Mark D. Baker

Some Like it REALLYREALLY Hot!Studying Matter Under Extreme Conditions

Mark D. BakerChemistry Department

Brookhaven National Laboratory

What is the universe made of?&

What holds it together?

Mark D. Baker

What is the universe made of?

Placeholder

Mark D. Baker

What holds it together?:The Fundamental Forces

Mark D. Baker

Let’s smash some atoms!

+ -

-

u

u u u u u

d

u d u du du d

neutron

proton

pion ()

uud

Mark D. Baker

If you can’t smash it, heat it!

Temperature

Plasma

+

---

-+

Pressure

Mark D. Baker

Sideways slide - How much heat?

Placeholder

Mark D. Baker

Heat is also a window back in time

Mark D. Baker

Hot and Dense Laboratory MatterTry # 1: Diamond Anvil

Achieved Our Goal

T 2000 K 2 1012 K

p 106 atm 5x1021 atm

r ~10 mm

t hours

Mark D. Baker

Hot and Dense Laboratory MatterTry # 2: X-pinch plasma

Achieved Our Goal

T 107 K 2 1012 K

p ? 5x1021 atm

r 10 m

t 1 ns

Mark D. Baker

Hot and Dense Laboratory MatterTry # 3: Free Electron Laser

Planned Our Goal

T 108 K 2 1012 K

p ? 5x1021 atm

~ 0.1 nm planned (6 nm achieved)

XFEL, Tellerhoop, Germany

Mark D. Baker

Collide Gold nuclei at 99.99% of the speed of light

But: Will these fast violent collisions teach us anything?

10-23 seconds, 10-38 liters

Hot and Dense Laboratory MatterTry # 4: Heavy Ion Collisions

2x1012 K, 5x1021 atm

Mark D. Baker

RHIC...

Mark D. Baker

ARGONNE NATIONAL LABORATORY

BROOKHAVEN NATIONAL LABORATORY

INSTITUTE OF NUCLEAR PHYSICS, KRAKOW

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

NATIONAL CENTRAL UNIVERSITY, TAIWAN

UNIVERSITY OF ROCHESTER

UNIVERSITY OF ILLINOIS AT CHICAGO

UNIVERSITY OF MARYLAND

Birger Back, Alan Wuosmaa

Mark Baker, Donald Barton, Alan Carroll, Nigel George, Stephen Gushue, George Heintzelman, Burt Holzman, Robert Pak, Louis Remsberg, Peter Steinberg, Andrei Sukhanov

Andrzej Budzanowski, Roman Holynski, Jerzy Michalowski, Andrzej Olszewski, Pawel Sawicki , Marek Stodulski, Adam Trzupek, Barbara Wosiek, Krzysztof Wozniak

Wit Busza (Spokesperson), Patrick Decowski, Kristjan Gulbrandsen, Conor Henderson, Jay Kane , Judith Katzy, Piotr Kulinich, Johannes Muelmenstaedt, Heinz Pernegger, Corey Reed, Christof Roland, Gunther Roland, Leslie Rosenberg, Pradeep Sarin, Stephen Steadman, George Stephans, Gerrit van Nieuwenhuizen, Carla Vale, Robin Verdier, Bernard Wadsworth, Bolek Wyslouch Chia Ming Kuo, Willis Lin, Jaw-Luen Tang

Joshua Hamblen , Erik Johnson, Nazim Khan, Steven Manly,Inkyu Park, Wojtek Skulski, Ray Teng, Frank Wolfs

Russell Betts, Edmundo Garcia, Clive Halliwell, David Hofman, Richard Hollis, Aneta Iordanova, Wojtek Kucewicz, Don McLeod, Rachid Nouicer, Michael Reuter, Joe Sagerer

Richard Bindel, Alice Mignerey

The PHOBOS Collaboration

Mark D. Baker

135,000 Silicon Pad channels

PHOBOS Apparatus

12 meters of Beryllium beampipe

Mark D. Baker

Ring Counter

Octagon Detector

Vertex Detector

PHOBOS Silicon Detector

Octagon Detector: 2.7 x 8.8 mm2

Vertex Detector: 0.4 x 12 mm2

Mark D. Baker

RHIC Computing Facility

PHOBOS writes ~ 1 Gigabyte of data / minute!

