mike lisa - recent developments in femtoscopy at rhic - ismd aug 2005 - kroměříž czech republic1...

mike lisa - Recent developments in femtoscopy at RHIC - ISMD Aug 2005 - Kroměříž Czech Republic 1

Recent developments infemtoscopy at RHIC*

Mike Lisa

Ohio State University

* not an overview talk


Outline

• Motivation & Reminders: space-time, H.I.C., pion correlations

• Status of present program: exploiting huge systematics

• Selected results• femtoscopy of identical and non-identical particles

• Harmonic decomposition - isolating geometrical effects

• comparison with p+p collisions (in same detector!)

• Harmonic decomposition - isolating non-femtoscopic correlations

• Summary


“”

Rischke, Gyulassy, NP A 608 (1996) 479

Ro

ut/R

sid

e

R(√SNN, b, Npart, A, B, mT, y, , PID) R(√SNN) – simple signal ?

No glaring signal in simple measures

The „real” (experimentalist’s) „puzzle”

mass

|b|

pT


• Vary colliding system• does physics change?• requires dedicated program

• Vary kinematic variables• space-time dynamics• requires large acceptance

• Vary particle type• consistent picture?• unique probe of dynamical structure• requires good particle identification & acceptance

R(√SNN, b, Npart, A, B, mT, y, , PID)


Possibilities in a dedicated program: 5 years @RHIC

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Also: p+p @ 62.4 & 200 GeV

Gunther Roland, QM05


R(√SNN, b, Npart, A, B, mT, y, , PID)

MA

L, P

ratt

, S

oltz

, W

iede

man

n nu

cl-e

x/05

0501

4


R(√SNN, b, Npart, A, B, y, mT, , PID)

Lisa

, P

ratt

, S

oltz

, W

iede

man

n, n

ucl-e

x/05

0501

4

Z. Chajecki, QM05


R(√SNN, b, Npart, A, B, y, mT, , PID)

Lisa

, P

ratt

, S

oltz

, W

iede

man

n, n

ucl-e

x/05

0501

4

Z. Chajecki, QM05



MAL, Pratt, Soltz, Wiedemann nucl-ex/0505014 STAR, PRL 2004


• Usual 1D out-side-long “Cartesian projections”

• limited view of data• ~set of zero measure of

3D CF

• Fit-violating trends may be hidden

• Salient geometrical effects non-trivially convoluted

• acceptance-dependent (unlike 3D CF)

1D projections: a limited view

“Gaussian fit”(remember: notGaussian CF)

out

side long

STAR PRC71 044906 (2005)

Harmonic Decomposition Analysis• exploits full symmetry of q-space

• explicit isolation of femtoscopic(& non-femtoscopic) effects

• full 3D CF seen clearly in few plots

• acceptance-robust (*)

• Cartesian HD Danielewicz & Pratt nucl-th/0501003nucl-th/0501003

• Spherical HD Chajecki,Gutierrez,MAL,Lopez nucl-ex/0505009nucl-ex/0505009

Michael Lisa:“Salient geometrical...” bullet just means: if I want to know “Rlong” or so, I *mostly* just look at width of long projection, but there are also acceptance effects

Michael Lisa:“Salient geometrical...” bullet just means: if I want to know “Rlong” or so, I *mostly* just look at width of long projection, but there are also acceptance effects


Spherical harmonic decomposition of Spherical harmonic decomposition of CFCF

∑→→ ΔΔ

=binsall

iiiiimlml QCYQA

.

,

cos

, ),cos|,(|),(|)(| φθφθπ

φθ

4

QOUT

QSIDE

QLONG Q

• Cartesian-space (out-side-long) naturally encodes physics, but is “inefficient” representation

• Harmonic Moments -- 1::1 connection to source geometry [Danielewicz,Pratt: nucl-th/0501003]

• ~immune to acceptance

• full information content at a glance[thanks to symmetries]

OUT

SIDE

TOT

LONG

LONGSIDEOUT

Q

Q

Q

Q

QQQQ

arctan

)cos(

222

=

=

++=

φ

Chajecki., Gutierrez, MAL, Lopez-Noriega, nucl-ex/0505009


STAR preliminary

A00

A20

A22

SH Moments

STAR Central Au+Au collisions -- Spherical STAR Central Au+Au collisions -- Spherical HDHD

C(Qout)

C(Qside)

C(Qlong)

1D o-s-l projections

∑→→ ΔΔ

=binsall

iiiiimlml QCYQA

.

