bedanga mohanty soft and intermediate p t physics highlights from qm2006 baryon production flow...
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Bedanga Mohanty
Soft and intermediate pT physics highlights from QM2006
Baryon productionFlowIntermediate pT ~ RecombinationNew data at forward rapidityFreeze-out propertiesPredictions for LHC
Selected topics ……
HIT12th December 2006
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Baryon production
Change of shape most pronounced at SPS energies : Peak dip structure
Mid-rapidity net-baryon density decreases rapidly
We had seen this result Low energy SPS results got added at QM2006
Results from : C. Blume (NA49), B. Mohanty(STAR), I.G. Bearden (BRAHMS)
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Baryon production
NA49 preliminary
3HeCentral Pb+Pb
Helium - supposed to be formed from p + n have a opposite shape (concave) - independent of energy Insight into coalescence mechanism ?
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Baryon production
Proton yields : Interplay of baryon production and baryon transport at mid rapidity
peripheral central
Averaged rapidity shift y :
∫ −−=
−=
py BB
partp
p
dydy
dNy
Ny
yyy
0
)(2
δ
Degree of stopping similar at AGS and SPS - less at RHIC
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Conclusion : Baryon production
Change in shape of dN/dy of net baryons occurs around SPS energy (Peak to dip structure)
The nuclei production (coalescence of nucleons) have a dN/dy shape which is independent of collision energy
Proton production is similar for beam energy : 17.3 to 200 GeV. Unique interplay of baryon production and transport
Degree of stopping similar for AGS and SPS. More transparency at RHIC
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Measurements : collision energy, collision species, particle type, pT, rapidity, centrality This QM : Summary and Future directions for the flow studies
Flow
Results from : S. Voloshin (STAR), P. Sorensen (STAR), Y. Bai (STAR), G. Wang (STAR),R. Nouicer (PHOBOS), C. Loizides (PHOBOS), A. Taranenko (PHENIX), S. Sanders (BRAHMS)H. Liu (STAR), R. Bhalerao, I. G. Bearden (BRAHMS), D. Hoffman (PHOBOS), A. Tang, S.L. Blyth (STAR), S. Esumi (PHENIX)
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Elliptic flow : Mass ordering, KE scaling,baryon-meson effect
Low pT :Mass ordering
Low pT : Scaling when plotted as mT - m0 Scenario qualitatively as
expected from hydrodynamics
At intermediate pT - may due to particle mass or due to baryon-meson
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Elliptic flow : Quark number and universal scaling
Universal scaling observed when data presented normalized to quark content
Universal scaling holds for different centrality Note = integrated v2 not eccentricityhydro models eccentricity proportional to int. v2
Is it really true ?
STAR preliminary
0-80% Au+Au
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Elliptic flow : Driven by collision geometry
PHOBOS claims collision geometrycontrols the dynamical evolution of heavyIon collisions - v2 what about v1 ?
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Directed flow : depends on beam energy
v1 depends on energy, not on system size.
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Elliptic flow : D-mesons and thermalization ?
Nbinary scaling indicates charm production at initial stage of thecollisions
Substantial non-photonic electron v2 observed
expected D meson v2 from non-photonic electron v2
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Charm collectivity : thermalization ?
Model dependent (Blast Wave) analysis of J/ and non-photonic electrons (from semi-leptonic decays of mesons having charm quarks) spectra consistent with small transverse radial flow and larger freeze-out temperature
AuAu Central
charm hadron
AuAu Central , K, p
AuAu Central strangeness
hadron
SQM06, Yifei Zhang
Peter Braun-MunzingerShinchi Esumi
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Flow : Degree of thermalization
•Scaled flow values allow constraints for several transport coefficients.
Star Preliminary
v4 /v22 a detailed probe of ideal hydro behavior and related to the degree of thermalization!
Large systematic uncertainty (from non-flow) difficult to conclude about thermalization
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Elliptic flow : Situation at SPS ?
Scaling at low pT notso prominent when plotted as mT - m0
pT reach may be notsufficient to see the quark number scaling
SPS way below hydro-dynamical results. RHIC is in that regime
V2 ~ dN/dy
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Flow : Longitudinal scaling
We observed this for multiplicity Seem to understand this as v2 ~ dN/dy
See similar thing for v1 and v4 also…
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Elliptic flow : next steps (Theory/phenomenology) Scaled flow values allow constraints for several transport coefficients
Attempts are being made to study properties of the matter formed in heavy ion collisions
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Elliptic flow : next steps (experimental)
All the previous results we saw are average value which varies e-by-e by 35-40%Most of this variation is understood in terms of e-by-e variation in initial event shape
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Elliptic flow : next steps - how to take care of effect of initial geometry
x
'x
y'y
2 2
2 2Std
y x
y x
−=
+
2 2
2 2
' '
' 'part
y x
y x
−=
+
[neglecting shift ]
cos(2 )std part ≈ ΔΨ
Same impact parameter - shapes can be different at participant level
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Conclusion : Flow
From the experimental data Future directions
At low pT mass ordering of v2 values observed and at intermediate pT ordering by quark content (baryon-meson)
Universal scaling observed across pT, centrality, ion species and particle type - when data presented as a function of v2/n* Vs. mT-m0/n
v2 is driven by collision geometry and v1 by beam energy
Longitudinal scaling observed for all components of measured flow
Time to draw conclusions about property of the medium from the experimental measurements
Understand the event-by-event variation in flow values
How to calculate the eccentricity Experimental work needed on D-
meson flow and v4/v22 to address
the issue of thermalization Lee-Yang Zeroes method is less
biased by non-flow correlation.
