What We’ve Learned & Have Yet to Learn John Harris (Yale) AIM Session, ALICE Physics Week, April...

What We’ve Learned

& Have Yet to Learn

John Harris (Yale) AIM Session, ALICE Physics Week, April 19, 2012

My disclaimer – My charge from the ALICE “Brass”:“Summary of differences compared to RHIC, what we have not done to compare to RHIC results, where should we focus effort to gain knowledge?”

My view today – what we have done, still need to do….on the “standard menu” of measurements

for better precisiondetermination of properties of the QGP!

People in ALICE are working on all of this….tremendous progress!

Emphasis on gaining physics knowledge from ALICE!Apologies to those whose work I have not noted here…..

Why this Talk?


“LHC & RHIC provide consistent picture” of dynamics & evolution of collisions

multiplicities, system size & lifetimes from RHIC to LHC

properties of medium (e, h/s, vs, ….?)

What Have We Learned? – Spacetime Evolution


Muller, Schukraft & Wylsouch, arXiv:1202.3233

Small differences due to initial conditions (PDF shadowing vs geometry, hard

processes ~ # binary collisions at LHC vs RHIC)?

ALICE, Phys. Rev. Lett. 105, 252301 (2010)

Must establish initial conditions – p-Pb and Pb-p this year!

“LHC & RHIC provide consistent picture” of dynamics & evolution of collisions

multiplicities, system size & lifetimes from RHIC to LHC

properties of medium (e, h/s, vs, ….?)

More on Spacetime Evolution – Constraints


Size Volume ~ dN/dh

tf (LHC) ~ 1.4 x tf (RHIC) !

VLHC ~ 2 x VRHIC !

ALICE, Phys.Lett. B696 (2011) 328

tf ~ dNch/dh 1/3 tf (central PbPb) ~ 10 – 11 fm/c

Lifetime hydrodynamic expansion

More on Spacetime Evolution


Blast Wave Fits

RHIC

LHC

Slope changes at LHC vs RHIC

Smooth extrapolation?

Somewhat stronger radial flow, b ≈ 0.66, at LHC


Blast Wave Fits

RHIC

LHC

Slope changes at LHC vs RHIC

Smooth extrapolation?

Somewhat stronger radial flow, b ≈ 0.66, at LHC

x3

PID Spectra – more particles & higher statistics to higher pT

Enhanced baryon/meson ratio

at LHC like RHIC

Increases with centrality

Central B/m peak ratio 3x pp



x3Enhanced baryon/meson ratio

at LHC like RHIC


Peak central B/m ratio 3x pp value


P. Kalinak APW

Enhanced baryon/meson ratio

at LHC like RHIC






Blast Wave Fits

RHIC

LHC

x3Enhanced baryon/meson ratio

at LHC like RHIC


Peak central B/m ratio 3x pp value


P. Kalinak APW

P. Christiansen APWEnhanced baryon/meson ratio

at LHC like RHIC



Mounting Evidence from Thermal Fits!


Same at LHC, but more work needed:

(also to understand proton yields)

Calculation - A. Andronic et al., Phys. Lett. B 673:142,2009

Particles yields at RHIC

equilibrium abundances

universal hadronization Tcritical

Need to complete the ratio studies!

extrapolations, feed-down, …

protons?

Elliptic Flow vs Collision Energy

v2 vs transverse momentum (pT)same for 2.76 TeV down to 39 GeV!

ALICE, Phys. Rev. Lett .105, 252302 (2010)STAR: PRC 77 (2008) 054901; PRC 75 (2007) 054906

v 2 {E

P}

pT (GeV/c)

Change in v2 vs pT

below 39 GeV (at 7.7 & 11.5 GeV)!

pT (GeV/c)

v 2 {4

}

STARpreliminary


Elliptic Flow – Identified ParticlesALICE, M. Krzewicki, R. Snellings, QM 2011

PHENIX bands: Phys. Rev. Lett. 91, 182301 (2003) STAR bands: Phys. Rev C 77, 054901 (2008)

Larger mass splitting at LHC than at RHIC

Hydro: CGC initial conditions, h/s = 0.2

ALICE (p, K, p) data points

Hydro curves: Shen, Heinz, Huovinen & Song, arXiv:1105.3226


Identified Particle Elliptic Flow


Hydro: Shen, Heinz, Huovinen, Song, Phys. Rev. C84 (2011) 044903.

Clear mass ordering! nq scaling? Dynamics more complicated!

J/y Elliptic Flow!


