Lets stick to Root. JJ ________________________________ Jens Jørgen Gaardhøje Assoc. prof. Dr. Scient. Chair Ph.D: school of Physics NBI.f.AFG. (secretariat. 35 32 04 41) Chair science committee. UNESCO Natl. Commission. (secretariat. 33 92 52 16) Office: Niels Bohr Institute, Blegdamsvej 17, 2100, Copenhagen, Denmark. Tlf: (+45) 35 32 53 09 Fax: (+45) 35 32 50 16 ________________________________ ----- Original Message ----- From: "Stephen J. Sanders" <ssanders@ku.edu> To: <brahms-l@bnl.gov> Sent: Wednesday, November 28, 2001 6:20 AM Subject: mult version 3.8 > Dear Jens Jorgen, Michael, Trine, and all... > I am attaching version 3.8 at the end of this messages. Also, the > kansas account has been updated. > > For people wanting a stable version to edit for final comments, please wait > for version 3.9 (3.10?) that should be ready by midday tomorrow > (US east coast time). There are still some final questions about > consistencies > of some of the numbers that need to be resolved. In particular, > I couldn't locate the final (Hijing?) Ncoll numbers that we want to quote in > the flurry of email messages sent earlier today. I also need to double > check with > Hiro some of the quoted cross sections in the table. > > JJ- I removed the statement " ...the largest number of particles > observed so far > in energetic nuclear collisions" since this would certainly be disputed by > any of the Phobos collaborators. Although Phobos does not quote a > comparable > total charged particle number in their paper, they do show a 200 GeV > pseudorapidity distribution for central events. I also trimmed in a few > other spots > to get the length back down to four pages. > > Michael and JJ-- Some the newer suggestions for the figures will be > very difficult > to achieve unless we give up on only using ROOT macros for their production. > Hiro can probably do some of them (such as changing from closed to open > symbols), > but others, such as closing the gaps between the four pane figures, are > not going to > be as readily accomplished. > > Regards, Steve > > ==========================================================%% ****** > Start of file template.aps ****** > %% This file is part of the APS files in the REVTeX 3.0 distribution. > %% Version 3.0 of REVTeX,! November 10, 1992. > %% > %% Copyright (c) 1992 The American Physical Society. > %% > %% See the REVTeX 3.0 README file for restrictions and more information. > %% > %% > %% This is a template for producing files for use with REVTEX 3.0. > %% Copy this file to another name and then work on that file. > %% That way, you always have this original template file to use. > %% > %% > %% > %% THIS FILE: dndeta200-draft37.tex > %% > %% October 13-2001. 23.00 GMT+1 > %% Based on first text by SS and JJG > %% REVISED: > %% Oct 14-2001 JJG. Update text > %% Oct 16-2001 JJG. Update text > %% Oct 17-2001 JJG. Include hard/soft fit results + update text > %% Oct 17-2001 JJG. Fill out Table + update text, author > %% list,figure 4. > %% Oct 18-2001 JJG. update references and include eta = 1.5 > %% for fits. > %% Oct 19-2001 JJG. smaller updates and corrections after > %% input from CEJ and TST > %% Nov 12-2001 JJG. text adjusted to HIRO's new figures > %% Nov 15-2001 JJG. text shortened. Prepare for 5 figures. > %% Nov 16-2001 JJG. various text revisions > %% Nov 19-2001 JJG. text revision with various input from > %% others. New fig 5 not described yet. > %% Nov 20-2001 MM + SS changed to Revtex 4. SS update > %% numbers + some text. > %% JJG. update text. Go back to Npart figure 5. > %% Keep figure 2. > %% Nov 21-2001 JJG. incorporated many comments from CC, MM, > %% PS, CEJ, etc... > %% Nov 25-2001 SJS incorporated comments of FV and JN > %% Nov 27-2001 JJG small text revisions, add discussion on > width decrease and p+p > %% Nov 27-2001 SJS small text revisions > %% > ************************************************************************** > > > \documentclass[twocolumn,showpacs,preprintnumbers,amsmath,amssymb,superscrip taddress,unsortedaddress]{revtex4} > > %%\documentclass[preprint,showpacs,preprintnumbers,amsmath,amssymb]{revtex4} > %% Some other (several out of many) possibilities > %%\documentclass[preprint,aps]{revtex4} > %%\documentclass[preprint,aps,draft]{revtex4} > %%\documentclass[prb]{revtex4}% Physical Review B > > \usepackage{graphicx}% Include figure files > \usepackage{dcolumn}% Align table columns on decimal point > \usepackage{bm}% bold math > \usepackage{epsf,epsfig,latexsym} > > \newcommand{\Version}{Version: dndeta200-draft38.tex, Nov. 27, 2001} > > %% Conditinal use of BIBTeX database > \newif\ifUseBibTeX\UseBibTeXtrue > %% LaTeX bibliography > \UseBibTeXfalse > > %% conditional RevTeX style author > \newif\ifRevTexAuthor\RevTexAuthortrue > %% Old style author > \RevTexAuthorfalse > > \ifRevTexAuthor > \newcommand{\bnl}{Brookhaven National Laboratory, Upton,New York > 11973} > \newcommand{\ires}{Institut de Recherches Subatomiques and > Universit{\'e} Louis Pasteur,Strasbourg, France} > \newcommand{\kraknuc}{Institute of Nuclear Physics, Krakow, Poland} > \newcommand{\krakow}{Jagiellonian University, Krakow, Poland} > \newcommand{\baltimore}{Johns Hopkins University, Baltimore, Maryland > 21218} > \newcommand{\newyork}{New York University, New York, New York 10003} > \newcommand{\nbi}{Niels Bohr Institute, University of Copenhagen, > Denmark} > \newcommand{\texas}{Texas A$\&$M University, College Station,Texas > 77843} > \newcommand{\bergen}{University of Bergen, Department of Physics, > Bergen,Norway} > \newcommand{\bucharest}{University of Bucharest,Romania} > \newcommand{\kansas}{University of Kansas, Lawrence, Kansas 66049} > \newcommand{\oslo}{University of Oslo, Department of Physics, > Oslo,Norway} > \else > \newcommand{\bnl} {$\rm^{1}$} > \newcommand{\ires} {$\rm^{2}$} > \newcommand{\kraknuc} {$\rm^{3}$} > \newcommand{\krakow} {$\rm^{4}$} > \newcommand{\baltimore} {$\rm^{5}$} > \newcommand{\newyork} {$\rm^{6}$} > \newcommand{\nbi} {$\rm^{7}$} > \newcommand{\texas} {$\rm^{8}$} > \newcommand{\bergen} {$\rm^{9}$} > \newcommand{\bucharest} {$\rm^{10}$} > \newcommand{\kansas} {$\rm^{11}$} > \newcommand{\oslo} {$\rm^{12}$} > \fi > > \begin{document} > > \title{Pseudorapidity distributions of charged particles from Au+Au > collisions at the maximum RHIC energy.} > \ifRevTexAuthor > \author{I.~G.~Bearden}\affiliation{\nbi} > \author{D.~Beavis}\affiliation{\bnl} > \author{C.~Besliu}\affiliation{\bucharest} > \author{Y.~Blyakhman}\affiliation{\newyork} > \author{J.~Brzychczyk}\affiliation{\krakow} > \author{B.~Budick}\affiliation{\newyork} > \author{H.~B{\o}ggild}\affiliation{\nbi} > \author{C.~Chasman}\affiliation{\bnl} > \author{C.~H.~Christensen}\affiliation{\nbi} > \author{P.~Christiansen}\affiliation{\nbi} > \author{J.~Cibor}\affiliation{\kraknuc} > \author{R.~Debbe}\affiliation{\bnl} > \author{E. Enger}\affiliation{\oslo} %\and > \author{J.~J.~Gaardh{\o}je}\affiliation{\nbi} > \author{K.~Grotowski}\affiliation{\krakow} > \author{K.~Hagel}\affiliation{\texas} > \author{O.~Hansen}\affiliation{\nbi} > \author{A.~Holm}\affiliation{\nbi} > \author{A.~K.~Holme}\affiliation{\oslo} > \author{H.~Ito}\affiliation{\kansas} > \author{E.~Jakobsen}\affiliation{\nbi} > \author{A.~Jipa}\affiliation{\bucharest} > \author{J.~I.~J{\o}rdre}\affiliation{\bergen} > \author{F.~Jundt}\affiliation{\ires} > \author{C.~E.~J{\o}rgensen}\affiliation{\nbi} > \author{T.~Keutgen}\affiliation{\texas} > \author{E.~J.~Kim}\affiliation{\bnl} > \author{T.~Kozik}\affiliation{\krakow} > \author{T.~M.~Larsen}\affiliation{\oslo} > \author{J.~H.~Lee}\affiliation{\bnl} > \author{Y.~K.~Lee}\affiliation{\baltimore} > \author{G.~L{\o}vh{\o}iden}\affiliation{\oslo} > \author{Z.~Majka}\affiliation{\krakow} > \author{A.~Makeev}\affiliation{\texas} > \author{B.~McBreen}\affiliation{\bnl} > \author{M.~Mikelsen}\affiliation{\oslo} > \author{M.~Murray}\affiliation{\texas} > \author{J.~Natowitz}\affiliation{\texas} > \author{B.~S.~Nielsen}\affiliation{\nbi} > \author{J.~Norris}\affiliation{\kansas} > \author{K.~Olchanski}\affiliation{\bnl} > \author{J.~Olness}\affiliation{\bnl} > \author{D.~Ouerdane}\affiliation{\nbi} > \author{R.~P\l aneta}\affiliation{\krakow} > \author{F.~Rami}\affiliation{\ires} > \author{D.~R{\"o}hrich}\affiliation{\bergen} > \author{B.~H.~Samset}\affiliation{\oslo} > \author{D.~Sandberg}\affiliation{\nbi} > \author{S.~J.~Sanders}\affiliation{\kansas} > \author{R.