STAR STAR Andr Andr é é Mischke Mischke for the STAR Collaboration for the STAR Collaboration ICPAQGP, Kolkata, India, February 8-12, 2005 Recent Recent “high-p “high-p T T ” ” measurements measurements in STAR in STAR
Jan 13, 2016
STARSTAR
AndrAndréé Mischke Mischke
for the STAR Collaborationfor the STAR Collaboration
ICPAQGP, Kolkata, India, February 8-12, 2005
Recent Recent “high-p“high-pTT” measurements ” measurements
in STAR in STAR
Andre Mischke, Utrecht University CINPP 2005 2
STARSTAR
modified
modified
• High incident energy opens up hard scattering regime where High incident energy opens up hard scattering regime where pQCD pQCD is applicable in theoryis applicable in theory
• Hard scattered partons to probe the properties of the produced Hard scattered partons to probe the properties of the produced densedense colored mediumcolored medium
• High-pHigh-pTT (> 2 GeV/c) particle production (> 2 GeV/c) particle production p-p:p-p: - parton distribution function (PDF)- parton distribution function (PDF)
- hard scattering cross section- hard scattering cross section - fragmentation function (FF)- fragmentation function (FF)
A-A:A-A: - - modifiedmodified PDF PDF (e.g. shadowing)(e.g. shadowing) -- Cronin effect Cronin effect - hard scattering cross section- hard scattering cross section
-- partonic energy losspartonic energy loss (gluon radiation)(gluon radiation) - FF - FF softenedsoftened
• Measurable effects: medium-induced modification of jet FF Measurable effects: medium-induced modification of jet FF - suppression of high-p- suppression of high-pTT hadron production hadron production - jet broadening- jet broadening
High-pHigh-pTT probes at RHIC probes at RHIC
q q
q
qhadronic
partonic
q ?
Andre Mischke, Utrecht University CINPP 2005 3
STARSTAR
Central TriggerBarrel (CTB)
ZDC
Time Projection Chamber(TPC)
Barrel EMCal (BEMC)
Silicon Vertex Tracker (SVT)
Forward-TPC
Endcap EMCal (EEMC)
Time-of-Flight (TOF)
The STAR detectorThe STAR detectorNIM 499, 624 (2003)Solenoidal Tracker at RHIC
0
Andre Mischke, Utrecht University CINPP 2005 4
STARSTAR STAR results so farSTAR results so far
v2 {2-particle}v2 {AuAu – pp}v2 {4-particle}
• Au-Au collisions at Au-Au collisions at s=s=200 GeV:200 GeV:
- strong high-pstrong high-pTT particle particle
suppressionsuppression- disappearance of the away-side disappearance of the away-side
jetjet - large and saturated elliptic flowlarge and saturated elliptic flow
Consistent with the picture of Consistent with the picture of
parton parton
energy loss in the dense medium energy loss in the dense medium
(jet-quenching)(jet-quenching)
• d-Au measurementsd-Au measurements
Jet-quenching is an effect happens Jet-quenching is an effect happens
in in
the final state of the collisionthe final state of the collisionAndre Mischke, Utrecht University CINPP 2005 4
STARSTAR
PRL 91, 172302 PRL 91, 172302 (2003)(2003)PRL 91, 072304 PRL 91, 072304 (2003)(2003)PRL 90, 082302 PRL 90, 082302 (2003)(2003)PRL 93, 252301 PRL 93, 252301 (2004)(2004)
Andre Mischke, Utrecht University CINPP 2005 5
STARSTAR
00 ~2~2 ~6~6 ppTT(GeV/c)(GeV/c)
low-plow-pTT intermediate pintermediate pTT high-phigh-pTT
OutlineOutline• soft particle soft particle production:production: bulk matterbulk matter
• nuclear effectsnuclear effects• probe-mediumprobe-medium interplayinterplay
• “ “clean” jet fragmentationclean” jet fragmentation regime (pQCD)regime (pQCD)
VariablesVariables
• Incl. particle spectra (RIncl. particle spectra (RCPCP)) asymmetry in d-Au
identified particle
• Two-particle azimuthalTwo-particle azimuthal away-side hadrons
correlationcorrelation identified particle triggered
near-side
• Incident energy (62 GeV)Incident energy (62 GeV) charged hadron spectra
Andre Mischke, Utrecht University CINPP 2005 6
STARSTAR
• d-Au (p-p): pQCD works at high-pd-Au (p-p): pQCD works at high-pTT at RHIC at RHIC
• Study nuclear effects like Cronin and shadowing Study nuclear effects like Cronin and shadowing baseline baseline
