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ma lisa - Femtoscopy in small systems & EMCICs - Kent State Univers ity - January 2007 1 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki & Mike Lisa Ohio State University nucl-th/0612080

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Page 1: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 1

Conservation laws & femtoscopy of small systems

Zbigniew Chajeçki & Mike Lisa

Ohio State University

nucl-th/0612080

Page 2: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 2

Outline

• Introduction– RHI, femtoscopy, & collectivity in bulk matter– including: new representation of correlation functions

• the p+p “reference”– intriguing features pp versus AA– non-femtoscopic effects

• Global conservation effects (EMCICs)– Restricted phasespace calculations: GenBod (FOWL)– Analytic EMCIC calculations– Experimentalists’ recipe:– Fitting correlation functions [in progress]

• Summary

Page 3: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 4

RHIC BRAHMSPHOBOS

PHENIXSTAR

AGS

TANDEMS

Nuclear Particle

Page 4: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 5

Why heavy ion collisions?

Nuclear Particle

STAR ~500 Collaborators

Page 5: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 6

2 types (?) of collisions...

looks like fun...

looks like a mess...

Page 6: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 7

A dynamical but crude view of the collision

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

In this model, insufficient re-interactionsc/o UrQMD Collaboration, Frankfurt

Page 7: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 8

A dynamical but crude view of the collision

In this model, insufficient re-interactions

Page 8: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 9

R.H.I.C. defined...

• collision of nuclei sufficiently large that nuclear details unimportant– distinct from nuclear or particle physics– “Geranium on Linoleum”

• sufficiently large for meaningful bulk & thermodynamic quantities

• non-trivial spatial scales & geometry drive bulk dynamics (e.g. flow)

• how big is “sufficient” ?– important reference issue

Page 9: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 10

phase structure of bulk system:

• driving symmetries

• long-range collective behaviour

• “new” physics [superfluidity in l-He]

• relevance of meaningful EoS

Page 10: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 11

Generating a deconfined state

Nuclear Matter(confined)

Hadronic Matter(confined)

Quark Gluon Plasmadeconfined !

Present understanding of Quantum Chromodynamics (QCD)• heating• compression deconfined color matter !

Page 11: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 12

Expectations from Lattice QCD

/T4 ~ # degrees of freedom

confined:few d.o.f.

deconfined:many d.o.f.

TC ≈ 173 MeV ≈ 21012 K ≈ 130,000T[Sun’s core]

Page 12: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 13

The four elements from 400 BC to 2000AD

400 BC : all creation

Earth Fire

Air Water

?

Page 13: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 14

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

RHIC energies: the first quantitative success of hydro• direct access to EoS (phase transitions, lattice, etc.)

EoS: P versus versus n(Heinz et al)

Page 14: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 15

Microexplosions Femtoexplosions

1017 J/m3 5 GeV/fm3 = 1036 J/m3

s 0.1 J 1 J

T 106 K 200 MeV = 1012 K

rate 1018 K/sec 1035 K/s

• energy quickly deposited• enter plasma phase• expand hydrodynamically• cool back to original phase• do geometric “postmortem” & infer momentum

Page 15: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 16

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

• energy quickly deposited• enter plasma phase• expand hydrodynamically• cool back to original phase• do geometric “postmortem” & infer momentum

Page 16: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 17

Impact parameter & Reaction plane

b = 0 “central collision”many particles produced

“peripheral collision”fewer particles produced

br

Page 17: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 18

Impact parameter & Reaction plane

b = 0 “central collision”many particles produced

“peripheral collision”fewer particles produced

br br

Reaction plane:

spanned by beam direction and br

Page 18: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 19

How do semi-central collisions evolve?

br

1) Superposition of independent p+p:momenta pointed at randomrelative to reaction plane

Page 19: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 20

How do semi-central collisions evolve?

br

1) Superposition of independent p+p:

2) Evolution as a bulk system

momenta pointed at randomrelative to reaction plane

highdensity / pressure

at center

“zero” pressurein surrounding vacuum

Pressure gradients (larger in-plane) push bulk “out” “flow”

more, faster particles seen in-plane

Page 20: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 21

How do semi-central collisions evolve?

