cipanp '03jets and high pt hadrons in star1 jets and high p t hadrons: results from star peter...
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CIPANP '03 Jets and high pT hadrons in STAR 1
Jets and high pT hadrons: results from STARPeter Jacobs
Lawrence Berkeley National LaboratorySTAR Collaboration
• Au+Au at 200 GeV:• inclusive hadron distributions
confrontation with theory• two-particle correlations
• first results from d+Au
STARSTAR
Other STAR high pT talks:A.Tang: Anisotropic Flow (Session 4, Thurs.)M. Miller: High pT correlations (Session 6, Fri.)J. Klay: High pT spectra (Session 6, Fri.)
CIPANP '03 Jets and high pT hadrons in STAR 2
E-M Calorimeter
Time of Flight
Projection Chamber
STAR
CIPANP '03 Jets and high pT hadrons in STAR 3
Partonic energy loss in dense matter
Thick plasma (Baier et al.):
glueSglue
Debye
sRBDMS
q
vLqC
E
2
2
ˆ
~ˆ4
Strong dependence of energy loss on gluon density gluemeasure color charge density at early hot, dense phase
Gluon bremsstrahlung
Thin plasma (GLV, WW):
32
2( , ( )) jet
A a s glue
EE C C d r Log
L
CIPANP '03 Jets and high pT hadrons in STAR 4
Jets at RHIC
p+p jet+jet (STAR@RHIC)
Au+Au ??? (STAR@RHIC)
nucleon nucleonparton
jet
Find this……….in this
CIPANP '03 Jets and high pT hadrons in STAR 5
Jet energy loss via leading hadrons
-
Wang and Gyulassy: partonic energy loss effective softening of fragmentation suppression of leading hadron yield
CIPANP '03 Jets and high pT hadrons in STAR 6
Au+Au and p+p: inclusive charged hadrons
STAR PRL 89, 202301 nucl-ex/0305015
p+p spectrum measured at RHIC
CIPANP '03 Jets and high pT hadrons in STAR 7
Measuring hadron suppression
ddpdT
ddpNdpR
TNN
AA
TAA
TAA /
/)(
2
2
<Nbinary>/inelp+p
p+p cross section
1. Au+Au yield relative to binary-scaled nucleon-nucleon cross section:
2. Au+Au central/peripheral yields scaled by <Nbinary>
Nuclear geometry via Glauber model <Nbinary>
CIPANP '03 Jets and high pT hadrons in STAR 8
Au+Au relative to measured p+p
ddpdT
ddpNdpR
TNN
AA
TAA
TAA /
/)(
2
2
Central collisions: factor ~4-5 suppression
nucl-ex/0305015
CIPANP '03 Jets and high pT hadrons in STAR 9
Binary-scaled central/peripheral
• central collisions: factor ~4-5 suppression • pT>5 GeV/c: suppression ~ independent of pT
nucl-ex/0305015
CIPANP '03 Jets and high pT hadrons in STAR 10
Central/peripheral: dependence on particle species
STAR preliminary
• 1.5<pT<3.5 GeV/c: scales ~Nbinary, K0s suppressed
• pT~ 6 GeV/c: , K0s, charged hadrons scale similarly
• “baryon enhancement”: partonic flow? modified fragmentation? Cronin effect? …
CIPANP '03 Jets and high pT hadrons in STAR 11
Jets and two-particle correlations
p+p dijet
Two-particle azimuthal correlations:
• select highest pT track
• distribution of other tracks (pT>2 GeV/c) in the event
• normalize to # of triggers …
CIPANP '03 Jets and high pT hadrons in STAR 12
High pT correlations: Au+Au vs p+pPRL 90, 082302 (2003)
Central Au + Au
Peripheral Au + Au
Back-to-back jets are suppressed in central collisions
22 2 2( ) ( ) (1 cos(2 ))D Au Au D p p B v
near side
away side
peripheral central
CIPANP '03 Jets and high pT hadrons in STAR 13
Theory vs. Data pQCD-I: Wang, nucl-th/0305010pQCD-II: Vitev and Gyulassy, PRL 89, 252301Saturation: KLM, Phys Lett B561, 93
pT>5 GeV/c: well described by saturation model (up to 60% central) and pQCD+jet quenching
nucl-ex/0305015
CIPANP '03 Jets and high pT hadrons in STAR 14
Do we see jet quenching?
