Femtoscopy at the highest energies:
Expectations and directions at the LHC
Mike Lisa
Ohio State University
malisa - SPHIC - Catania Italy - Sept 2006
1
Outline
• Femtoscopic expectations @ LHC
• NNUS: systematic extrapolation of existing systematics
• naïve
• CGC
• cascade
• HRM: microscopic hadronic rescattering model
• AMPT: HIJING+parton cascade+string frag+hadronic cascade
• hydro
• scales
• shapes
• p+p
• Pythia (+HRM, jets)
• Black holes
• Some directions at LHC
• Summary
malisa - SPHIC - Catania Italy - Sept 2006
2
Femtoscopic information
xa
pa
pa
pb
pb
xa
xb
C (q) 
ab
P
Sab
( r )
P
xb
 d r S
3
ab
P
( r )   (q, r )
2
= x a - x b  distribution
 (q, r ) = (a,b) relative wavefctn

know/assume relative wavefunction
 extract spatial distributions

malisa - SPHIC - Catania Italy - Sept 2006
OR
know/assume source distrib
 extract interaction (scat. length..)
3
malisa - SPHIC - Catania Italy - Sept 2006
Microexplosions
Femtoexplosions
• energy quickly deposited
0.1phase
J
1 J
•senter plasma
•expand hydrodynamically
1017 J/m3
5 GeV/fm3 = 1036 J/m3
•Tcool back to
phase 200 MeV = 1012 K
6 K
10original
• do geometric “postmortem” & infer momentum
rate
1018 K/sec
1035 K/s
4
malisa - SPHIC - Catania Italy - Sept 2006
Microexplosions
Femtoexplosions
• energy quickly deposited
0.1phase
J
1 J
•senter plasma
•expand hydrodynamically
1017 J/m3
5 GeV/fm3 = 1036 J/m3
•Tcool back to
phase 200 MeV = 1012 K
6 K
10original
• do geometric “postmortem” & infer momentum
rate
1018 K/sec
1035 K/s
5
Baseline: 20-year-old systematic program
ˆ
HBT( s ;p T , y, b ,b,m
1 ,m2 ,Asys )
Experimental HBT Refereed Journal Publications
y
20
Heinz/Jacak
Wiedemann/Heinz
Csorgo
18
16
Tomasik/
Wiedemann
14
#
12
|b|
Lisa/Pratt/
Solts/Wiedemann
10
8
6
4
2
0
1985
pT
1990
1995
2000
2005
2010
Year
• Pion HBT @ Bevalac: “largely confirming nuclear dimensions”
• Since 90’s: increasingly detailed understanding and study w/ high stats
malisa - SPHIC - Catania Italy - Sept 2006
6
R(√SNN, b, Npart, A, B, y, mT, , PID)
R i mT  
fast  region
Ri
mTi

fast  region
malisa - SPHIC - Catania Italy - Sept 2006
7
R(√SNN, b, Npart, A, B, mT, y, , PID)
PRC 71 044906 (2005)
Spectra
v2
PRL 93 012301 ‘04
HBT
PRL 87 082301 (2001)
PRL 93 012301 (2004)
PRC 71 044906 (2005)
malisa - SPHIC - Catania Italy - Sept 2006
8
R(√SNN, b, Npart, A, B, y, mT, , PID)
R i mT  

malisa - SPHIC - Catania Italy - Sept 2006
Ri
mTi
Z. Chajecki, QM05
9
R(√SNN, b, Npart, A, B, mT, y, , PID)
D. Flierl, PhD thesis 2002
PRC 71 044906 (2005)
Spectra
v2
PRL 91 262301 (2003)
PRL 93 012301 ‘04
HBT
 emission region
PRL 87 082301 (2001)
PRL 93 012301 (2004)
PRC 71 044906 (2005)
K emission region
malisa - SPHIC - Catania Italy - Sept 2006
10
R(√SNN, b, Npart, A, B, mT, y, , PID)
D. Flierl, PhD thesis 2002
PRC 71 044906 (2005)
+
-
K+
K-
K0
p
p
S







STAR, PRL 2004
Spectra

p




p


v2

 emission region






K0
PRL 91 262301 (2003)