~A.~Sheetz}\affiliation{\bnl} > \author{Z.~Sosin}\affiliation{\krakow} > \author{P.~Staszel}\affiliation{\nbi} > \author{T.~F.~Thorsteinsen\textsuperscript{\dag}}\affiliation{\bergen,\textr m{\textsuperscript{\dag}\textit{Deceased}}} > \author{T.~S.~Tveter}\affiliation{\oslo} > \author{F.~Videb{\ae}k}\affiliation{\bnl} > \author{R.~Wada}\affiliation{\texas} > \author{A.~Wieloch}\affiliation{\krakow} > \author{I.~S.~Zgura}\affiliation{\bucharest} > \collaboration{BRAHMS Collaboration} > \noaffiliation > \else > \author{ > I.~G.~Bearden\nbi, % \and > D.~Beavis\bnl, % \and > C.~Besliu\bucharest, % \and > Y.~Blyakhman\newyork, % \and > B.~Budick\newyork, % \and > H.~B{\o}ggild\nbi, % \and > C.~Chasman\bnl, % \and > C.~H.~Christensen\nbi, % \and > P.~Christiansen\nbi, % \and > J.~Cibor\kraknuc, % \and > R.~Debbe\bnl, % \and > E. Enger\oslo, %\and > J.~J.~Gaardh{\o}je\nbi, % \and > K.~Hagel\texas, % \and > O.~Hansen\nbi, % \and > A.~Holm\nbi, % \and > A.~K.~Holme\oslo, % \and > H.~Ito\kansas, % \and > E.~Jakobsen\nbi, % \and > A.~Jipa\bucharest, % \and > J.~I.~J{\o}rdre\bergen, % \and > F.~Jundt\ires, % \and > C.~E.~J{\o}rgensen\nbi, % \and > R.~Karabowicz\krakow, % \and > T.~Keutgen\texas, % \and > E.~J.~Kim\bnl, % \and > T.~Kozik\krakow, % \and > T.~M.~Larsen\oslo, % \and > J.~H.~Lee\bnl, % \and > Y.~K.~Lee\baltimore, % \and > G.~L{\o}vh{\o}iden\oslo, % \and > Z.~Majka\krakow, % \and > A.~Makeev\texas, % \and > B.~McBreen\bnl, % \and > M.~Mikelsen\oslo, % \and > M.~Murray\texas, % \and > J.~Natowitz\texas, % \and > B.~S.~Nielsen\nbi, % \and > J.~Norris\kansas, % \and > K.~Olchanski\bnl, % \and > J.~Olness\bnl, % \and > D.~Ouerdane\nbi, % \and > R.~P\l aneta\krakow, % \and > F.~Rami\ires, % \and > D.~R{\"o}hrich\bergen, % \and > B.~H.~Samset\oslo, % \and > D.~Sandberg\nbi, % \and > S.~J.~Sanders\kansas, % \and > R.~A.~Sheetz\bnl, % \and > P.~Staszel\nbi, % \and > T.~F.~Thorsteinsen\bergen$^+$,% \and > T.~S.~Tveter\oslo, % \and > F.~Videb{\ae}k\bnl, % \and > R.~Wada\texas, % \and > A.~Wieloch\krakow, and > I.~S.~Zgura\bucharest\\% \and > (BRAHMS Collaboration )\\[1ex] > \bnl~Brookhaven National Laboratory, Upton,New York 11973, > \ires~Institut de Recherches Subatomiques and Universit{\'e} Louis > Pasteur, Strasbourg, France, > \kraknuc~Institute of Nuclear Physics, Krakow, Poland, > \krakow~Jagiellonian University, Krakow, Poland, > \baltimore~Johns Hopkins University, Baltimore, Maryland 21218, > \newyork~New York University, New York, New York 10003, > \nbi~Niels Bohr Institute, University of Copenhagen, Denmark, > \texas~Texas A$\&$M University, College Station,Texas 77843, > \bergen~University of Bergen, Department of Physics, Bergen,Norway, > \bucharest~University of Bucharest,Romania, > \kansas~University of Kansas, Lawrence, Kansas 66049, > \oslo~University of Oslo, Department of Physics, Oslo,Norway, > $^+ Deceased$} > \noaffiliation > \fi > \date{\Version} > > \begin{abstract} > We present charged particle densities as a function of > pseudorapidity and collision centrality for the > $^{197}$Au+$^{197}$Au reaction at $\sqrt{s_{NN}}$=200~GeV, the > maximum energy for RHIC. The charged particle multiplicity for the > 5\% most central events is 632 $\pm$1 (stat) $\pm$55 (syst), i.e. a > 14\% increase relative to $\sqrt{s_{NN}}$=130~GeV collisions. The > total multiplicity of charged particles for $-4.7\le \eta \le 4.7$ > is 4630 $\pm$370, an increase by 20\% over the lower energy. The > data show an increase from 2.9 to 3.7 in the production of charged > particles per pair of participant nucleons from peripheral (40-50\%) > to central (0-5\%) collisions around midrapidity. These results > constrain current models based on high density QCD gluon saturation > and on the superposition of particle production from soft hadronic > and hard partonic collisions. > \end{abstract} > \pacs{25.75.Dw} % Revtex 4 > \maketitle > > A central question in the study of collisions between heavy nuclei at > the maximum energy of the RHIC facility, > $\sqrt{s_{NN}}$=200~GeV, is the role of hard scatterings between > partons and the interactions of these partons in a high density > environment. Indeed, it has been conjectured that new phenomena > related to non-perturbative