1) Superposition of independent p+p:

2) Evolution as a bulk system

momenta pointed at randomrelative to reaction plane

Pressure gradients (larger in-plane) push bulk “out” “flow”

more, faster particles seen in-plane

N

-RP (rad)0 /2 /4 3/4

N

-RP (rad)0 /2 /4 3/4

Page 21: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 22

Azimuthal distributions at RHIC

STAR, PRL90 032301 (2003)

b ≈ 4 fm

“central” collisions

b ≈ 6.5 fm

midcentral collisions

Page 22: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 23

Azimuthal distributions at RHIC

STAR, PRL90 032301 (2003)

b ≈ 4 fmb ≈ 6.5 fmb ≈ 10 fm

peripheral collisions

Page 23: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 24

Beyond press releases

Nature of EoS under investigation ; agreement with

data may be accidental ; viscous hydro under

development ; assumptionof thermalization in question

sensitive to modeling ofinitial state,

presently under study

The detailed work now underway is what can probe & constrain sQGP properties

It is probably not press-release material......but, hey, you’ve already got your coffee mug

Page 24: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 26

Beyond press releases:Access to the dynamically-generated geometric substructure?

The feature of collectivity:

space

is globally correlated with

momentum

Page 25: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 27

222111 p)xr(i22

p)xr(i11T e)p,x(Ue)p,x(U

rrrrrr rrrr ⋅−⋅−=ψ

probing source geometry through interferometry

12 ppqrrr −=

2

21

2121 )q(~1

)p(P)p(P)p,p(P

)p,p(C ρ+== C (Qinv)

Qinv (GeV/c)

1

2

0.05 0.10

Width ~ 1/R

Measurable! F.T. of pion source

( ))xx(iq2

*21

*1T

*T

21e1UUUU −⋅+⋅⋅=ψψ

Creation probability ρ(x,p) = U*U5 fm

1 m sourceρ(x)

r1

r2

x1

x2

{2

1

}e)p,x(Ue)p,x(U 212121 p)xr(i21

p)xr(i12

rrrrrr rrrr ⋅−⋅−+

p1

p2

The Bottom line…if a pion is emitted, it is more likely to emit another

pion with very similar momentum if the source is small

experimentally measuring this enhanced probability: quite challenging

Page 26: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 28

Correlation functions for different colliding systemsC

2(Q

inv)

Qinv (GeV/c)

STAR preliminary p+pR ~ 1 fm

d+AuR ~ 2 fm

Au+AuR ~ 6 fm

Different colliding systems studied at RHIC

Interferometry probes the smallest scales ever measured !

Au+Au: central collisions

C(Qout)

C(Qside)

C(Qlong)

3 “radii” by using3-D vector q

Page 27: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 29

Femtoscopic information

C r P

ab(r q ) = d3 ′

r r ⋅Sr

P

ab( ′ r r )∫ ⋅ φ(

r ′ q ,r ′ r )

2

xaxb

pa

pbxa

xb

pa

pb

Sr P

ab( ′ r r ) =

r x a -

r x b( ) distribution

φ(r ′ q ,r ′ r ) = (a,b) relative wavefctn

• femtoscopic correlation at low |q|• must vanish at high |q|. [indep “direction”]

Au+Au: central collisions

C(Qout)

C(Qside)

C(Qlong)

3 “radii” by using3-D vector q

Page 28: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 30

Femtoscopic information - Spherical harmonic representation

• femtoscopic correlation at low |q|• must vanish at high |q|. [indep “direction”]

Au+Au: central collisions

C(Qout)

C(Qside)

C(Qlong)

3 “radii” by using3-D vector q

QOUT

QSIDE

QLONG Q

∑→→ ΔΔ

=binsall

iiiiimlml QCYQA

.

,

cos

, ),cos|,(|),(|)(| φθφθπ

φθ

4

This new method of analysis represents a real breakthrough. ...(should) become a standard tool in all experiments.