,cos

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

|)(| φθφθπ

φθ

Chajecki., Gutierrez, MALLopez-Noriega, nucl-ex/0505009


“Mental calibration” - a Gaussian CF

Simple, Gaussian source calculations

~acceptance freeRL < RT

RL > RT

RO < RS

RO > RS

• Full 3D structure

• (high-L (fine structure) coefficients drop off)

• Different geometrical aspects separate &

use “all” relevant information in the CF

• AL≠0 vanishes in non-femtoscopic region


( )

( )

1 11

1 11

.... ........

.... ........

( ) ( ) (1)

( ) ( ) (2)

l ll

l ll

l lq

l

l lr

l

R q R q

S r S r

α α α αα α

α α α αα α

= Α Ω

= Α Ω

∑ ∑

∑ ∑

r

r

3( ) ( ) 1 4 ( , ) ( )R q C q dr K q r S rπ= − = ∫r r r r r

KooninPrattKooninPratt

1 1

2.... ....

( ) 4 ( , ) ( ) (4)l l

l llR q drr K q r S rα α α α

π= ∫1 1

2.... ....

( ) 4 ( , ) ( ) (4)l l

l llR q drr K q r S rα α α α

π= ∫

( )

( )1 1

1 1

.... ....

.... ....

2 1 !!( ) ( ) ( ) (4)

! 42 1 !!

( ) ( ) ( ) (5)! 4

l l

l l

ql lq

l lrr

dlR q R q

ll d

S r S rl

α α α α

α α α α

π

π

Ω+= Α Ω

+ Ω= Α Ω

∫

∫

r

r

( )

( )1 1

1 1

.... ....

.... ....

2 1 !!( ) ( ) ( ) (4)

! 42 1 !!

( ) ( ) ( ) (5)! 4

l l

l l

ql lq

l lrr

dlR q R q

ll d

S r S rl

α α α α

α α α α

π

π

Ω+= Α Ω

+ Ω= Α Ω

∫

∫

r

r

Danielewicz and Pratt nucl-th/0501003Danielewicz and Pratt nucl-th/0501003

P. Chung, QM05Alternative: Cartesian Harmonic Decomposition

Correlation function

Source function


PHENIX Preliminary P. Chung, QM05

CHD: π from central Au+Au collisionsL = 1

out

side

long

L = 0

L = 2

out

side

long

L = 4

out

side

long

• “Size”

• C0(qinv) C1D(qinv)

• Source deformation manifest

• “Rlong” > “Rout” > “Rside”

• higher-order structure

• symmetry: odd L vanish here• But, interesting for non-id


RHIC femtoscopy with wide variety of particle species

π+ π- K+ K- K0S p p

π+

π-

- K+

K-

- - K0S

p

p

!

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

= prelim or final result available


π±-± correlations in 200 GeV Au+Aulike-sign vs unlike-sign

central vs peripheral

++ & --• consistent• Coulomb-dominated

+- & -+• consistent• Coulomb + strong

Expected centralitydependence

• “*” sensitive

Wonderful...but there’s more!...

P. Chaloupka, QM05


Geometric effects of collective flow

● Correlation between momentum and emission point

● reduces source sizeshifts average emission point

● Effect increases with mT

Pionpt = 0.15 GeV/c

Protonpt = 1. GeV/c

Ξ-

pt = 1.4 GeV/cΩ-

pt = 1.8 GeV/c

Emission points from Blast-waveβt = 0.73 for all species

Non-identical particle correlations uniquely probe dynamic structureR. Lednicky, nucl-th/0112011

Retiere & MAL, PRC70 044907 2004


SHD of non-identical particle correlations

• A00 - monopole size

• A11 - dipole shift

• A2m - quadrupole shape

• .....


