soft hadron production at rhic
DESCRIPTION
Soft Hadron Production at RHIC. Masahiro Konno (University of Tsukuba). 金野正裕(筑波大学).TRANSCRIPT
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Soft Hadron Production at RHIC
Masahiro Konno(University of Tsukuba)
金野正裕(筑波大学)
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Outline
- A Picture of Relativistic Heavy Ion Collisions- Motivation (this talk)- RHIC-PHENIX
- Single spectra at low pT ( 2 GeV/c)
- Single spectra at Intermediate pT (2~5 GeV/c)
- Elliptic flow- Jet modification in the medium
- Summary
Res
ults
<~
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Z
Space-time evolution
1. Hard scattering
2. Thermalization & QGP
4. Cooling, Freeze-out3. Hadronization
Picture of Relativistic Heavy Ion Collisions• the created system lasts for only ~10 fm/c.
time
phenix (05)
Bjorken energy density:
€
ε(τ 0) =1
τ 0πR2
dET (τ 0)
dy
Well above ec (~1 GeV/fm3) fromlattice QCD if assuming t = 1 fm/c.
x5 !
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Motivation
Useful Observables: - Single particle spectra - Azimuthal anisotropy of particle emission - Modification of jet shape/yield in the medium
Why soft particle production important to heavy ion collisions?
=> Soft particle productionSoft particle production dominates the bulk yield. dominates the bulk yield. Through this study, we can know bulk properties of the system including collective flow. Hadrons interact strongly so it is a probe to know the evolution of the system and medium effect to hadronization.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
RHIC-PHENIX
Aerogel Cherenkov (PID)
EM Calorimeter (PID)TOF (PID)
Drift Chamber (momentum meas.)
Tracking detectors (PC1,PC2,PC3)
- Central Arm Detectors (magnetic spectrometer)- Event Characterization detectors
• Centrality and Reaction Plane
determined on an Event-by-Event basis.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
No Cut
Aerogel Veto
Clear Proton Line!Clear Proton Line!
π+
K+p
PID detectors(PID = Particle Identification)
• PID is a powerful tool to study hadron production!
Aerogel Cherenkov
Time of Flight (TOF)
p (p) ID up to 4 GeV/c-
p (p) ID up to 8 GeV/c-
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Single spectra (low pT)pT spectra for /K/p (mid rapidity)
Tkin ~ 100 MeV<vT/c> ~ 0.5
particle spectra (blast wave fit) => kinetic freeze-out properties.
PRC 69, 034909 (2004)
<pT>: <K<p (mass dependence)• consistent with radial flow picture.
Spectra for heavier particleshas a convex shape due to radial flow.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Single spectra (low pT)
nucl-th/0405068
particle ratios (statistical model) => chemical freeze-out properties. Tch ~160 MeV, gs ~1.0
- Hadron yields and spectra are consistent with
thermal emission from a strongly expanding
source (radial flow driven by pressure gradient).
- The observed strangeness production is
consistent with complete chemical equilibrium.
Statistical mode fit
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
- High-pT suppression due to parton energy loss in the medium (jet quenching).- The suppression patterns depend on particle type. Protons are enhanced, while pions and kaons are suppressed.
Au+Au 200 GeV nucl-ex/0603010
Nuclear Modification Factor RAA
€
RAA =Yield AA/⟨Nbinary⟩AA
Yield pp
Single spectra (intermediate pT)
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
PRL 91, 172301 (2003)
- p/ ratio ~1 for central Au+Au at intermediate pT (2-4 GeV/c).- Larger than expected from jet fragmentation (measured in pp, e+e-).- Baryon / Meson difference at intermediate pT. (on RAA (nuclear modification factor) , v2 (elliptic flow) etc.)
Baryon Enhancement
Elliptic flow (v2)p/ ratio
What is the origin of (anti-)proton
enhancement at intermediate pT?
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
A number of models predicted a turnoverin the B/M ratio at pT just above where the available data finished…
p/
Fries, R et al PRC 68 (2003) 044902Greco, V et al PRL 90 (2003) 202302Hwa, R et al PRC 70(2004) 024905
qq M→
qqq B→
Quark Recombination
At intermediate pT, recombination ofpartons may be a more efficient mechanismof hadron production than fragmentation.
=> pT spectra and particle ratio (Baryon/Meson) at higher pT
provide most basic tool to study the hadronization mechanism.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
pT spectra
pT reach extendedfor (anti-)protonswith fine centrality bins.
Using Aerogel Cherenkov detector
for (anti-)protons
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
p/ vs. pT
* No feed-down correction.
- p/ (pbar/) ratios seem to turn over at intermediate pT, and close to the value of fragmentation at higher pT.- Indicating transition from soft to hard at intermediate pT.
p/ p/
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
p/ vs. pT (centrality dependence)
p/ p/
* No feed-down correction.* p+p data (nucl-ex/0603010)
- p/ ratios look to have a peak at intermediate pT (2-4 GeV/c).- Clear peak in central events than that in peripheral.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
• p/+ ratio : decreasing as a function of sNN. p/- ratio : increasing as a function sNN.
