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
1
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
2
Microexplosions
Femtoexplosions
• fast
 plasma 1 J
s energy deposition
0.1 J
3 = 1036phase
hydro expansion
to original
1017 J/m3  cooling
5 GeV/fm
J/m3
T
106 K
200 MeV = 1012 K
• do
geometric
& infer
rate
1018 “postmortem”
K/sec
1035momentum
K/s
Mike Lisa - ISMD, Berkeley - August 2007
3
Microexplosions
Femtoexplosions
• fast
 plasma 1 J
s energy deposition
0.1 J
3 = 1036phase
hydro expansion
to original
1017 J/m3  cooling
5 GeV/fm
J/m3
T
106 K
200 MeV = 1012 K
• do
geometric
& infer
rate
1018 “postmortem”
K/sec
1035momentum
K/s
Mike Lisa - ISMD, Berkeley - August 2007
4
measure explosive pattern of the thermalized bulk matter (low-pT)
B2B jets?
access to bulk properties (EoS) driving dynamics
Microexplosions
Femtoexplosions
• fast
 plasma 1 J
s energy deposition
0.1 J
3 = 1036phase
hydro expansion
to original
1017 J/m3  cooling
5 GeV/fm
J/m3
T
106 K
200 MeV = 1012 K
• do
geometric
& infer
rate
1018 “postmortem”
K/sec
1035momentum
K/s
Mike Lisa - ISMD, Berkeley - August 2007
5
measure explosive pattern of the thermalized bulk matter (low-pT)
collective pT component: m*vT
Spectra
v2
HBT
hydro expectation
(off-center collision)
Mike Lisa - ISMD, Berkeley - August 2007
6
measure explosive pattern of the thermalized bulk matter (low-pT)
Spectra
v2
HBT
“elliptic flow”
Mike Lisa - ISMD, Berkeley - August 2007
7
measure explosive pattern of the thermalized bulk matter (low-pT)
Spectra
v2
HBT
femtoscopy
probes x-p
substructure
Mike Lisa - ISMD, Berkeley - August 2007
8
At RHIC: Explosive signature sensitive to physics in models
cascade
hydro
Boltzmann models
- collisions between particles
ideal fluid dynamics
3 talks later
What might we expect at LHC?
Mike Lisa - ISMD, Berkeley - August 2007
9
“All” soft-physics observables at RHIC (& often SPS/AGS)
are multiplicity-driven
H. Caines (STAR) QM05
S. Manly (PHOBOS) QM05
MAL,Pratt Soltz,Wiedemann nucl-ex/0505014
NA57 (open)
STAR (filled)
NA57 (open)
STAR (filled)
E-by-E fluctuation in K/
G. Westfall, WPCF 2007
Mike Lisa - ISMD, Berkeley - August 2007
Entropy dominance?
10
6.4 = RHICx1.6
6
5
1000
5.5 TeV
PHOBOS White Paper: NPA 757, 28
Mike Lisa - ISMD, Berkeley - August 2007
11
NNUS*: Multiplicity sets scale: all else fixed
6.4 = RHICx1.6
• PHOBOS-based extrapolation:
• RLHC / RRHIC = (1.6)1/3 = 1.17
6
5
1000
5.5 TeV
PHOBOS White Paper: NPA 757, 28
Mike Lisa - ISMD, Berkeley - August 2007
* NNUS = Nothing New Under the Sun
12
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
Mike Lisa - ISMD, Berkeley - August 2007
Kharzeev, Levin & Nardi NPA747 609 (2005)
13
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
14
NNUS*: Multiplicity sets scale: all else fixed
• RLHC / RRHIC = (1.6)1/3 = 1.17
• CGC prediction of multiplicity
• RLHC / RRHIC = (11/3.6)1/3 = 31/3 = 1.45
STAR PRC71 044906 (2005)
• PHOBOS-based extrapolation:
• R <~ 11 fm
•
•
•
•
well within experimental reach
Rfit ~ 1/(q2)
q ~ 1 MeV/c
qmin ~ 2 MeV/c
Lisa
- ISMD,
- August
2007
ALICE PPR (vol 2):Mike
J. Phys
G. Part.
Nucl.Berkeley
Phys. 32 1295
(2006)
15
Access to long-range non-Gaussian tail
PHENIX, PRL 98, 132301 (2007) ,
• 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
Brown, Soltz, Newby, Kisiel
nucl-th/0705.1337
* c.f. talks of P. Danielewicz & P. Chung
Mike Lisa - ISMD, Berkeley - August 2007
16
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
17
Boltzmann-type models
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
• Humanic/Hadron Rescattering Model
• “real” model predicting flow & HBT
dN/d
• (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
Mike Lisa - ISMD, Berkeley - August 2007
18
• Humanic/Hadron Rescattering Model
• “real” model predicting flow & HBT
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
dN/dt
Boltzmann-type models
• (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
• LHC / RHIC = 2 :: (recall Rlong~~ )
• dynamic effect
• all are connected??
Mike Lisa - ISMD, Berkeley - August 2007
Rlong (fm)
• Rlong[LHC] / Rlong[RHIC] ~ 2
19
Boltzmann-type models
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
• 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
Mike Lisa - ISMD, Berkeley - August 2007
20
Boltzmann-type models
T. Humanic,
Int.J.Mod.Phys.E15197(2006)
• 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
Mike Lisa - ISMD, Berkeley - August 2007
21
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
Mike Lisa - ISMD, Berkeley - August 2007
22
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
Mike Lisa - ISMD, Berkeley - August 2007
23
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
Mike Lisa - ISMD, Berkeley - August 2007
24
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
Mike Lisa - ISMD, Berkeley - August 2007
25
Hydro predictions II: Shapes
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
• easy prediction: importance of -dep
measurements will continue @ LHC
• RP resolution at least as good as STAR
• asHBT
• measures source shape at freezeout
STAR 200 GeV
Mike Lisa - ISMD, Berkeley - August 2007
PRL93 012301 (‘04)
26
Hydro predictions II: Shapes
• easy prediction: importance of -dep
measurements will continue @ LHC