- A. Bialas, ISMD 2005

nucl-ex/0505009

Page 29: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 31

Femtoscopic information - Spherical harmonic representation

• femtoscopic correlation at low |q|• must vanish at high |q|. [indep “direction”]

•ALM(Q) = L,0

Au+Au: central collisions

C(Qout)

C(Qside)

C(Qlong)

3 “radii” by using3-D vector q

∑→→ ΔΔ

=binsall

iiiiimlml QCYQA

.

,

cos

, ),cos|,(|),(|)(| φθφθπ

φθ

4

L=0

L=2M=0

L=2M=2

nucl-ex/0505009

Page 30: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 32

Why do the radii fallwith increasing momentum ??

(3 "radii" corresponding to the three components of r q )

Page 31: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 33

It’s collective flow !!

Direct geometrical/dynamical evidencefor bulk behaviour!!!

Amount of flow consistent with p-space nucl-th/0312024

Huge, diverse systematics consistent with this substructurenucl-ex/0505014

Why do the radii fallwith increasing momentum ??

Page 32: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 35

p+p: A clear reference system?

Page 33: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 36

STAR preliminary

mT (GeV) mT (GeV)

Z. Chajecki QM05nucl-ex/0510014femtoscopy in p+p @ STAR

• Decades of femtoscopy in p+p and in A+A, but...

• for the first time: femtoscopy in p+p and A+A in same experiment, same analysis definitions...

• unique opportunity to compare physics

• ~ 1 fm makes sense, but...

• pT-dependence in p+p?

• (same cause as in A+A?)

Page 34: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 37

Surprising („puzzling”) scaling

HBT radii scale with pp

Scary coincidence or something deeper?

On the face: same geometric substructure

pp, dAu, CuCu - STAR preliminary

Ratio of (AuAu, CuCu, dAu) HBT radii by pp

A. Bialasz (ISMD05):I personally feel that its solution may provide new insight into the hadronization process of QCD

Page 35: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 38

BUT... Clear BUT... Clear interpretationinterpretation clouded by clouded by datadata features features

STAR preliminary d+Au peripheral collisions

Gaussian fitNon-femtoscopic q-anisotropicbehaviour at large |q|

does this structure affect femtoscopic region as well?

Page 36: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 39

STAR preliminary d+Au peripheral collisions

Gaussian fit

∑→→ ΔΔ

=binsall

iiiiimlml QCYQA

.

,cos

, ),cos|,(|),(4

|)(| φθφθπ

φθ

Decomposition of CF onto Spherical Harmonics

Z.Ch., Gutierrez, MAL, Lopez-Noriega, nucl-ex/0505009

non-femtoscopic structure(not just “non-Gaussian”)

Page 37: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 40

Just push on....?

• ... no!– Irresponsible to ad-hoc fit (often the practice) or ignore (!!) & interpret

without understanding data– no particular reason to expect non-femtoscopic effect to be limited to

non-femtoscopic (large-q) region• not-understood or -controlled contaminating correlated effects

at low q ?

• A possibility: energy-momentum conservation?– must be there somewhere!– but how to calculate / model ?

(Upon consideration, non-trivial...)

Page 38: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 42

energy-momentum conservation in n-body states

f α( ) =d

dαM

2⋅Rn( )

where

M = matrix element describing interaction

(M =1 → all spectra given by phasespace)

spectrum of kinematic quantity (angle, momentum) given by

Rn = δ 4 P − p j

j=1

n

∑ ⎛

⎝ ⎜ ⎜

⎠ ⎟ ⎟ δ pi

2 − mi2

( )d4pi

i=1

n

∏4n

where

P = total 4 - momentum of n - particle system

pi = 4 - momentum of particle i

mi = mass of particle i

n-body Phasespace factor Rn

pi2 − mi

2( )d

4pi =r p i

2

E i

dr p i ⋅d cosθ i( ) ⋅dφi

statistics: “density of states”

larger particle momentum more available states

P conservation

4 P − p j

j=1

n

∑ ⎛

⎝ ⎜ ⎜

⎠ ⎟ ⎟

Induces “trivial” correlations(i.e. even for M=1)

Page 39: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 43

Example of use of total phase space integral

• In absence of “physics” in M : (i.e. phase-space dominated)

Γ pp → πππ( )Γ pp → ππππ( )