S
K-


K+


-


+


Full program just started
MAL,Pratt Soltz,Wiedemann nucl-ex/0505014
93 012301 ‘04
Evolution withPRL
energy?
HBT
PRL 87 082301 (2001)
PRL 93 012301 (2004)
PRC 71 044906 (2005)
K emission region
malisa - SPHIC - Catania Italy - Sept 2006
11
R(√SNN, b, Npart, A, B, y, mT, , PID)
STAR, PRL 2004
MAL, Pratt, Soltz, Wiedemann nucl-ex/0505014
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
R i mT  

malisa - SPHIC - Catania Italy - Sept 2006
Ri
mTi
Z. Chajecki, QM05
12
R(√SNN, b, Npart, A, B, y, mT, , PID)
STAR, PRL 2004
MAL, Pratt, Soltz, Wiedemann nucl-ex/0505014
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
R i mT  

Ri
mTi
MAL,Pratt Soltz,Wiedemann nuclex/0505014
Z. Chajecki, QM05
Little data
Shape Evolution with energy?
malisa - SPHIC - Catania Italy - Sept 2006
Naïve (?) : multiplicity dominance continues @ LHC
(though two unexplored areas...)
13
Source imaging - inverting Koonin-Pratt equation
C (q) 
ab
P
Sab
( r )
P
 d r S
3
ab
P
( r )   (q, r )
2
= x a - x b  distribution
 (q, r ) = (a,b) relative wavefctn
• Non-Gaussian source in 1D
(long-known)
• imaging resolves long-range
component
• STAR sees similar
(see talk of M. Bysterský
• Resonances? [check size scaling]
PHENIX nucl-ex/0605032
malisa - SPHIC - Catania Italy - Sept 2006
14
R(√SNN, b, Npart, A, B, y, mT, , PID)
STAR, PRL 2004
MAL, Pratt, Soltz, Wiedemann nucl-ex/0505014
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
R i mT  