Accessing asymmetry

• A11

≠ 0 in correlation

regions

Asymmetry in the average emission point between π

• In the “right” direction (cf BW)

details: P. Chaloupka @ WPCF


femtoscopy in p+p @ STAR

DELPHI

Z0 decay @ LEP

m, mT (GeV)

R (

fm)

R Z

(fm

)

hep-ph/0108194

π

π

K

p

STAR preliminary

mT (GeV) mT (GeV)

1. Heisenberg uncertainty?

• e.g. G. Alexander• “plausible” in z-direction• unlikely in transvrse

2. String fragmentation? (Lund)

• pT dependence maybe (??)

• mass dependence probably no

[Andersson, Moriond 2000]

3. Resonance effects?

• e.g. Wiedemann & Heinz ‘97

• maybe, but presumably significantly different effect than for Au+Au

• under investigation

Zbigniew Chajecki QM05

p+p and A+A measured in sameexperiment• great opportunity to compare physics• what causes pT-dependence in p+p?• same cause as in A+A?


femtoscopy in p+p @ STAR

DELPHI

Z0 decay @ LEP

m, mT (GeV)

R (

fm)

R Z

(fm

)

hep-ph/0108194

π

π

K

p

STAR preliminary

mT (GeV) mT (GeV)

1. Heisenberg uncertainty?

2. String fragmentation? (Lund)

3. Resonance effects?

Zbigniew Chajecki QM05

p+p and A+A measured in sameexperiment• great opportunity to compare physics• what causes pT-dependence in p+p?• same cause as in A+A?

d+Au : Rlong doesn’t change with centrality

flow not expected in such a small system as p+p

e.g. Shuryak: hep-ph/0405066

Csorgo et al.: Buda-Lund treatment of p+p collision as bulk system(w/ temperature gradients)hep-ph/0406042

ROUTRSIDE RLONG

mT-m (GeV)

1/(2

πmT)d

2n

/(d

mTd

y)

πK

p

mT (GeV)

4. Bulk system („hydro”) in pp?


Surprising („puzzling”) scaling

All pT(mT) dependences of HBT radii observed by STAR scale with pp although it’s expected that different origins drive these dependences

HBT radii scale with pp

Scary coincidence or something deeper?

pp, dAu, CuCu - STAR preliminary

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


Baseline problems with smallest Baseline problems with smallest systemssystems

STAR preliminary d+Au peripheral collisions

Gaussian fit

ad hoc, but try it...



NA22 fit

Try NA22 empirical formTry NA22 empirical form

NA22 fit

data

Spherical harmonics

L =1M=0

L =2M=0

L =1M=1

L =2M=2


““account for” constant offset in L=2 account for” constant offset in L=2 componentscomponents


Gaussian fit

|Q| |Q|

|Q|

A02

A22

A00

Gaussian

+ constant A02, A2

2


With L=2 shifts, message remains

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

Fit w/o baseline parameterization NEW fit w/ baseline parameterization

STAR preliminary

To be continued...


Summary• Very active, systematic femtoscopic program at RHIC

• A few new results

• detailed shape studies: (for many particle types)

• exotic correlations: substructure of space-time dynamics of

• experimental comparison of femtoscopy in hadronic/nuclear collisions

• New methods

• Harmonic analysis : much to offer

• New questions

• dynamic substructure picture “confirmed”... eliminate theories/models?

• similarity of p+p & Au+Au (& d+Au) : “deep” or coincidental?

• A healthy, important (sub)field !

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


Conclusion/summary

• COMPLETE experimental program: huge multidimensional systematic effort at dedicated facility with large acceptance

• new method [important to exploit the new data]• fully exploits q-space symmetries: efficient representation of full 3D correlation

function [my opinion: this is the end of Cartesian projections]• different physics aspects separated cleanly (l=0,1,2...)• excellent diagnostic for identifying/characterizing nonfemtoscopic correlation

effects (& including them in fit)

• new data• extend PID beyond pions for sizes: consistency of scenario• non-id for shifts: new information also (qualitatively) consistent• vary system [A,B,√s, Npart] (CuCu,AuAu,dAu,200,64GeV)

• multiplicity scaling

• “elementary” systems “3rd HBT puzzle”