Mark D. Baker

The plan of attack

• Collide gold nuclei at high energy– Collider, detectors, computers

• Understand the collision dynamics– Collective motion, equilibrium– Temperature, density

• Learn about the strong interaction– Quantum ChromoDynamics– Confinement

Mark D. Baker

How many produced particles?

Measured # of charged particles in ahead-on collision:

4100±210 @ 130 GeV

5055±250 @ 200 GeV0 +3-3 +5.5-5.5

simulation

Mark D. Baker

Multiplicity at mid-rapidityModels in 1999

Models: NPA 698, (2002) 78c,299c

PRL 88 (2002) 022302

Models in 2000

Mark D. Baker• Data favors models with minimal entropy production

Energy Dependence

Soft

Hard

PRL 88 (2002) 022302

90% C.L. band

Mark D. Baker

Implications:• The initial state is dominated by soft physics• Limited entropy production in late stages.

Colliding Nuclei HardCollisions

Parton Cascade

Hadron Gas & Freeze-out

1 2 3 4

Geometry/Saturation QGP? / Fragmentation Gentle Freeze-out

QCD

Mark D. Baker

Many ways to slice pz

FTTz xs

pymp2

sinhsinh:

Away from mid-rapidity:

epem Ty

T TT pmy ln

Rapidity: Generalized velocity

Pseudorapidity: ~y: easier to measure

Feynman x: scaled pz

Mark D. Baker

dN/d

dN/d

dN/d

dN

/d

dN/d

dN/d

200 GeV130 GeV

Central

Peripheral

Typical Systematic Errors

Latest PHOBOS results

Mark D. Baker

Naïve expectation (boost-invariance)

y y

Increasing E

y’=y-ybeam

0

dN/dy’Fragmentation Region

Mark D. Baker

Results : Limiting Fragmentation

Systematic errors not shown

PHOBOS results in “target frame”

PHOBOS 200 0-6%PHOBOS 130 0-6%EMU-13 17 0-9.4% (different frame)

Limit curve; extent grows with energy

SPS data (20 GeVRHIC coming soon)

Mark D. Baker

Can we see the “Limit Curves”?

p + p inel.

UA5, Z.Phys.C33, 1 (1986)

Line “p”to guide the eye

Au+Au

Systematic errors not included

1.45 x line “p”

Systematic errors not shown

Mark D. Baker

Elliptic Flow: A collective effect

Hydrodynamic modelV2

Normalized Multiplicity

midrapidity : || < 1.0

Preliminary

No collective motion

Hydrodynamic “Flow”

dN/d(R ) = N0 (1 + 2V1cos (R) + 2V2cos (2(R)) + ... )

Mark D. Baker

Elliptic Flow

Hydrodynamic model

V2

Normalized Multiplicity

midrapidity : || < 1.0

Preliminary

Particle asymmetry

Mark D. Baker

v2

Flow also non-boost-invariant

v2: quantifies elliptical anisotropy

Azimuthal shape changes as strong function of

Consistent withlarge suggestedby saturation(and required bysome hydro models)

Averaged over centrality PHOBOS Preliminary

Errors are statistical only (systematic errors ~ 0.007)

Mark D. Baker

Plan of attack - where are we?

• Collide gold nuclei at high energy– Collider, detectors, computers

• Understand the collision dynamics–Collective motion, equilibrium–Temperature, density

• Learn about the strong interaction– Quantum ChromoDynamics

– Confinement

Mark D. Baker

We see the conditions at freezeout(a lower limit to the maximum Temperature)

FreezeoutHottest period

RT

1

Expansion cooling

Mark D. Baker

1.7 1012 oK

RHIC shows rapid expansion& a high temperature

!3

2

c

vEffectiveTemperature(GeV)

CERN NA49

STAR Preliminary

2

2

. 3c

vmTTeff

Mark D. Baker

Another thermometer

In an equilibrium system, twoparameters are sufficient to predict the “chemical” mix:

(# pions) / (# protons)(# kaons) / (# pions)(# anti-protons)/(# protons) et cetera.

Temperature (T)and “net amount of matter” (B)

Mark D. Baker

Particle Ratios tell us about final state

Braun-Munzinger et. al., Phys. Lett. B 518 (2001) 41

T = 176 MeVB = 46 MeV

Statistical modelsconsistent withparticle ratio data:simple filling of phasespace?