for Au-Au for Au-Au • Significant Significant dependence at highest centrality bin dependence at highest centrality bin• Yields are well described by AMPT and saturation modelYields are well described by AMPT and saturation model
Pseudo-rapidity asymmetry andPseudo-rapidity asymmetry andcentrality dependence in d-Aucentrality dependence in d-Au
Pt spectra
AuAudd
PRC 70, 064907 PRC 70, 064907 (2004)(2004)h±
Andre Mischke, Utrecht University CINPP 2005 7
STARSTARCharged hadron yield asymmetry Charged hadron yield asymmetry in d-Auin d-Au
• Back(Au)-forward(d) asymmetry ratio for two Back(Au)-forward(d) asymmetry ratio for two
rangesranges
• Cronin effect more pronounced in Au-direction Cronin effect more pronounced in Au-direction
• In qualitatively agreement with predictions from In qualitatively agreement with predictions from
saturation and coalescencesaturation and coalescence
• Different trend for initial parton scattering model Different trend for initial parton scattering model
(Hijing)(Hijing)
PRC 70, 064907 PRC 70, 064907 (2004)(2004)
ppTT
-1-1 -0.5-0.5 0.50.5 1100
open symbolsopen symbolssolid symbolssolid symbols
off mid-rapidityoff mid-rapidity
at mid-rapidityat mid-rapidity
Andre Mischke, Utrecht University CINPP 2005 8
STARSTAR RRCPCP for for and K and K00ss in d-Au in d-Au
• Yields enhanced for pYields enhanced for pTT > 1 GeV/c > 1 GeV/c• Not dominated by jet fragmentation (expectation: one Not dominated by jet fragmentation (expectation: one curve curve for all particles)for all particles)• Different behavior for mesons and baryons Different behavior for mesons and baryons Cronin effect depending on quark content; initial or Cronin effect depending on quark content; initial or final ?final ?
STAR preliminary
peripheralbinperipheral
centralbincentral
CPNyield
NyieldR
/
/
Andre Mischke, Utrecht University CINPP 2005 9
STARSTAR Flavor dependence of Flavor dependence of particle spectra in Au-Auparticle spectra in Au-Au
• Suppression at high-pSuppression at high-pTT
• More significant meson-baryon pattern in More significant meson-baryon pattern in Au-Au Au-Au • Collective hadron production mechanism: Collective hadron production mechanism: quark quark recombination/coalescence recombination/coalescence
RCP
PRL 92, 052302 (2004)PRL 92, 052302 (2004)J.Phys. G30, S963 (2004)J.Phys. G30, S963 (2004)
expectations from expectations from jet fragmentationjet fragmentation
Andre Mischke, Utrecht University CINPP 2005 10
STARSTAR
• Correlate high-pCorrelate high-pTT trigger particlestrigger particles with with associated associated
particlesparticles above a certain kinematical threshold above a certain kinematical threshold• Define correlation function: probability to find Define correlation function: probability to find
another particle in (another particle in (, , ))• Advantage of the Advantage of the STAR detectorSTAR detector: large acceptance : large acceptance • Corrections for flow (v2) and non-flow Corrections for flow (v2) and non-flow
contributionscontributions
• Correlation variables: Correlation variables: - peak width (- peak width (,,))
- N- Nchch(asso.)(asso.)
• Method favored the selection of high-pMethod favored the selection of high-pTT trigger trigger
particle near the medium surfaceparticle near the medium surface
Jetlike correlations: Jetlike correlations: study two-particle angular study two-particle angular
distributiondistribution
Trigger: leading hadron
ppzz
pp
ppxx
ppyy
Trigger: leading hadron
Andre Mischke, Utrecht University CINPP 2005 11
STARSTAR
• Parton energy loss dependsParton energy loss depends on the path length traversedon the path length traversed
• Consistent with jet-quenching Consistent with jet-quenching picture: picture: E E ss½qL½qL22
• Crosscheck at higher pCrosscheck at higher pTT
in-plane
out-of-plane
PRL 93, 252301 (2004)
correlation distribution wrt. to correlation distribution wrt. to the reaction plane in Au-Authe reaction plane in Au-Au
4 < pT(trig.) < 6 GeV/c 2 GeV/c< pT(asso.) < pT(trig.)
