# Presentation: 430255

## Femtoscopy in heavy ion collisions:Wherefore, Whence, & Whither?

- Femtoscopy in heavy ion collisions:Wherefore, Whence, & Whither?

- Mike Lisa
*Ohio State University*

- MAL, Pratt, Soltz, Wiedemann
- Ann Rev Nucl Part Sci **55** (2005)

- Wherefore (=“why?”)
- motivation & (basic) formalism

- Whence (=“from where?”)
- systematics over 2 decades

- Whither (=“to where?”)
- or “wither”...?

**http://www-rnc.lbl.gov/TBS**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
questions:
tilt?
“prediction” for LHC?

Have these ppt files open:
* TBS lecture 1&2 (gaussian etc)
Zibi’s talk -- backup slides are good
WPCF

## Spacetime - The characteristic of H.I.C.

- Spacetime - *The* characteristic of H.I.C.

- Non-trivial space-time - _**the**_ hallmark of R.H.I.C.
- Initial state: dominates further dynamics
- Intermediate state: impt element in exciting signals
- Final state:
- Geometric structural scale is THE defining feature of QGP

-   Temporal scale sensitive to deconfinement transition (?)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Space-time more important to rhic than to any other accelerator-based physics

Unlike Jlab or so, where beam energy dictates scale probed, the main goal of rhic is to find QGP, in which FUNDAMENTAL physics sets the scale

Evolution: system GROWS and changes SHAPE

FINAL STATE PROBED BY HBT (NEXT)

## Extraction of length scales

- usually used
- (even for non-id)

- maximum-likelihood fit to

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
CF NOT Gaussian

## Reminder

- Two-particle interferometry: p-space separation  space-time separation

- Pratt-Bertsch (“out-side-long”) decomposition designed to help disentangle space & time

- source s**p**(x)   = homogeneity region  [Sinyukov(95)]
-  connections with “whole source” *always* model-dependent

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Disintegration timescale - INITIAL expectation

- 3D 1-fluid Hydrodynamics

**Rischke & Gyulassy, NPA 608, 479 (1996)**

**with**
**transition**

- “”

- “”

- Long-standing favorite signature of QGP:
- increase in , ROUT/RSIDE due to deconfinement  confinement transition
- hoped-for “turn on” as QGP threshold is reached

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Two decades of systematics

- Pion HBT @ Bevalac: “largely confirming nuclear dimensions”
- Since 90’s: increasingly detailed understanding and study w/ high stats

- “R = 5 fm”

**Lisa, Pratt, Soltz, Wiedemann**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Well, some folks would say that since it has generated little insight (grrr....), spending so much
Effort on HBT has indeed been decadent

BTW, *I* do not claim that Bevalac (and MSU for that matter) was trivial, but it’s been stated that way

## Two decades of systematics

- Pion HBT @ Bevalac: “largely confirming nuclear dimensions”
- Since 90’s: increasingly detailed understanding and study w/ high stats

**Lisa, Pratt, Soltz, Wiedemann**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Well, some folks would say that since it has generated little insight (grrr....), spending so much
Effort on HBT has indeed been decadent

BTW, *I* do not claim that Bevalac (and MSU for that matter) was trivial, but it’s been stated that way

## Repeating most basic sanity check at relativistic energies... 

- Do femtoscopic length scales increase when they “should?”

-  Also
-  SPS [NA44(‘99),NA49(‘00)]
-  RHIC [STAR(‘05)]

- Repeating most basic sanity check at relativistic energies...

**p-p correlations**
*** big bump ******** small source**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
if THIS would not work, then we should forget any claim that we know what is going on

Since puzzles abound, it is worthwhile to start here, then!!

## Generalize A1/3 Npart1/3

- Generalize A1/3 Npart1/3
- not bad @ RHIC!
- connection w/ init. size?

