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Reaction plane reconstruction

Reaction plane reconstruction. M.Kapishin, L.Lytkin, D.Nikitin Motivation Methods, generators Analysis results Summary and proposal Detector layout. Motivation:. Directed flow v 1 & elliptic flow v 2. z. x. Motivation:. Non-central Au+Au collisions:. V.Toneev et al.

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Reaction plane reconstruction

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  1. Reaction plane reconstruction • M.Kapishin, L.Lytkin, D.Nikitin • Motivation • Methods, generators • Analysis results • Summary and proposal • Detector layout Reaction plane peconstruction

  2. Motivation: Reaction plane peconstruction

  3. Directed flow v1 & elliptic flow v2 z x Motivation: Non-central Au+Au collisions: V.Toneev et al. Interactions between constituents leads to a pressure gradients => spartial asymmetry is converted in asymmetry in momentum space => collective flows - directed flow V2>0 indicates in-plane emission of particles V2<0 corresponds to out-of-plane emission (squeeze-out perpendicular to the reaction plane)‏ - elliptic flow Reaction plane peconstruction

  4. Generators, Conditions, Tasks • Two independent generators UrQMD and QGSM to estimate model uncertainty • → predict different distributions of nucleus fragments • Min Bias events, Au-Au collisions, √s = 3.8, 5, 9 GeV • → generated events available in nc2.jinr.ru • Analysis based on ensemble of generated stable particles; • No momentum smearing, particle identification efficiency, azimuthal rotation of charged particles in magnetic field implemented yet • Tasks → optimize method, kinematical range, type of particles, weight to increase sensitivity, estimate achievable RP resolution, formulate requirements to detectors, propose additional detectors if needed Reaction plane peconstruction

  5. Pseudo-rapidity η / Rapidity y QGSM UrQMD UrQMD QGSM Reaction plane peconstruction

  6. Directed flow of pions and protonsAu + Au collisions at √sNN = 7 GeV, b = 5 – 9 fm Results of NICA Physics Group UrQMD Reaction plane peconstruction

  7. Directed Flow v1 vs Rapidity y nucleons π-mesons UrQMD QGSM Reaction plane peconstruction

  8. G.Musulmanbekov et al. NICA Physics Group → approximate agreement in shape of directed flow v1 between NA49 experiment and UrQMD predictions Reaction plane peconstruction

  9. Methods of reaction plane reconstruction • Using 1-st Fourier harmonics → directed flow in a collision in Lab frame: Method 1: b φR Method 2: → Optimize weight wi to increase sensitivity to RP → combine measurements for η<0 and η>0 to improve precision, study as a function of impact parameter b Reaction plane peconstruction

  10. Relation between b and centrality Impact parameter b: 0 - 3 fm 3 – 6 fm 6 – 9 fm 9 – 12 fm Fraction of σincltot : 0 - 5% 5 – 15% 15 – 30% 30 – 60% → assume that b is measured using independent method (ZDC calorimeter, TPC multiplicity, ZD Neutron calorimeter) Reaction plane peconstruction

  11. b = 0 - 3 fm b = 3 - 6 fm px/pt distribution vs b Nucleons, UrQMD • px is defined in reaction plane • <px/pt> is positive for nucleons (η>0) • Precision of RP reconstruction ~ (px/pt) / δ(px/pt) → φR • To increase sensitivity to RP take particles with weight 1 / δφR • py is ┴ to reaction plane • <py/pt>~0 for nucleons and π-mesons → no sensitivity to RP b = 6 - 9 fm b = 9 -12 fm Reaction plane peconstruction

  12. b = 0 - 3 fm b = 3 - 6 fm px/pt distribution vs b • π-mesons, UrQMD • <px/pt> negative for π-mesons (η>0) • →π-mesons can improve resolution of RP reconstruction • → but reduce sensitivity to RP if π-mesons are combine with nucleons without identification • weight 1 / δφR(η,b) is calculated as a function of η and impact parameter b separately for nucleons andπ-mesons • → next slide b = 6 - 9 fm b = 9 -12 fm Reaction plane peconstruction

