Reaction plane reconstruction 1

Reaction plane reconstruction in extZDC

Michael Kapishin kapishin@mail.desy.de

Presented by A.Litvinenko

Reaction plane reconstruction 2

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 reconstruction 3

extZDC

Reaction plane reconstruction 4

Methods of reaction plane reconstruction

1-st Fourier harmonics → directed flow:

))φ-cos(φ2v +(12π

N

φd

dNRn

tot ∑=

∑∑

i,xi

i,yi

Rpw

pwarctanφ =

Ew ii =

iii p/Ew =

Reaction plane reconstruction 5

Methods of reaction plane reconstruction

Method 1:

2222 +=

+==

ii

ii

ii

ii

ii

iinuclR

xy

xφcos;

xy

yφsin;

φcosEΔ

φsinEΔarctanφ

∑∑

Method 2:

2π2

2ππ2

δ1+δ1δπ++δ

=)φ()φ(

)φ()φ()φ(φφ

RnuclR

RRnuclR

nuclR

R

→ combine measurements for η<0 and η>0 to improve precision, study as a function of impact parameter b

;

∑∑

ii

iinuclR

xEΔ

yEΔarctanφ =

Extended ZDC detector

Reaction plane reconstruction 6

Simulation of extended ZDC within mpdroot:

• L = 120 (60, 40) cm

• 5 < R < 61 cm (inscribed circle), z0=270 cm, 1<θ<12.5o (2.2<η<4.8)

• dcell = 5x5,10x10 cm

• wi=Σ Evis 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

dcell = 5x5 cm, 420 cells in each side of MPD

dcell = 10x10 cm, 121 cells in each side of MPD

Resolution δφRP vs b

Reaction plane reconstruction 7

δφRPo = φZDC-φRP

Extended ZDC, QGSM 9 AGeV AuAu, Geant4 QGSP_BIC modeldcell = 5x5cm, L=120cm2.2 < η < 4.8, method 1, w=Evis

No PID (π vs p/ion)

b = 0 – 16 fm in 8 bins, 2 fm / bin

cos δφRP vs b

Reaction plane reconstruction 8

b = 0 – 16 fm in 8 bins, 2 fm / bin

cos(δφRP) = cos(φZDC-φRP)

Extended ZDC, QGSM 9 AGeV AuAu, Geant4 QGSP_BIC modeldcell = 5x5cm, L=120cm2.2 < η < 4.8, method 1, w=Evis

No PID (π vs p/ion)

Resolution δφRP vs b

Reaction plane reconstruction 9

• 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 δφRP and <cos δφRP> vs b

Reaction plane reconstruction 10

Effects of ZDC cell size and length, beam energy and interaction model

Effect of magnetic field: <φZDC-φRP> vs b

Reaction plane reconstruction 11

→ Systematic effect of magnetic field increases from ~1o at 9 AGeV to ~3o at 3 AGeV, QGSM and UrQMD model give consistent results

QGSM UrQMD

Effect of magnetic field: <φZDC-φRP> vs b

reaction plane reconstruction 12

• Systematic effect of magnetic field increases from ~1o at 9 AGeV to ~3o 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 δφRP~22-35o in AuAu collisions at energies 5-9 AGeV, RP resolution deteriorates to δφRP~45-65o at 3 AGeV

• Sensitivity of extended ZDC to RP azimuthal angle in central (b<3 fm) and peripheral collisions (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: dcell=10x10cm, L=60cm are sufficient for RP measurement. ZDC length is more crucial for energy flow measurement

• Magnetic field systematics to φRP is ~1o at 9 AGeV which increases to ~3o at 3 AGeV. Reduced magnetic field at the lowest energy would decrease systematics

Summary

13

Backup

Reaction plane reconstruction 14

Reaction plane peconstruction 15

Reaction plane peconstruction 16

LAQGSM generator: all nucleons in 1000 events

directed to rectangle 10x10cm for 3 regions of impact parameter

b <= 10.84 (60%)

19707 nucleons

10.84<b<=12.5 (60-80%)

47826 nucleons

b>12.5 (after 80%)

60431 nucleons

LAQGSM generator: all nucleons in 1000 events

directed to new ZDC for 3 regions of impact parameter

b <= 10.84 (60%)

71041 nucleons

10.84<b<=12.5 (60-80%)

22848 nucleons

b>12.5 (after 80%)4787 nucleons

Elliptic Flow vs. Beam Energy25% most central mid-rapidity

six decades

In-planeelliptic flow

squeeze-out

bounce-off

A. Wetzler

“old” and extended ZDC

cell 10 x 10 (cm x cm)

PHENIXReaction Plane Resolution

O30ΔΨ 0.4)ΔΨ2cos( == ⇒

O40ΔΨ 0.2)ΔΨ2cos( == ⇒

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

PHENIXReaction Plane Detector

L=38 cm 2.8< η< 0.8

O18ΔΨ 0.8)ΔΨ2cos( == ⇒

GeV .SNN 98=

GeV .SNN 98=

Fast evaluations: the movement of spectators at NICA/MPD

bpXY

Z

T 1 B

QB0.3Ap

- Ap

zQB0.3cos

QB0.3Ap

)z(y

ApzQB0.3

sinQB0.3Ap

)z(x

T

z

T

z

T

ApzQB0.3

cos12QB0.3Ap

yx )z,B(z

T22

Ap

zQBz

p

pzB

Ap

zQB

zz

T

z

0.3

2

1 ; ),( 0.2

0.3

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

06

zT p/p

LAQGSM generator: all nucleons in 1000 events

directed to new ZDC for 3 regions of impact parameter

b <= 10.84 (60%)

71041 nucleons

10.84<b<=12.5 (60-80%)

22848 nucleons

b>12.5 (after 80%)4787 nucleons

G4 physics model: QGSP_BIC vs QGSP_BERT

Reaction plane peconstruction 29

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 peconstruction 30

Evis (0.1zdc) / Evis (full zdc) Evis (zdc) / Egen

hadrons, light ions (A=2,3,4), em particles

G4 physics model: QGSP_BIC vs QGSP_BERT

Reaction plane peconstruction 31

Evis (zdc) vs Egen Evis (zdc) / Egen vs Egen

hadrons, light ions (A=2,3,4), em particles

Non-linear response because of shower leakage

Reaction plane peconstruction 32

Extended ZDC: Evis vs impact parameter b

b = 0 – 16 fm in 8 bins, 2 fm / bin

b measurement using Evis (ZDC):

QGSM model: Evis has peak at b=8-10 fm, → double solution in b measurement based on Evis

UrQMD model: monotonic dependence of Evis on b

QGSM, 9 AGeV

Reaction plane peconstruction 33

Extended ZDC: Fvis(R<25cm) vs b

b = 0 – 16 fm in 8 bins, 2 fm / bin

b measurement using Fvis=Evis(R<25cm)/Evis(full zdc):

QGSM model: Fvis is monotonic except at highest b>12fm→ large fluctuations of Fvis

→ double solution for b measurement based on Fvis

UrQMD model: monotonic dependence of Fvis on b

QGSM, 9 AGeV

Reaction plane peconstruction 34

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 reconstruction 35

ExtZDC: <Evis> and <Fvis> (R<25cm) vs b

QGSM vs UrQMD:

• model dependence is big for Evis at large b (b>10fm)

• effect is smaller for Fvis(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 peconstruction 36

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 peconstruction 38

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%

Total multiplicity of charged tracks is a measure of impact parameter b (and centrality of nucleus-nucleus interaction)