Post on 20-Jan-2016
description
Charged Particle Charged Particle Multiplicities from Multiplicities from
Cu+Cu, Au+Au and Cu+Cu, Au+Au and d+Au Collisions at RHICd+Au Collisions at RHIC
Aneta IordanovaAneta Iordanova
University of Illinois at ChicagoUniversity of Illinois at Chicago
for the collaborationfor the collaboration
22DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Phobos CollaborationPhobos Collaboration
Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard
Bindel,
Wit Busza (Spokesperson), Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Joshua
Hamblen, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta
Iordanova, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey,
Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Christof
Roland, Gunther Roland, Joe Sagerer, Peter Steinberg, George Stephans, Andrei Sukhanov,
Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter
Walters, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Bolek Wysłouch
ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORYINSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY
NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGOUNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER
33DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
PHOBOS detector
44DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
OutlineOutline
Control parameters of a heavy ion collisionControl parameters of a heavy ion collision EnergyEnergy
19.6 - 200 GeV19.6 - 200 GeV Colliding system sizeColliding system size
centrality Ncentrality Npartpart from 3.5 (d+Au) – 360 (Au+Au) from 3.5 (d+Au) – 360 (Au+Au) SpeciesSpecies
p+p, d+Au, Cu+Cu and Au+Aup+p, d+Au, Cu+Cu and Au+Au
Global features of charged particle production Global features of charged particle production (observables)(observables) dNdNchch/d/d shapes (particle distributions in shapes (particle distributions in )) Mid-rapidity factorizationMid-rapidity factorization
DataData
comparison of Au+Au and Cu+Cucomparison of Au+Au and Cu+Cu
d+Au and p+pd+Au and p+p
66DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
d+Au
Charged hadron dNCharged hadron dNchch/d/d distribution distribution
centrality
Au+Au : PRL 91, 052303 (2003) Au+Au : PRC 74, 021901 (2006) d+Au : PRC 72, 031901 (2005)
19.6 GeV 62.4 GeV 130 GeV 200 GeV
dN/d distribution
preliminary preliminary
Au
+A
u d
ata
Cu
+C
u d
ata
With energy:With energy: Height increasesHeight increases Width increases (in Width increases (in space) space)
With centrality(0-50% central):With centrality(0-50% central): Height increasesHeight increases
With species:With species: Same systematic trendsSame systematic trends
77DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Comparison of Au+Au and Cu+CuComparison of Au+Au and Cu+Cu
For the same For the same collision system collision system size (Nsize (Npartpart) dN) dNchch/d/d
shape is very shape is very similar forsimilar for central Cu+Cu with central Cu+Cu with
mid-central Au+Au mid-central Au+Au collisionscollisions
mid-central Cu+Cu mid-central Cu+Cu with peripheral with peripheral Au+Au collisionsAu+Au collisions
200 GeV
Cu+CuPreliminary
3-6%, Npart = 100
central
Au+Au35-40%, Npart = 99
dN/d distribution
Cu+CuPreliminary
15-25%, Npart = 61Au+Au45-55%, Npart = 56
midcentral
88DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Comparison of Au+Au, d+Au and Comparison of Au+Au, d+Au and p+p collisions at 200 GeVp+p collisions at 200 GeV
Scale by NScale by Npartpart/2/2 allows for a direct allows for a direct
comparison to p+pcomparison to p+p i.e. normalized to 1 i.e. normalized to 1
participating pairparticipating pair
Multiplicity obtained at the Multiplicity obtained at the same center-of-mass same center-of-mass energy is similar in p+p energy is similar in p+p and d+Auand d+Au
Multiplicity is larger for Multiplicity is larger for Au+Au collisions at the Au+Au collisions at the same energysame energy
All at √s = 200 GeV
dN/d distribution
d+Au : PRL 93, 082301 (2004)
99DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Comparison of d+Au and p+pComparison of d+Au and p+p
More detailed More detailed comparison of d+Au comparison of d+Au and p+p showsand p+p shows More peripheral More peripheral
collisions tend toward collisions tend toward p+p shapep+p shape
dN/d distribution
2
dN
ch
Npa
rt
dη
-6 -4 -2 0 2 4 6 η
PHOBOS d+Au and p+pData at √s = 200 GeV
0
1
2
3
d+Au : PRC 72, 031901 (2005)p+p : 2004 J.Phys.G 30 S1133-1137
factorizationfactorization
at midrapidityat midrapidity
in energy and centralityin energy and centrality
1111DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Au+Au
PHOBOS
Cu+Cupreliminary
Au+Au
PHOBOS
200 GeV (UA5)
90 % C.L.
