Partha Pratim Bhaduri Subhasis Chattopadhyay VECC, Kolkata
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Transcript of Partha Pratim Bhaduri Subhasis Chattopadhyay VECC, Kolkata
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Differential elliptic flow of identified hadrons & number of constituent quark
(NCQ) scaling at FAIR
Partha Pratim Bhaduri
Subhasis Chattopadhyay
VECC, Kolkata
Over past two decades, relativistic heavy-ion collision experiments are performed around the world; ultimate aim is to map the QCD phase diagram & to discover the new state of QCD matter the Quark Gluon Plasma (QGP).
The Compressed Baryonic Matter (CBM) experiment at FAIR : exploration of the QCD phase diagram at high net baryon densities and moderate temperatures. EL = 10 – 40 GeV/n.
Main challenge is to predict unambiguous & experimentally viable probes to indicate the formation of dense partonic medium.
Collective flow of the produced particles in the transverse plane of the collision signature of the creation of thermalized matter nuclear collisions.
Of particular interest is the elliptic flow parameter (v2) ; signals a strong evidence for the creation of a hot & dense system at a very early stage in the non-central collisions.
Introduction
M. Oldenburg 3
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● non-central collisions: azimuthal anisotropy in coordinate-space● interactions asymmetry in momentum-space● sensitive to early time in the system’s evolution
● Measurement: Fourier expansion of the azimuth particle distribution
Elliptic flow v2
...)2cos2cos21(2
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vv
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dN 12 cos 2 , tan ( )y
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v2 (pT) : Differential elliptic flow
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Elliptic Flow at RHIC
• A large elliptic flow is found for identified hadrons• Data is well described by hydrodynamics in low pT region.• Hydrodynamic mass ordering at low pT (pT<= 1.5 GeV/c)• Baryon-Meson crossing at intermediate pT (1.5 < pT < 5 GeV/c)• NCQ scaling
Recombination Extended to Elliptic Flow
Number of constituent quark (NCQ) scaling
For hadron formation by
coalescenc e or recombination of partons
v2
meson pT
2 v2
quark pT
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v2
baryon pT
3 v2
quark pT
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NCQ scaling in KENCQ scaling in KETT /n /n
KET = mT – m0
mT2 = pT
2 + m02
Excellent KET/n scaling for the full measured range Contrast to pT scaling
Models used for the study :
1. UrQMD (hadronic transport model)2. AMPT - string melting (partonic transport model)
3. AMPT- default (hadronic transport model)
System : Au + AuEnergy : EL = 25 GeV/n & 40 GeV/nImpact parameter : b = 5 - 9 fm.
What we have done:1. To study the differential elliptic flow of identified hadrons in the FAIR energy regime.
2. To test the NCQ scaling of v2 of identified hadrons .
Hydrodynamic mass ordering at low pT
Baryon-Meson crossing at high pT
Differential elliptic flow at top (40A GeV) & intermediate (25A GeV) FAIR energies
Elliptic Flow : comparison of different models
Partonic scatterings enhance the flow
Accepted for publication in PRC
Constituent Quark Number Scaling
No reasonable NCQ scaling in pT over the investigated pT range Ruling out of recombination picture ?
Accepted for publication in PRC
Transverse Kinetic Energy (KET = mT – m0) scaling
Remarkable scaling behaviour by UrQMD (hadronic) & AMPT with string melting (partonic)
Accepted for publication in PRC
Summary
• Observations at FAIR are quite in-line with the elliptic flow measurements at RHIC. Hadron mass ordering at low pT ; switch over at high pT.
• Partonic scattering enhances the flow.
• No, reasonable NCQ scaling is found in pT , over the investigated pT range
• Remarkable scaling is found with respect to KET by both UrQMD & string melting version of AMPT.
• Insensitive to distinguish between hadronic & partonic phase.
• Relative values of v2 might serve as a better observable at FAIR to indicate the formation of a partonic medium .
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Thank you
Back Ups
Observations
• However a remarkable scaling behavior is indeed found with respect to KET by both UrQMD & string melting version of AMPT.
• This can be attributed to hydrodynamic mass scaling
• The degree of scaling seems to be better for UrQMD than AMPT.
• Observation of NCQ scaling w.r.t KET by both hadronic & partonic model makes this observable rather insensitive to indicate the formation of partonic matter at FAIR.
• If at all, a universal scaling behavior of elliptic flow is observed at RHIC, whether it should be interpreted as a signature of color de-confinement is still a debated issue.
• Relative values of v2 might serve as a better observable.
Comparison with existing data (NA49)
AMPT with string-melting slightly over estimates the flow UrQMD & default AMPT under estimates the flow at high pT
Large error bar in the data !! No conclusive picture
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Why Elliptic Flow ?
