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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
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• 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
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DefinitionsMultiplicity n
Event mean transverse momentum
String fusion model
n
i
ti
t pn
p1
1
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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
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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
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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
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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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