• RP resolution at least as good as STAR
• asHBT
O’Hara, et al, Science 298 2179 (2002)
• measures source shape at freezeout
• probes timescale & dynamics
• non-trivial (& incomplete!) excitation fctn
E895 2 GeV
Mike Lisa - ISMD, Berkeley - August 2007
PLB496 1 (2000)
STAR 200 GeV
PRL93 012301 (‘04)
27
Hydro predictions II: Shapes
• 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
“RHIC”
Mike Lisa - ISMD,
Berkeley
August 2007
Heinz&Kolb,
PLB542 216- (2002)
STAR PRL93 012301 (2004)
28
Hydro predictions II: Shapes
• 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“RHIC”
in shape & oscillations
PLB542 216 (2002)
MikeHeinz&Kolb,
Lisa - ISMD,
Berkeley - August 2007
Sign flip in oscillations reflects
transition to in-plane geometry
(more flow, more time)
“IPES” (LHC)
Heinz&Kolb, PLB542 216 (2002)
29
p+p: A clear reference system?
Mike Lisa - ISMD, Berkeley - August 2007
30
e+e- (and p+p, +p...) -- “similar” HBT radii
• high-quality/stats data sparse
• diversity of methods
OPAL e+e- -> Z
July 2007 CERN-PH-EP/2007-025
• corrections
• coordinate systems
• jet axis in e+e-...
• mixing...
• physics?
Mike Lisa - ISMD, Berkeley - August 2007
31
e+e- (and p+p, +p...) -- “similar” HBT radii
• high-quality/stats data sparse
• diversity of methods
L. Lonnblad - WPCF2007
• corrections
• coordinate systems
• jet axis in e+e-...
• mixing...
• physics of “x-p” correlations in very
small systems?
•
•
•
•
strings?
pT signal?
jets?
pythia + rescattering?
else?
i-th particle
Initial “disk”
of radius r
Paic and Skowronski
J. Phys. G31 1045 (2005)
see also Csorgo & Zajc
hep-ph/0412243 (ISMD04)
Mike Lisa - ISMD, Berkeley - August
talk by T.
2007
Humanic
32
Caution: femtoscopy in p+p @ STAR
Z. Chajecki WPCF05
• 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??
STAR preliminary
mT (GeV)
Mike Lisa - ISMD, Berkeley - August 2007
mT (GeV)
33
Surprising („puzzling”) scaling
!! But !! significant issues with nontrivial
interplay non-femtoscopic correlations
(restricted
phasespace)
• p+p and A+A measured
in same
Ratio of (AuAu, CuCu, dAu) HBT
should
be less of a problemradii
at by
LHC
experiment with -same
method
pp
[see
talk of
T. Humanic]
• great opportunity- to
compare
physics
• what causes pT-dependence in p+p?
• same cause as in A+A?
A. Białasz (ISMD):
I personally feel that its solution may provide new
HBT radii scale with
insightpp
into the hadronization process of QCD
Scary coincidence
or something deeper?
Mike Lisa - ISMD, Berkeley - August 2007
pp, dAu, CuCu - STAR preliminary
34
le menu des espérances au LHC
boissons
entrées
hydro
p+p
• signif pT dep
• R increase w/ mult
jet
p
jet
p
• R increase w/ mult
• other details??
• very large RO in high mult??
p+p “=“ A+A ???
RL small increase (~30%)
[huge flow  rapid cooling  short ]
RO,S : huge flow 
• larger increase (~60%)
• steeper pT dep
shape inversion; oscillation sign flip
large tilt for central region?
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%
Mike Lisa - ISMD, Berkeley - August 2007
HRM and AMPT
RL (50-100% 30%increase)
[dynamics / chemistry / both ??]
RO,S
• smaller increase (~30% 10%)
• higher flow  steeper pT dep
35
Mike Lisa - ISMD, Berkeley - August 2007
36
R(√SNN, b, Npart, A, B, mT, y, , PID1, PID2)
+
-
K+
K-
p
p