• The probe for early time– The dense nuclear overlap is
ellipsoid at the beginning of heavy ion collisions
– Pressure gradient is largest in the shortest direction of the ellipsoid
– The initial spatial anisotropy evolves (via interactions and
density gradients ) Momentum-space anisotropy
– Signal is self-quenching with time
React
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dN
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2 π1 2 v
1cos Ï• 2 v
2cos 2 Ï• . . . 1
2 cos 2 , tan ( )y
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Coordinate-SpaceAnisotropy
Momentum-SpaceAnisotropy
Elliptic flow v2
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Why Elliptic Flow ?
• The probe for early time– The dense nuclear overlap is
ellipsoid at the beginning of heavy ion collisions
– Pressure gradient is largest in the shortest direction of the ellipsoid
– The initial spatial anisotropy evolves (via interactions and
density gradients ) Momentum-space anisotropy
– Signal is self-quenching with time
React
ion
plan
e
X
Z
Y
Px
Py Pz
dN
dÏ •
1
2 π1 2 v
1cos Ï• 2 v
2cos 2 Ï• . . . 1
2 cos 2 , tan ( )y
x
pv
p
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Why Elliptic Flow ?
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Interactions among the produced particles lead to pressure gradients which generate an azimuthal anisotropy in particle emission or elliptic flow, measured by v2, from which can be obtained valuable information about the early dynamics after the collision
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Spatial anisotropy Momentum anisotropy
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Resent PHENIX Elliptic Flow Data
Detailed differential measurements now available for π, K, p, φ, d, D
22Substantial elliptic flowSubstantial elliptic flow signals are observed for a variety signals are observed for a variety
of particle species at RHIC. Indication of of particle species at RHIC. Indication of rapid rapid thermalizationthermalization? ?
RHIC Elliptic Flow Data
23Substantial elliptic flowSubstantial elliptic flow signals are observed for a variety signals are observed for a variety
of particle species at RHIC. Indication of of particle species at RHIC. Indication of rapid rapid thermalizationthermalization? ?
RHIC Elliptic Flow Data
Quark Matter 2006, Shanghai China
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Identified particle v2 at 200 GeV
• v2 appears to saturate at ~0.13 for K0.13 for KSS and ~0.20 for 0.20 for with the saturation setting in at different pT.
PRL 92(04) 052302
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Elliptic flow at RHIC and perfect fluid hydrodynamics Elliptic flow at RHIC and perfect fluid hydrodynamics
The v2 measurements at RHIC are in a good agreement with the predictions of ideal relativistic hydrodynamics
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Scaling breaks
Elliptic flow scales with KET up to KET ~1 GeV Indicates hydrodynamic behavior Possible hint of quark degrees of freedom become apparent at higher KET
Baryons scale togetherMesons scale together
PHENIX preliminary
= mT
– m
Transverse kinetic energy scalingTransverse kinetic energy scaling
( WHY ? )( WHY ? ) 21
2Therm colKE KE KE m u
P PHENIX article submitted to PRL: nucl-ex/0608033
Quark Matter 2006, Shanghai China
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In this scenario we can infer the value of the parton v2 in the relevant pT region (~7%).
For hadron formation by
coalescence of co-moving partons
v2
meson pT
2 v2
quark pT
2
v2
baryon pT
3 v2
quark pT
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NCQ-scaling: Partonic flow
Hiroshi Masui / University of Tsukuba
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Partonic Collectivity (ii)
• Hydro + NCQ scaling describes v2 for a variety of particles measured at RHIC– Scaling breaks for higher pT
PHENIX PRELIMINARY WWND 2006, M. Issah
K0S, (STAR) : PR 92, 052302 (2004)
(STAR) : PRL 95, 122301 (2005)
(STAR) : preliminary
Data :QM2005, PHENIX
K0S
STAR preliminary0-80% Au+Au 200GeVYan Lu SQM05P. Sorensen SQM05M. Oldenburg QM05
SQM2006, S. Esumi
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NCQ (pNCQ (pTT/n) scaling compared to KE/n) scaling compared to KETT /n /n
KET/n scaling works for the full measured range with deviation less than 10% from the universal scaling curve NCQ- scaling works only at 20% level for pt>2 GeV/c and breakes below with clear systematic dependence on the mass
PHENIX Preliminary
NCQ- Scaling
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Elliptic flow of multistrange hadrons (φ, Ξ and ) with their large masses and small hadronic behave like
other particles → consistent with the creation of elliptic flow on partonic level before hadron formation
Multi-strange baryon elliptic flow at RHIC (STAR)
STAR preliminary
200 GeV Au+Au
From M. Oldenburg SQM2006 talk (STAR)
J. Phys G 32, S563 (2006)
Scaling test
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Elliptic flow at FAIR
AMPT calculations: C.M. Ko at CPOD 2007
Measure flow for all particles over CBM energy range
DJ/
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QCD Phase Diagram
What does theory expect? → mainly predictions from lattice QCD:
• crossover transition from partonic to hadronic matter at small B and high T
• critical endpoint in intermediate range of the phase diagram • first order deconfinement phase transition at high B but moderate T
The Compressed Baryonic Matter (CBM) experiment : Exploration of the phase diagram at very high baryon densities and moderate temperatures to look for :
De-confinement phase transition at high temperature & baryon densityIn-medium modification of hadrons – signal of the onset of chiral symmetry restoration.Location of the critical end point
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Thank you
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C. Blume et al. (NA49 at CERN-SPS), nucl-ex/0409008
Discontinuity in strangeness production: signature for phase transition ?