QCD may come into play at this energy. > Among these, a saturation of the number of parton (mainly gluon) > collisions in central nucleus-nucleus collisions has been predicted to > limit the production of charged > particles~\cite{partonsat83,Eskola00,Kharzeev_and_Levin}. Recently, > indications for a reduction in the number of hadrons at high > transverse momentum for $\sqrt{s_{NN}}$=130~GeV collisions have been > presented that may hint at suppression of hadronic jets at high matter > densities~\cite{Phenix-jets,Star-jets}. > > The present Letter addresses these issues with the first comprehensive > investigation of multiplicity distributions of emitted charged > particles in relativistic heavy ion collisions between $^{197}$Au > nuclei at the maximum RHIC energy. In particular, we have measured > pseudorapidity distributions of charged particles in the range $-4.7 > \le \eta \le 4.7$ for such collisions at > $\sqrt{s_{\small{NN}}}$=200~GeV as a function of collision > centrality. The production of charged particles in these highly > energetic nuclear collisions can be due to hadronic as well as > partonic collision processes and thus depends on the presence of gluon > shadowing effects and, in general, on the relative importance of soft > and hard scattering processes. We find in this work that the > production of charged particles at midrapidity increases by 14$\pm$1\% > for the most central collisions relative to $\sqrt{s_{NN}}$=130~GeV > collisions~\cite{back00,Star-mult130,adcox01,bearden01a}, in agreement > with the results of the PHOBOS experiment~\cite{Phobos-mult200-1}. For > more peripheral collisions we find a slightly smaller increase, while > we observe a saturation of the baryon excitations at larger rapidities. > > The BRAHMS experiment consists of two magnetic spectrometers for > measuring spectra of identified charged particles over a wide range of > rapidity and transverse momentum and a number of global > detectors for determining the location of the collision vertex, the > time of the collision, the collision centrality and the charged > particle densities~\cite{bearden01b}. > The present data were obtained using three of the > global detector systems at BRAHMS: the Multiplicity Array (MA), the > Beam-Beam Counter arrays (BBC), and the Zero-degree Calorimeters > (ZDC). An analysis of > charged particle densities for Au+Au reactions at > $\sqrt{s_{NN}}$=130~GeV that is very similar in method to that > presented here is described fully in ref.~\cite{bearden01a}. > > The MA determines charged particle densities around midrapidity and > consist of a hexagonal-sided double barrel arrangment with a modestly > segmented Si strip detector array (SiMA) surrounded by an outer > plastic scintillator tile array (TMA). > Each of the 25 Si detectors (4~cm x 6~cm x 300~$\mu$m), placed 5.3~cm from > the beam axis, is subdivided into seven active strips. The TMA > was comprised of 35 plastic scintillator tiles (12~cm x 12~cm x 0.5~cm) > located 13.9 cm from the beam axis. Both the SiMA and TMA > cover a pseudorapidity range of $-2.2\le\eta\le2.2$ for collisions > occurring at the nominal interaction vertex. Using an extended range > of collision vertices, the effective coverage of the array is > $-3.0\le\eta\le3.0$ . Particle densities are deduced from the observed > energy loss in the SiMA elements using GEANT simulations~\cite{Geant} > to relate energy loss to the number of particles hitting > a given detector element~\cite{bearden01a}. > > The BBC Arrays consist of two sets of Cherenkov UV transmitting > plastic radiators coupled to photomultiplier tubes. They are > positioned around the beam pipe on either side of the nominal > interaction point at a distance of 2.20~m. The time resolution of the > BBC elements permits the determination of the interaction point with an > accuracy of $\approx$ 0.9~cm. Charged particle multiplicities in the > pseudorapidity range $2.1\le |\eta| \le 4.7$ are deduced from the > number of particles hitting each tube, as found by dividing the > measured ADC signal by that corresponding to a single > particle hitting the detector. > > The ZDC detectors are located $\pm$18m from the nominal > interaction