Ri
mTi
MAL,Pratt Soltz,Wiedemann nuclex/0505014
Z. Chajecki, QM05
Little data
Shape Evolution with energy?
malisa - SPHIC - Catania Italy - Sept 2006
Naïve (?) : multiplicity dominance continues @ LHC
(though two unexplored areas...)
15
6.4 = RHICx1.6
6
5
1000
5.5 TeV
PHOBOS White Paper: NPA 757, 28
malisa - SPHIC - Catania Italy - Sept 2006
16
Multiplicity sets scale: all else fixed
6.4 = RHICx1.6
6
5
MAL,Pratt Soltz,Wiedemann nucl-ex/0505014
1000
5.5 TeV
PHOBOS White Paper: NPA 757, 28
malisa - SPHIC - Catania Italy - Sept 2006
17
Multiplicity sets scale: all else fixed
6.4 = RHICx1.6
• PHOBOS-based extrapolation:
6
• RLHC / RRHIC = (1.6)1/3 = 1.17
5
1000
5.5 TeV
PHOBOS White Paper: NPA 757, 28
malisa - SPHIC - Catania Italy - Sept 2006
18
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
malisa - SPHIC - Catania Italy - Sept 2006
Kharzeev, Levin & Nardi NPA747 609 (2005)
19
Beyond multiplicity
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
• PHOBOS-based extrapolation:
• RLHC / RRHIC = (1.6)1/3 = 1.17
• RLHC / RRHIC = (11/3.6)1/3 = 31/3 = 1.45
dN/d
• CGC prediction of multiplicity
• Humanic Rescattering Model
• “real” model predicting dN/d and HBT
• (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
malisa - SPHIC - Catania Italy - Sept 2006
20
• PHOBOS-based extrapolation:
• RLHC / RRHIC = (1.6)1/3 = 1.17
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
dN/dt
Beyond multiplicity
• CGC prediction of multiplicity
• RLHC / RRHIC = (11/3.6)1/3 = 31/3 = 1.45
• “real” model predicting dN/d and HBT
• (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
• LHC / RHIC = 2 :: (recall Rlong~~ )
Rlong (fm)
• Humanic Rescattering Model
• dynamic effect
• Rlong[LHC] / Rlong[RHIC] ~ 1.5-2
• all are connected??
malisa - SPHIC - Catania Italy - Sept 2006
21
Beyond multiplicity
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
• 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
• Humanic Rescattering Model
• “real” model predicting dN/d and 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
malisa - SPHIC - Catania Italy - Sept 2006
22
Beyond multiplicity
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
• 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
• Humanic Rescattering Model
• “real” model predicting dN/d and 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?
malisa -• SPHIC
- Catania
Italy - Sept 2006
dynamic
effect
23
Cascade / Hydro models versus RHIC data
cascade
• AMPT does ~Ok
- needs string melting
& 6-10 mb parton
malisa - SPHIC - Catania Italy - Sept 2006
hydro
• does not do as well as
cascades, but nevertheless
we’ll look next for guidance...
24
AMPT @ LHC
• All radii increase
• ~10% for transverse
• ~30% for long
• RO/RS [LHC] < RO/RS [RHIC]
• But... RHIC radii too large in this
configuration of model ???
C.M. Ko; WPCF Sept. 2006
malisa - SPHIC - Catania Italy - Sept 2006
25
Eskola et al PRC72044904 (2005)
Hydro predictions I: Scales
• Neglecting flow, to cool to C[QGP] :
C = 0(C /0)3/4
• Cno flow[RHIC] = 6 fm/c
initial conditions from
pQCD+saturation
• Cno flow[LHC] = 20 fm/c
malisa - SPHIC - Catania Italy - Sept 2006
26
Eskola et al PRC72044904 (2005)
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
• Much larger flow @LHC
• signif. reduction of timescale @ LHC
[similar to RHIC]
• larger transverse size @ FO
malisa - SPHIC - Catania Italy - Sept 2006
27
Eskola et al PRC72044904 (2005)
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
• 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
malisa - SPHIC - Catania Italy - Sept 2006
28
Eskola et al PRC72044904 (2005)
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
• Much larger flow @LHC
• signif. reduction of timescale @ LHC
[similar to RHIC]
• larger transverse size @ FO
• No HBT prediction per se, but...
Heinz&Kolb, PLB542 216 (2002)
• 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
malisa - SPHIC - Catania Italy - Sept 2006
29
Hydro predictions II: Shapes
• easy prediction: importance of -dep
measurements will continue @ LHC
• asHBT
O’Hara, et al, Science 298 2179 (2002)
• probes timescale & dynamics
• non-trivial (& incomplete!) excitation fctn
malisa - SPHIC - Catania Italy - Sept 2006
E895 2 GeV
PLB496 1 (2000)
STAR 200 GeV
PRL93 012301 (‘04)
30
Hydro predictions II: Shapes
• easy prediction: importance of -dep
measurements will continue @ LHC
• asHBT
• probes timescale & dynamics
• non-trivial (& incomplete!) excitation fctn
• hydro @ RHIC
• misses scale (well-known)
• impressive agreement on -dep
“RHIC”
malisa - SPHIC - Catania ItalyHeinz&Kolb,
- Sept 2006
PLB542 216 (2002)
STAR PRL93 012301 (2004)
31
Hydro predictions II: Shapes
• easy prediction: importance of -dep
measurements will continue @ LHC
• asHBT
• 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
“RHIC”
Heinz&Kolb, PLB542 216 (2002)
malisa - SPHIC - Catania
Italy - Sept 2006
“IPES” (LHC)
Heinz&Kolb, PLB542 216 (2002)
32
• easy prediction: importance of -dep
measurements will continue @ LHC
• asHBT
• 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
• qualitatively different kT dependence (*)
“RHIC”
F. Retière & MAL PRC70 044907 (2004)
Hydro predictions II: Shapes
* simple formula will not work @ LHC   2
“IPES” (LHC)
2
R S,2
2
R S,0