=R3 1.876;π ,π ,π( )

R4 1.876;π ,π ,π ,π( )

In limit where "α "="event" = collection of momenta r p i

"spectrum of events" = f α( ) =d

dαRn

→ Probevent α ∝d3n

dpi3

i=1

n

∏Rn

• single-particle spectrum of :

f α( ) =d

dαRn

• “spectrum of events”:

F. James, CERN REPORT 68-15 (1968)

Page 40: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 44

Genbod:phasespace sampling w/ P-conservation

• F. James, Monte Carlo Phase Space CERN REPORT 68-15 (1 May 1968)

• Sampling a parent phasespace, conserves energy & momentum explicitly

– no other correlations between particles

Events generated randomly, buteach has an Event Weight

WT =1

Mm

M i+1R2 M i+1;M i,mi+1( ){ }i=1

n−1

WT ~ probability of event to occur

ALL EVENTS ARE

EQUAL, BUT SOME EVENTS ARE

MORE EQUAL THAN OTHERS

Page 41: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 45

“Rounder” events: higher WT

ALL EVENTS ARE

EQUAL, BUT SOME EVENTS ARE

MORE EQUAL THAN OTHERS

larger particle momentum more available states

Rn = δ 4 P − p j

j=1

n

∑ ⎛

⎝ ⎜ ⎜

⎠ ⎟ ⎟ δ pi

2 − mi2

( )d4pi

i=1

n

∏4n

δ pi2 − mi

2( )d

4pi =r p i

2

E i

dr p i ⋅d cosθ i( ) ⋅dφi

6 particles

Page 42: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 46

“Rounder” events: higher WT

ALL EVENTS ARE

EQUAL, BUT SOME EVENTS ARE

MORE EQUAL THAN OTHERS

larger particle momentum more available states

Rn = δ 4 P − p j

j=1

n

∑ ⎛

⎝ ⎜ ⎜

⎠ ⎟ ⎟ δ pi

2 − mi2

( )d4pi

i=1

n

∏4n

δ pi2 − mi

2( )d

4pi =r p i

2

E i

dr p i ⋅d cosθ i( ) ⋅dφi

30 particles

Page 43: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 47

Genbod:phasespace sampling w/ P-conservation

WT =1

Mm

M i+1R2 M i+1;M i,mi+1( ){ }i=1

n−1

• Treat identical to measured events

• use WT directly• MC sample WT

• Form CF and SHD

Page 44: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 48

Effect of varying frame & kinematic cuts

Watch the green squares --

Page 45: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 49

N=18 <K>=0.9 GeV; LabCMS Frame - no cuts

Watch the green squares

Page 46: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 50

N=18 <K>=0.9 GeV; LabCMS Frame - ||<0.5

kinematic cuts have strong effect!

Watch the green squares

Page 47: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 51

N=18 <K>=0.9 GeV, LCMS - no cuts

kinematic cuts have strong effect!

as does choice of frame!

Watch the green squares

Page 48: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 52

N=18 <K>=0.9 GeV; LCMS - ||<0.5

kinematic cuts have strong effect!

as does choice of frame!

Watch the green squares

Page 49: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 53

N=18 <K>=0.9 GeV; PRF - no cuts

kinematic cuts have strong effect!

as does choice of frame!

Watch the green squares

Page 50: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 54

N=18 <K>=0.9 GeV; PRF - ||<0.5

kinematic cuts have strong effect!

as does choice of frame!

Watch the green squares

Page 51: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 55

Effect of varying multiplicity & total energy

Watch the green squares --

Page 52: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 56

GenBod : 6 pions, <K>=0.5 GeV/c

Page 53: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 57

GenBod : 9 pions, <K>=0.5 GeV/cincreasing mult reduces P.S. constraint

Page 54: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 58

GenBod : 15 pions, <K>=0.5 GeV/cincreasing mult reduces P.S. constraint

Page 55: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 59

GenBod : 18 pions, <K>=0.5 GeV/cincreasing mult reduces P.S. constraint

Page 56: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 60

GenBod : 18 pions, <K>=0.7 GeV/cincreasing mult reduces P.S. constraint

increasing s reduces P.S. constraint

Page 57: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 61

GenBod : 18 pions, <K>=0.9 GeV/cincreasing mult reduces P.S. constraint

increasing s reduces P.S. constraint

Page 58: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 62

So...