vertex and measure neutrons that are emitted at small > angles with respect to the beam direction~\cite{adler00}. Clean > selection of minimum-biased events required a coincidence between the two > ZDCs and a minimum of 4 ``hits'' in the TMA and is estimated to > include 95\% of the nuclear reaction cross section of 7.1~b. > The ZDCs also > locate the interaction point with an accuracy of $\approx$~3.6~cm. > > Reaction centrality is determined by selecting different regions > in the total multiplicity distribution in either the MA or BBC arrays. > In analyzing particle densities in dN/d$\eta$, the centrality dependence > of the MA and BBC distributions are based on the total multiplicity > measurements of the corresponding array. In the pseudorapidity range of > 3.0$\le\eta\le$4.2, where it was possible to analyze the BBC data > using both centrality selections, the two analyses give > identical results to within 2\%. In general, statistical error on > the measurements are less than 1\%, while we estimate that the > systematic errors are 8\% and 10\% for the SiMA and BBC arrays, > respectively. > > \begin{figure} > \epsfig{file=fig1.eps,width=8.5cm} > \caption{ > Distributions of $dN_{ch}/d\eta$ for centrality ranges of, top to > bottom, 0-5\%, 5-10\%, 10-20\%, 20-30\%, 30-40\%, and 40-50\%. > The SiMA and BBC results are indicated by the circles and > triangles, respectively. Statistical error are shown for all > points where larger than the symbol size. Systematic errors are > 8\% and 10\% for the SiMA and BBC points respectively.} > \label{dndeta} > \end{figure} > > > In Fig.~\ref{dndeta} we show the measured pseudorapidity distributions > for charged particles for centrality cuts of 0-5\%, 5-10\%, 10-20\%, > 20-30\%, 30-40\% and 40-50\%. The > $dN/d\eta$ values for these cuts at $\eta$=0, 1.5, 3.0, 4.5 are listed > in Table~\ref{tb:dndeta}, together with the number of participating > baryons estimated from the HIJING model. For the most central > collisions (0-5\%) the multiplicities reach $dN/d\eta$=632 $\pm 55$ at > midrapidity. This corresponds to $3.7 \pm 0.3$ charged particles per > participating baryon > pair and indicates an increase in the multiplicities of about > 14\% relative to $^{197}$Au+$^{197}$Au reactions at > $\sqrt{s_{NN}}$=130~GeV > ~\cite{bearden01a,back00,Phobos-mult200-1,adcox01,Star-mult130}. By > integrating the 0-5\% multiplicity distribution we deduce that $N=4630 > \pm 370$ charged particles are emitted in the considered rapidity > range. This value is 20$\pm$1\% higher than for > $\sqrt{s_{NN}}$=130~GeV reactions~\cite{bearden01a}. More detailed > inspection shows that the distributions at the two energies are quite > similar in shape. Indeed, the FWHM of the most central distributions > is $\Delta \eta = 7.5 \pm 0.5$ for $\sqrt{s_{NN}}$=200~GeV, as > compared to $\Delta \eta = 7.2 \pm 0.8$ for $\sqrt{s_{NN}}$=130~GeV > collisions. For the most peripheral collisions analyzed here (40-50\%) > the multiplicities at $\eta=0$ reach $dN/d\eta=110\pm 10$ while the > corresponding value scaled to the number of participating pairs is > 2.9$\pm 0.3$. For comparison, the similar number for proton-proton > collisions at this energy is 2.5, also a 14\% increase over the lower > energy. > \begin{table} [ht] > \caption{\label{tb:dndeta} Charged particle densities in > $dN_{ch}/d\eta$ as a function of > centrality and pseudorapidity. Total uncertainties, dominated by > the systematics, are indicated. The average > number of participants $\langle N_{part}\rangle$ and collisions > $\langle N_{coll}\rangle$ is given for each centrality > class. $N_{ch}$ is the > integral charged particle multiplicity within %the pseudorapidity range > $-4.7 \le \eta \le 4.7$.