Andre Mischke, Utrecht University CINPP 2005 12
STARSTAR Identified particle Identified particle correlations: correlations: and K and K00
s s in d-Auin d-Au
• Integrated yields of correlation Integrated yields of correlation peakspeaks
• Comparable to PHENIX Comparable to PHENIX
measurements measurements
• Associated charged hadron Associated charged hadron
multiplicity similar for meson multiplicity similar for meson
and baryon triggersand baryon triggers
• No significant flavor dependence No significant flavor dependence
at intermediate pat intermediate pTT
||ηη|<0.7|<0.7
preliminary
<Npart>
Andre Mischke, Utrecht University CINPP 2005 13
STARSTAR Away-side associate charged Away-side associate charged hadrons: low-phadrons: low-pTT part part
• Observation so far: back–to-back jets Observation so far: back–to-back jets
disappear for pdisappear for pTT(asso.) > 2 GeV/c(asso.) > 2 GeV/c
• For lower pFor lower pTT(asso.) threshold: (asso.) threshold:
- correlation widely dispersed- correlation widely dispersed
- momentum balance shape- momentum balance shape
- higher fragmentation multiplicity- higher fragmentation multiplicity
- p- pTT distribution softened distribution softened
• Indication for thermal equilibrationIndication for thermal equilibration
of the away-side fragmentation of the away-side fragmentation
products with the bulk mediumproducts with the bulk medium
nucl-ex/0501016
STAR preliminary
4 < pT(trig.) < 6 GeV/c
0.15<pT(asso.)<4 GeV/c
Andre Mischke, Utrecht University CINPP 2005 14
STARSTAR near-side correlationsnear-side correlations
• In central Au-Au: In central Au-Au:
- jet-like correlation (short range) - jet-like correlation (short range)
sits on top of a wide, nearly flat sits on top of a wide, nearly flat
correlation (long range)correlation (long range)
- evidence for near-side jet - evidence for near-side jet
broadening in broadening in direction direction
d+Au, 40-100%
Au+Au, 0-5%
STAR preliminary
3 < pT(trig.) < 6 GeV/c2 < pT(asso.) < pT(trig.)
Andre Mischke, Utrecht University CINPP 2005 15
STARSTAR near-side correlations (cont’d)near-side correlations (cont’d)
• Significant broadening at low pSignificant broadening at low pTT(trig.), (trig.),
disappears with increasing pdisappears with increasing pTT(trig.)(trig.)
• NNchch(asso.) invariant with collision system (asso.) invariant with collision system • Interpretation: - Recombination effects ?Interpretation: - Recombination effects ?
- Interplay of - Interplay of medium-induced medium-induced gluon radiation gluon radiation and collective and collective longitudinal flow ?longitudinal flow ?
correlation width
Armesto et al., Armesto et al., PRL93, 242301 PRL93, 242301 (2004) (2004) S.A. Voloshin, nucl-th/0312065S.A. Voloshin, nucl-th/0312065
STAR preliminarySTAR preliminary correlated yield
3 < pT(trig.) < 4 GeV/c2 < pT(asso.) < pT(trig.)
|| < 1.0
Andre Mischke, Utrecht University CINPP 2005 16
STARSTARInclusive charged hadron spectra Inclusive charged hadron spectra in 62 GeV Au-Au in 62 GeV Au-Au
• High-pHigh-pTT absolute yield one order absolute yield one order
of magnitude lowerof magnitude lower
• Spectrum shapes similar to 200GeVSpectrum shapes similar to 200GeV
• RRAAAA~1 at SPS. What happens ~1 at SPS. What happens
at at
intermediate energies ? intermediate energies ?
• More quark jets expected at More quark jets expected at
62 GeV62 GeV less suppression less suppression
• Energy dependence of the Energy dependence of the
suppression factorsuppression factor
Andre Mischke, Utrecht University CINPP 2005 17
STARSTAR RRCPCP in 62 GeV Au-Au in 62 GeV Au-Au
• Same pSame pTT threshold for both threshold for both
energiesenergies
• Splitting at intermediate pSplitting at intermediate pTT
(due to Cronin effect ?)(due to Cronin effect ?)
