# Presentation: 870746

## A menu of expectations forfemtoscopy* 1.0 at LHC/ALICE

- Mike Lisa
- Ohio State University

*******	****femtoscopy** (fem-ta-skö-pee) *noun*
- 	The measurement of spatial scales at the fermi level.
- 	Non-trivially related to the “HBT effect” invented to measure stellar scales

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
why to put “AGS/SPS/RHIC” into title with “highest energies?”  Because, keep in mind, those machines were, in their day, the “highest energy.”  Heavy ion collisions, ESPECIALLY in the soft (bulk) sector (domain of PW2) has long history, and any expectation must be viewed in light of that.

## Outline

- Brief motivation / review
- Model expectations for H.I. collisions [ mostly]
- The importance of femtoscopy in p+p collisions
- A menu

- Mike Lisa - ISMD, Berkeley - August 2007

## fast energy deposition  plasma   hydro expansion  cooling to original phase

|  | Microexplosions | Femtoexplosions |
| --- | --- | --- |
| s | 0.1 J |  1 J |
|  | 1017 J/m3 | 5 GeV/fm3 = 1036 J/m3 |
| T | 106 K | 200 MeV = 1012 K |
| rate | 1018 K/sec | 1035 K/s |

- fast energy deposition  plasma   hydro expansion  cooling to original phase
- do ***geometric*** “postmortem” & infer momentum

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
hey, we are making/studying MATTER, too!  Folks outside of our field do not think of us as “matter” but instead as high energy (“particle”) physicists.  
like us:
go into plasma phase
expand hydrodynamically, cool, and wind up back in the phase where they started, and they have to do a “postmortem” (which focuses on space) to figure out what happened 
a difference is the “inverse situation” in the postmortem:
they can measure spatial information directly (during a static postmortem) and only infer about momentum
we measure momentum directly and only infer space (during a dynamic postmoretem)

## fast energy deposition  plasma   hydro expansion  cooling to original phase

|  | Microexplosions | Femtoexplosions |
| --- | --- | --- |
| s | 0.1 J |  1 J |
|  | 1017 J/m3 | 5 GeV/fm3 = 1036 J/m3 |
| T | 106 K | 200 MeV = 1012 K |
| rate | 1018 K/sec | 1035 K/s |

- fast energy deposition  plasma   hydro expansion  cooling to original phase
- do ***geometric*** “postmortem” & infer momentum

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
hey, we are making/studying MATTER, too!  Folks outside of our field do not think of us as “matter” but instead as high energy (“particle”) physicists.  
like us:
go into plasma phase
expand hydrodynamically, cool, and wind up back in the phase where they started, and they have to do a “postmortem” (which focuses on space) to figure out what happened 
a difference is the “inverse situation” in the postmortem:
they can measure spatial information directly (during a static postmortem) and only infer about momentum
we measure momentum directly and only infer space (during a dynamic postmoretem)

## measure explosive pattern of the thermalized bulk matter (low-pT)

|  | Microexplosions | Femtoexplosions |
| --- | --- | --- |
| s | 0.1 J |  1 J |
|  | 1017 J/m3 | 5 GeV/fm3 = 1036 J/m3 |
| T | 106 K | 200 MeV = 1012 K |
| rate | 1018 K/sec | 1035 K/s |

- fast energy deposition  plasma   hydro expansion  cooling to original phase
- do ***geometric*** “postmortem” & infer momentum

- measure explosive pattern of the thermalized *bulk* matter (low-pT)

- B2B jets?

- access to bulk properties (EoS) driving dynamics

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
hey, we are making/studying MATTER, too!  Folks outside of our field do not think of us as “matter” but instead as high energy (“particle”) physicists.  
like us:
go into plasma phase
expand hydrodynamically, cool, and wind up back in the phase where they started, and they have to do a “postmortem” (which focuses on space) to figure out what happened 
a difference is the “inverse situation” in the postmortem:
they can measure spatial information directly (during a static postmortem) and only infer about momentum
we measure momentum directly and only infer space (during a dynamic postmoretem)

## measure explosive pattern of the thermalized bulk matter (low-pT)

- measure explosive pattern of the thermalized *bulk* matter (low-pT)