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
With pions (instead of, say, baryons) can go into more detailed systematics

Start with “sanity check” which works and gives comfort

End with unexpected (?) scaling law

## Generalize A1/3 Npart1/3

- not bad @ RHIC!
- connection w/ init. size?
- Heavy *and light* data from AGS, **SPS**, RHIC
- ~s-ordering in “geometrical” Rlong, Rside
- Mult ~ K(s)*Npart
- source of residual s dep?
- ...Yes! common scaling
- final state drives radii, not init. geometry
- (breaks down s < 5 GeV)

- LPSW nucl-ex/0505014

- NB: not constant density

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Start with “sanity check” which works and gives comfort

go through what is plotted there carefully.
For each energy, several centralities
includes also Si+Al and Si+Au...

End with unexpected (?) scaling law

## We are not alone...

**We are not alone...**

- Entropy determines “everything” at bulk level (soft sector) ?
- c.f. Helen’s talk

- NB: scaling violated s < 4 GeV
- (as with femtoscopy)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Roy’s talk: v2 vanishes and even goes negative below top AGS-- a really peripheral Au+Au collision at RHIC will not have v2<0 !

## Refinement: chemical effects

- different behaviour below/above AGS
- violates “universal” scaling
- baryon  meson dominance
- neglect time/dynamics: gross F.O. geometry appears determined by
- chemistry
- “universal” mean free path ~ **1 fm** **(!?)**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
so, let’s see if we can understand the violation for femtoscopy....

This may be crude, but at least it’s an attempt to explain/simplify EXCITATION FUNCTION (and not just one energy)

This CERES analysis looks only at central collisions and neglects lots of stuff, but it
“explains” violation of  multiplicity-scaling law so nicely
puts a simple but physics-driven principle on the table

## Messages from systematics

- AB, |**b**|, Npart systematics
- sanity check on overall size dependence ****
- final state multiplicity/chemistry determines rough geometry...

- collective/flow-like expansion?
-  probe anisotropically!

- ...and that geometry is ~2x initial size

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
point is that if one wants to get dynamical / flow-related information at RHIC, then naturally one looks anisotropically, since that’s the main characteristic of collective motion at RHIC

## What can we learn?

- Strongly-interacting 6Li released from an asymmetric trap
- O’Hara, *et al*, Science **298** 2179 (2002)

**Teaney, Lauret, & Shuryak nucl-th/0110037**

- transverse FO shape
- + collective velocity
-  evolution time estimate
- check independent of RL(pT)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## observe the source from all angles with respect to RP

- expect oscillations in HBT radii

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## R2out-side<0

- expect oscillations in HBT radii (including “new” cross-terms)

- R2out-side<0
- when pair=135o

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Measured final source* shape

- Measured *final* source* shape

***** model-dependent, but see Retiere & MAL PRC70 044907 2004

- R2out-side<0
- when pair=135o

- ever see that symmetry at ycm ?

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Measured final source* shape

- Measured *final* source* shape

***** model-dependent, but see Retiere & MAL PRC70 044907 2004

- Expected evolution:

*?*

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Evolution of size and shape - “the rule of two”

- Initial size/shape estimated by Glauber calculation
- Final config according to Retiere & MAL PRC70 044907 2004

- ~ x2 size increase

- ~ 1/2 shape reduction

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## “Anisotropic sanity check”

- does it make sense?  Is it related to *bulk* dynamics?
-  **YES**

**“****Anisotropic sanity check”**

**(in a *****toy***** model yes - for****discusison if asked)**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
we finally see something that changes with energy!!  yay!

But does it make sense?   Yes!!