  13. Weight 1/δφR as a function of η and b π-mesons nucleons • Maximum shifts to larger |η| in collisions with larger impact parameter b Reaction plane peconstruction

  14. b = 0 - 3 fm b = 3 - 6 fm Reaction plane resolution vs b • Nucleons + π-mesons, UrQMD • best RP resolution ~15-18○ for b=3-9 fm • RP resolution deteriorates to ~45○ for central collision and to ~25○ in peripheral collisions Next slide: → plot r.m.s. values as a function of b b = 6 - 9 fm b = 9 -12 fm Reaction plane peconstruction

  15. Resolution φR○ for nucleons and π-mesons nucleons + π-mesons nucleus fragments + π-mesons UrQMD QGSM • Best resolution is for nucleons (nucleus fragments), adding π-mesons improve resolution a little Reaction plane peconstruction

  16. b = 0 - 3 fm b = 3 - 6 fm Reaction plane resolution vs b UrQMD • if nucleons and π-mesons are combined without identification b = 6 - 9 fm b = 9 -12 fm Reaction plane peconstruction

  17. Resolution φR○ for methods 1 and 2 nucleons + π-mesons nucleus fragments + π-mesons UrQMD QGSM → Precise measurement of particle φ is more crucial than pt Reaction plane peconstruction

  18. Resolution φR○ vs CME √s = 3.8, 5, 9 GeV nucleons + π-mesons nucleus fragments + π-mesons UrQMD QGSM → No big change in topology of A-A collisions for NICA energy range Reaction plane peconstruction

  19. Analysis summary • directed flow of nucleons (nucleus fragments) provides best sensitivity for RP measurement in pseudo-rapidity range 1 < |η| < 5 • best RP azimuthal resolution of ~15○ can be achieved for impact parameter of nucleus-nucleus collision b = 3 - 9 fm (centrality 5 - 30%), worst resolution - for central collisions • impact parameter of nucleus-nucleus collision should be measured by independent methods (ZDC, ZDN, TPC detectors) • identification of π-mesons and nucleons is important in η range where flux of π-mesons is comparable with that of nucleons (0.5 < |η| < 3) • measurement neutrons is important to improve resolution of RP reconstruction • two methods give comparable results → precise measurement of particle azimuthal angle φ is more crucial than pt Reaction plane peconstruction

  20. Detector proposal • TPC, straw ECT, end-cap IT and ToF detectors provide measurement of momentum and identification of charged particles for |η| < 3 • implementation of Pre-shower detector in front of ZDC calorimeter should improve RP resolution in pseudo-rapidity range 2 < |η| < 5 • coordinate resolution of Pre-shower detector and sensitivity to neutrons is crucial for RP measurement, but energy resolution could be moderate • simulation of Pre-shower detector response is needed to estimate RP resolution based hadron clusters and optimize detector layout • Pre-shower detector in combination with ZDC calorimeter will also provide energy flow measurement in nucleus fragmentation region Reaction plane peconstruction

  21. Position of Pre-shower detector Pre-shower can be installed into available space in front of ZDC (≤ 2 λ) Outer Pre-shower Inner Pre-shower Reaction plane peconstruction

  22. Layout of Pre-shower detector • Pb / Scintillator “sandwich” calorimeter: layers of 16:4mm, hexahedrons with rin = 27.5mm • Inner Pre-shower (IPD) in front of ZDC: RIPD< 330mm, dIPD≤ 400mm (~1.8λ) • Outer Pre-shower (OPD) outside ZDC: 330 <ROPD< 715mm, dOPD= (2-3)dIPD • WLS fibers embedded into grooves in Scint tiles, WLS fibers spliced to clear light-guide fibers readout by MAPD (or PMT) Reaction plane peconstruction

  23. Layout of Pre-shower detector To improve coordinate resolution: • 3 successive Scint layers form triplet, hexahedrons in triplet are shifted to form triangle area in coincidence, hexahedron layers with same shift are combined into one longitudinal stack readout by one MAPD (or PMT) • 458 hexahedrons (90 in IPD + 368 in OPD), 1374 readout channels (270 in IPD + 1104 in OPD) → one side detector ( x2 to cover η>0 and η<0) Reaction plane peconstruction

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