- hydro expectation
- (off-center collision)

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
* clearly we need a more differential study

Note: this need for systematics is not specific to HBT
-- just as geometry is the PHYSICS hallmark
-- so systematics is the METHODOLOGICAL hallmark

## measure explosive pattern of the thermalized bulk matter (low-pT)

- measure explosive pattern of the thermalized *bulk* matter (low-pT)

- “elliptic flow”

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
* clearly we need a more differential study

Note: this need for systematics is not specific to HBT
-- just as geometry is the PHYSICS hallmark
-- so systematics is the METHODOLOGICAL hallmark

## measure explosive pattern of the thermalized bulk matter (low-pT)

- measure explosive pattern of the thermalized *bulk* matter (low-pT)

- femtoscopy
- probes x-p
- substructure

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
* clearly we need a more differential study

Note: this need for systematics is not specific to HBT
-- just as geometry is the PHYSICS hallmark
-- so systematics is the METHODOLOGICAL hallmark

## At RHIC: Explosive signature sensitive to physics in models

- What might we expect at LHC?

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
HRM (and AMPT??) will be discussed later today
(You don’t see HRM on left plot, because its points lie under the data !)

## “All” soft-physics observables at RHIC (& often SPS/AGS)are multiplicity-driven

**Entropy dominance?**

- Mike Lisa - ISMD, Berkeley - August 2007

## 6.4 = RHICx1.6

- PHOBOS White Paper: NPA 757, 28

**6.4 = RHICx1.6**

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
roughly to scale by using R=2.0 2.5 m for TPC OFC in STAR and ALICE, repectively

## NNUS*: Multiplicity sets scale: all else fixed

- PHOBOS-based extrapolation:
- RLHC / RRHIC = (1.6)1/3 = 1.17

- * NNUS = **N**othing **N**ew **U**nder the **S**un

- Mike Lisa - ISMD, Berkeley - August 2007

## NNUS*: Multiplicity sets scale: all else fixed

- PHOBOS-based extrapolation:
- RLHC / RRHIC = (1.6)1/3 = 1.17
- CGC prediction of multiplicity
- RLHC / RRHIC = (11/3.6)1/3 = 31/3 = 1.45

**Kharzeev, Levin & Nardi NPA747 609 (2005)**

- Mike Lisa - ISMD, Berkeley - August 2007

## NNUS*: Multiplicity sets scale: all else fixed

- NNUS*: Multiplicity sets scale: all else fixed

- PHOBOS-based extrapolation:
- RLHC / RRHIC = (1.6)1/3 = 1.17
- CGC prediction of multiplicity
- RLHC / RRHIC = (11/3.6)1/3 = 31/3 = 1.45
- R <~ 11 fm [low pT pions generate largest separation distribution]

- Mike Lisa - ISMD, Berkeley - August 2007

## NNUS*: Multiplicity sets scale: all else fixed

- NNUS*: Multiplicity sets scale: all else fixed

- PHOBOS-based extrapolation:
- RLHC / RRHIC = (1.6)1/3 = 1.17
- CGC prediction of multiplicity
- RLHC / RRHIC = (11/3.6)1/3 = 31/3 = 1.45
- R <~ 11 fm
- well within experimental reach
- Rfit ~ 1/(q2)
- q ~ 1 MeV/c
- qmin ~ 2 MeV/c

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Access to long-range non-Gaussian tail

- Generalized imaging* fit probes long-R / low-q
- access to resonance tail
- small below s ~ 10 GeV
- LHC should be ~RHIC
- (... and/or “other” tails...)
- details beyond gross size

-  PHENIX, PRL 98, 132301 (2007) ,

***** c.f. talks of P. Danielewicz & P. Chung

- Mike Lisa - ISMD, Berkeley - August 2007

## Physics from (Gaussian) scales - dynamic models

**Boltzmann models**
- particle rescattering
- thermalization not assumed
- typically “hard” EoS
- softening must be put in by hand (“string melting” etc)
**Hydrodynamic models**
- thermalization / “perfect fluid”
- EoS varied.  Typically a “soft point” used

- Mike Lisa - ISMD, Berkeley - August 2007

## Boltzmann-type models

- Humanic/Hadron Rescattering Model
- “real” model predicting flow & HBT
- (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9

- T. Humanic,
- Int.J.Mod.Phys.**E15**197(2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Boltzmann-type models

- Humanic/Hadron Rescattering Model
- “real” model predicting flow & HBT
- (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
- LHC / RHIC = 2   ::  (recall Rlong~~ )
**dynamic** effect
- Rlong[LHC] / Rlong[RHIC] ~ 2
- all are connected??