Suggest thermalizationat T ~ Tc, nonzeronet baryon density(SPS value: B = 270 MeV) 65 + 65 GeV beam energy

Mark D. Baker

Temperature at Freezeout

• Temperature in MeV units

– Chemical: T = (170 ± 20) MeV

– Kinetic: T = (150 ± 40) MeV

• Temperature in oK (1eV = 11,600 K)

– Chemical: T = (2.0 ± 0.2) 1012 oK

– Kinetic: T = (1.7 ± 0.3) 1012 oK

• We did reach ~ 2 trillion K!

Mark D. Baker

Fully reversiblemagnetic field

Particle ratios at 100+100 GeV!

p

K+

+

Positive

Charge

Negative

Charge

K-

p

-

Tru

ncat

ed <

dE/d

x> [

MIP

]

)(03.0)(02.074.0

)(04.0)(03.095.0

)(020.0)(006.0025.1

sysstatp

p

sysstatK

K

sysstat

Preliminary

Mark D. Baker

Excitation function of B

Nucl. Phy. A697: 902-912 (2002)

Extrapolation of fit

Mark D. Baker

Energy Density Estimate (Bj)

Latticec

Bj~ 5 GeV/fm3

Bj~ 25 GeV/fm3

02j

TB

1 1 d

c dy

E

R

formation time: 0.2 - 1 fm

PRL 87 (2001) 052301

Mark D. Baker

If you just believe the lattice...

CERN SPS (s = 17 GeV) i ~ 3-10 GeV/fm3

Ti ~ 220-290 MeV

BNL RHIC (s = 200 GeV) i ~ 5-25 GeV/fm3 Ti ~ 250-350 MeV

TT

Karsch et al.

Mark D. Baker

Putting it all together

• Universal curve!• RHIC:

– “bulk” matter

– high energy density

initial ~ 5-25 GeV/fm3

(lattice Ti >250 MeV)

– freezeout near TC

– early collective expansionvt ~ 0.65 c

quark gluonplasma

SIS

AGS

SPS

RHIC

hadron gas

Tem

per

atur

e (M

eV)

50

200

150

100

250

350

300

400

Baryonic chemical potential B (GeV)0.2 0.4 0.6 0.8 1 1.2 1.4

LEP!

Mark D. Baker

Summary so far

• We’ve learned a lot about the system– The system is behaving collectively.– We have reached 2-4 trillion degrees K.– The system is expanding rapidly.

• AA may illuminate QCD “directly”– Low Nch: soft initial state effects dominate

• Thermal partons?

– The source is not boost invariant• dN/d limit curve from QCD and GAu(x)

Mark D. Baker

PHOBOS Future I (analysis)

Quantum MechanicalSource imaging (HBT)

Mark D. Baker

Plan of attack - where do we go?

• Collide gold nuclei at high energy– Collider, detectors, computers

• Understand the collision dynamics– Collective motion, equilibrium– Temperature, density

• Learn about the strong interaction– Quantum ChromoDynamics– Confinement

Mark D. Baker

What happens before freeze-out?•Energetic particles come from quark or gluon “jets”.•They interact with the dense medium, but can’t thermalize.•Jet energy loss (“quenching”) is predicted.•Jet quenching measures the density early in the collision.

pion

Mark D. Baker

Failure to scale! (jet quenching?)

Details need to be understood before conclusions can be drawn.

Mark D. Baker

PHOBOS Future II

I. Faster!!

Upgrade DAQ from40 Hz to 500-700 Hz

Upgrade triggering

II. Better particle IDMove TOF wall+...

Compare high Pt behavior of: pp, dA, AA(as well as soft behavior)

R.Pak

Sukhanov

Mark D. Baker

PHOBOS future III (analysis)Lower pT at pp midrapidity

ISR data is inelastic

Universality?

Mark D. Baker

Brookhaven Future (!): eRHIC

•Directly probe dense strongly interacting matter.• Nonabelian QCD effects in the low x nuclear structure function...

Mark D. Baker

Conclusion

• We’ve accomplished a lot already– Detector, physics, papers.

• RHIC should illuminate QCD “directly”– dN/d limit curve from QCD and GAu(x)

– Universality of “fragmentation”– “Jet quenching” or new scaling law– Something we haven’t thought of yet...

• Physics on the distant horizon– eRHIC - probing QCD in a different way.