• Energy & Momentum Conservation Induced Correlations (EMCICs) “resemble” our data

• So... on the right track...

• But what to do with that?– Sensitivity to s, Mult of particles of interest and other particles

– will depend on p1 and p2 of particles forming pairs in |Q| bins

risky to “correct” data with Genbod...

• Solution: calculate EMCICs using data!!– Danielewicz et al, PRC38 120 (1988)– Borghini, Dinh, & Ollitraut PRC62 034902 (2000)

– Chajecki & MAL, nucl-th/0612080 - generalization of the above

Page 59: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 63

Distributions w/ phasespace constraints

˜ f ( pi) = 2E i f ( pi) = 2E i

dN

d3 pi

single-particle distributionw/o P.S. restriction

Page 60: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 64

Distributions w/ phasespace constraints

˜ f ( pi) = 2E i f ( pi) = 2E i

dN

d3 pi

single-particle distributionw/o P.S. restriction

˜ f c(p1,...,pk ) ≡ ˜ f (pi)i=1

k

∏ ⎛ ⎝ ⎜ ⎞

⎠ ⎟⋅

d3pi

2E i

˜ f (pi)i= k +1

N

∏ ⎛

⎝ ⎜

⎠ ⎟∫ δ 4 pi

i=1

N

∑ − P ⎛

⎝ ⎜

⎠ ⎟

d3pi

2E i

˜ f (pi)i=1

N

∏ ⎛

⎝ ⎜

⎠ ⎟∫ δ 4 pi

i=1

N

∑ − P ⎛

⎝ ⎜

⎠ ⎟

= ˜ f (pi)i=1

k

∏ ⎛ ⎝ ⎜ ⎞

⎠ ⎟⋅

d4piδ(pi2 − mi

2)˜ f (pi)i= k +1

N

∏ ⎛ ⎝ ⎜ ⎞

⎠ ⎟∫ δ 4 pi

i=1

N

∑ − P ⎛

⎝ ⎜

⎠ ⎟

d4piδ(pi2 − mi

2)˜ f (pi)i=1

N

∏ ⎛ ⎝ ⎜ ⎞

⎠ ⎟∫ δ 4 pi

i=1

N

∑ − P ⎛

⎝ ⎜

⎠ ⎟

k-particle distribution (k<N) with P.S. restriction

Page 61: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 65

Using central limit theorem (“large N-k”)

˜ f c(p1,...,pk ) = ˜ f (pi)i=1

k

∏ ⎛ ⎝ ⎜ ⎞

⎠ ⎟ N

N − k

⎝ ⎜

⎠ ⎟2

exp −

pi,μ − pμ( )i=1

k

∑ ⎛

⎝ ⎜

⎠ ⎟

2

2(N − k)σ μ2

μ = 0

3

⎜ ⎜ ⎜ ⎜ ⎜

⎟ ⎟ ⎟ ⎟ ⎟

where

σ μ2 = pμ

2 − pμ

2

pμ = 0 for μ =1,2,3

(*) For simplicity, I from now on assume identical particles (e.g. pions). I.e. all particles have the same average energy and RMS’s of energy and momentum. Similar results (esp “experimentalist recipe) but more cumbersome notation otherwise

k-particle distribution in N-particle system

pμ2 ≡ d3p ⋅pμ

2 ⋅ ˜ f p( )unmeasuredparent distrib

{∫ ≠ d3p ⋅pμ2 ⋅ ˜ f c p( )

measured{∫N.B.

relevant later

Page 62: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 66

Effects on single-particle distribution

˜ f c(pi) = ˜ f (pi)N

N −1

⎝ ⎜

⎠ ⎟2

exp −pi,μ − pμ( )

2

2(N −1)σ μ2

μ = 0

3

∑ ⎛

⎜ ⎜

⎟ ⎟

= ˜ f (pi)N

N −1

⎝ ⎜

⎠ ⎟2

exp −1

2(N −1)

px,i2

px2

+py,i

2

py2

+pz,i

2

pz2

+E i − E( )