H. Yang APW

J/y m+m- in ALICE Muon Arm

finite v2 observed

Most central bin

dominated by fluctuations

H. Yang APWFor different bkgds.

J/y m+m- in ALICE Muon

Arm

20 – 60 % centrality

v2 (pT) dependence

J/y Elliptic Flow!


H. Yang APWFor different bkgds.

J/y m+m- in ALICE Muon Arm

finite v2 observed

Most central bin

dominated by fluctuations

J/y e+e- in STAR


no v2 signal!

J/y m+m- in ALICE Muon

Arm


v2 observed 1.5 < pT < 4

GeV/c

Direct g Elliptic Flow..


v2inc = v2 of inclusive g

from conversions

V2decays = v2 of decay g’s

D. Lohner, reported by C. Loizides APW

v2dir = v2

inc +v2

inc – v2decays

Rg –

1(Rγ = Ninc/Ndecays)

Next step: extract -g dirv2

Direct g Elliptic Flow from PHENIX


Au+Au at 200 GeV PHENIX, arXiv:1105.4126

-g dirv2 using technique outlined on previous slide

Large -g dirv2 at lower pT ~ v20p

Too large for theory!

-g dirv2 at higher pT ~ hard

scattering?

Theorists Working on Shear Viscosities


Hydro: Qui, Shen, Heinz, Phys. Lett. B707 (2012) 151.

Zeroing in on h/s and initial conditions?

Shear Viscosity from v2 & v3


Hydro: Schenke, Jeon, Gale, Phys. Lett. B702 (2011) 59.

Sensitivities of h/s and initial conditions to vn

Elliptic Flow at Large pT


High pT v2 from jets?

Elliptic Flow at Large pT


CMS, arXiv:submit/0450742

CMS and ATLAS high pT results


“We understand the shear viscosity, sound

velocity, EOS, other properties of the Medium!”

e.g. – constituents?

c-symmetry?

deconfinement?

Should ask ourselves

“What Will it Take to Be Able to Say…?”

e+e- in PHENIX….. Properties of the Medium


Min. Bias Au+Au

PHENIX, PRC81, 034911(2010), arXiv:0912.0244

Low mass di-leptons

The original case for

medium effects!

Space-time evolution?Shuryak, arXiv:1203.1012v1

Au + Au e+e- in STAR


Inconsistent with PHENIX?Still work to be done!

Au + Au e+e- vs Centrality in PHENIX


Centrality dependence:

PHENIX, PRC81, 034911(2010), arXiv:0912.0244

Low mass di-leptonEnhancement!

Increases with centrality.

Central Au + Au e+e- in STAR


Difficult…consistency…!


Vector Meson Studies in ALICE pp

ALICE, Phys. Lett. B710 (2012) 557.


Cocktail not quite complete…. “enhancement apparent”

ALICE Central Collision e+e- data, C. Baumann APW

Towards Properties of the Medium (ALICE)

Towards Properties of the Medium (ALICE)


ALICE 20 – 80 % centrality e+e- data, C. Baumann APW

Clearly a difficult task! Much can be done prior to upgrades!

Suppression of High pT Particles


/AA

AA /coll pp

NR

N N

γ

γ

CMS, arXiv:1202.2554v1

Suppression of High pT Particles


/AA

AA /coll pp

NR

N N

γ

γ

RAA at LHC theory:

pQCD behavior!

Inconsistent with CGCinitial conditions.

Requires running coupling constant!

Isn’t this now purely pQCD with running a?

B. Betz and M. Gyulassy, arXiv:1201.0281

Suppression of “Intermediate pT” Particles


/AA

AA /coll pp

NR

N N

γ

γ

RAA at LHC theory:

pQCD behavior!

A few more details left.

B. Betz and M. Gyulassy, arXiv:1201.0281

Begs for RAA for all i.d.’ed particles – to confront theory!

Suppression of “Intermediate pT” Pions

John Harris (Yale) AIM Session, ALICE Physics Week, April 19, 2012ALICE, P. Christiansen APW

Suppression of “Intermediate pT” Kaons


Suppression of “Intermediate pT” Protons


Suppression of “Intermediate pT” p0


Work of Dmitri Peresunko, reported by C. Loizides APW

Consistent with charged pions. Progress!

More to do on Photons!


RAAdir-g vs pT

PHENIX, PRL 96 (2006) 202301

PHENIX, PRL 104 (2010) 132301

“Enhanced production of Direct g ...