+







-

-


K+



K-
-
-
K0S




p



p
K0S

Does lock pattern break?




•
•
•
•
•
extract phaseshifts (inversion of K-P paradigm)
p+p in multiplicity classes [esp very low multiplicity]
HBT relative to jets in p+p and A+A
excitation function
Mike Lisa
- ISMD, Berkeley - August 2007
- (direct
 yield)


37
The end
(...finally...)
Mike Lisa - ISMD, Berkeley - August 2007
38
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
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 :-)
Mike Lisa - ISMD, Berkeley - August 2007
40
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
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
Mike Lisa - ISMD, Berkeley - August 2007
41
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
The ITS helps remove merging effects
• Ros = 0 as figure of merit
• Cutting on ITS separation reduces
bias to ~0.1-0.2 fm
“similar triangles” : qmin/pT = separationMin/radius
Mike Lisa - ISMD, Berkeley - August 2007
42
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
Momentum resolution correction
• “Triple-ratio” correction first (?) used by NA44
• uses single-particle resolution (assumed known)
to smear “ideal” CF
• rapid convergence
method of NA44/E895/STAR/...
Mike Lisa - ISMD, Berkeley - August 2007
43
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
HBT radii : “out versus in”
• good to ~15 fm
Mike Lisa - ISMD, Berkeley - August 2007
44
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
Event-by-event femtoscopy in Pb+Pb
Mike Lisa - ISMD, Berkeley - August 2007
45
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
reactionplane resolution
Mike Lisa - ISMD, Berkeley - August 2007
Plot from T. Hirano 2005
• At least as good as RHIC/STAR
46