19.6 and 62.4 GeV (ISR)
Mid-rapidity factorization
Measured pseudorapidity density per Measured pseudorapidity density per participant pair as a function of Nparticipant pair as a function of Npartpart
0-50% cross-section0-50% cross-section
Mid-rapidity dNMid-rapidity dNchch/d/d Information about the Information about the
created matter →energy created matter →energy densitydensity
Particle production in Particle production in A+A: interplay between A+A: interplay between collision centrality collision centrality (geometry) and collision (geometry) and collision energy?energy?
balance of binary/soft balance of binary/soft processesprocesses
Au+Au : PRC 74, 021901 (2006)
1212DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Midrapidity RatiosMidrapidity Ratios
200/19.6
200/62.4
200/130Cu+Cupreliminary
Au+Au
PHOBOS
HIJING
Saturation
Data ratio 200/X Data ratio 200/X no centrality (geometry) no centrality (geometry)
dependencedependence
Models Models HIJING HIJING
disagrees with datadisagrees with data
Saturation Model Saturation Model (KLN) (KLN)
flat centrality flat centrality dependence as in datadependence as in data
Mid-rapidity factorization
KLN
HIJING:Comput.Phys.Commun. 83 (1994) 307,v 1.35KLN: Phys.Lett.B523 79 (2001) & arXiv:hep-ph/0111315
Au+Au : PRC 74, 021901 (2006)
factorizationfactorization
at midrapidityat midrapidity
versus pversus pTT
1414DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Transverse Momentum Transverse Momentum FactorizationFactorization
So far discussed So far discussed factorization of bulk factorization of bulk mattermatter ~p~pTT<1GeV/c<1GeV/c
Can look at Can look at differential differential factorization for pfactorization for pTT
binsbins
pT factorization
1515DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Au+AuCu+Cu
Au+Au: PRL 94, 082304 (2005)
<pT> = 0.25 GeV/c <pT> = 1.25 GeV/c <pT> = 2.5 GeV/c <pT> = 3.38 GeV/c <pT> = 3.88 GeV/c
Ratio of charged hadron yields inRatio of charged hadron yields in 200 and 62.4 GeV 200 and 62.4 GeV factorization up to pfactorization up to pTT ≈ 4 GeV/c for N ≈ 4 GeV/c for Npartpart > 40 > 40
pT factorization
Transverse Momentum Transverse Momentum FactorizationFactorization
1616DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
SummarySummaryPHOBOS has measured multiplicity forPHOBOS has measured multiplicity for
large systematic dataset large systematic dataset -5.4<η<5.4-5.4<η<5.4 2 to 360 participants2 to 360 participants √√s = 19.6 to 200 GeVs = 19.6 to 200 GeV
Au+Au and Cu+Cu data are similar at the same NAu+Au and Cu+Cu data are similar at the same Npartpart
Scaling and factorization properties are found in the Au+Au Scaling and factorization properties are found in the Au+Au datadata
extended longitudinal scalingextended longitudinal scaling mid-rapidity factorization in bulk yield and versus pmid-rapidity factorization in bulk yield and versus pTT seem to persist into the Cu+Cu collision systemseem to persist into the Cu+Cu collision system
Observed factorization in energy and centrality is seen in Observed factorization in energy and centrality is seen in multiplicity and versus pmultiplicity and versus pTT
implies that this is set at an early stage of the collision and is implies that this is set at an early stage of the collision and is connected with the geometry of the collisionconnected with the geometry of the collision
The EndThe End
1818DNP, Nashville, 28 Oct 200DNP, Nashville, 28 Oct 20066
Aneta Iordanova Aneta Iordanova
Ratio of yield forRatio of yield for 200 and 62.4 GeV is centrality 200 and 62.4 GeV is centrality independent for all measured pindependent for all measured pTT bins bins
Transverse Momentum Transverse Momentum FactorizationFactorization
pT factorization
Data from PRL 94, 082304 (2005)