2

E 2 − E2

⎜ ⎜

⎟ ⎟

⎜ ⎜

⎟ ⎟

Page 63: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 67

k-particle correlation function

C(p1,...,pk ) ≡˜ f c(p1,...,pk )

˜ f c(p1)....̃ f c(pk )

=

N

N − k

⎝ ⎜

⎠ ⎟2

N

N −1

⎝ ⎜

⎠ ⎟2k

exp −1

2(N − k)

px,ii=1

k

∑ ⎛ ⎝ ⎜ ⎞

⎠ ⎟2

px2

+py,ii=1

k

∑ ⎛ ⎝ ⎜ ⎞

⎠ ⎟2

py2

+pz,ii=1

k

∑ ⎛ ⎝ ⎜ ⎞

⎠ ⎟2

pz2

+E i − E( )

i=1

k

∑ ⎛ ⎝ ⎜ ⎞

⎠ ⎟2

E 2 − E2

⎜ ⎜ ⎜

⎟ ⎟ ⎟

⎜ ⎜ ⎜

⎟ ⎟ ⎟

exp −1

2(N −1)

px,i2

px2

+py,i

2

py2

+pz,i

2

pz2

+E i − E( )

2

E 2 − E2

⎜ ⎜

⎟ ⎟

i=1

k

∑ ⎛

⎜ ⎜

⎟ ⎟

Dependence on “parent” distrib f vanishes,except for energy/momentum means and RMS

2-particle correlation function (1st term in 1/N expansion)

C(p1,p2) ≅1−1

N2

r p T,1 ⋅

r p T,2

pT2

+pz,1 ⋅pz,2

pz2

+E1 − E( ) ⋅ E 2 − E( )

E 2 − E2

⎝ ⎜ ⎜

⎠ ⎟ ⎟

Page 64: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 68

C(p1,p2) ≅1−1

N2

r p T,1 ⋅

r p T,2

pT2

+pz,1 ⋅pz,2

pz2

+E1 − E( ) ⋅ E 2 − E( )

E 2 − E2

⎝ ⎜ ⎜

⎠ ⎟ ⎟

2-particle correlation function (1st term in 1/N expansion)

“The pT term” “The pZ term” “The E term”

Names used in the following plots

Page 65: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 69

Effect of varying multiplicity & total energy

Same plots as before, but now we look at:

• pT (), pz () and E () first-order terms

• full () versus first-order () calculation

• simulation () versus first-order () calculation

Page 66: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 70

GenBod : 6 pions, <K>=0.5 GeV/c

Page 67: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 71

GenBod : 9 pions, <K>=0.5 GeV/c

Page 68: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 72

GenBod : 15 pions, <K>=0.5 GeV/c

Page 69: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 73

GenBod : 18 pions, <K>=0.5 GeV/c

Page 70: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 74

GenBod : 18 pions, <K>=0.7 GeV/c

Page 71: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 75

Findings

• first-order and full calculations agree well for N>9– will be important for “experimentalist’s recipe”

• Non-trivial competition/cooperation between pT, pz, E terms

– all three important

• pT1•pT2 term does affect “out-versus-side” (A22)

• pz term has finite contribution to A22 (“out-versus-side”)

• calculations come close to reproducing simulation for reasonable (N-2) and energy, but don’t nail it. Why?– neither (N-k) nor s is infinite– however, probably more important... [next slide]...

Page 72: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 76

Remember...

C(p1,p2) ≅1−1

N2

r p T,1 ⋅

r p T,2

pT2

+pz,1 ⋅pz,2

pz2

+E1 − E( ) ⋅ E 2 − E( )

E 2 − E2

⎝ ⎜ ⎜

⎠ ⎟ ⎟

pμ2 ≡ d3p ⋅pμ

2 ⋅ ˜ f p( )unmeasuredparent distrib

{∫ ≠ pμ2

c≡ d3p ⋅pμ

2 ⋅ ˜ f c p( )measured{∫

relevant quantities are average over the (unmeasured) “parent” distribution,not the physical distribution

expect pμ2

c< pμ

2

of course, the experimentalist never measures all particles(including neutrinos) or <pT

