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

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)

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 ?

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

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

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)

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

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

Elliptic flow : Driven by collision geometry

PHOBOS claims collision geometrycontrols the dynamical evolution of heavyIon collisions - v2 what about v1 ?

Directed flow : depends on beam energy

v1 depends on energy, not on system size.

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

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

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

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

Flow : Longitudinal scaling

We observed this for multiplicity Seem to understand this as v2 ~ dN/dy

See similar thing for v1 and v4 also…

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

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

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

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

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

are needed to see this picture.

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

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

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 ?

Recombination : Correlation

Correlation observed - prominent peak at near sideNo dependence on strange quark content Does that mean recombination mechanism has failed ?

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

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

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”

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)

RdAu vs eta

We had seen this : RdAu is suppressed as we go to forward rapidity

What about RAA ?

Inclusive charged hadron RAA similar

Inclusive charged hadron RAA similar at mid and forward rapidity

Identified particle RAA, 200GeV Au+Au

y=0 y=1 y=3.1

pions

kaons

protons

Identified RAA similar at mid and forward rapidity

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

How about K/ vs. pbar/p?

Chemistry changes with rapidity at RHIC. Forward rapidity at RHIC ~ mid rapidity at SPS

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

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

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

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

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

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

LHC predictions : Freeze-out conditions

Chemical Freeze-out temperature : similar to RHIC

Baryon chemical potential ~ 1 MeV

LHC predictions : Flow

Based on simple extrapolation : v2 ~ 0.08

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!