Prezentacja programu PowerPoint

1
Possibilities and limitations of momentum
correlation studies at ALICE

...waiting for eruption
Jan Pluta, Warsaw University of Technology
2
Today Femtoscopy session
3
(8 reports directly related to Femtoscopy
particle correlations as a tool to analyse
geometry and dynamics of particle/nuclear
collisions

• T. Trainor Dynamics of low Q2 partons
• minijet structure
• 2. M. Lisa Femtoscopy from pp to AA
• from
  STAR to ALICE
• 3. J.P. Possobilities and limitations
• of femtoscopy at ALICE
• 4. M.Chojnacki Software tools
• of femtoscopy for
  ALICE
• 5. H.Gos Proton femtoscopy in STAR
• 6. R. Romita Spectra and HBT in NA57
• 7. M.Bystersky Source imaging...
• 8. K.Mikhailov Residual correlations...

4
before ALICE short RHIC summary
5
HBT Excitation Function
6
System expansion Initial vs Final Size
Collisions at 200GeV only
Smooth expansion of the system from pp to
AuAu
AuAu system expands pp (dAu) no or less
expansion
Proton initial size 0.89 fm from e-scattering
7
RHIC HBT puzzle

• unexpected (small) sizes
• Rout/Rside (approx.)1
• Pt dependence do not agree with hydro
• The same Pt dependence for pp, dAu and AuAu

8
Expectations for ALICE
9
Tom Humanic
Pion freezeout time and z-position for LHC form
rescattering calculations
10
Transverse radius parameters for LHC vs. RHIC
Transverse radius parameters are somewhat larger
and show a stronger pT dependence for LHC
compared with RHIC
11
...and expectations for LHC
RHIC/AGS/SPS Systematics
Assuming the same tendency dN/dy 17281/312 4096
1/316 80001/320
8
Rexpected lt 10fm
20
12
ALICE limits
13
Two-pion correlation functions for the sizes R
indicated in the figure
14
Two-proton correlation functions for the sizes R
indicated in the figure
15
Two-particle kinematics
LCMS (P1P2)z0
16
Two Particle Resolutions
17
Simulation chain for momentum correlations at
ALICE
18
Track Splitting

• We did not observe track splitting in our data
• Tracking program filters them out itself
• Anyway we have implemented STAR algorithm

• Fq can range from -0.5 (low likelihood of being
  splitted track) to 1.0 (high likelihood)

• In sample of 150 events we did not found
  single pair having Fq bigger then 0.6

19
Track Merging
20
ALICE possibilities
21
Nonidentical particle correlations (The idea
assymmetry analysis)

• Catching up
• Effective interaction time larger
• Stronger correlation

• Moving away
• Effective interaction time smaller
• Weaker correlation

• Double ratio
• Sensitive to the space-time asymmetry in the
  emission process

Kinematics selection
R.Lednicky, V. L.Lyuboshitz, B.Erazmus,
D.Nouais, Phys.Lett. B373 (1996) 30.
22
STAR Correlation functions and ratios
Good agreement for like- sign and unlike-sign
pairs points to similar emission process for K
and K-
CF
Out
Clear sign of emission asymmetry
Side
Two other ratios done as a double check
expected to be flat
Long
Preliminary
by Adam Kisiel
23
Space asymmetry from flow
pion emission points

• Transverse momentum of particles is composed of
  the thermal (randomly distributed) and flow
  (directed outwards) components
• With no flow average emission point is at center
  of the source and the length of homogeneity is
  the whole source
• Flow makes the source smaller (size-p
  correlation) AND shifted in outwards direction
  (x-p correlation)
• For particles with large mass thermal motion
  matters less they are shifted more in out
  direction. The difference is measured as emission
  asymmetry.

side
out
kaon emission points
proton emission points
THERMINATOR calculation
24
STAR Hit merging in the TPC

• Tracks can cross in the TPC for pairs with only
  one sign of kSide
• If the tracks cross they can merge, if they
  merge at the outer part of the TPC, they are not
  tracked
• Cut rejects from the denominator pairs, that
  would be merged if in the same event

Merging in ALICE
25
Double ratios out,side,long (t1-t2)10fm/c
by Emilia Lubanska
(physics merging)
26
Single event pion-pion interferometry (with
FSI)... by Zbyszek Chajecki, (ro8fm)
Hopes for single event interferometry at ALICE
27
Single event pion-pion interferometry by Hania
GOS
28
Direct photons interferometry with PHOS ( Dmitri
Peressounko )

• Specific features of direct photons
• emitted in all stages of the collision,
• keep information about the beginning/hottest
  stage of the collision,
• KT dependence select contribution from different
  stages
• Large KT, (3-5)GeV gt QGP, small KT, (1GeV) gt
  hadron gas
• do not suffer from FSI, direct interpretation of
  the correlation funct.
• but most of photons are produced in decay of long
  living hadrons,
• this contribution can be estimated and
  subtracted.

