Reaction plane reconstruction1 Reaction plane reconstruction in extZDC Michael Kapishin Presented by A.Litvinenko

Reaction plane reconstruction2 Reaction plane reconstruction in extZDC Topics discussed in the report Dependence from:  beam energy  ZDC cell size  ZDC length  magnetic field

Position of extZDC within MPD set-up Reaction plane reconstruction3 extZDC

Reaction plane reconstruction4 Methods of reaction plane reconstruction 1-st Fourier harmonics → directed flow:

Reaction plane reconstruction5 Methods of reaction plane reconstruction Method 1: Method 2: → combine measurements for η 0 to improve precision, study as a function of impact parameter b ;

Extended ZDC detector Reaction plane reconstruction6 Simulation of extended ZDC within mpdroot: L = 120 (60, 40) cm 5 < R < 61 cm (inscribed circle), z 0 =270 cm, 1<θ<12.5 o (2.2< η<4.8) d cell = 5x5,10x10 cm w i =Σ E vis in active layers of 1 module → use methods 1 and 2 for RP reconstruction No π vs p/ion identification Geant 4, QGSP_BIC physics model d cell = 5x5 cm, 420 cells in each side of MPD d cell = 10x10 cm, 121 cells in each side of MPD

Resolution δφ RP vs b Reaction plane reconstruction7 δφ RP o = φ ZDC -φ RP Extended ZDC, QGSM 9 AGeV AuAu, Geant4 QGSP_BIC model d cell = 5x5cm, L=120cm 2.2 < η < 4.8, method 1, w=E vis No PID (π vs p/ion) b = 0 – 16 fm in 8 bins, 2 fm / bin

cos δφ RP vs b Reaction plane reconstruction8 b = 0 – 16 fm in 8 bins, 2 fm / bin cos(δφ RP ) = cos(φ ZDC -φ RP ) Extended ZDC, QGSM 9 AGeV AuAu, Geant4 QGSP_BIC model d cell = 5x5cm, L=120cm 2.2 < η < 4.8, method 1, w=E vis No PID (π vs p/ion)

Resolution δφ RP vs b Reaction plane reconstruction9 methods 1 and 2 give consistent results for RP resolution in azimuthal angle φ RP resolution for the case if only ZDC from one side of MPD set-up is used vs full ZDC set-up (lower plot)

Resolution δφ RP and vs b Reaction plane reconstruction10 Effects of ZDC cell size and length, beam energy and interaction model

Effect of magnetic field: vs b Reaction plane reconstruction11 → Systematic effect of magnetic field increases from ~1 o at 9 AGeV to ~3 o at 3 AGeV, QGSM and UrQMD model give consistent results QGSMUrQMD

Effect of magnetic field: vs b reaction plane reconstruction12 Systematic effect of magnetic field increases from ~1 o at 9 AGeV to ~3 o at 3 AGeV Magnetic field systematics is small compared to RP resolution QGSM and UrQMD models give consistent results → systematics could be corrected based on model predictions

Extended ZDC detector (2.2<η<4.8) provides RP measurement at medium b (4<b<10 fm) with resolution of δφ RP ~22-35 o in AuAu collisions at energies 5-9 AGeV, RP resolution deteriorates to δφ RP ~45-65 o at 3 AGeV Sensitivity of extended ZDC to RP azimuthal angle in central (b 12 fm) is much weaker QGSM and UrQMD models give consistent results for RP resolution of extended ZDC, model dependence increases at low beam energies ZDC cell size and length is not critical: d cell =10x10cm, L=60cm are sufficient for RP measurement. ZDC length is more crucial for energy flow measurement Magnetic field systematics to φ RP is ~1 o at 9 AGeV which increases to ~3 o at 3 AGeV. Reduced magnetic field at the lowest energy would decrease systematics Summary 13

Backup Reaction plane reconstruction14

Reaction plane peconstruction15

Reaction plane peconstruction16

LAQGSM generator: all nucleons in 1000 events directed to rectangle 10x10cm for 3 regions of impact parameter b <= (60%) nucleons 10.84<b<=12.5 (60-80%) nucleons b>12.5 (after 80%) nucleons

LAQGSM generator: all nucleons in 1000 events directed to new ZDC for 3 regions of impact parameter b <= (60%) nucleons 10.84<b<=12.5 (60-80%) nucleons b>12.5 (after 80%) 4787 nucleons

Elliptic Flow vs. Beam Energy 25% most central mid-rapidity six decades In-plane elliptic flow squeeze-out bounce-off A. Wetzler

