current status of the long- range correlations analysis in be+be at 150 agev/c e. andronov, a....

Current status of the long-range correlations

analysis in Be+Be at 150 AGeV/c

E. Andronov, A. SeryakovNA61/NA49 Collaboration meeting

Dubna, 10/04/14

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Layout• Two stage scenario of particles production• String fusion model• Long range correlations• Analysis technique• Recent BeBe 150 AGeV/c results• Plans

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Two stage scenario of particles

production

p-p case, low energy

I stage: strings formation.

[1]A.Capella,  U.P.Sukhatme,  C.I.Tan  and  J.Tran  Thanh  Van,  Phys.  Lett.  B81  (1979)  68;  Phys.  Rep. 236  (1994)  225.     [2]A.B.Kaidalov,  Phys.  Lett.,  116B(1982)459

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Two stage scenario of particles

production

II stage: string decay.

[1]A.Capella,  U.P.Sukhatme,  C.I.Tan  and  J.Tran  Thanh  Van,  Phys.  Lett.  B81  (1979)  68;  Phys.  Rep. 236  (1994)  225.     [2]A.B.Kaidalov,  Phys.  Lett.,  116B(1982)459

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Two stage scenario of particles

production

p-p case, low energy

[1]A.Capella,  U.P.Sukhatme,  C.I.Tan  and  J.Tran  Thanh  Van,  Phys.  Lett.  B81  (1979)  68;  Phys.  Rep. 236  (1994)  225.     [2]A.B.Kaidalov,  Phys.  Lett.,  116B(1982)459

p-p case, high energy

I stage: strings formation.

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Two stage scenario of particles

productionA-A case

[1]A.Capella,  U.P.Sukhatme,  C.I.Tan  and  J.Tran  Thanh  Van,  Phys.  Lett.  B81  (1979)  68;  Phys.  Rep. 236  (1994)  225.     [2]A.B.Kaidalov,  Phys.  Lett.,  116B(1982)459

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String fusion model“In case of AA collisions with growing energy and atomic number the number of strings grows and one has also to take into account the string fusion.”

[1]M.A.Braun  and  C.Pajares,  Phys.  Rev.  Lett.  85  (2000)  4864;     [2]M.A.Braun  and  C.Pajares,  Phys.  Lett.  B287  (1992)  154; Nucl.  Phys.  B390  (1993)  542,  549;     [3]N.S.Amelin,  M.A.Braun  and  C.Pajares,  Phys.  Lett. B306 (1993)  312; [4]M.A.Braun,  C.Pajares  and  V.V.Vechernin,  Low  pT  Distributions  in  the  Central  Region  and  the  Fusion  of  Colour  Strings,  Internal  Note/FMD  ALICE- ‐INT- ‐2001- ‐16

String (r~0.2fm)Transverse

plane

• Each cluster in the overlaps of strings could be considered as a new string with new properties

• The color field of cluster is the vector sum of fields of strings

• Individual string colors may be oriented in an arbitrary manner, then

• Last formula could be modified for not fully overlapping strings but arbitrary overlapping

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QQ NN 1

String fusion model

i

iN QQ 1

2

2

DefinitionsMultiplicity n

Event mean transverse momentum

String fusion model

n

i

ti

t pn

p1

1

DefinitionsMultiplicity n

Event mean transverse momentum

String fusion model

n

i

ti

t pn

p1

1

Single string

Color field

Multiplicity

Event mean transverse momentum

DefinitionsMultiplicity n

Event mean transverse momentum

String fusion model

n

i

ti

t pn

p1

1

Single string

Overlapping strings

onetstr

newt pNp 22

Color field

Multiplicity

Event mean transverse momentum

12I. Bautista, J. G. Milhano, C. Pajares and J. Dias de Deus, Phys. Lett. B715 (2012) 230

Low energy(SFM + wounded nucleon model)