2> anyway, so maybe not a big loss

Page 73: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 77

C(p1,p2) ≅ 1−2

N pT2

NEW PARAM 11 2 3

⋅r p 1,T ⋅

r p 2,T{ } −

1

N pZ2

NEW PARAM 21 2 3

⋅ p1,z ⋅p2,z{ }

−1

N E 2 − E2

( )

NEW PARAM 31 2 4 4 3 4 4

⋅ E1 ⋅E 2{ } +E

N E 2 − E2

( )

NEW PARAM 41 2 4 4 3 4 4

⋅ E1 + E 2{ } +E

2

N E 2 − E2

( )

UNIMPORTANT"NORMALIZED AWAY"

1 2 4 4 3 4 4

where

X{ } denotes the average of X over the (p1,p2) bin. (or r q - bin or whatever we are binning in)

I.e. it is just another histogram which the experimentalist makes, from the data

momenta and energy are measured in the lab frame.

The experimentalist’s recipeTreat the not-precisely-known factors as fit parameters (4 of them)• values determined mostly by large-|Q|; should not cause “fitting hell”• look, you will either ignore it or fit it ad-hoc anyway (both wrong)• this recipe provides physically meaningful, justified form

Page 74: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 78

18 pions, <K>=0.9 GeV

Page 75: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 79

Highly correlatedEMCIC parameters

Page 76: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 80

C(p1,p2) = Norm 1− M1 ⋅r p 1,T ⋅

r p 2,T{ } − M2 ⋅ p1,z ⋅p2,z{ } − M3 ⋅ E1 ⋅E 2{ } + M4 ⋅ E1 + E 2{ }+"λ ⋅e

− Rα2 qα

2

α =o,s,l

∑"

⎣ ⎢ ⎢

⎦ ⎥ ⎥

The COMPLETE experimentalist’s recipe

C(q) + M1 ⋅r p 1,T ⋅

r p 2,T{ } + M2 ⋅ p1,z ⋅p2,z{ } + M3 ⋅ E1 ⋅E 2{ } − M4 ⋅ E1 + E 2{ }

femtoscopicfunction ofchoicefit this...

...or image this...

Page 77: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 81

Summary• H.I.C raison d’etre & distinction from p+p

– bulk, thermalized, collective matter

• Momentum-space and femtoscopic probes support bulk collectivity

• The p+p “reference” - [femtoscopic apples-to-apples for the first time]– is it understood?– is it really different than a “small A+A” ?– full understanding must be high priority

Page 78: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 82

Famous picture from famous article by famous guy

Energy loss of energetic partons in quark-gluon plasma:Possible extinction of high pT jets in hadron-hadron collisions

J.D. Bjorken, 1982b

Page 79: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 83

Summary• H.I.C raison d’etre & distinction from p+p

– bulk, thermalized, collective matter

• Momentum-space and femtoscopic probes support bulk collectivity

• The p+p “reference” - [femtoscopic apples-to-apples for the first time]– is it understood?– is it really different than a “small A+A” ?– full understanding must be high priority

• Interpretation complicated by non-femtoscopic correlations

• May be largely due to P.S. restrictions (EMCICs)– numerical studies track data– analytic formulation of EMCIC projection onto femtoscopic analysis

presented– highly non-trivial interplay between cuts, frames, and conserved

components (pz, pT, E)– first-order expansion --> experimentalists’ formula– application to STAR underway

• Hotter spotlight due to impending LHC (December 2007!!)

Page 80: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

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Page 81: Ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 20071 Conservation laws & femtoscopy of small systems Zbigniew Chajeçki

ma lisa - Femtoscopy in small systems & EMCICs - Kent State University - January 2007 85

Thanks to...

• Alexy Stavinsky & Konstantin Mikhaylov (Moscow) [suggestion to use Genbod]

• Jean-Yves Ollitrault (Saclay) & Nicolas Borghini (Bielefeld)[original correlation formula]

• Adam Kisiel (Warsaw) [don’t forget energy conservation]

• Ulrich Heinz (Columbus)[validating energy constraint in CLT]