• High-pHigh-pTT suppression at 62 suppression at 62
GeV GeV similar to 200 GeVsimilar to 200 GeV
• High-pHigh-pTT part (>6 GeV) part (>6 GeV)
suggest suggest that suppression is driven that suppression is driven by by nuclear geometrynuclear geometry
RCP
Andre Mischke, Utrecht University CINPP 2005 18
STARSTAR correlations in 62 GeV Au-Aucorrelations in 62 GeV Au-Au
• Near-side associated yields are reduced (factor of ~3) at 62 GeV Near-side associated yields are reduced (factor of ~3) at 62 GeV
• Similar suppression of the away-side correlation Similar suppression of the away-side correlation
preliminary
Andre Mischke, Utrecht University CINPP 2005 19
STARSTAR Particle production rangesParticle production ranges
• soft particle soft particle production:production: bulk matterbulk matter
• nuclear effectsnuclear effects• probe mediumprobe medium interplayinterplay
• “ “clean” jet fragmentationclean” jet fragmentation regime (pQCD)regime (pQCD)
VariablesVariables
• Incl. particle spectra (RIncl. particle spectra (RCPCP) ) asymmetry in d-Au
identified particle
• Two-particle azimuthal Two-particle azimuthal away-side hadrons
correlationcorrelation identified particle triggered
near-side
• Incident energy (62 GeV)Incident energy (62 GeV) charged hadron spectra
00 ~2~2 ~6~6 ppTT(GeV/c)(GeV/c)
low-plow-pTT intermediate pintermediate pTT high-phigh-pTT
Andre Mischke, Utrecht University CINPP 2005 20
STARSTAR
• Barrel-EMCalBarrel-EMCal- ||||1 and full azimuthal coverage1 and full azimuthal coverage
- EETT spectra: PRC 70, 054907 (2004) spectra: PRC 70, 054907 (2004)
Neutral pions in d-AuNeutral pions in d-Aunucl-ex/nucl-ex/04100320410032
see poster by R. Sahoo
0
=pT/2, pT and 2pT
0<<1
• First hadron measurement First hadron measurement
with with
BEMCBEMC- 10% normalization uncertainty10% normalization uncertainty- NLO pQCD calculations, NLO pQCD calculations, W. W.
Vogelsang Vogelsang
- Reasonable agreement within Reasonable agreement within
errorserrors- Lower the systematic errors, Lower the systematic errors,
work in progress work in progress
Andre Mischke, Utrecht University CINPP 2005 21
STARSTAR
• Trigger on high-ETrigger on high-ETT photons measured in the Barrel-EMCal photons measured in the Barrel-EMCal
• EETT(trig.) up to 11 GeV (Au-Au: up to 20 GeV/c) (trig.) up to 11 GeV (Au-Au: up to 20 GeV/c)
Photon - charged hadron Photon - charged hadron azimuthal correlation in 200 GeV d-Au azimuthal correlation in 200 GeV d-Au
preliminary
see poster by S. Chattopadhyay
Andre Mischke, Utrecht University CINPP 2005 22
STARSTAR ““The overall picture”The overall picture”• d-Au provides essential information for deeper understanding d-Au provides essential information for deeper understanding of the underlying mechanismsof the underlying mechanisms in Au-Au in Au-Au
• Baryon-meson pattern present in d-Au and Au-Au (due to quark Baryon-meson pattern present in d-Au and Au-Au (due to quark coalescence ?)coalescence ?)
• Near-side correlations:Near-side correlations: - - : similar for p-p, d-Au and Au-Au: similar for p-p, d-Au and Au-Au - - : interplay between parton energy loss and collective flow: interplay between parton energy loss and collective flow
• Away-side correlation:Away-side correlation: - jets traverse through the produced dense medium - jets traverse through the produced dense medium - associate hadrons appear at low-p- associate hadrons appear at low-pTT
- first indications of thermal equilibration with the bulk matter- first indications of thermal equilibration with the bulk matter
• High-pHigh-pTT hadron suppression similar in 62 and 200 GeV hadron suppression similar in 62 and 200 GeV
Suppression seems to be driven by nuclear geometrySuppression seems to be driven by nuclear geometry
Andre Mischke, Utrecht University CINPP 2005 23
STARSTAR Future challengesFuture challengesSTAR white paper, STAR white paper, nucl-ex/0501009nucl-ex/0501009
• Identified particle spectra at still higher pIdentified particle spectra at still higher pTT to see where to see where pQCD pQCD becomes dominantbecomes dominant high statistic data set: run IV at 200 GeV, analysis high statistic data set: run IV at 200 GeV, analysis underwayunderway