Implications for Initial Temperature”!

Tinit ~ 370 MeV

T = 221 +/- 19 +/- 19 MeV

Parton Energy Loss in the Medium


Heavy Flavor production, flow and propagation (RAA)

Muller, Schukraft & Wylsouch, arXiv:1202.3233

To understand:

quark, gluon & flavor

dependence.

Looks like ~pQCD at pT > 10 GeV/c…except need…

Heavy Quark Energy Loss in the Medium


Will B-quarks Behave as pQCD predicts?

WHDG prediction for B

M. Gyulassy, BNL Seminar 2012

Heavy Quark Energy Loss in the Medium


ALICE, arXiv:1203.2160 “Suppression of high pT D mesons in central Pb-Pb at √sNN = 2.76 TeV”

pQCD with parton E-loss describes both charm & light hadrons!…….with little nuclear shadowing! Extend pT range !

Aside – J/y in pp at 7 TeV!


Mid-rapidity J/y more likely produced in high multiplicity pp events!Theory in a quandary!?

J/ Y Suppression at SPS & RHIC

J/ψ – more suppressed forward.Partly due to cold nuclear matter!


J/ψ suppressed at RHIC ~ SPS!

Increases with centrality(not shown here).

J/ Y Suppression at RHIC & LHC

CMS, PRL 107 (2011) 052302

High pT J/ψ near ycm more suppressed than at RHIC

→ energy loss of charm quark


J/ψ less suppressed than at RHIC

Recent Word by PHENIX – J/ Y Suppression at RHIC

Suppression of J/y at forward rapidity stronger than at midrapidity.

Have compared to recent calculations that include

gluon saturationgluon shadowinginitial-state parton energy losscold nuclear matter breakupcolor screeningcharm recombination.

J/y suppressed beyond cold-nuclear-matter effects.

Disagreement between models and d+Au data precludes using these models to quantify hot nuclear matter suppression.


PHENIX, arXiv:1103.6269v1

ALICE – Emphasizes importance of p-Pb and Pb-p this year!

U Suppression at RHIC & LHC

U(2s), U(3s) suppressed wr to U(1s),& relative to p+p collisions


CMS, PRL 107 (2011) 052302

U Suppression at RHIC & LHC

U(2s), U(3s) suppressed wr to U(1s),& relative to p+p collisions


ALICE – Progress! Should also be able to analyze Y in e+e- channel in EMCal!

ALICE, J. Castillo, reported by D. Das APW

Mmm (GeV/c2)

ALICE in progress!

CMS, PRL 107 (2011) 052302

Jets at the LHC – Di-Jet Energy Imbalance!

Azimuthal Angular Correlations

Triggerjet

Away-side jet

Energy Asymmetry: AJ = ET1 – ET2 / ET1 + ET2

for > Df p/2

ET1 > 100 GeV ET2 > 25 GeV


Where does the Energy Go? – CMSdevPRC 84 (2011) 024906

Energy/momentum balance in event is carried bylow momentum particles at large angles to jets!


pQCD, vacuum fragmentation, thermalization of lost energy?


Must understand parton propagation energy loss processes in the medium!

A Lot to Do & Still to Come from Jets in ALICE

Jets – (relative to reaction plane for geometry / pathlength selection)

(relative to pp)

spectra (understand soft background in Pb-Pb)

changes in intra-jet structure

correlations & energy balance

jet-hadron

hadron-jet

g-jet

di-jet

B-jets (for quark propagation in medium)

vn of jet (impact on flow analyses)

Use some of above for event selection criteria

e.g. di-jet energy imbalance



Tremendous effort on many different analyses! Need to consider physics message papers across analyses

(e.g. v2,3,…, RAA for ID’ed particles)

- How does the system evolve and thermalize from its initial state?

What is the initial state (CGC?)?

- What are the properties & constituents (vs. T) of the QGP?

- Can we understand parton propagation & energy loss at fundamental level?

What can we learn about the medium response?

- How does hadronization take place?

- Can we understand & extract all contributions to quarkonium suppression?

What does it tell us?

- Is the QCD Phase Diagram featureless above Tc? Coupling strength vs T….

- Are there new phenomena? Whatever happened to c-symmetry?....

- Can there be new developments in theory (lattice, hydro, parton E-loss,

string theory…) and understanding……across fields……?

Big Questions – QGP at RHIC & LHC


What We’ve Learned & Have Yet to Learn John Harris (Yale) AIM Session, ALICE Physics Week, April...

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