• Insert closing comment / “big picture conclusion” here


Geometric effects of collective flow

● Correlation between momentum and emission point

● reduces source sizeshifts average emission point

● Effect increases with mT

Pionpt = 0.15 GeV/c

Protonpt = 1. GeV/c

Ξ-

pt = 1.4 GeV/cΩ-

pt = 1.8 GeV/c

Emission points from Blast-waveβt = 0.73 for all species

Non-identical particle correlations uniquely probe dynamic structureR. Lednicky, nucl-th/0112011

Petr Chaloupka QM05

Retiere & MAL, PRC70 044907 2004

Comment:• Cramer/Miller: 12 parameters to

reproduce one particletype

• BW+stat: 5+2 parameters to reproduce “all” particletypes


Spacetime - an annoying detail in H.I.C. ?

• Non-trivial space-time - the hallmark of rhic• Initial state: dominates further dynamics• Intermediate state: impt element in exciting signals• Final state:

• Geometric structural scale is THE defining feature of QGP

STAR, PRC66 (2002) 034904 STAR, PRL93 (2004) 252301


qout

qside

qlong

Hanbury Brown-Twiss interferometry

Rsi

de

R long

Rout

x1

x2

12 ppqrrr −=

p1

p2

qr

( )12 pp2

1k

rrr+=

• Two-particle interferometry: p-space separation space-time separation

• HBT: Quantum interference between identical particles

pairsevent mixed

pairsevent real

)(P)(P

),(P),(

21

2121 ==

pppp

ppC

2long

2long

2side

2side

2out

2out)(1),(

RqRqRqekkqC

−−−λ+=vrr

q (GeV/c)q (GeV/c)

C (

q)C

(q)

11

22R

1~

• Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for

Gaussian model (3-d):


qout

qside

qlong

Hanbury Brown-Twiss interferometry

Rsi

de

R long

Rout

x1

x2

12 ppqrrr −=

p1

p2

qr

( )12 pp2

1k

rrr+=

• Two-particle interferometry: p-space separation space-time separation

RRsideside

RRoutout


Spacetime - an annoying detail in H.I.C. ?

• Non-trivial space-time - the hallmark of rhic• Initial state: dominates further dynamics• Intermediate state: impt element in exciting signals• Final state:

• Geometric structural scale is THE defining feature of QGP• Temporal scale sensitive to deconfinement transition (?)



Ann.Rev.Nucl.Part.Sci. 46 (1996) 71


C(Qout)

C(Qside)

C(Qlong)

STAR preliminary

A00

A20

A22

SH Moments

STAR Central Au+Au collisions -- Spherical STAR Central Au+Au collisions -- Spherical HDHD

1D o-s-l projections

∑→→ ΔΔ

=binsall

iiiiimlml QCYQA

.

,cos

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

|)(| φθφθπ

φθ

Chajecki., Gutierrez, MALLopez-Noriega, nucl-ex/0505009

A04

A24

A44


Baseline in p+p, d+Au and Au+AuBaseline in p+p, d+Au and Au+Au

Some coefficients don’t vanish for large Q

Bias from zero is larger for more peripheral collisions

This problem is getting more significant for small systems (pp & dAu)

It can be due to

an experimental artifact

long range correlations (e.g. Jets)

problem with momentum conservation ?

or ?


LongLong--range correlations : JETS ?range correlations : JETS ?

Jets as a origin of the baseline problem ??

The idea was to try to eliminate pions coming from jet fragmentation from data sample. It can be done by applying an event cut which accepts only events that have no high-pt tracks (jets).

HBT analyses where done for three classes of events

all - all events accepted – as a reference

soft – only events without high-pT tracks ( highest-pT < 1.2 GeV/c was chosen)

hard - only events with least one track with pT > 2 GeV/c


D

Momentum conservation study with Momentum conservation study with NexusNexus

Correlation function for pions from events generated with EPOS

No correlation effect included (as BE, FSI)

Background created by mixing particles comming from different events (same procedure like for experiemental CF)

No evidence of a problem with baseline of CF !

Nexus, p+p @ 200 GeV

mike lisa - recent developments in femtoscopy at rhic - ismd aug 2005 - kroměříž czech republic1...

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