} > %% Centrality & $N_{coll}$& $N_{part}$& $\eta = 0$ & $\eta =1.5$ > %% $\eta = 3.0$ & > %% $\eta = 4.5$ & $N_{ch}$ \\ > %% \begin{tabular}{|c|c|c|c|c|c|c|c|} > \begin{tabular}{cccccccc} > \hline > Cent- & > $\eta = 0$ & > $\eta =1.5$ & > $\eta = 3.0$ & > $\eta = 4.5$ & > $N_{ch}$ & > $N_{coll}$& > $N_{part}$ > \\ > rality & & & & & & & \\ > 0-5 & 632$\pm$55 & 628$\pm$57 & 453$\pm$41 > & 181 $\pm$21 & 4630$\pm$370& 1086& 345 \\ > 5-10 & 498$\pm$44 & 509$\pm$46 & 379$\pm$37 > & 156$\pm$17 & 3810$\pm$300& 866 & 293 \\ > 10-20 & 373$\pm$33 & 385$\pm$35 & 296$\pm$29 > & 124$\pm$13 & 2920$\pm$230 & 561 & 228 \\ > 20-30 & 257$\pm$23 & 265$\pm$24 & 207$\pm$21 > & 89 $\pm$10 & 2020$\pm$160 & 389 & 164 \\ > 30-40 & 170$\pm$15 & 178$\pm$16 & 140$\pm$15 > & 62 $\pm$7 & 1380$\pm$110 & 232 & 114 \\ > 40-50 & 110$\pm$10 & 115$\pm$10 & 90$\pm$9 > & 42 $\pm$5 & 890$\pm$70 & 114 & 75 \\ > \hline > \end{tabular} > \end{table} > > Figure~\ref{dndeta_fragment} shows, on the other hand, that the charged > particle multiplicities in an interval of approximately 0.5-1.5 units > below the beam rapidity are independent of the collision centrality > and energy, from CERN-SPS energy ($\sqrt{s_{NN}}$=17~GeV) > \cite{deines00} to the present RHIC energy. This is consistent with a > limiting fragmentation picture in which the excitations of the > fragment baryons saturate already at moderate collision energies > independently of the system size~\cite{bearden01a}. In contrast, the > increased projectile kinetic energy is utilized for particle > production in the region around midrapidity, as evidenced by the > observed increase of the multiplicities per participant pair around > the center of mass rapidity. > \begin{figure} > \epsfig{file=fig2.eps,width=8.5cm} > \caption{ > Charged particle densities normalized to the number of participant > pairs (see table) for the present 0-5\% central (open circles) and > 40-50\% central (open squares) Au+Au results at > $\sqrt{s_{NN}}$=200~GeV, the BRAHMS Au+Au > results~\cite{bearden01a} at $\sqrt{s_{NN}}$=130~GeV (closed > circles) and the 9.4\% central Pb+Pb data at > $\sqrt{s_{NN}}$=17~GeV(closed triangles) of ref~\cite{deines00}. > Data at different beam energies are plotted as a function of the > pseudorapidity shifted by the relevant beam rapidity. Representative > total > uncertainties are shown for a few Au+Au points. } > \label{dndeta_fragment} > \end{figure} > > Figure~\ref{dndeta_models} presents the $dN/d\eta$ distributions > obtained by mirroring and averaging the negative and positive halves > of the measured distributions to further decrease errors. We also > compare the distributions with model calculations. The solid > lines are calculations using the model of Kharzeev and > Levin~\cite{Kharzeev_and_Levin} which is based on a classical QCD > calculation using parameters fixed to the $\sqrt{s_{NN}}$=130~GeV > data. This approach is able to reproduce the magnitude and shape of > the observed multiplicity distributions quite well. Also shown in > Fig.~\ref{dndeta_models} (dashed lines) are the results of > calculations with the AMPT model~\cite{zhang01,lin01a,lin01b}, which > is a cascade model based on HIJING~\cite{wang91} but including final > state rescattering of produced particles. The AMPT model is also able > to account for the general trend of the measured distributions, > particularly for the most central collisions. We also plot the similar > distributions~\cite{Alner86}from $p\bar p$ collisions at > ($\sqrt{s}$=200~GeV) > scaled by the number of participant pairs. > For central collisions the Au+Au data > show a strong enhancement over the entire range relative to $p\bar p$, > decreasing to about 10\% for the most peripheral collisions. > The observed multiplicity excess of > $48\pm 9\%$ above the corresponding value for $p\bar p$ collisions clearly > demonstrates significant medium effects. > We note that > the measured distributions show a small increase in width with > decreasing centrality (from $\sigma_{RMS}=2.33\pm 0.02$ for 0-5\% > to $2.4 \pm 0.02$ for 40-50\%), to be compared to $RMS= 2.38 \pm 0.05$ > for the p+p data. > > \begin{figure} > \epsfig{file=fig3.eps,width=8.5cm} > \caption{ > (a-d) Measured $dN_{ch}/d\eta$ distributions for centrality > ranges of 0-5\%, 10-20\%, 20-30\% and 40-50\%. Theoretical > predictions by Kharzeev and Levin (solid line) and by the > AMPT model (dashed line) are also shown. Result from p+p collisions > at this energy~\cite{Alner86} are shown with stars (a,d).} > \label{dndeta_models} > \end{figure} > > The ratio of the pseudorapidity densities measured at > $\sqrt{s_{NN}}$=130~GeV and $\sqrt{s_{NN}}$=200~GeV for different > centralities are shown in Fig.