Anisotropic flow measurements in MPD
experiment using two- and three-particle
correlation scalar product method
Petr Parfenov, Vinh Ba Luong, Dim Idrisov, Arkadiy Taranenko, Alexander Demanov
NRNU MEPhI
20th Lomonosov Conference on Elementary Particle Physics
19-25 August 2021
MSU, Moscow, Russia
This work is supported by:
the RFBR grant No. 18-02-40086, the European Union‘s Horizon 2020 program No. 871072, the Russian Academic Excellence Project (contract No. 02.a03.21.0005, 27.08.2013),
the Ministry of Science and Higher Education of the Russian Federation, Project "Fundamental properties of elementary particles and cosmology" No. 0723-2020-0041

Outline• Anisotropic flow at energies from LHC to NICA
• Scalar product (SP) method implementation• Comparison of elliptic flow using 2- and 3-particle correlation SPmethod• Summary and outlook

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Anisotropic flow at RHIC/LHC
Gale, Jeon, et al., Phys. Rev. Lett. 110, 012302

Ψ%&Spatial anisotropy:
𝜀! =𝑟 ' cos 𝑛𝜑 ' + 𝑟 ' sin 𝑛𝜑 '𝑟'𝜑 – azimuthal angle of nucleon
𝜙 – azimuthal angle of produced particle

Momentum anisotropy:𝑑𝑁∝ 1 + 2 ( 𝒗𝒏 cos 𝑛 𝜙 − Ψ%&𝑑𝜙!"#𝑣# - directed flow
𝑣! = cos 𝑛 𝜙 − Ψ%&𝑣' - elliptic flowØInitial eccentricity (and its attendant fluctuations) 𝜀!
drives momentum anisotropy 𝑣! with specific viscous
modulationØ𝒗𝒏 (𝒑𝑻 , 𝒄𝒆𝒏𝒕𝒓𝒂𝒍𝒊𝒕𝒚) sensitive to the early stages ofcollision:ØImportant constraint for transport properties: EOS, 𝜂/𝑠, 𝜁/𝑠,etc.
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Anisotropic flow at STAR BES and NICA energies
EPJ Web Conf. 204 (2019) 03009
Phys. Rev. C 88 (2013) 14902

Taranenko et. al., Phys. Part. Nuclei 51 (2020), 309–313

𝑠!! , GeV

Strong energy dependence of the difference in 𝒗𝟐 of particles and antiparticles
Anisotropic flow at NICA energies is a delicate balance between:
I.
The ability of pressure developed early in the reaction zone andII. The passage time for removal of the shadowing by spectators
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MPD experiment at NICA
• Symmetry plane• FHCal (2 < 𝜂 < 5) or TPC ( 𝜂 < 1.5)

• Time projection chamber (TPC)• Tracking of charged particles within( 𝜂 < 1.5, 2𝜋 in 𝜙)• PID at low momenta• Time of flight (TOF)• PID at high momenta
FHCal L

−5 < 𝜂 < −2TPC
𝜂 < 1.5FHCal L

2<𝜂<5Multi-Purpose Detector (MPD) Stage 1
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Scalar product (SP) method−5 < 𝜂 < −2Unit particle vector 𝑢" and event flow vector 𝑄" :(𝑢" = 𝑒#"$,(a%𝑄" = , 𝑢" = , 𝑒 #"$!
%&'%&'

3-particle correlation:
8 9 0,1∗𝑄𝑄3 𝑢)
3𝑣)*+ 𝑄3,45/67 =≈ 𝑣) + 𝒪8 9∗𝑄3 𝑄3bFHCal L2<𝜂<5cdΔ𝜂 = 0.1

Where:• 𝜙 – azimuthal angle of the particle• 𝑀 – particle multiplicity in the given set of particles (subevent)2-particle correlation:
0,1 1,0∗𝑢1) 𝑄)*+𝑣) 𝑄),-./ =≈ 𝑣) + 𝒪,𝑣𝑀)𝑄)1 𝑄)0∗TPC𝜂 < 1.5FHCal L

80M min. bias events

1𝛿~𝑀1𝑣) 𝑀 𝑣3 𝑀,𝛿~1𝑀)

SP method based on 3-particle correlation has a stronger suppressionof non-flow contribution 𝜹I. Selyuzhenkov and S. Voloshin, Phys. Rev. C 77 (2008) 034904
N. Borghini, P.M. Dinh, J.Y. Ollitrault, Phys.Rev. C 66 (2002) 014905
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Comparison of the SP methods• UrQMD 3.4, Au+Au, 𝑠!! = 7.7 GeV, 80M min. bias events• Centrality determination: impact parameter selection basedon the MC-Glauber method (see Idrisov’s talk)• Track selection:• 0.05 < 𝜂 < 1.5• 𝑝" < 3 GeV/c• PDG based particle idetification

SP method based on 3 particle correlation can be used tostudy flow in peripheral collisions
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Summary• 𝒗𝟐 at NICA energies shows strong energy dependence• There’s a lack of differential measurements of 𝑣7 at NICA energy range• Comparison of SP methods for 𝒗𝟐 measurements:• Method that uses 3 particle correlation has a stronger non-flow suppression
and can be used for flow measurements in case of peripheral collisions• Additional difference can be attributed to the flow fluctuations (see Luong’stalk)

ToDo:• Implementation of the SP based on 3 particle correlation for the fullyreconstructed data in MPD (NICA)
This work is supported by:
the RFBR grant No. 18-02-40086, the European Union‘s Horizon 2020 program No. 871072, the Russian Academic Excellence Project (contract No. 02.a03.21.0005, 27.08.2013),
the Ministry of Science and Higher Education of the Russian Federation, Project "Fundamental properties of elementary particles and cosmology" No. 0723-2020-0041
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Thank you for your attention!

Backup slides

SP vs EP methods

𝑣$%& 𝑄$,(&) ≈ 𝑣$ Ψ$,(&) > 𝑣$*) Ψ+, ≥ 𝒗𝑺𝑷𝟐 𝑸𝟏,𝑭𝑯𝑪𝒂𝒍 ≈ 𝒗𝟐 𝚿𝟏,𝑭𝑯𝑪𝒂𝒍
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