1

Status of PPR 6.3,

Momentum Correlations

Soft Physics Meeting, 03.05.2005, Jan Pluta, Warsaw University of Technology

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The structure

C

- shifted by Mercedes

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The structure (2)

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• Consistent notation • New version of “Conclusion from experiments at

AGS, SPS and RHIC”• Some changes in the structure,• Language corrections•New figures

Mercedes changes in the text

Jan’s comment: Keep “small relative velocities”.

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addedby Mercedes

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...addedby Mercedes

...but pleasse,suply the

“oscillations in transverse

radii”(M.Lisa et al.)

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NonidenticalParticleCorrelations

New Elements

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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 processKinematics selection

R.Lednicky, V. L.Lyuboshitz,B.Erazmus, D.Nouais,Phys.Lett. B373 (1996) 30.

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STAR: Correlation functions and ratios

Good agreement for like-sign and unlike-sign pairs points to similar emission process for K+ and K- Out

Side

Long

CF

Clear sign of emission asymmetry

Two other ratios done as a double check – expectedto be flat

Preliminaryby Adam Kisiel

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STAR: Hit merging in the TPC

Tracks can cross in the TPC for pairs with only one sign of k*SideIf the tracks cross – they can merge, if they merge at the outer part of the TPC, they are not trackedCut rejects from the denominator pairs, that would be merged if in the same event

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ALICE: Nonidentical particles (pi+,K-)

Assumed time shift

by Emilia Lubańska

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ALICE: Correlation functions (pi+,K-)

by Emilia Lubańska

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Double ratios: out,side,long

by Emilia Lubańska

(physics + merging)

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HBT correlationsin ITS

stand alone

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Stand alone ITS for HBT analysis(Alberto Pulvirenti)

Motivation:•some running time for a “high rate” data taking, e.g. for muon studies,

•in this case the TPC (slow response) cannot be used,

•is ITS capable to perform track reconstruction and perform HBT studies?

Tracking in the ITS stand alone:the first attempt made in (1999) Alice-ITS-99-34, SUBATECH-99-09new version based on the Denby-Peterson Neural Tracking,full C++ implementation into AliRoot,

SIMULATIONS• 160 events, HIJING param. 4000 particles/event• “good” track - 5 points sharing the same GEANT label,•efficiency - (70-80)%

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Stand alone ITS for HBT analysis(Alberto Pulvirenti)

ANALYSIS:

•only one dim. analysis with respect to Qinv

•The method of “weights” by R.Lednicky used to create correlations

• Perfect PID assumed ( realistic PID “under study”)

•HBT analyser of P. Skowronski used to calculate correlation function

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Stand alone ITS for HBT analysis(Alberto Pulvirenti)

RESULTS•Gaussian source distribution with (6, 8, 10, 12)fm assumed•Intercept parameter: lambda (0.5,0.75, 1.0)

corrected correlation functionopen points - no correlationsfull points - R=8fm

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Stand alone ITS for HBT analysis(Alberto Pulvirenti)

CONCLUSIONS

•Correlation effect is clearly visible.•Linear correlations of the results with the simulated values.•Reconstructed values underestimate the simulated ones.•Works are in progress.

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Direct photonsinterferometry

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Direct photons interferometry with PHOS(by 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,•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:•R=5fm => Q=50MeV•If Kt=1GeV, Q/Kt=0.05; 460cm*0.05=23cm - 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

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Direct photons interferometry with PHOS(by Dmitri Peressounko )

Unfolding algorithm

Probability to unfolded (filed boxes) and find cluster separated (empty boxes)as a function of distance between them

Resolution of: • relative distance - 0.4cm• energy: sig(E)/E - 4%

systematic - increasing(small influence on correl.)

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Direct photons interferometry with PHOS(by Dmitri Peressounko )

Resolution:

Qside Qout

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Direct photons interferometry with PHOS(by Dmitri Peressounko )

Splitting of complicated clusters: p, p(bar), n, n(bar)

Contribution much smaller than those of direct photons

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Direct photons interferometry with PHOS(by Dmitri Peressounko )

Photon pairs in high multiplicity envirnmentHILING, central Pb+Pb collisions

photon conversion before PHOS, heavier resonances

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Direct photons interferometry with PHOS(by Dmitri Peressounko )

CONCLUSION

Possibility of measurement of two-photon correlations

up to Kt=3MeV, even in central Pb+Pb collisions

accessing space-time informatin

about all major stages of the collisions.

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Influence ofResonances

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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: sigma=400mb

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Resonance influence on particle correlations(Ludmila Malinina and Boris Batiounia)

Correlation function for different resonance sources

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Resonance influence on particle correlations(Ludmila Malinina and Boris Batiounia)

3-dim. correlation function for omega source and rescattering

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Simulation chain

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Correlationsin

(pp) collisions

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Correlations in (pp) collisions(Piotr Skowroński)

1. The size expected ...1-2 fm (1fm assumed in simulations)2. 105 events generated using PYTHIA (correlatins outside the interferometry region for very small multiplicities, Nch>5 taken)3. Analysis the same as for Pb+Pb

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Correlations in (pp) collisions(Piotr Skowroński)

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Two Particle Resolution(Piotr Skowroński, Grzegorz Gałązka)

Resolution values are very close to the ones in Technical Proposal Improvement in Qout is connected to better pt

resolution and higher magnetic field

11.30.50.6116.3600 < pt

0.81.10.40.46.44.2300< pt < 600

0.80.90.40.43.42.7pt < 300

TPPDC04TPPDC04TPPDC04

QlongQsideQout

Resolution (r.m.s) [MeV]pt range [MeV]

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Two Particle Resolutions (2)

 

Resolution (r.m.s) [MeV]Qinv Qout Qside Qlong

PDC04 TP PDC04 TP PDC04 TP PDC04 TP+ 0.9 1.3 3.4 3.8 0.4 0.4 1 0.8 2.3 4.2 6.4 9.5 0.6 0.5 1.9 2.3pp 4.0 8.0 9.4 13.0 0.8 0.7 3.2 4.3-  x x 4.4 4.1 1.2 0.7 1.7 1.1p  x x 5.8 4.2 2.1 0.7 1.8 1.2p  x x 6.4 8.3 1.9 1.0 2.6 3.2

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New data on reslution

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New data on reslution

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New data on reslution

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New data on reslution

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Track Merging – ident. (1)

Anti-Merging cut as implemented by STAR Cutting on average distance between two tracks in

TPC Space coordinates of tracks are calculated

assuming helix shape using track parameters as reconstructed in the inner part of TPC

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P I D

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Single event pion-pion interferometry... by Hania GOS

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CorrFit

CorrFit is a tool developed in STAR by Adam Kisiel CorrFit is able to find parameters that fits correlation function taking to the account: Final State Interaction (Coulomb and strong)

They are not corrected for but treated as a source of correlations!

Detector resolutionCan work with any model of the freeze-out distribution Not limited to Gaussian source distribution !

Is able to fit non-identical particles correlation functions

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2 notes in preparation

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...to do

•Finish the text of PPR (2-4 weeks)•Continue works with resoltion, PID, mergind etc.•Finish works with CORFIT•Cooperate with other groups of Soft Physics at ALICE (asHBT, strange particles etc.)•Cooperate with theorists; EPOS+Hydro, etc. •Be ready for data taking!!! (2007)