- T. Humanic,
- Int.J.Mod.Phys.**E15**197(2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Boltzmann-type models

- Humanic/Hadron Rescattering Model
- “real” model predicting flow & HBT
- (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
- LHC / RHIC = 2   ::  (recall Rlong~~ )
**dynamic** effect
- Rlong[LHC] / Rlong[RHIC] ~ 2
- all are connected?
- RS, RO larger, but not a simple factor

- T. Humanic,
- Int.J.Mod.Phys.**E15**197(2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Boltzmann-type models

- Humanic/Hadron Rescattering Model
- “real” model predicting flow & HBT
- (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
- LHC / RHIC = 2   ::  (recall Rlong~~ )
**dynamic** effect
- Rlong[LHC] / Rlong[RHIC] ~ 2
- all are connected?
- RS, RO larger, but not a simple factor
- steeper pT-dep due to more flow?
**dynamic** effect
- Hard EoS rescattering models: _dynamic effects superimposed on chemistry_
- similar for AMPD C.M. Ko; WPCF06

- T. Humanic,
- Int.J.Mod.Phys.**E15**197(2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Hydro predictions I: Scales

- Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
- Cno flow[RHIC] = 6 fm/c
- Cno flow[LHC] = 20 fm/c

- Eskola *et al* PR**C72**044904 (2005)

- Mike Lisa - ISMD, Berkeley - August 2007

## Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
Cno flow[RHIC] = 6 fm/c
Cno flow[LHC] = 20 fm/c
Much larger flow @LHC
signif. reduction of timescale @ LHC [similar to RHIC]
larger transverse size @ FO

- Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
- Cno flow[RHIC] = 6 fm/c
- Cno flow[LHC] = 20 fm/c
- Much larger flow @LHC
- signif. reduction of timescale @ LHC [similar to RHIC]
- larger transverse size @ FO

- Eskola *et al* PR**C72**044904 (2005)

- Hydro predictions I: Scales

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
with flow, t[RHIC]~4.5 and t[LHC]~7
(look where red curve hits y-axis)

## Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
Cno flow[RHIC] = 6 fm/c
Cno flow[LHC] = 20 fm/c
Much larger flow @LHC
signif. reduction of timescale @ LHC [similar to RHIC]
larger transverse size @ FO
 No HBT prediction per se, but...
RL[LHC] / RL[RHIC] ~ 1.1 ÷ 1.2
RS[LHC] / RS[RHIC] ~ 1.5 ÷ 2
(different than HRM)
steeper pT-dependence

- Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
- Cno flow[RHIC] = 6 fm/c
- Cno flow[LHC] = 20 fm/c
- Much larger flow @LHC
- signif. reduction of timescale @ LHC [similar to RHIC]
- larger transverse size @ FO
-  No HBT prediction per se, but...
- RL[LHC] / RL[RHIC] ~ 1.1 ÷ 1.2
- RS[LHC] / RS[RHIC] ~ 1.5 ÷ 2
- (different than HRM)
- steeper pT-dependence

- Eskola *et al* PR**C72**044904 (2005)

- Hydro predictions I: Scales

- Mike Lisa - ISMD, Berkeley - August 2007

## Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
Cno flow[RHIC] = 6 fm/c
Cno flow[LHC] = 20 fm/c
Much larger flow @LHC
signif. reduction of timescale @ LHC [similar to RHIC]
larger transverse size @ FO
 No HBT prediction per se, but...
RL[LHC] / RL[RHIC] ~ 1.1 ÷ 1.2
RS[LHC] / RS[RHIC] ~ 1.5 ÷ 2
(different than HRM)
steeper pT-dependence
Consistent w/ independent hydrofor non-central collisions

