Femtoscopy at the highest energies: Expectations and directions at the LHC
A menu of expectations for femtoscopy * 1.0 at LHC /ALICE
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Transcript of A menu of expectations for femtoscopy * 1.0 at LHC /ALICE
Mike Lisa - ISMD, Berkeley - August 2007 1
A menu of expectations forfemtoscopy* 1.0 at
LHC/ALICEMike Lisa
Ohio State University
* femtoscopy (fem-ta-skö-pee) nounThe 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 2
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 3
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 4
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 5
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 6
Spectra
v2
HBT
measure explosive pattern of the thermalized bulk matter (low-pT)
hydro expectation(off-center collision)
collective pT component: m*vT
Mike Lisa - ISMD, Berkeley - August 2007 7
Spectra
v2
HBT
measure explosive pattern of the thermalized bulk matter (low-pT)
“elliptic flow”
Mike Lisa - ISMD, Berkeley - August 2007 8
Spectra
v2
HBT
measure explosive pattern of the thermalized bulk matter (low-pT)
femtoscopyprobes x-psubstructure
Mike Lisa - ISMD, Berkeley - August 2007 9
hydro
ideal fluid dynamics
At RHIC: Explosive signature sensitive to physics in models
cascade
Boltzmann models
- collisions between particles
3 talks later
What might we expect at LHC?
Mike Lisa - ISMD, Berkeley - August 2007 10
“All” soft-physics observables at RHIC (& often SPS/AGS)
are multiplicity-driven
S. Manly (PHOBOS) QM05
H. Caines (STAR) QM05
NA57 (open)STAR (filled)
NA57 (open)STAR (filled)
G. Westfall, WPCF 2007
E-by-E fluctuation in K/
MAL,Pratt Soltz,Wiedemann nucl-ex/0505014
Entropy dominance?
Mike Lisa - ISMD, Berkeley - August 2007 11
PHOBOS White Paper: NPA 757, 28
1000 5.5 TeV
5
6
6.4 = RHICx1.6
Mike Lisa - ISMD, Berkeley - August 2007 12
NNUS*: Multiplicity sets scale: all else fixed
• PHOBOS-based extrapolation:•RLHC / RRHIC = (1.6)1/3 = 1.17
PHOBOS White Paper: NPA 757, 28
1000 5.5 TeV
5
6
6.4 = RHICx1.6
* NNUS = Nothing New Under the Sun
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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)
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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]
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ST
AR
PR
C71 044906 (2005)
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)
Access to low-q -> high R
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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 Brown, Soltz, Newby, Kisielnucl-th/0705.1337
PH
EN
IX, P
RL 98, 13
2301 (2007) ,
* c.f. talks of P. Danielewicz & P. Chung
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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
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Boltzmann-type models
• Humanic/Hadron Rescattering Model
• “real” model predicting flow & HBT
• (dN/d[LHC] / dN/d[RHIC])1/3 ~ 1.9
dN
/d
T. Humanic,Int.J.Mod.Phys.E15197(2006)
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Boltzmann-type models
Rlo
ng (
fm)
dN
/dt
• 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.E15197(2006)
Mike Lisa - ISMD, Berkeley - August 2007 20
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.E15197(2006)
Mike Lisa - ISMD, Berkeley - August 2007 21
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.E15197(2006)
Mike Lisa - ISMD, Berkeley - August 2007 22
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 PRC72044904 (2005)
initial conditions frompQCD+saturation
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• 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 PRC72044904 (2005)Hydro predictions I: Scales
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• 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 PRC72044904 (2005)Hydro predictions I: Scales
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• 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 PRC72044904 (2005)Hydro predictions I: Scales
Heinz&Kolb, PLB542 216 (2002)
(LHC)
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• 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
STAR 200 GeV
PRL93 012301 (‘04)
ALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
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• 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 predictions II: Shapes
E895 2 GeVPLB496 1 (2000)
STAR 200 GeV
PRL93 012301 (‘04)
O’H
ara
, e
t a
l, S
cie
nce
29
8 2
17
9 (
20
02
)
Mike Lisa - ISMD, Berkeley - August 2007 28
• 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
STAR PRL93 012301 (2004)Heinz&Kolb, PLB542 216 (2002)
“RHIC”
Mike Lisa - ISMD, Berkeley - August 2007 29
• 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
Hydro predictions II: Shapes
Heinz&Kolb, PLB542 216 (2002)
“RHIC”
Heinz&Kolb, PLB542 216 (2002)
“IPES” (LHC)
Sign flip in oscillations reflects transition to in-plane geometry(more flow, more time)
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p+p: A clear reference system?
Mike Lisa - ISMD, Berkeley - August 2007 31
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?
OPAL e+e- -> ZJuly 2007 CERN-PH-EP/2007-025
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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?
i-th particle
Initial “disk” of radius r
talk by T. Humanic
L. Lonnblad - WPCF2007
Paic and SkowronskiJ. Phys. G31 1045 (2005)
see also Csorgo & Zajchep-ph/0412243 (ISMD04)
pT signal?
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STAR preliminary
mT (GeV) mT (GeV)
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 34
Surprising („puzzling”) scaling
HBT radii scale with pp
Scary coincidence or something deeper?
pp, dAu, CuCu - STAR preliminary
Ratio of (AuAu, CuCu, dAu) HBT radii by pp
• 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 nontrivialinterplay 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
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5
as before (same pT dep etc)but scale by ~17%
as before (same pT dep etc)but scale by ~45%
NNUS: naive extrapolation HRM and AMPT
RL (50-100% 30%increase)[dynamics / chemistry / both ??]
RO,S • smaller increase (~30% 10%)• higher flow steeper pT dep
plats principaux
boissonsentrées
le menu des espérances au LHC
hydro
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?
p+p
pp
jet
jet
• signif pT dep• R increase w/ mult
• R increase w/ mult• other details??
• very large RO in high mult??
p+p “=“ A+A ???
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Mike Lisa - ISMD, Berkeley - August 2007 37
+ - K+ K- K0S p p
+
-
- K+
K-
- - K0S
p
p
R(√SNN, b, Npart, A, B, mT, y, , PID1, PID2)
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 - (direct yield)
Mike Lisa - ISMD, Berkeley - August 2007 38
The end(...finally...)
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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 41
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)
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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
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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)
method of NA44/E895/STAR/...
Mike Lisa - ISMD, Berkeley - August 2007 44
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 45
Event-by-event femtoscopy in Pb+PbALICE PPR (vol 2): J. Phys G. Part. Nucl. Phys. 32 1295 (2006)
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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. H
irano 2005