Heinz&Kolb, PLB542 216 (2002)
malisa - SPHIC - Catania
Italy - Sept 2006
Heinz&Kolb, PLB542 216 (2002)
33
p+p: a short diversion and “practice,” or a crucial question?
• “minimalist” physics
• Momenta & parentage from PYTHIA
• space by hand: x= “1 fm” + p/E
• pT-dep from x-p correlations
• resonances
• formation time 
• some from rescatt
• mult dep from rescatt only
i-th particle
Initial “disk”
of radius r
T. Humanic, presentation
to ALICE PW2 (March 2006)
malisa - SPHIC - Catania Italy - Sept 2006
34
p+p: a short diversion and “practice,” or a crucial question?
• “minimalist” physics
• Momenta & parentage from PYTHIA
• space by hand: x= “1 fm” + p/E
• pT-dep from x-p correlations
• resonances
• formation time 
• some from rescatt
• mult dep from rescatt only
jet
p
p
jet
• R(dN/d)  space-time properties of jet
fragmentation/hadronization? [fundamental]
• prediction of pT-dependence needed to test
whether hard processes are really dominant here
Paic and Skowronski
J. Phys. G31 1045 (2005)
see also Csorgo & Zajc
hep-ph/0412243 (ISMD04)
malisa - SPHIC - Catania Italy - Sept 2006
35
p+p: a short diversion and “practice,” or a crucial question?
• “minimalist” physics
• Momenta & parentage from PYTHIA
• space by hand: x= “1 fm” + p/E
• pT-dep from x-p correlations
• resonances
• formation time 
• some from rescatt
• mult dep from rescatt only
• R(dN/d)  space-time properties of jet
fragmentation/hadronization? [fundamental]
• prediction of pT-dependence needed to test
whether hard processes are really dominant here
• may be copiously produced (depending on mass)
• look for long lifetimes (if d large) in high mult events
???
• even more fundamental, but expectations unclear
[prelim from T. Humanic: small effect on HBT...]
malisa - SPHIC - Catania Italy - Sept 2006
Hossenfelder, Hofmann, Bleicher, Stocker
Phys.Rev. D66 (2002) 101502
• Black Holes / extra dimensions at LHC p+p ?
Humanic, Koch, Stocker hep-ph/0607097
36
femtoscopy in p+p @ STAR
Z. Chajecki WPCF05
• p+p and A+A measured in same
experiment
• great opportunity to compare physics
• what causes pT-dependence in p+p?
• same cause as in A+A?
STAR preliminary
mT (GeV)
malisa - SPHIC - Catania Italy - Sept 2006
mT (GeV)
37
Surprising („puzzling”) scaling
!! But !! major issues with nontrivial
interplay non-femtoscopic correlations
• p+p and A+A measured in same
experiment
• great opportunity to compare physics
• what causes pT-dependence in p+p?
• same cause as in A+A?
Ratio of (AuAu, CuCu, dAu) HBT
radii by pp
HBT radii scale with pp
Scary coincidence
or something deeper?
malisa - SPHIC - Catania Italy - Sept 2006
pp, dAu, CuCu - STAR preliminary
38
le menu des espérances au LHC
boissons
entrées
hydro
p+p
jet
p
jet
p
• signif pT dep
• R increase w/ mult
RL small increase (~30%)
[huge flow  rapid cooling  short ]
• R increase w/ mult
• other details??
RO,S : huge flow 
• larger increase (~60%)
• steeper pT dep
• very large RO in high mult??
shape inversion; oscillation sign flip
plats principaux
NNUS: naive extrapolation
5
as before (same pT dep etc)
but scale by ~17%
as before (same pT dep etc)
but scale by ~45%
malisa - SPHIC - Catania Italy - Sept 2006
HRM and AMPT
RL (50-100% 30%increase)
[dynamics / chemistry / both ??]
RO,S
• smaller increase (~30% 10%)
• higher flow  steeper pT dep
39
“Inverting the femtoscopic paradigm”
• First-ever p-, p-, p correlations
• Consistency from baryon sector for
flow-generated x-p correlations
• Extraction of real/imaginary p-,
p- scattering lengths from CF !!
• important new physics direction
• “invert the femtoscopic paradigm”
• c.f. K0-K0 / p-p
• possible effect of residual
correlations - could not reliably
calculate (for now...)
• significant technical effort (and
more information) required
malisa - SPHIC - Catania Italy - Sept 2006
STAR, accepted to Phys Rev
40
nouvelles directions