- Neglecting flow, to cool to C[QGP] :C = 0(C /0)3/4
- Cno flow[RHIC] = 6 fm/c
- Cno flow[LHC] = 20 fm/c
- Much larger flow @LHC
- signif. reduction of timescale @ LHC [similar to RHIC]
- larger transverse size @ FO
-  No HBT prediction per se, but...
- RL[LHC] / RL[RHIC] ~ 1.1 ÷ 1.2
- RS[LHC] / RS[RHIC] ~ 1.5 ÷ 2
- (different than HRM)
- steeper pT-dependence
- Consistent w/ independent hydrofor *non-*central collisions

- Eskola *et al* PR**C72**044904 (2005)

- Hydro predictions I: Scales

**(LHC)**

- Mike Lisa - ISMD, Berkeley - August 2007

## easy prediction: importance of -dep measurements will continue @ LHC
RP resolution at least as good as STAR
asHBT
measures source shape at freezeout

- easy prediction: importance of -dep measurements will continue @ LHC
- RP resolution at least as good as STAR
- asHBT
- measures source shape at freezeout

- Hydro predictions II: Shapes

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
the eccentricity “excitation function” is often panel (e) of our global femtoscopy excitation function plot, and it doesn’t get much attention, which is weird, since it is probably the most non-trivial root(s) dependence of all of them.

## easy prediction: importance of -dep measurements will continue @ LHC
RP resolution at least as good as STAR
asHBT
measures source shape at freezeout
probes timescale & dynamics
non-trivial (& incomplete!) excitation fctn

- RP resolution at least as good as STAR
- asHBT
- measures source shape at freezeout
- probes timescale & dynamics
- non-trivial (& incomplete!) excitation fctn

- Hydro predictions II: Shapes

****

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
the eccentricity “excitation function” is often panel (e) of our global femtoscopy excitation function plot, and it doesn’t get much attention, which is weird, since it is probably the most non-trivial root(s) dependence of all of them.

## easy prediction: importance of -dep measurements will continue @ LHC
RP resolution at least as good as STAR
asHBT
measures source shape at freezeout
probes timescale & dynamics
non-trivial (& incomplete!) excitation fctn
hydro @ RHIC
misses scale (well-known)
impressive agreement on -dep 

- easy prediction: importance of -dep measurements will continue @ LHC
- RP resolution at least as good as STAR
- asHBT
- measures source shape at freezeout
- probes timescale & dynamics
- non-trivial (& incomplete!) excitation fctn
- hydro @ RHIC
- misses scale (well-known)
- impressive agreement on -dep

- Hydro predictions II: Shapes

****

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
the eccentricity “excitation function” is often panel (e) of our global femtoscopy excitation function plot, and it doesn’t get much attention, which is wierd, since it is probably the most non-trivial root(s) dependence of all of them.

## easy prediction: importance of -dep measurements will continue @ LHC
RP resolution at least as good as STAR
asHBT
measures source shape at freezeout
probes timescale & dynamics
non-trivial (& incomplete!) excitation fctn
hydro @ RHIC
misses scale (well-known)
impressive agreement on -dep
prediction @ LHC
sign change in shape & oscillations

- RP resolution at least as good as STAR
- asHBT
- measures source shape at freezeout
- probes timescale & dynamics
- non-trivial (& incomplete!) excitation fctn
- hydro @ RHIC
- misses scale (well-known)
- impressive agreement on -dep
- prediction @ LHC
- sign change in shape & oscillations

- Hydro predictions II: Shapes

- Sign flip in oscillations reflects transition to in-plane geometry
- (more flow, more time)

****

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
the eccentricity “excitation function” is often panel (e) of our global femtoscopy excitation function plot, and it doesn’t get much attention, which is wierd, since it is probably the most non-trivial root(s) dependence of all of them.

## p+p: A clear reference system?

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
apparently quite different in
hard sector
p-space only...
by our diagrams
should not treat p+p hydrodynamically...

## e+e- (and p+p, +p...) -- “similar” HBT radii

- high-quality/stats data sparse
- diversity of methods
- corrections
- coordinate systems
- jet axis in e+e-...
- mixing...
- physics?