## Messages from systematics

- AB, |**b**|, Npart systematics
- sanity check on overall size dependence ****
- final state multiplicity/chemistry determines rough geometry...
- , |**b**|, s systematics
- sanity check on shape evolution ****
- geometric evolution ~ consistent with collective bulk dynamics (flow)

- look for dynamic signatures & substructure

- more than T versus mass
- more than spectral shapes
- more than v2
- ...
**flow is **_**defined by**_** space-momentum correlations**
- only femtoscopy can probe substructure
- of dynamic bulk behaviour

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
point is that if one wants to get dynamical / flow-related information at RHIC, then naturally one looks anisotropically, since that’s the main characteristic of collective motion at RHIC

## Geometric substructure?

- random (non-)system:
- all observers measure the
- “whole source”

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
   x-p correlations are NONTRIVIAL!!  The particle emitted at the upper right edge “knows” that he is emitted from there

## Flow-generated substructure

- space-momentum (x-p) correlations
- faster (high pT) particles come from
**smaller** source
- closer to “the **edge**”

- random (non-)system:
- all observers measure the
- “whole source”

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
   x-p correlations are NONTRIVIAL!!  The particle emitted at the upper right edge “knows” that he is emitted from there

## Strong flow confirmed by all expts...

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
BUT we need to remember that “all experiments” have not been done at RHIC...

the “What agreement!” refers to consistent data.
the “What agreement?” refers to the models (which do not have the excuse like at SPS that well anyway the experiments don’t agree so what can we do...?)

## Flow-dominated

- “Blast-wave” model
- PR**C70** 044907 (2004)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
we saw geometric TIME EVOLUTION

BW suggests collective flow - let’s see if there is such flow

Why do those radii fall ??

## Decreasing R(pT)

- Decreasing R(pT)
- usually attributed to collective flow
- flow integral to our understanding of R.H.I.C.; taken for granted
- femtoscopy the *only* way to confirm **x-p** correlations – impt check

- Non-flow possibilities
- cooling, *thermally* (not collectively) expanding source
- combo of x-t and t-p correlations

- early times: small, hot source

- late times: large, cool source

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Decreasing R(pT)

- Decreasing R(pT)
- usually attributed to collective flow
- flow integral to our understanding of R.H.I.C.; taken for granted
- femtoscopy the *only* way to confirm **x-p** correlations – impt check

- Non-flow possibilities
- cooling, *thermally* (not collectively) expanding source
- combo of x-t and t-p correlations

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Decreasing R(pT)

- Decreasing R(pT)
- usually attributed to collective flow
- flow integral to our understanding of R.H.I.C.; taken for granted
- femtoscopy the *only* way to confirm **x-p** correlations – impt check

- Non-flow possibilities
- cooling, *thermally* (not collectively) expanding source
- combo of x-t and t-p correlations
- hot core surrounded by cool shell
- important ingredient of Buda-Lund hydro picturee.g. Csörgő & LörstadPR**C54** 1390 (1996)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Decreasing R(pT)

- Decreasing R(pT)
- usually attributed to collective flow
- flow integral to our understanding of R.H.I.C.; taken for granted
- femtoscopy the *only* way to confirm **x-p** correlations – impt check

- Non-flow possibilities
- cooling, *thermally* (not collectively) expanding source
- combo of x-t and t-p correlations
- hot core surrounded by cool shell
- important ingredient of Buda-Lund hydro picturee.g. Csörgő & LörstadPR**C54** 1390 (1996)

- t

- Each scenario generates
- x-p correlations

- but...

- x2-p correlation:	yes
- x-p correlation:		yes

- x2-p correlation:	yes
- x-p correlation:		no

- x2-p correlation:	yes
- x-p correlation:		no

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## 

- Flow-dominated
- “Blast-wave” model
- PR**C70** 044907 (2004)

- K

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
OK OK clearly it is flow.  We are QUANTITATIVE here!

## RHIC femtoscopy with wide variety of particle species

| + | - | K+ | K- | K0S | p | p |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |  |  |  |  | + |
|  |  |  |  |  |  |  |  |  |  |  | - |
|  |  |  | - |  |  |  |  |  |  |  | K+ |
|  |  |  |  |  |  |  |  |  |  |  | K- |
|  |  |  |  |  | - | - |  |  |  |  | K0S |
|  |  |  |  |  |  |  |  |  |  |  | p |
|  |  |  |  |  |  |  |  |  |  |  | p |
|  |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  |  |  |  |  |

**R(****√S****NN****, b, N****part****, A, B****, ****m****T****, y, ********, ****PID****1****, PID****2****) **

****** ****= prelim or final result available**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
! Be impressed !

## Trends, soft sector, and RHI history

- A. Wetzler (2005)

- Then: p-dependent potentials, surface effects, hard-cores, absoption...

