity distributions could be expected to scale. The number of collisions (per participant pair) is found to be the same for Au+Au and Cu+Cu collisions, at the same N part. Central Cu+Cu is very similar to Au+Au for the same N part. From a very simple consideration of N part and N coll scaling one can see that this is not inconsistent with the trend seen in the data, although large errors preclude a definitive statement. Possible N coll scaling has been recently discounted in the context of ratios of hadron production versus centrality at different energies. An alternative methodology ocounting whether nucleons are struck once (N MONO ) or multiply (N MULTI ) by other nucleons. The resulting functions oevolve slowly with energy (geometrical quantities). This could give some insight as to why the ratios of mid-rapidity yields for two energies (versus centrality) are flat, oare significantly different for different colliding species − the geometry at the same number of participants is very different. This difference is superficially the same as observed in the data, see mid- rapidity below. Again, it is difficult to distinguish between physics effects and systematic effects. Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard Bindel, Wit Busza (Spokesperson), Zhengwei Chai, Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Kristjan Gulbrandsen, Clive Halliwell, Joshua Hamblen, Ian Harnarine, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Jay Kane, Piotr Kulinich, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Eric Richardson, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Chadd Smith, Maciej Stankiewicz, Peter Steinberg, George Stephans, Andrei Sukhanov, Artur Szostak, Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger, Donald Willhelm, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Shaun Wyngaardt, Bolek Wysłouch ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER Particle production in the region close to the rest frame (y beam ) of one of the colliding nuclei is theorized to be independent of the collision energy. The longitudinal scaling is observed in PHOBOS Au+Au data: for all energies (√s = 19.6 to 200 GeV), extends further from y beam with increasing energy. The two Cu+Cu datasets are found to exhibit the same extended longitudinal scaling. As in Au+Au, the yield in the region η-y beam >0 is found to increase for more peripheral data, approximately canceling the decrease at mid-rapidity. A detailed observation on extended longitudinal scaling is the limiting slope as a function of centrality which decreases for more peripheral data. oThis slope is observed for all energies in Cu+Cu and Au+Au collisions. oNot seen in d+Au collisions. glauber monte-carlo: participants and collisions The geometry scaled mid-rapidity density, versus centrality, is found to be ≈ 40% higher in 0-50% central Au+Au than in p+p collisions Preliminary Cu+Cu is also found to be higher than p+p Mid-rapidity densities at different energies versus centrality are found to factorize such that the ratios of different energies are consistent with geometrical scaling. Ratios in Cu+Cu data are also found to be consistent with this scaling. The expected rise in mid-rapidity density (from hard/N coll - like processes) with increasing energy and centrality is not apparent in the data. The pseudorapidity density distributions in Au+Au data have been measured for a large variety of systems and energies. In Au+Au collisions, the data are found to factorize in energy and centrality. Preliminary Cu+Cu data is found to be consistent with the observations made in Au+Au in terms of oExtended longitudinal scaling, oMid-rapidity yield and oEnergy and centrality scaling. Au+Au Cu+Cu Limiting Slope d+Au preliminary 62.4 GeV preliminary 62.4 GeV preliminary 200 GeV130 GeV preliminary 62.4 GeV 19.6 GeV preliminary