# Presentation: 944065

## Some Like it REALLY Hot!Studying Matter Under Extreme Conditions Mark D. BakerChemistry 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**

**d**

**u**

**d**

**u**

**d**

**neutron**

**proton**

**pion (************)**

**u**

**u**

**d**

- 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 MatterTry # 1: Diamond Anvil

- Mark D. Baker

## Hot and Dense Laboratory MatterTry # 2: X-pinch plasma

- Mark D. Baker

## Hot and Dense Laboratory MatterTry # 3: Free Electron Laser

******~ 0.1 nm planned (6 nm achieved)**

**XFEL, Tellerhoop, Germany**

- Mark D. Baker

## Hot and Dense Laboratory MatterTry # 4: Heavy Ion Collisions

**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

**2x10****12**** K,  5x10****21**** atm**

- Mark D. Baker

## RHIC...

- Mark D. Baker

## The   PHOBOS   Collaboration

**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**

- Mark D. Baker

## PHOBOS Apparatus

**135,000 Silicon Pad channels**

**12 meters of Beryllium beampipe**

- Mark D. Baker

## PHOBOS Silicon Detector

- Ring Counter

**Octagon Detector**

**Vertex Detector**

**Octagon Detector: 2.7 x 8.8 mm****2**
**Vertex Detector:  0.4 x 12 mm****2**

- 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 GeV

**simulation**

- Mark D. Baker

## Multiplicity at mid-rapidity

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

**PRL 88 (2002) 022302**

- Mark D. Baker

## 

Data favors models with minimal entropy production

- 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

_**Away from mid-rapidity:**_

**Rapidity: Generalized velocity**

**Pseudorapidity: ~y: easier to measure**

**Feynman x: scaled p****z**

- Mark D. Baker

## Latest PHOBOS results

- dN/d

- dN/d

- dN/d

- dN/d

- dN/d

- dN/d

- 

- 

- 

- 

- 

- 

**200 GeV**

**130 GeV**

**Central **

**Peripheral**

**Typical Systematic Errors**

- Mark D. Baker

**Notes:**
So now lets look at the data.  First of all let me show some distributions for a selected set of centrality bins, here described by the fraction of the cross section they correspond to. The colors are there just to show you that the data from these disparate pieces of the experiment actually match up together quite nicely.  And just looking at these distributions you can start to get a sense of  what’s happening as the data evolve with centrality.  For instance, its clear that for the most central collisions the data in the fragmentation region are relatively lower to those at mid rapidity than for more peripheral collisions.  But lets look at these things in a bit more detail.

## Naïve expectation (boost-invariance)

**y**

**y**

**Increasing E**

**y’=y-y****beam**

**0**

**dN/dy’**

**Fragmentation **
**Region**

- Mark D. Baker

## Results : Limiting Fragmentation  

**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

- 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 model**

**V****2**

**Normalized Multiplicity**** **

- midrapidity : || < 1.0

**Preliminary**

**No collective motion**

**Hydrodynamic**
**      “****Flow”**

**dN/d(********R ****) = N****0 ****(1 + 2V****1****cos (********R****) + 2****V****2****cos (2(********R****)) + ... ) **

- Mark D. Baker

## Elliptic Flow

**Hydrodynamic model**

**V****2**

**Normalized Multiplicity**** **

- midrapidity : || < 1.0

**Preliminary**

**Particle **
**asymmetry**

- Mark D. Baker

## Flow also non-boost-invariant

- v2: quantifies elliptical anisotropy

- Azimuthal shape changes as strong function of 

- Consistent with
- large  suggested
- by saturation
- (and required by
- some 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)

**Freezeout**

**Hottest period**

**Expansion**
**   ****cooling**

- Mark D. Baker

## RHIC shows rapid expansion

**1.7 10****12 o****K**

- & a high temperature

**Effective**
**Temperature**
**(GeV)**

**CERN NA49**

**STAR Preliminary**

- Mark D. Baker

## Another thermometer

**In an equilibrium system, two**
**parameters 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 MeV
- B = 46 MeV

- Statistical models
- consistent with
- particle ratio data:
- simple filling of phase
- space?

- Suggest thermalization
- at T ~ Tc, nonzero
- net 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 **o****K ****(1eV = 11,600 K)**
- Chemical: **T = (2.0 **±** 0.2) 10****12 o****K**
-  Kinetic:    **T = (1.7 **±** 0.3) 10****12 o****K**
** ****We did reach ~ 2 trillion K!**

- Mark D. Baker

## Particle ratios at 100+100 GeV!

- Fully reversible
- magnetic field

- p

- K+

- +

**Positive **
**Charge **

**Negative**
**Charge **

- K-

- p

- -

- Truncated <dE/dx> [MIP]

- Preliminary

- Mark D. Baker

## Excitation function of B

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

- Extrapolation of fit

- Mark D. Baker

## Energy Density Estimate (Bj)

**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/fm****3**
**      ****T****i ****~ 220-290 MeV**
**BNL RHIC      (********s = 200 GeV) **
**      ********i**** ~ 5-25 GeV/fm****3**** **
**      ****T****i ****~ 250-350 MeV     **
**      **

**	**

** **

**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 expansion
- 	vt ~ 0.65 c

**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 Mechanical**
**Source 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 from**
**40 Hz to 500-700 Hz**
**Upgrade triggering**
**II. Better particle ID**
**Move 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.

- Mark D. Baker