- unlike hard and “intermediate” sectors, soft sector has “decades” of systematics

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
At Bevalac, there were several claims of successful EoS’s, but they fell one-by-one as systematic comparisons were performed

Especially in soft sector (where systematics exist), match systematics!

## model comparisons

- unlike hard and “intermediate” sectors, soft sector has “decades” of systematics
- single-point agreement a bit unsatisfying...
- femtoscopic model comparisons: mostly “HBT radii” in b=0 collisions
- RHIC models *only* expected to work at highest energies...

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Comparison to “perfect” hydro calculations

-  model sensitivity (not just R=5)
- Rout  too big (too long emission time?)
-  Rlong too big (too long evolution time?)
-  Rside too small (?)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
BUT we need to remember that “all experiments” have not been done at RHIC...

the “What agreement!” refers to consistent data.
the “What agreement?” refers to the models (which do not have the excuse like at SPS that well anyway the experiments don’t agree so what can we do...?)

## Comparison to Boltzmann/cascade models

- better!  (better than “perfect”...?)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
The “perfect” point here is that we advertize “PERFECT LIQUID” based on hydro, but  cascade is doing better in spacetime, so is it better than perfect?

## What’s the difference?

-  freeeze-out........ EoS............viscosity

- should be the same **IF** source is Gaussian

- hydro

- cascade

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
note: WITHIN each 

## Non-Gaussian Effects and Model Comparisons - Hydro/BW

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Wherefore & Whence

- size & shape;  timescale estimate
- space-momentum substructure of a flowing system;dynamics and evolution of
- radial flow (size and _shift_)
- elliptic flow (shape and timescale)
- directed flow (shape and _tilt_)         [did not show due to time]
- hadronic particle potentials / phase shifts
- Femtoscopy:
- well-calibrated, well-established tool
- the one most directly connected to space-time - **THE **defining feature of R.H.I.C.
- huge set of systematics of consistent measurements
- sensitive to physics in models
- with care: the femtoscope is a precision tool to apply to new systemsLHC, **p+p**, etc

**R(****√S****NN****, b, N****part****, A, B****, ****m****T****, y, ********, ****PID****1****, PID****2****) **

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
methods better understood  /  CONSISTENT RESULTS (better than SPS)   /   Specificc workshops like this are appropriate  -- thanks to people like JAN and SERGEI

 technical (like we tackled Coulomb together)  /   physical  (imaging...)

## Whither?

- non-id correlations for b≠0  [Retiere & Lisa PRCPR**C70** 044907 (2004)]
- invert the problem : low-energy phaseshifts from exotic pairs (e.g. -) [talk of H. Gos] & [P. Chaloupta QM05]
- space-time substructure in p+p ??  - “direct comparison] [talk of Z. Chajecki][Chajecki et al, WW05]
- imaging - beyond sizes and shifts [Brown, Danielewicz, Pratt, & others]
- first-order azimuthally-sensitive femtoscopy - spacetime aspects of v1[Lisa et al, PLB489 287; PLB496 1]
- relative jets, spin.... (?)
- continue/expand rich program @ ALICE/LHC

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## THEEND

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Strong flow confirmed by all expts...

- Strong flow confirmed by ***all*** expts...

**Central (~10%) AuAu (PbPb) collisions at y~0**

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
BUT we need to remember that “all experiments” have not been done at RHIC...

the “What agreement!” refers to consistent data.
the “What agreement?” refers to the models (which do not have the excuse like at SPS that well anyway the experiments don’t agree so what can we do...?)