• p+p - very interesting in itself!
• understanding non-femtoscopic correlations crucial
• Beyond Gaussian imaging (3D)
• see M. Bystersky
• shape inversion?
• correlate femtoscopy with global event plane
• non-id systematics
• including “exotica”
• will seriously need to understand correlated feed-down
• see talk of H. Gos
• a “complication” and a new source of information !
• hadronic physics - extracing phaseshifts
• turning the problem around
malisa - SPHIC - Catania Italy - Sept 2006
41
THE END
malisa - SPHIC - Catania Italy - Sept 2006
42
references
• RHIC-tested predictions for low-pT and high-pT hadron spectra
in nearly central Pb+Pb collisions at the LHC
• Eskola et al hep-ph/0506049; PRC72044904 (2005)
• hydro predictions for spectra
• no HBT per se, but timescales and sizes of freezeout at
LHC versus RHIC are shown
• Emission angle dependent pion interferometry at RHIC and
beyond
• Heinz and Kolb PLB542 216 (2002)
• RHIC and LHC predictions for asHBT from hydro
• Signatures for Black Hole production from hadronic
observables at the Large Hadron Collider
• Humanic, Koch, Stocker hep-ph/0607097
• surprisingly, no HBT, but discussion of possible BH
formation, rates, and how to trigger on them (high-mult:
will it follow multiplicity systematics if physics changes so
much??)
• Femtoscopy in heavy ion collisions: Wherefore, whence, and
whither?
• Lisa nucl-ex/0506049 (WPCF05)
• systematics and PHOBOS-extrapolation-based “prediction”
for LHC
• Color Glass Condensate at the LHC: hadron multiplicities in pp,
pA and AA collisions
• Kharzeev, Levin & Nardi; NPA747 609 (2005)
• not HBT, but multiplicity predictions, which of course can be
coupled to HBT multiplicity systematics
malisa - SPHIC - Catania Italy - Sept 2006
• Hanbury-Brown-Twiss interferometry with identical bosons
in relativistic heavy ion collisions: Comparisons with
hadronic scattering models
• Humanic, Int.J.Mod.Phys.E15:197-236,2006; nuclth/0510049
• Tom’s review article; contains LHC predictions
For proton-proton collisions:
• Signatures for Black Hole production from hadronic
observables at the Large Hadron Collider
• Humanic, Koch, Stocker hep-ph/0607097
• surprisingly, no HBT, but discussion of possible BH
formation, rates, and how to trigger on them (high-mult:
will it follow multiplicity systematics if physics changes
so much??)
• Quasi-stable black holes at LHC
• Hossenfieder, Hoffman, Bleicher, Stocker hepph/0109085; Phys.Rev. D66 (2002) 101502
• VERY nice plot of lifetime versus number of dimensions
• Pion HBT for LHC p+p collisions using a simple causality
model
• Humanic, ppt presentation at PW2 meeting March 06
• Pythia and HRM - nice, simple calculations showing pT
dep from simple formation time effect
• Effect of hard processes on momentum correlations in pp
and ppbar collisions
• Paic and Skowronski; J. Phys. G31 1045 (2005)
• from size and mult dep, make a connection to spacetime properties of jet fragmentation
• unfortunately, no pT prediction
43
Why can’t
HBT be more
like v2?
malisa - SPHIC - Catania Italy - Sept 2006
44
Why can’t HBT be more like v2...?
pT-integrated v2 excitation function
STAR preliminary
NA49: Phys.Rev. C68 (2003) 034903
malisa - SPHIC - Catania Italy - Sept 2006
slide of Raimond Snellings HIF 2003
45
Why can’t HBT be more like v2...?
• v2(pT) very similar
• <pt> 158 A GeV ≈
400 MeV/c
• <pt> 200 GeV
≈ 500 MeV/c
v2(pt) SPS-RHIC
• Integrated v2
mainly driven by
<pt>
• Note: In comparison SPS
data the slight difference in
centrality and systematic
uncertainties, about 1.5% are
not plotted
STAR Preliminary
NA49: Phys.Rev. C68 (2003) 034903; CERES: nucl-ex/0303014
malisa - SPHIC - Catania Italy - Sept 2006
slide of Raimond Snellings HIF 2003
46
Why can’t HBT be more like v2...?
It can!
.....
Just gotta look in less detail!
malisa - SPHIC - Catania Italy - Sept 2006
47