Decrease of baryon-chemicalpotential: transition frombaryon-dominatedto meson-dominated
matter
?
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Extra Slides
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Net-baryon densities in central Au+Au collisions at FAIR:consistent picture from transport models
Compilation by J. Randrup, CBM Physics Book, in preparationsee also I.C. Arsene et al., Phys. Rev. C 75 (2007) 034902
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High density matter at CBM
• high baryon and energy densities created in central Au+Au collisions
• remarkable agreement between different models
• maximum net baryon densities from 5 - 40 AGeV ~ 1 - 2 fm-3 ~ (6 – 12) 0
(net baryon density = 1 fm-3 ~60)
• max. excitation energy densities from 5 - 40 AGeV ~ (0.8 – 6) GeV/fm3
(* = – mN, total energy density)
net baryon density
CBM physics book (to be published)
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Introduction• States of matter, their defining features and transition between them always been one of the fundamental issues
of physics. Strongly interacting matter opens up a new chapter for such studies.
• Statistical QCD predicts at high temperature and/or densities, strongly interacting matter will undergo a transition from color neutral hadronic phase to a state of de-confined color charged quarks & gluons – quark gluon plasma (QGP)
Neutron starsEarly universe
Compression heating quark-gluon matter (pion production)
baryons hadrons partons
In laboratory Relativistic heavy-ion collisions (RHIC) are the only tool to produce such exotic states of QCD matter
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CBM Physics : keywords
• physics program complementary to RHIC, LHC
• rare probes
What does theory expect? → mainly predictions from lattice QCD:
• crossover transition from partonic to hadronic matter at small B and high T
• critical endpoint in intermediate range of the phase diagram
• first order deconfinement phase transition at high B but moderate T
However ...
• deconfinement = chiral phase transition ?
• hadrons and quarks at high ?
• signatures (measurable!) for these structures/ phases?
• how to characterize the medium?
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RHIC result: new state of matter = perfect liquid? Tf = 160 – 165 MeV
L-QCD Predictions: TC = 151 ± 7 ± 4 MeV ( μB=0 ) (Z. Fodor, arXiv:0712.2930 hep-lat) TC = 192 ± 7 ± 4 MeV ( μB=0 ) (F. Karsch, arXiv:0711.0661 hep-lat) crossover transition at μB=0 (Z. Fodor, arXiv:0712.2930 hep-lat) 1. order phase transition with critical endpoint at μB > 0
High-energy heavy-ion collision experiments:
RHIC, LHC: cross over transition, QGP at high T and low ρLow-energy RHIC: search for QCD-CP with bulk observables NA61@SPS: search for QCD-CP with bulk observables CBM@FAIR: scan of the phase diagram with bulk and rare observables
Exploring the QCD Phase diagram
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SIS 100 Tm
SIS 300 Tm
Structure of Nuclei far from Stability
cooled antiproton beam:Hadron Spectroscopy
Compressed Baryonic Matter
The future Facility for Antiproton an Ion Research (FAIR)
Ion and Laser Induced Plasmas:
High Energy Density in Matter
low-energy antiproton beam:antihydrogen
Primary beams:1012 /s 238U28+ 1-2 AGeV4·1013/s Protons 90 GeV1010/s U 35 AGeV (Ni 45 AGeV)
Secondary beams:rare isotopes 1-2 AGeVantiprotons up to 30 GeV
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In medium effects: Dileptons
[Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/9909229]
• dileptons are penetrating probes!
