# Presentation: 119264

## Future Directions in HBT

- This title has been used before
- These predictions are seldom right

- Title

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT-Puzzle For Dummies

- Some very smart people have contributed to our understanding of HBT
- They just don’t care to be associated with it anymore

- Possible copyright infringement suit!

- Title #2

- and by one, but not of...

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Solving the HBT Puzzle:Noble quest or trivial pursuit 

- I will try to convince you of the former
- But, some will remain unconvinced ...

- For those of you in this category
- - watch for embedded trivia questions
- - answer all correctly and collect your beer(s)

- Final Title

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Volumes & Lifetimes2nd Law Thermodynamics

- Ideal Gas
- Relativistic Fermi/Bose Gas=0
- Pions (**3**)    vs.    QGP (**37**)

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT (GGLP) Basics

- In the simplest approximation, the technique has not changed since before most of you were born
**	****Goldhaber, Goldhaber, Lee, and Pais, PR 120:300 (1960)**
- For identical bosons/fermions

- But this (plane wave) approximation neglects many effects

- P(p1,p2;r1,r2) =

- Gaussian source in xi yields Gaussian correlation
- in conjugate variable qi=p1i-p2i

**Who made first use of this pedagogic picture?**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT Complexities

- We have neglected
- Final state interactions
- Coulomb interaction
- Strong interaction
- Weak decays
- Position-momentum correlations
- Things more subtle, such as special relativity

- State of the art analysis incorporates most of these, but not all

**1/R****side**

**Who performed first “correction” for Coulomb?**

**Where is the first mention of Lorentz effects in HBT?**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT - current state of the art

- Bowler/Sinyukov factorization
- Assumes |C+C*|2 = FC •|+*|2
- Still an approximation to 2-3% for kaons

- ~50 ways to handle Coulomb/Weak decays

- All subsequent data shown use the first technique

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT Radius Definitions (b=0) 

- Rlong  ~ F

- Rside  kT   ~  Rgeo

- Rout || kT

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT Radius Dynamics

- Transverse Expansion profile
- Transverse Freeze-out profile

- Positive x-p correlations _reduce all R_
-  Hydrodynamic :  ~ x ; R~1/√mT
-  Heisenberg :  ~ 1/x ; R~1/mT

- Positive x-t correlations=>_reduce R_out

- R2out = x2

- t)2

- xt

- “inside-outside” cascade

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT Experimental Results

- Excellent agreement (phobos too)
- Systematics well under control
- A Precision Tool !

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## More Experimental Systematics

**STAR PRL 93:12301 (2004)**

**PHENIX nucl-ex/0401003**

- Don’t tell me HBT radii don’t relate to a physical size

- b≠0

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Model Comparison (the puzzle)

**No model correct**
**Does R****out****/R****side**** of unity imply no long-lived mixed phase?**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Model Calculation Systematics

- Each theory paper has explored systematic changes in at least one important variable
-  Tf = Freeze-out Temp/profile
-  Tc = Critical Temp.
-  el = parton scattering cross-section
-  E = Latent Heat/transition order
-  Tch = chem. Freeze-out temp
-  n    = viscoscity (-20% Rout, -60% Rlong)

**D. Teany, nucl-th/0301099**

-  Instead of looking for correct answer, explore systematics

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## HBT radii vs. S(x,p) and x-t corr.

- Using x-rms incorrect (at least for low kT pions)

- Extract radii or check for equivalence
- Freeze-out matters

- x-t term comparable to x and t

**Z. Lin et al, PRL 89:152301 (2002)**

**What was the first reference to explore x-t correlations in a cascade model?**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Partonic cross-sections

- Variation in radii for *reasonable *el/opacity less than sys. errors

- AMPT shows little sensitivity for el=3,6,10,16 mb

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Tc in hybrid model

- Results for kaons
- Lower TC 160 vs. 200 MeV
- shortens hadronic phase
-  E ~ 1.5 vs. 2.9 GeV
- slight drop Rout
- ~20% drop in Rout/Rside

**S. Soff, et al., PRL 88:072301 (2002)**

- Rout/Rside sensitive to TC & latent heat

**R****O**

**R****S**

**R****L**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Tf & latent heat in chiral model

- --- TF = 130 MeV, --- TF = 80 MeV
- Predictions for Rside and Rout only
- Significant drop in Rout/Rside for 2nd order transition

**D. Zschiesche, PRC 65:064902 (2002)**

- Rout/Rside sensitive to TF and transition order

******E=0 GeV**

******E=1.7 GeV**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## 3D w/ Tch with hybrid approach

- Rlong nailed !
- Sudden freeze-out may be too sudden but 2D Hybrid has larger Rlong,side

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Review of Models

- Rout/Rside is particularly sensitive to _freeze-out dynamics_, perhaps uniquely so
- could be used to “tune” freeze-out profile
- better to calculate with re-scattering model
- Radii sensitive to ___E and T__C __and T__F_
- No evidence yet for strong dependence on partonic phase, except perhaps at _higher p__T_

- In a physical model, all these things are coupled

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Solving the Puzzle

- First
- abandon sudden freeze-out
- Second
- run 3D hydro with small E, low TC, and short hadronic re-scattering phase to define freeze-out
- Ultimate Goal
- run hydro hybrid to map out complete 2 complete parameter space for realistic EOS and init. cond. comparing to full set of observables

- How much person and computing power would this require?

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## A job for parameterizations?

- Can parameterizations be used to speed up mapping of the 2 space?
- Maybe
- Worth investigating

- First benchmark parameterizations to full calculations

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## And for the experiments...

- Extend asHBT to higher kT >0.5 GeV
- more complete test of spatial evolution
- Extend pion radii to higher kT > 1 GeV
- more sensitive to pre-hadronic phase
- Extend to kaons, protons
- investigate meson/baryon dynamics
- HBT with 2-photons
- probe early dynamics

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## The proton-proton “conundrum”

- Evidence for same expansion dynamics in p-p collisions
- Are we seeing a universal property of particle production?
- Maybe - this is not (yet) a precision test
- 4 bins is not enough to study differences in dynamics

**T. Gutierrez, nucl-ex/0403012 (2004)**

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Solving the Puzzle

- First
- abandon sudden freeze-out
- Second
- run 3D hydro with small E, low TC, and short hadronic re-scattering phase to define freeze-out
- Ultimate Goal
- run hydro hybrid to map out complete 2 complete parameter space for realistic EOS and init. cond. comparing to full set of observables

- How much person and computing power would this require?

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004

## Size & Lifetime

- Bose-Einstein Correlations

- R. Soltz, Hot Quarks, Taos, NM

- July 22, 2004