High energy(SFM + multiple scattering)

nucleus.per nucleons ingparticipat ofnumber average theAN

String fusion modelComparison with data

13I. Bautista, J. G. Milhano, C. Pajares and J. Dias de Deus, Phys. Lett. B715 (2012) 230

Low energy(SFM + wounded nucleon model)

High energy(SFM + multiple scattering)

nucleus.per nucleons ingparticipat ofnumber average theAN

String fusion modelComparison with data

PbPb/AuAuCuCupp

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Long-range correlationsDefinitions

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Long-range correlations

A.Capella et al., Phys.Rep. 236,225(1994)

Definitions

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Long-range correlations

• - the correlation between charged particle multiplicities in backward (B) and forward (F) rapidity windows

• - the correlation between the event mean transverse momentum in B and multiplicity in F

• -the correlation between the event mean transverse momenta in B and F

• - the correlation between the event net charges in B and F

Types of correlations

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oneF

FF nFPFn

oneBB

B nBPBn

Single string case

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In case of sufficiently large gap between windows one string produces particles in both windows independently!

oneF

FF nFPFn

oneBB

B nBPBn

FBBF

FB nnBFPBFnn ,

,

BPFPBFP ,

Single string case

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In case of sufficiently large gap between windows one string produces particles in both windows independently!

oneF

FF nFPFn

oneBB

B nBPBn

FBBF

FB nnBFPBFnn ,

,

BPFPBFP ,

Single string case annihilation at 29GeV

Phys.Rev.D vol.13, num.11(1986)

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FBBF

FB nnFBPBFnn ,

,

BPFPBFP ,

Long-range correlationsLinear regression case

R.E. Ansorge et al. (UA5 Collaboration). Z. Phys., C37-191, (1988).

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String fusion model

onestrtotalnNn

onestr

totaln

Nn

22

onet

totalt pp 22

onet

totalT pp 22 2

Decrease of mean multiplicity and increase of mean transverse momentum lead to negative pT-n correlations!

Negative correlationsFixed number of strings case

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Analysis techniqueEvent cuts: 1. T22. WFA 1.5 μs 3. ZCharge (by Emil) 4. BPD 5. Fitted Vertex 6. Fit Quality 7. Number of good vertex track

> 2 8. Z coordinate +/- 5cm

Track cuts: 1. Vertex track status and has

track2. Impact parameter X < 4cm Y

< 2cm3. VTPC clusters > 14 or

GapTPC > 44. All TPC clusters > 145. Pt < 1.5 GeV/c6. P > 300 MeV/c7. Acceptance map (new)Method (based on MC data from EOS):

1. Loop through all simulated primary tracks.2. Fill 3D histogram of generated tracks with (φsim, pTsim, ηsim)3. Loop through all primary tracks from RecEvent passed track cuts4. Fill 3D histogram of selected tracks (φrec, pTrec, ηrec)5. Calculate efficiency 3D histogram by dividing selected by generated.6. Calculate acceptance map:For each (φ,pT, η) bin in efficiency histogram: if efficiency is < 0.9 or if there is < 20 tracks in generated, the bin is not acceptedStill no MC corrections due to lxbatch quota!

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Long-range correlationsDefinitions: relative variables

Exclude trivial dependences

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Results: BeBe 150 AGeV/c

Data without acceptance cutData with acceptance cutMC with acceptance

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Results: BeBe 150 AGeV/c

Data without acceptance cutData with acceptance cutMC with acceptance

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Results: BeBe 150 AGeV/c

Data without acceptance cutData with acceptance cutMC with acceptance

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Results: BeBe 150 AGeV/c

Data without acceptance cutData with acceptance cutMC with acceptance

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Results

• Testing acceptance cut (changing binomization, critical efficiency, matching etc.)

• Comparison with generated MC data• MC-based corrections• Centrality analysis (with new centrality classes from E. Kaptur)• Azimuthal analysis• Systematics

Plans

• Long-Range correlations analysis is going on for BeBe 150GeV/c.

• new Acceptance map is done• new Comparison to reconstructed MC (EPOS) with acceptance map is

done

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