“old” and extended ZDC cell 10 x 10 (cm x cm)

PHENIX Reaction Plane Resolution

Reaction plane resolution vs. numbers of particle and value of the flow

PHENIX Reaction Plane Detector L=38 cm

Fast evaluations: the movement of spectators at NICA/MPD The conclusion: Magnetic field of MPD will not change the polar angles for spectators at ZDC position it will only slightly changes the azimutal angles

LAQGSM generator: all nucleons in 1000 events directed to new ZDC for 3 regions of impact parameter b <= (60%) nucleons 10.84<b<=12.5 (60-80%) nucleons b>12.5 (after 80%) 4787 nucleons

G4 physics model: QGSP_BIC vs QGSP_BERT Reaction plane peconstruction29 Gean4 physics models : QGSP_BERT uses Geant4 Bertini cascade for primary protons, neutrons, pions and Kaons below ~10GeV. In comparison to experimental data we find improved agreement to data compared to QGSP which uses the low energy parameterised (LEP) model for all particles at these energies. The Bertini model produces more secondary neutrons and protons than the LEP model, yielding a better agreement to experimental data. QGSP_BIC uses Geant4 Binary cascade for primary protons and neutrons with energies below ~10GeV, thus replacing the use of the LEP model for protons and neutrons In comparison to the LEP model, Binary cascade better describes production of secondary particles produced in interactions of protons and neutrons with nuclei. QGSP_BIC also uses the binary light ion cascade to model inelastic interaction of ions up to few GeV/nucleon with matter. QGSP_BIC is selected → more reasonable description of interactions of light ions (A=2,3,4) with medium, see also next slides Shower radius in ZDC: hadrons, light ions (A=2,3,4), em particles

G4 physics model: QGSP_BIC vs QGSP_BERT Reaction plane peconstruction30 E vis (0.1zdc) / E vis (full zdc) E vis (zdc) / E gen hadrons, light ions (A=2,3,4), em particles

G4 physics model: QGSP_BIC vs QGSP_BERT Reaction plane peconstruction31 E vis (zdc) vs E gen E vis (zdc) / E gen vs E gen hadrons, light ions (A=2,3,4), em particles Non-linear response because of shower leakage

Reaction plane peconstruction32 Extended ZDC: E vis vs impact parameter b b = 0 – 16 fm in 8 bins, 2 fm / bin b measurement using E vis (ZDC): QGSM model: E vis has peak at b=8-10 fm, → double solution in b measurement based on E vis UrQMD model: monotonic dependence of E vis on b QGSM, 9 AGeV

Reaction plane peconstruction33 Extended ZDC: F vis (R<25cm) vs b b = 0 – 16 fm in 8 bins, 2 fm / bin b measurement using F vis =E vis (R<25cm)/E vis (full zdc): QGSM model: F vis is monotonic except at highest b>12fm → large fluctuations of F vis → double solution for b measurement based on F vis UrQMD model: monotonic dependence of F vis on b QGSM, 9 AGeV

Reaction plane peconstruction34 QGSM vs UrQMD: particle and energy flow extZDC  QGSM and UrQMD generate very different particle and energy flow spectra in pseudo-rapidity range of extZDC

Reaction plane reconstruction35 ExtZDC: and (R<25cm) vs b QGSM vs UrQMD: model dependence is big for E vis at large b (b>10fm) effect is smaller for F vis (ZDC, R<25cm), but is not negligible QGSM and UrQMD predictions for particle and energy flow in ZDC pseudo-rapidity range are very different → energy flow measurement in extended ZDC will distinguish between models What can one get from TPC data? Effect of beam energy and AuAu interaction model

Reaction plane peconstruction36 Multiplicity and Σ p (π,K,p in TPC) vs b Σ p of charged tracks in TPC (|η|<1.2) is a measure of impact parameter b or centrality of nucleus- nucleus interaction. It is less model dependent (QGSM vs UrQMD) in comparison with multiplicity of TPC tracks (lower plot) Model dependence of b measurement with Σ p of charged particles in TPC decreases at low beam energies

Reaction plane peconstruction38 Relation between b and centrality Impact parameter b: fm 3 – 6 fm 6 – 9 fm 9 – 12 fm Fraction of σ incl tot : 0 - 5% 5 – 15% 15 – 30% 30 – 60% Total multiplicity of charged tracks is a measure of impact parameter b (and centrality of nucleus-nucleus interaction)