• d-Au analysis at higher pd-Au analysis at higher pTT for deeper understanding of the for deeper understanding of the underlying mechanismsunderlying mechanisms (e.g. initial and final Cronin effect) (e.g. initial and final Cronin effect) identified particle spectra, e.g. neutral pions identified particle spectra, e.g. neutral pions • Evolution of jet quenching effectEvolution of jet quenching effect system size (geometric scaling uncertainties): Cu-Cu system size (geometric scaling uncertainties): Cu-Cu (run V, (run V, data taking right now) vs. peripheral Au-Audata taking right now) vs. peripheral Au-Au energy: range mapping between top SPS and 62 GeVenergy: range mapping between top SPS and 62 GeV
• More details on the modification of the FF are needed, e.g. More details on the modification of the FF are needed, e.g. quantification of partonic energy lossquantification of partonic energy loss direct photon tag direct photon tag heavy quark tag (discrimination between quark and heavy quark tag (discrimination between quark and gluon jets)gluon jets)
Andre Mischke, Utrecht University CINPP 2005 24
STARSTAR
49 institutes from 13 countries, 522 49 institutes from 13 countries, 522 participantsparticipants
The STAR CollaborationThe STAR Collaboration
Andre Mischke, Utrecht University CINPP 2005 26
STARSTAR
• Neutral pion pNeutral pion pTT
measurement up measurement up to 13-16 GeV/cto 13-16 GeV/c
• Agreement with Agreement with
PHENIX PHENIX measurementmeasurement
within 10%within 10%
PHENIX data: PRL 91, 072303 (2003)PHENIX data: PRL 91, 072303 (2003)
0 0 transverse masstransverse mass spectrum spectrum
Andre Mischke, Utrecht University CINPP 2005 27
STARSTAR Nuclear modification factor RNuclear modification factor RAAAA
in 62 GeV Au-Au in 62 GeV Au-Au
• p-p reference data from p-p reference data from ISRISR (25-30% uncertainties)(25-30% uncertainties)
• Same pSame pTT threshold for threshold for bothboth energiesenergies
Andre Mischke, Utrecht University CINPP 2005 28
STARSTARInclusive hadron spectra in Au-Au Inclusive hadron spectra in Au-Au
Andre Mischke, Utrecht University CINPP 2005 29
STARSTAR
Compiled references: π0, h±
62 GeV data: p-p reference62 GeV data: p-p reference
Andre Mischke, Utrecht University CINPP 2005 30
STARSTAR Azimuthal anisotropy at 62 GeV Azimuthal anisotropy at 62 GeV publication in preparationpublication in preparation
Similar pSimilar pTT dependence v dependence v22
for 62 GeV to 200GeVfor 62 GeV to 200GeV
solid colored symbols: 62 GeVopen symbols: 200 GeV
two- (squares) and four- particle (triangles) culumant method
Andre Mischke, Utrecht University CINPP 2005 31
STARSTAR
Away
syst. error
Near
4 < pT(trig.) < 6 GeV/c0.15 < pT(asso.) < 4 GeV/c
Andre Mischke, Utrecht University CINPP 2005 32
STARSTARIdentified strange particles in d-AuIdentified strange particles in d-Au
STAR preliminary
Yields measured up to (mYields measured up to (mTT-m-m00) ~ 5 GeV/c vs. centrality) ~ 5 GeV/c vs. centrality
Andre Mischke, Utrecht University CINPP 2005 33
STARSTAR
• Systematic studies underway with , K0s as trig, assoc. particles
h-Λh-Λ
pt (trig
)
K0s-hh-h
STAR preliminary
d+Au200 GeV
Andre Mischke, Utrecht University CINPP 2005 34
STARSTAR
1.5 < pT(trig) < 3 GeV1.5 < pT(assoc) < 3 GeV
(0-5)% (10-30)%
(30-50)% (50-70)% p+p
(5-10)%
Au+Au200 GeV
STAR preliminary
h-Λ
Andre Mischke, Utrecht University ICPAQGP 2005 35
STARSTAR
~ jet cone width
~ jet co-planarity
• Width of near- and away-side peak decreases slightly with EWidth of near- and away-side peak decreases slightly with ETT(trig.)(trig.)
• <j<jTT> stays constant; > stays constant; <k<kTT22> saturates at high-E> saturates at high-ETT
Photon- and charged-charged Photon- and charged-charged azimuthal correlation in 200 GeV d-Au azimuthal correlation in 200 GeV d-Au
STAR preliminary
Andre Mischke, Utrecht University CINPP 2005 36
STARSTARAzimuthal anisotropy in 200GeV Au-AuAzimuthal anisotropy in 200GeV Au-Au
In central Au-Au collisions, azimuthal In central Au-Au collisions, azimuthal anisotropy at high-panisotropy at high-pTT (>5 GeV/c) dominated (>5 GeV/c) dominated
by non-flow effectsby non-flow effects
Multiplicity independent quantity
PRL 93, 252301 (2004)