~\ref{dndeta_ratios}. The figure shows a > systematic increase in multiplicity as a function of > energy for a central plateau in the range $\eta= 0-2.5 $. The increase is > 14\% for the most central collisions and 12\% for the most peripheral. > The upturn of the ratios at the forward rapidities is due to the > widening of the multiplicity distribution at the higher energy > consistent with the increase in beam rapidity ($\Delta y = 0.45$). > The overlaid curves show the corresponding ratios resulting from the > two model calculations. > \begin{figure} > \epsfig{file=fig4.eps,width=8.5cm} > \caption{ > Ratio of particle densities at $\sqrt{s_{NN}}$=200~GeV and 130~GeV > compared to the models. Points are only shown with statistical > errors as systematic errors tend to cancel out } > \label{dndeta_ratios} > \end{figure} > > Finally in Fig.~\ref{Npart} we plot the dependence of the multiplicity > of charged particles per pair of participant baryons as a function of > the number of participants, $N_{part}$, for three narrow pseudrapidity > regions ($\Delta \eta \approx 0.2$) around $\eta$ =0, 3.0 and > 4.5. While the figure shows that particle production per participant > pair is remarkably constant at the forward rapidities characteristic > of the fragmentation region and close to unity, this is not the case > for the central rapidities. Indeed, we find a significant increase of > particle production per pair of participant nucleons for the more > central collisions at $\eta=0$. Plotted using the $N_{part}$ values > listed in table 1, the curves for these rapidities rise as a function > of collision centrality. This has previously been attributed to the > onset of hard scatterings which are dependent on the number of > binary nucleon collisions > $N_{coll}$ rather than $N_{part}$. > Using for $N_{coll}$ the values from HIJING > ~\cite{wang91} we fit the observed dependencies to a > functional $dN/d\eta=\alpha\cdot N_{part}+\beta \cdot N_{coll}$. For > rapidities $\eta=$ 0 and 3.0 we obtain: $\alpha=0.98 \pm 0.10$ and > $1.05 \pm 0.08$ and $\beta=0.25 \pm 0.04, 0.09 \pm 0.03$, > respectively. For comparison we find $\alpha=0.99 \pm 0.09, 0.99 \pm > 0.07, $ and $\beta=0.18 \pm 0.04, 0.02 \pm 0.04 $ at > $\sqrt{s_{NN}}$=130~GeV. At $\eta=0.0$ we find that the hard > scattering component to the charged particle production increases from > 36$\pm$7\% at the lower energy to about 43$\pm$7\% at > $\sqrt{s_{NN}}$=200~GeV. It should be stressed, however, that this > interpretation is highly model dependent. Using the $N_{part}$ values > from ~\cite{Kharzeev_and_Nardi} which are smaller than the > corresponding HIJING numbers for the more peripheral collisions the > curves become practically flat ($\beta \approx 0$) and thus inconstent > with a mixing of soft and hard scatterings. > \begin{figure} > \epsfig{file=fig5.eps,width=8.5cm} > \caption{ > Distributions of $dN_{ch}/d\eta$ per participant pair as a > function of the number of participants (see table) > %% for $\eta$= 0, 3.0 and 4.5. The curves show predictions by the > %% Kharzeev and Levin model (solid line) and the AMPT > %% model (dashed > for $\eta$= 0,1.5, 3.0 and 4.5. The curves show predictions by > Kharzeev and Levin (solid line) and the AMPT model (dashed > line). The star denotes the p+p result at $\eta=0$.} > \label{Npart} > \end{figure} > > In conclusion, we find that the charged particle production scales > smoothly from $\sqrt{s_{NN}}$=130~GeV to $\sqrt{s_{NN}}$=200~GeV in a > wide region around midrapidity. The data are well reproduced by > calculations based on high density QCD and by the AMPT/HIJING > microscopic parton model. A phenomenological two component analysis in > terms of a superposition of particle production due to soft/hard > scatterings also accounts well for the data but does not show > significant differences between the two energies. We find good > consistency with the gluon saturation model of Kharzeev and Levin, but > stress that within errors of models and data alike, the data can be > equally well reproduced by other models not requiring saturation > effects in the description of parton collisions. While the current > work establishes the baseline