– Cu+Cu 22.5 GeV central data reaches the p+p values.– Cu+Cu 62.4 GeV central data is higher than that in 22.5 GeV.
Beam energy dependence in Cu+Cu
Suggesting a significant contribution of incoming protons(not produced protons) in lower energies Cu+Cu.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Beam energy dependence of net protons
nucl-ex/0313023 nucl-ex/0410003
- The shape of net proton distribution change dramatically with beam energy.
SPS AGS
- pbar/ ratio could be a good indicator of thermalization.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Pions suppressed by a factor of ~5 with respect to protons
RdAu vs. RAuAu
- In d+Au Particle type dependence: , K < p (recombination in d+Au?)
- Cronin effect (in d+Au) cannot account for the huge gap between protons and pions in central Au+Au collisions.
Proton Cronin effect larger by ~30%
preliminary preliminary
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
React
ion
plan
e
X
Z
Y
Px
Py Pz
- Overlap region is like ellipsoid at the beginning of collision.
- Spatial anisotropy of the system followed by multiple scattering of particles (pressure gradient) in the evolving system
- Spatial anisotropy => momentum anisotropy
v2: 2nd harmonic Fourier coefficient in azimuthal distribution of particles with respect to the reaction plane
Elliptic Flow
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
• KET ~ mT–m0 at y ~ 0
M. Issah, A. Taranenko, nucl-ex/0604011
Elliptic Flow
- Large elliptic flow observed.- Mass ordering seen at low pT (<1.5 GeV/c).- KET scaling (for hadronic flow) vanish this mass dependence but give clear splitting of meson/baryon v2.
PHENIX preliminary
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
PHENIX preliminary
v2q(pT) = v2
h(pT/n)/n, v2q(KET) = v2
h(KET/n)/n
Elliptic Flow
- Species dependence of v2 well accounted for by scaling v2 and pT (KET) with # of quarks.- Evidence of partonic flow! v2 is developed before hadrons form.
M. Issah, A. Taranenko, nucl-ex/0604011
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
meson -- A test of recombination( -> KK)
- RAA looks like 0 rather than
proton even if mass() ~ mass(p).- Suggest that it’s not mass effect (radial flow).
- Mass ordering at pT <2 GeV/c.- For pT >2 GeV/c, v2 favors quark composition rather than mass
- KET and Nq scaling works for .
- Thermal s recombined to form .
H.M
asui
CIP
AN
P06
centrality: 20-60%
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Jet modification in the medium- In heavy ion collisions, we expect: (1) Scattered partons travel through the medium. (2) Partons loose their energy because of a large gluon density. (3) Suppression of high-pT leading particles.
Observables: - Single spectra RAA -- to look at yield suppression - Angular correlation -- to look at jet modification
Jet partons interact with the medium via the strong force.So jet can be a probe of the medium.
Interests: - Mapping of momentum of trigger/partner. - Shape of away-side jet - Study the composition of the jets <= Focus on this.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Method of Jet study
- Using two-particle correlation function.- Should treat large combinatorial back ground (flow, decay) in heavy ion collisions.- Use mixed events for correction of pair acceptance.
€
1
N trig
dN pairs
dΔφ∝C Δφ( )
€
∝dNreal /dΔφ
dNmix /dΔφ
C()
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
PHENIX Preliminary
Jets at intermediate pT
Meson vs. Baryon associated partner (for fixed Hadron trigger)
- Particle species dependence of jet modification- BTW, how can hadrons at intermediate pT show jet-like structure? => pickup of soft quarks by jets?
W.Holzmann HardProbes06
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Meson vs. Baryon associated partner (for fixed Hadron trigger)
Jet Associated Identified Conditional Yield
- Different pT trends of associated meson and baryon yields.
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
- Near-side: like p+p, Away-side: Larger B/M ratio.
- Baryon/meson ratio can be an indicator for the degree
of thermalization (density of comoving constituents) in a jet.
Jet Associated Baryon to Meson RatioMeson vs. Baryon associated partner (for fixed Hadron trigger)
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RIKEN Workshop (7/8/2006)M.Konno (Univ. of Tsukuba)
Summary- The medium created in heavy ion collisions: (1) has bulk properties like collective flow, thermalization (2) induce the jet modification.
- Recombination models seem to be matched to the experimental observations (B/M difference) : (1) particle ratios (p/ etc.) (2) Consistent quark scaling of v2 etc.
- p/ ratio indicates a transition from soft to hard production at intermediate pT.
- Soft particle production (flow, recombination, etc.) observed at low ~ intermediate pT ( 5 GeV/c). <~
Systematic study (especially for colliding species, √s)
with enhanced PID capabilities.