• Independent of particular model calculations:
Can we distinguish experimentally between initial and final state effects? measure partonic energy loss
• d+Au at 200 GeV: high pT hadrons
• 2-particle correlations: back-to-back jets observed?
• inclusive yield relative to p+p: enhancement (pQCD+Cronin) or suppression (saturation)?
CIPANP '03 Jets and high pT hadrons in STAR 15
d+Au centrality tagging
ZDCW
FTPCE
Au d
1. Neutron spectator from deuteron:• Observed via single neutron in ZDCW • Measured to be 20% of minbias • Glauber w/ Hulthen wavefn: also 20% of minbias
peripheral events2. Forward charged particle multiplicity (Au direction):
• FTPCE: -3.8<<-2.8
CIPANP '03 Jets and high pT hadrons in STAR 16
d+Au centrality tagging cont’d
• quantitative study in progress <Nbinary>• for now: use FTPCE multiplicity to bias towards central events
Cross check: FTPCE multiplicity for ZDCW peripheral events
strong correlation across 8 rapidity units
FTPCE mult sensitive to collision geometry
uncorrected FTPCE multiplicity
minbiasZDCW
peripheral
20% “central”
CIPANP '03 Jets and high pT hadrons in STAR 17
d+Au: two-particle correlations
• no normalization to underlying event
• “central”: top 20% FTPCE multiplicity
• near-side: correlation strength and width similar• underlying event grows: p+p d+Au minbias d+Au central•away-side: d+Au peak broadens but little centrality dependence
Back-to-back jets are observed in central d+Au
CIPANP '03 Jets and high pT hadrons in STAR 18
d+Au: minbias charged hadron yield
• compatible with expectations from Cronin enhancement• to do: centrality dependence
Charged hadron yield is enhanced in minbias d+Au
2
2
/
/
2 197
2.2
dAuT
dAu ppdAu T
dAu
d N dp dR
T d dp d
Tb
CIPANP '03 Jets and high pT hadrons in STAR 19
Summary
central Au+Au
Binary-scaled inclusive hadron yield:strong suppression central Au+Aumodest enhancement in minbias d+Au
Back-to-back jets:strong suppression central Au+Auno suppression in minbias and central d+Au
CIPANP '03 Jets and high pT hadrons in STAR 20
• Are initial state effects excluded as the dominant mechanisms of strong hadron suppression in heavy ion collisions?
• If so, have we therefore measured large partonic energy loss in very dense matter?
CIPANP '03 Jets and high pT hadrons in STAR 21
Russia:MEPHI - MoscowLPP/LHE JINR - DubnaIHEP - Protvino
U.S. Laboratories:ArgonneBerkeleyBrookhaven
U.S. Universities: Arkansas UniversityUC BerkeleyUC DavisUC Los AngelesCarnegie Mellon UniversityCreighton UniversityIndiana UniversityKent State UniversityMichigan State UniversityCity College of New YorkOhio State UniversityPenn. State UniversityPurdue UniversityRice UniversityTexas A&MUT AustinWashington UniversityWayne State UniversityYale University
Brazil: Universidade de Sao Paulo
China: IHEP – BeijingIMP - LanzouIPP – WuhanUSTCSINR – ShanghaiTsinghua University
Great Britain: University of Birmingham
France:IReS StrasbourgSUBATECH - Nantes
Germany: MPI – MunichUniversity of Frankfurt
India:IOP - BhubaneswarVECC - CalcuttaPanjab UniversityUniversity of RajasthanJammu UniversityIIT - BombayVECC – Kolcata
Poland:Warsaw University of Tech.
The STAR Collaboration
CIPANP '03 Jets and high pT hadrons in STAR 22
Extra slides
CIPANP '03 Jets and high pT hadrons in STAR 23
Theory vs data IILietava, Pisut, Pisutova and Tomasik, Eur. Phys. J. C28, 119
• similar pT dependence also expected from hadronic formation time effects (Gallmeister, Greiner and Xu, hep-ph/0212295)
Jet attenuation in cold matter