for particle production at the maximum > energy available for nucleus-nucleus collisions for several years to > come, the full understanding of these energetic collisions must await > more detailed analyses of hadronic and leptonic observables over a > wide region of phase space and rapidity. > > We thank the RHIC collider team for their efforts. > This work was supported by the Division of Nuclear Physics > of the U.S. Department of Energy, > %% under contracts DE-AC02-98-CH10886, DE-FG03-93-ER40773, > %% DE-FG03-96-ER40981, and DE-FG02-99-ER41121, > the Danish Natural Science Research Council, the Research Council of > Norway, the Polish State Committee for Scientific Research (KBN) > %%Grant > %%no. 5 P03B 015 21, the Korea Research Foundation, > and the Romanian > Ministry of Research. > %%(5003/1999,6077/2000). > We are grateful to Drs D. Kharzeev %%, BNL, and > E. Levin, %%Tel Aviv, > Zi-Wei Lin, and %%, Texas A\&M > H. Heiselberg for stimulating discussions and > %%for supplying us withthe > model calculations. %% shown and discussed in this article. > > \ifUseBibTeX > \bibliography{dndeta} > \else > \begin{thebibliography}{99} > %%Parton saturation. > \bibitem{partonsat83} L. V. Gribov, E. M. Levin and M. G. Ryskin, > Phys.Rep. {\bf 100} (1983) 1. > %% ``Centrality dependence of multiplicities in ultrarelativistic > nuclear collisions'' > \bibitem{Eskola00} K. J. Eskola, K. Kajantie and K. Tuominen, Phys. Lett. %% > {\bf B497}, 39 (2001). %; hep-ph/0009246. > \bibitem{Kharzeev_and_Levin} D. Kharzeev and E. Levin. nucl- th/0108006 > and private communication. % > %%jet quenching > \bibitem{Phenix-jets} K. Adcox {\it et al.}, subm. to Phys. Rev. Lett. > (2001), > nucl-ex/0109003. > \bibitem{Star-jets} > J. C. Dunlop {\it et al.}, %STAR Collaboration, > Nucl. Phys. {\bf A698} > 515c (2002), and > B. Lasiuk, Workshop on High $p_T$ phenomenen at RHIC, BNL (2002), > unpublished. > %, Nov. 2001 > % http://skipper.physics.sunysb.edu/highpt/lasiuk.ppt > %% > %% > %%Phobos dN/deta paper 2000 (56 and 130) > \bibitem{back00} B. B. Back {\it et al.}, Phys. Rev. Lett. {\bf 85}, > 3100 (2000). > %%STAR paper on mult at 130GeV > \bibitem{Star-mult130} C. Adler {\it et al.}, Phys. Rev Lett. {\bf 87}, > 112303 (2001) > %% > %%PHENIX dN/deta paper 130GeV > \bibitem{adcox01} K. Adcox {\it et al.}, Phys. Rev. Lett. {\bf 86}, 3500 > (2001). > %%BRAHMS mult 130 reference PLB > \bibitem{bearden01a} I. G. Bearden {\it et al.}, > Phys. Lett. B in press; nucl-ex/0108016. > % \bibitem{bearden01a} I. G. Bearden > {\it et al.}, accepted for pub in > % Phys. Lett. B.; nucl-ex/0108016. > %%Phobos 200 Gev mult at midrapidity 2001. subm to PRL > \bibitem{Phobos-mult200-1} B. B. Back {\it et al.}, submitted. to Phys. > Rev. Lett.(2001), nucl.exp/0108009. > %% > %%BRAHMS NIM reference > \bibitem{bearden01b} I. G. Bearden {\it et al.}, submitted to Nucl. > Inst. Meth A. > %%http://cyclotron.tamu.edu/hagel/BrahmsNimPaper.doc > %% > %%GEANT reference > \bibitem{Geant} GEANT 3.2.1, CERN program library. > %%ZDC reference > \bibitem{adler00} C. Adler, {\it et al.}, %A. Denisov, E. Garcia, M. > Murray, H. Stroebele and S. White, > Nucl. Inst. Meth., {\bf A470} 488 (2001). % nucl-ex/0008005. > %% > %% > %%SPS multiplicity > \bibitem{deines00} P. Deines-Jones {\it et al.} Phys. Rev. C {\bf 62}, > 014903(2000). %hep-ex/9912008. > %% > \bibitem{zhang01} Bin Zhang, C. M. Ko, Bao-An Li and Zi-wei Lin, > Phys. Rev. C {\bf 61} 067901 (2001). > \bibitem{lin01a} Zi-wei Lin, Subrata Pal, C. M. Ko, Bao-An Li and Bin > Zhang, % > Phys. Rev. C {\bf 64} 011902R (2001). > \bibitem{lin01b} Zi-wei Lin, Subrata Pal, C.M. Ko, Bao-An Li and Bin Zhang, > Nucl. Phys. {\bf A698} 375c-378c (2002), nucl-th/0105044; and Zi-wei > Lin, private communication. > %% p+p at 200 GeV > \bibitem{Alner86} G. J. Alner {\it et al.}, Zeit. Phys. {\bf 33}, 1 (1986). > %%Hijing Paper > \bibitem{wang91} X. N. Wang and M. Gyulasy, Phys. Rev. D {\bf 44}, 3501 > (1991). > %% > %%AMPT model > %% > \bibitem{Kharzeev_and_Nardi} D. Kharzeev and M. Nardi. > Phys. Lett. {\bf B507}, 121 (2001). %, nucl-th/0012025. > \end{thebibliography} > \fi > > \end{document} > > > > > > >
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