• modifications in hot and dense matter expected –
see CERES, NA50, NA60, HADES
best way to measure? e+e- ↔ +-
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Quarkonium dissociation temperatures: (Digal, Karsch, Satz)
Measure excitation functions of J/ψ and ψ' in p+p, p+A and A+A collisions !
rescaled to 158 GeV
Probing the quark-pluon plasma with charmonium
J/ψ ψ'
sequential dissociation?
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High density matter at CBM
• high baryon and energy densities created in central Au+Au collisions
• remarkable agreement between different models
• maximum net baryon densities from 5 - 40 AGeV ~ 1 - 2 fm-3 ~ (6 – 12) 0
(net baryon density = 1 fm-3 ~60)
• max. excitation energy densities from 5 - 40 AGeV ~ (0.8 – 6) GeV/fm3
(* = – mN, total energy density)
net baryon density
CBM physics book (to be published)
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Collapse of proton flow : order of transition??
• collapse elliptic flow of protons at lower energies signal for first order phase transition?! [e.g. Stoecker, NPA 750 (2005) 121, E. Shuryak, hep-ph/0504048]
• full energy dependence needed!central
midcentral
peripheral
[NA49, PRC68, 034903 (2003)]
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Summary: CBM physics topics and observables
Onset of chiral symmetry restoration at high B
in-medium modifications of hadrons (,, e+e-(μ+μ-), D)
Deconfinement phase transition at high B
excitation function and flow of strangeness (K, , , , ) excitation function and flow of charm (J/ψ, ψ', D0, D, c) (e.g. melting of J/ψ and ψ') exitation function of low-mass lepton pairs
The equation-of-state at high B
collective flow of hadrons particle production at threshold energies (open charm?)
QCD critical endpoint excitation function of event-by-event fluctuations (K/π,...)
CBM Physics Book in preparation
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Detector requirements
Systematic investigations:A+A collisions from 8 to 45 (35) AGeV, Z/A=0.5 (0.4) (up to 8 AGeV: HADES)p+A and p+p collisions from 8 to 90 GeV
observables detector requirements & challenges
strangeness production: K,
charm production: J/, D
flow excitation function
event-by-event fluctuations
e+e-
open charm
tracking in high track density environment (~ 1000)
hadron ID
lepton ID
myons, photons
secondary vertex reconstruction
(resolution 50 m)
large statistics: large integrated luminosity:
high beam intensity (109 ions/sec.) and duty cycle
beam available for several months per year
high interaction rates (10 MHz)
fast, radiation hard detector
efficient trigger
rare signals!
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SIS100/300
Multiplicity in central Au+Au collisionsW. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745
Rare particles with high statisticsHigh beam intensityInteraction rate: 10 MHzFast detectors/DAQ
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STS tracking – heart of CBM
Challenge: high track density 600 charged particles in 25o
Task
• track reconstruction:
0.1 GeV/c < p 10-12 GeV/c
p/p ~ 1% (p=1 GeV/c)
• primary and secondary vertex reconstruction (resolution 50 m)
• V0 track pattern recognition
D+ → ++K- (c = 312 m)
D0 → K-+ (c = 123 m)
silicon pixel
and strip detectors
add detectors for particle identification behind the STS
→ challenge for di-leptons!
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In medium : D-mesons
[E. Bratkovskaya, W. Cassing, private communication]
• Dropping D-meson masses with increasing light quark density
might give a large enhancement of the open charm yield at 25 A GeV !
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• In laboratory we create such conditions through high energy heavy ion collisions : hot and dense nuclear matter in the collision zone.
• Exploration of QCD phase diagram – address the fundamental aspects of QCD : – De-confinement phase transition at high temperature & baryon density
– In-medium modification of hadrons – signal of the onset of chiral symmetry restoration.
• SPS (CERN) & RHIC (BNL) : study the QCD phase diagram is studied in the region of high temperatures and low baryon densities.
• The up-coming LHC experiments will continue towards higher temperatures and lower net baryon densities.
• The Compressed Baryonic Matter (CBM) experiment will explore the phase diagram at very high baryon densities and moderate temperatures.
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• Low-mass: Medium modified
spectral density• Intermediate
mass: Radiation from
QGP• High mass: J/ etc.,
suppression
In medium effects: Dileptons
•Dileptons are penetrating probes
•Carries undistorted information of the collision zone
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CBM Physics – keywords
• physics program complementary to RHIC, LHC
• rare probes
What does theory expect? → mainly predictions from lattice QCD:
• crossover transition from partonic to hadronic matter at small B and high T
• critical endpoint in intermediate range of the phase diagram
• first order deconfinement phase transition at high B but moderate T
However ...
• deconfinement = chiral phase transition ?
• hadrons and quarks at high ?
• signatures (measurable!) for these structures/ phases?
• how to characterize the medium?
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