Nucl. Phy. A 727 (2003) 373-426
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RecombinationV. Greco, C.M. Ko and I. Vitev, PRC 71 (2005) 041901
Specific Energy dependence p/ (62.4 GeV) > p/ (200 GeV)
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (LZW) decompressor
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Since shower partons make insignificant contribution to , production for pT<8 GeV/c, no jets are involved.
Predict: no associated particles giving rise to peaks in Δ, near-side or away-side. Thermal partons are uncorrelated, so all associated particles are in the background.
Results from :B. Mohanty(STAR), S. Blyth (STAR), J. Bielcikova (STAR), C. Blume(NA49), L.Ruan (STAR)R. Hwa and C. B. yang
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Recombination : Baryon/Meson ratio
p/+(62.4) > p/+ (200)
p/-(62.4) < p/- (200)
Qualitative agreement with coalescence prediction
Lack of quantitativeagreement with models
V. Greco et al PRC 72 (2005) 041901R.J. Fries et al PRC 68 (2003) 044902
I. Vitev et al PRC 65 (2002) 04902
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Recombination : Baryon/Meson ratio
The shape of the ratios across 17-200 GeV energies around intermediate pT are similar.Can this feature be consistentwith recombination picture ?
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Recombination : Correlation
Correlation observed - prominent peak at near sideNo dependence on strange quark content Does that mean recombination mechanism has failed ?
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QuickTime™ and aTIFF (LZW) decompressor
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Rudi Hwa …..
STARAt face value the data falsify the prediction and discredits RM.
I now explain why the prediction was wrong and how the data above can be understood.
Recombination still works, but we need a new idea.
Yang’s talk tomorrow is still right.
Recombination failed ? - Not yet - there are new ideas
Phantom jet
J. PutschkeM. van Leeuwen
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Conclusion : Recombination
Baryon to meson ratios Azimuthal correlations
Some of the features are qualitatively consistent with recombination picture
Lack of quantitative agreement
Similar shape of the ratios across beam energy 17.3 to 200 GeV may not be consistent within the current recombination framework
Initially data on Omega-hadron correlation presented at QM2006 seemed to falsify the recombination picture
Subsequent discussions at QM2006 - led to the need for more careful understanding of the data from both theoretical and experimental side.
Data needs to be presented after taking care of the effect due to extended correlation structure in eta - “ridge”
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New results from forward rapidity
• What changes? • What doesn’t?
Results from : I. G. Bearden (BRAHMS), C. Nygaard (BRAHMS), S. J. Sanders (BRAHMS), T. M. Larsen (BRAHMS), J. H. Lee (BRAHMS), L. Molnar (STAR)
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RdAu vs eta
We had seen this : RdAu is suppressed as we go to forward rapidity
What about RAA ?
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Inclusive charged hadron RAA similar
Inclusive charged hadron RAA similar at mid and forward rapidity
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Identified particle RAA, 200GeV Au+Au
y=0 y=1 y=3.1
pions
kaons
protons
Identified RAA similar at mid and forward rapidity
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V2 Identified particles 200GeV Au+Au
=0 ≈3
K
p
v2(pT) similar at forward and mid rapidityRemember integrated v2 (shown by PHOBOS) changes with rapidity
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How about K/ vs. pbar/p?
Chemistry changes with rapidity at RHIC. Forward rapidity at RHIC ~ mid rapidity at SPS
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How about correlation : Forward and mid-rapidity
Trigger: 3<pTtrig<4 GeV/c,
Associated: FTPC: 0.2<pTassoc< 2 GeV/c, TPC: 0.2<pT
assoc< 3 GeV/c
• Away side in pp: broader at forward than mid-rapidity
pp MB
• Away side in dAu: similar between forward and mid-rapidity
dAu MB
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Compare correlation in Au+Au : Forward and mid-rapidity
AuAu 60-80%
Away-side correlations are very similar! Energy loss picture is the same for mid- and
forward rapidities?
AuAu 0-10%AuAu 0-5%
Trigger: 3<pTtrig<4 GeV/c,
Associated: FTPC: 0.2<pTassoc< 2 GeV/c, TPC: 0.2<pT
assoc< 3 GeV/c
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Conclusion : At forward rapidity
• What changes? – dN/dy– pbar/p– Chemistry– V2 (integral)– Initial state (RdAu)
• What doesn’t?
– Suppression (RAA)
– V2 (pt)
– Away-side azimuthal Correlation
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Conditions close to kinetic freeze-out STAR Preliminary
Results from : L. Ruan (STAR) A. Irodanova (STAR), D.Das (STAR)
STAR Preliminary
Smooth evolution of Freeze-out parameters with dNch/d
Seems dNch/dy finally matters or these are not the correct observable to study the dynamics
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Chemical Freeze-out conditions
STAR Preliminary
5% central10% centralMin-Bias
Kp thermal fit
Tch is fairly constant with dNch/d but s for Cu+Cu system seems bit higher
Cu+Cu @ 200 GeV Cu+Cu @ 62.4 GeV
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LHC predictions : MultiplicityMultiplicity
“net”
pro
ton
AGS
SPS
RHIC 62
RHIC 200
LHC 5500d
N/d
y
Fully transparent collisions ?Extrapolation for Rapidity loss - similar values at LHC as for 200 GeV
Net baryons
Results from :U. Wiedemann, J. Cleymans
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LHC predictions : Freeze-out conditions
Chemical Freeze-out temperature : similar to RHIC
Baryon chemical potential ~ 1 MeV
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LHC predictions : Flow
Based on simple extrapolation : v2 ~ 0.08
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Conclusion : LHC predictions
dN/dy ~ 1100 - 1600 at mid-rapidityRapidity loss ~ 2 - 2.5 units
Tch ~ 166 MeV at mid-rapidity
B ~ 1 MeV at mid-rapidity
v2 ~ 0.08 at mid-rapidity
Thanks for your attention!