## A simple estimate – 0 from init and final 

- BW → X, Y @ F.O.  (X > Y)
- hydro: flow velocity grows ~ t
- From RL(mT): 0 ~ 9 fm/c
- consistent picture
- Longer or shorter evolution times
-  inconsistent
- toy estimate: 0 ~ 0(BW)~ 9 fm/c
- too short to account for expansion??
- Need a real model comparison→ asHBT workable “evolutionary     clock” constraint for models

- MAL ISMD03

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Scott’s work (presented @ ISMD) might make this toy  BARELY consistent.

But my point here is only  to show that the thing is not crazy and that it can be quantifiably useful for modelers

## 1D projections: a limited view

- (remember: *not*
- Gaussian CF)

- Usually, quality of data and fit shown in 1D projections
- Narrow integration best
- limited view of data
- see talks of Adam, Scott, Sandra
- tomorrow: a better way

**out**

**side**

**long**

- STAR PRC71 044906 (2005)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## The perennial non-Gaussianness

- Source has never been fully Gaussian.  c.f. J. Sullivan @ SPS
- periodically re-discovered, with little change; information condensation needed to observe systematic data trends
- non-Gaussianness @ RHIC reported in first and subsequent HBT measurements
- imaging is probably best solution (but even then...)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## The perennial non-Gaussianness

- CF is “mostly” Gaussian
- STAR tried “Edgeworth”
-     functional expansion
-     (Csorgo 2000)
- among few quantitative estimates
- of non-Gaussian shape

- STAR PRC71 044906 (2005)

-  20% effect in Rlong!  systematic error...?
-  appears fit captures dominant length scale

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## Another implication of strong flow: ~ mT scaling

- Another implication of strong flow: ~ mT scaling

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
Did anyone realize what a huge range of systematics have been accumulated by now?!
And how consistent they are?!

I did not!

## transverse shape:

- transverse shape:
- non-trivial excitation function
- increased flow*time  rounder FO geometry @ RHIC
- insufficient [flow]x[time] to become in-plane

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
 EVOLUTION in root(s)

These (asHBT) are the only nontrivial femtoscopic excitation functions

## Au+Au sNN = 2.3 GeV; b5 fm

- Au+Au sNN = 2.3 GeV; b5 fm

- E895, PL**B496** 1 (2000)

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
what information is contained in these “new” radii Rol and Rsl ?

one reason I want to talk about this in a bit of detail:
it carries brand-new information which appeared only at the time of RHIC turn-on
Thus, despite my best efforts, maybe nobody knows it

Plus, Art played a big role in helping conceptually

## ?

**?**

**?**

- STAR: soon

- transverse shape:
- non-trivial excitation function
- increased flow*time  rounder FO geometry @ RHIC
- insufficient [flow]x[time] to become in-plane
- Spatial orientation:
- another handle on flow & time
- HUGE tilts @ AGS!!
- RHIC?
- QGP-induced orientation?

- AGS

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

## v1 predictions (QGP invoked)

- J. Brachmann et al., Phys. Rev. C. 61 024909 (2000)

- L.P. Csernai, D. Rohrich: Phys. Lett. B 458 (1999) 454

- x-p transverse-longitudinal coupling may be affected in early (v1) stage

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
just a few suggestions about nontrivial physics which might be probed.

we don’t discuss it here

## ?

**?**

**?**

- STAR: soon ?

- transverse shape:
- non-trivial excitation function
- increased flow*time  rounder FO geometry @ RHIC
- insufficient [flow]x[time] to become in-plane
- Spatial orientation:
- another handle on flow & time
- HUGE tilts @ AGS!!
- RHIC?
- QGP-induced orientation?
- requires true 3D dynamical model (explicitly non-B.I.)

- AGS

- mike lisa - Femtoscopy in relativistic heavy ion collisions - Hot Quarks 17 May 2006, Sardinia, Italy

**Notes:**
to study it, boost-invariance will need to go