• Registration of two photons by PHOS
• R5fm gt Q50MeV
• If Kt1GeV, Q/Kt0.05 460cm0.0523cm -
  distance between photons in PHOS
• One crystal unit 2.5cm
• Two local maxima should be separated by one
  crystal unit
• Size of the cluster increase logarithmically with
  energy

29
ALICE unfolding and resolution
Estimations Expected radii 6 (500 MeV) 2
(5GeV) fm Region of effect
Probability to unfolded (filed boxes) and find
cluster separated (empty boxes) as a function of
distance between them
30
Background in photon correlations

• Bose-Einstein neutral pion correlations
• Resonance decays
• Collective flow

g
g
p0

g
p0
g
p0
h

p0
p0
31
p0 BE residual correlations
A.Deloff and T.Siemiarczuk, ALICE internal note
INT-98-50
32
Dmitri Peresounko Direct photon interferometry
PHENIX dAu collisions at vsNN200 GeV
33
Direct photons interferometry with PHOS
CONCLUSION
Possibility of measurement of two-photon
correlations up to Kt3 GeV, even in central
PbPb collisions accessing space-time informatin
about all major stages of the collisions.
PHOS detector at ALICE is very promising tool
due to fine granularity and high spatial and
energy resolutions.

34
Femtoscopy of hard processes
nucl-th/0403007
35
Pair selection
36
Expected correlation functions
37
Resonance influence on particle
correlations (Ludmila Malinina and Boris
Batiounia)
Motivation 2/3 of pions comes from resonance
decays, It makes the interpretation of
correlation results more complicated

• Simulation
• Thermal source with Boltzmann gas of resonances
• short lived e.g. Rho - mean lifetime - 1.3 fm/c
• moderatelylived omega - mean lifetime - 23.4
  fm/c,
• long lived etha - mean lifetime - 1000 fm/c
• secondary interactions sigma400mb

38
Resonance influence on particle
correlations (Ludmila Malinina and Boris
Batiounia)
Correlation function for different resonance
sources
39
Resonance influence on particle
correlations (Ludmila Malinina and Boris
Batiounia)
3-dim. correlation function for omega source and
rescattering
40
ImagingTechnique
Paul Chung, Stony Brook
Technique Devised by D. Brown, P.
Danielewicz, PLB 398252 (1997). PRC 572474
(1998).
Inversion of Linear integral equation to obtain
source function
1D Koonin Pratt Eqn.
Encodes FSI
Source function (Distribution of pair separations)
Correlation function
Inversion of this integral equation ? Source
Function
41
StHbt in ALICE

• Mike Lisa
• Ohio State University

Soft Physics Meeting 27 April 2006
42
What is StHbt ?

• Briefly...
• A full-functionality, tested analysis system for
  two-particle correlation analysis in HE and HI
  experiments
• generation/fitting/correcting
• many techniques/features developed over years by
  experts publishing results from a very similar
  experiment
• ESD/DST/RQMD/EPOS... ? correlation functions
• ALICE-, STAR-independent
• Works in either framework, or in pure root.
• copy of STAR 2-particle analysis system,
  file-for-file
• http//www.star.bnl.gov/cgi-bin/cvsweb.cgi/StRoot/
  StHbtMaker/
• c.f. How

43
Why are we doing this ?

• StHbt is a unique resource perfectly suited for
  use in ALICE
• developed/debugged/vetted in simulation and real
  life (published)
• large, widely-spread, community of experts over 7
  years ( counting).
• Cooperative development and communal code sharing
• ? large-scale, diverse, and systematic
  femtoscopic physics program
• full range of experimental femtoscopy techniques
  implemented
• obvious similarities
• ALICE (STAR) femtoscopic leader at LHC (RHIC)
• long-term, diverse analysis physics program by
  group of significant size
• nontrivial (but very similar) experimental
  technical issues
• True code reuse and cross-fertilization.
• We want to ride software wheels to publication,
  not reinvent (or transcribe) them.
• ideas implemented in ALICE (STAR) may be copied
  (files!) to STAR (ALICE)
• really question is why wouldnt we exploit
  existing, easily available resource?

44
Femtoscopy group of ALICE/PW2

In statu nascendi

• Ohio State University M.Lisa and his team
• Warsaw University of Technology JP,
  M.Chojnacki, A. Kisiel, H. Gos
• ITEP- Moscow A. Stavinsky, K. Mikhailov
• RRC Kurchatov Institute - Moscow -
  D.Peressounko
• JINR, Dubna R. Lednicky, B. Batiounia, L.
  Malinina, N. Amelin,
• BITF AS Ukraina Yu. Sinyukov ...
• Nuclear Physics Institute ASCR Re/Prague M.
  umbera ..

45
ALICE femtoscopy plans

• Data analysis
• Clasic analysis R(vSNN, b, Npart, A, B, y, mT,
  ?, PID)
• Direct photon correlations
• Deuteron coalescence and pp correlations
• Assymetry in space-time by nonid. part.
  correlations
• BE correlations in jet-events
• Multiparticle effects
• Models
• Hydro-kinetic approach (Sinyukov, Amelin, Peryt
  )
• Resonances (WW(Cracow) Kisiel)
• New methods
• Imaging Sumbera, Bysterski...

46
Thank you Angela! Many thanks to All
the Organisers !
47
Possibilities and limitations of momentum
correlation studies at ALICE

...waiting for eruption
Jan Pluta, Warsaw University of Technology