Comparison of methods for elliptic flow
measurements at NICA energy range
Vinh Ba Luong, Dim Idrisov, Peter Parfenov, Arkadiy Taranenko, Alexander Demanov
National Research Nuclear University MEPhI
20th Lomonosov Conference on Elementary Particle Physics
MSU, Moscow, 19–25 Aug. 2021
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●

Elliptic flow v2 at NICA energies

Description of methods for flow measurements and theirsensitivity to flow fluctuations● Performance of v of identified charged hadrons in MPD
2●●Summary

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Elliptic flow at NICA energies

v2 is sensitive to the properties of the strongly interacting
matter produced in relativistic heavy-ion collisions
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Methods for v2 measurements and their sensitivity to fluctuations σv2●

Elliptic flow fluctuations:●Non-flow contribution:●Scalar product:●

Event plane:●Q-cumulants:

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80M min. bias events

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MPD Experiment at NICA
UrQMD
●GEANT4Reconstruction

Flow analysis

Au+Au:

20M at √sNN = 7.7 GeV► 10M at √s= 11.5 GeVNN►●Centrality determination:►b based on MC-Glauber method (see Idrisov’s talk)Event plane determination: TPC● Track selection:●Primary tracks
NTPC hits ≥ 16
► 0.2 < p < 3.0 GeV/cT► |η| < 1.5► PID based on PDG►►-5<η<-2FHCal
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0.2<pT<3 GeV/c2<η<5FHCal

Multi-Purpose Detector (MPD) Stage 1
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5Performance of v2 of pions and protons in MPD

Reconstructed and generated v2 of pions andprotons have a good agreement for all methods
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6Summary●v2 is sensitive to properties of the strongly interacting matter at NICA energy
range► At √s= 4.5 GeV, v2 from UrQMD, SMASH are in a good agreement with theNNexperimental data► At √s≥ 7.7 GeV, UrQMD & SMASH underestimate v 2 – need hybrid models with QGP
NNphase, such as vHLLE+UrQMD●Comparison of methods for v2 measurements:►●The differences between methods are well understood and could be attributed to nonflow and fluctuations

Feasibility study for elliptic flow in MPD:
► v of identified charged hadrons: results from reconstructed and generated data are in2
a good agreement for all methods

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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Backup slides

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8Phase Diagram of the Strongly-Interacting Matter●●

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Top RHIC/LHC:► Validationof the cross-overtransition leading to the sQGP
► Access to high T, small μB
Beam-energy scan programs:
RHIC/SPS/NICA/FAIR:► Broad domain of the (T,μ )-planeB► Accessto different systems,
search for first-order phasetransition and critical end point

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9Anisotropic Collective Flow at top RHIC/LHCPRL 110 (2013)
no.1, 012302

Initial eccentricity (and its attendant fluctuations) εndrives momentum anisotropy vn with specific viscous
modulation● v - directed flow, v - elliptic flow, v - triangular flow
123
● v (p , centrality):nT► sensitive to the early stages of collision► important constraint for transport properties: EoS,
η/s, ζ/s, etc.
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