- Mike Lisa - ISMD, Berkeley - August 2007

## e+e- (and p+p, +p...) -- “similar” HBT radii

- high-quality/stats data sparse
- diversity of methods
- corrections
- coordinate systems
- jet axis in e+e-...
- mixing...
- physics of “x-p” correlations in very small systems?
- strings?
- jets?
- pythia + rescattering?
- else?

- talk by T. Humanic

- Paic and Skowronski
- J. Phys. **G31** 1045 (2005)
- see also Csorgo & Zajc
- hep-ph/0412243 (ISMD04)

**pT signal?**

- Mike Lisa - ISMD, Berkeley - August 2007

## Caution: femtoscopy in p+p @ STAR

**Z. Chajecki WPCF05**

- Caution: femtoscopy in p+p @ STAR

- p+p and A+A measured in same experiment with **same method**
- great opportunity to compare physics
- what causes pT-dependence in p+p?
*same cause as in A+A??*

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
The Andersson reference is 2000 Recontres de Moriond meeting.  It is reference [4] f the cited Alexander paper

Csorgo: fit to star proton-proton coll
Shuryak: check again
Heinz: dependence on the size
More on dAu
More on pp
Rlong

## Surprising („puzzling”) scaling

**HBT radii scale with pp**
**Scary coincidence ****or somethi****n****g deeper?**

- p+p and A+A measured in same experiment with **same method**
- great opportunity to compare physics
- what causes pT-dependence in p+p?
*same cause as in A+A?*

**!! But !! significant issues with nontrivial**
**interplay non-femtoscopic correlations**
**(restricted phasespace)**
** ****should be less of a problem at LHC**
** ****[see talk of T. Humanic]**

- A. Białasz (ISMD):
*I personally feel that its solution may provide new*
*insight into the hadronization process of QCD*

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
Need more theoretical activities
Add STAR preliminary

## plats principaux

- boissons

- entrées

- le menu des espérances au LHC

- Mike Lisa - ISMD, Berkeley - August 2007

**Notes:**
Inspired by the very nice dinner we had last night!

## Slide 36

- Mike Lisa - ISMD, Berkeley - August 2007

## R(√SNN, b, Npart, A, B, mT, y, , PID1, PID2) 

| + | - | 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****) **

- Does lock pattern break?

- Mike Lisa - ISMD, Berkeley - August 2007

## The end

- (...finally...)

- Mike Lisa - ISMD, Berkeley - August 2007

## ALICE PPR2 plots

- Mike Lisa - ISMD, Berkeley - August 2007

## Relative momentum resolution

- ITS+TPC tracks
- 2 MeV/c (-> 100 fm, for scale only...)
- del-qside small since azim. angle well-known
- qout probes sagitta resolution
- heavier particles
- less bending -> smaller sagitta -> worse resolution
- but due to mT scaling, worse resolution is OK :-)

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Track merging effects in the TPC

- merging -> ~0.3 fm bias in HBT radius determination for 8 fm source
- less impt for smaller sources
- less impt if Coulomb FSI included (?)
- impact on imaging (non-Gaussian shapes) (?)
- merging correlated in qo-qs (can mimic “tilted source”)
- requiring separation in TPC helps remove effect, but convergence is slow

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## The ITS helps remove merging effects

- Ros = 0 as figure of merit
- Cutting on ITS separation reduces bias to ~0.1-0.2 fm

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- “similar triangles” : qmin/pT = separationMin/radius

- Mike Lisa - ISMD, Berkeley - August 2007

## Momentum resolution correction

- “Triple-ratio” correction first (?) used by NA44
- uses single-particle resolution (assumed known) to smear “ideal” CF
- rapid convergence

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## HBT radii : “out versus in”

- good to ~15 fm

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## Event-by-event femtoscopy in Pb+Pb

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Mike Lisa - ISMD, Berkeley - August 2007

## reactionplane resolution 

- reactionplane resolution

- At least as good as RHIC/STAR

- ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. **32** 1295 (2006)

- Plot from T. Hirano 2005

- Mike Lisa - ISMD, Berkeley - August 2007