Flow analysis in CBM experiment at FAIR

Transcription

1 2015 European Nuclear Physics Conference - Groningen 31 August 4 September Flow analysis in CBM experiment at FAIR Valerica Baban (1), Alexandru Jipa (2), Dănuţ Argintaru (3) (1) Constanţa Maritime University (2) Bucharest University Faculty of Physics 1

2 Outline 1. The CBM experiment at FAIR. 2. Flow analysis motivation.eliptic flow. Methods for flow analysis. 3. Simulations for eliptic flow using multiparticles correlations in CBM experiment. 4. Conclusions. 2

3 FAIR - The International Facility for Antiproton and Ion Research CBM Experiment /FAIR The Compressed Baryonic Matter Experiment FIX Target Experiment SIS ions/s beam intensity Beam Plab,max s NN max An Experimental Exploration of the QCD Phase Diagram nucl-ex > arxiv: Heavy ions (Au) 11AGeV 4.7 GeV Light ions (Z/A =5) 14AGeV 5.3 GeV Protons 29AGeV 7.5 GeV SIS-300 Nuclei Z/A = 0,5(0,4) till 45 GeV A Protons till 89 GeV near future (2-10/11) AGeV 3

4 Flow analysis - motivation Flow analysis = the study of the azimuthal distribution of particles emitted after collisions relative to the reaction plane EOS Termalization??? Signature of quark-gluon plasma Strong collective flow Anisotropies distribution of outgoing particles carry information about Exotic phenomena Parity or time - reversal violation 4

5 Anisotropic flow flow coefficients measure the anisotropy degree Reaction plane angle, can only be estimated Directed flow average Eliptic flow v 1 (p T, y) = cos(φ i Ψ RP particles events v 2 (p T, y) = cos 2(φ i Ψ RP particles events Reaction plane 5

6 SIS-100 Flow at FAIR s energies Beam Plab,max s NN max PbPb 20-30% nucl-ex/arxiv: Heavy ions (Au) 11AGeV 4.7 GeV Light ions (Z/A =5) 14AGeV 5.3 GeV Protons 29AGeV 7.5 GeV 6 v2 change the sign 2-4 GeV

7 1. Correlations with the event plane Event Plane Method Methods for flow analysis Detectors used for event plane estimations in CBM experiment 2. Correlations between particles (2A) Two-particles correlations (2A) Four-particles correlations (2B) Cumulants method... Multi-particles correlations (2B) All - particles correlations Lee-Yang Zeroes This work Non-flow effects wich affect the flow Resonance decays, Jets, Quatum statistics effects, Strong/Coulomb interactions 7

8 Lee-Yang Zeroes Method R.S. Bhalerao, N. Borghini, J.Y. Ollitrault validated from RHIC to LHC 1. For each event one define the global observable energies Q θ = M i=1 ω i cos n φ i θ, n the Fourier harmonic under study, n=2 for eliptic flow, θ arbitrary reference direction 2. Construct a generating function G n θ (ir) = e irq n θ events LYZS sum or G θ n (ir) = i=1 M (1 + irω i cos(n φ i θ ) events LYZP product 3. Evaluate G n θ (ir), r real positive number, plot G n θ (ir) function of r, find the first minimun r Gθ(ir) 4. v n θ = j 01 Mr 0 θ, j 01 =2.405 the first positive root of the Bessel function J 0 (x) Differential flow Average over all events v n θ p T, η v n θ M cos(n φ i θ )e ir 0 θ Q θ = Re p events LYZS Q θ e ir 0 θ Q θ events p means average for all particles in an event 8 Is not zero r

9 Lee-Yang Zeroes Method Method limitations statistical errors, if the flow and/or event multiplicity are too small. Ru-Ru /1,69 AGeV/ FOPI detector SIS18 Resolution parameter χ, related to the event plan resolution 1. χ > 1, statistical error not a problem < χ < 1, optimize weights ω i, method can be used 3. χ < 0.5, statistical error large, increase nr events.!!! Ilya Selyuzhenkov, 25th CBM Collaboration meeting,20 April 2015 χ 1.1 9

10 Simulations AuAu 10 AGeV Urqmd events minbias 0.6 < y < 2.6 all charges particles Diferential eliptic flow v 2 (p T ) (Urqmd) known in Urqmd v 2 (p T, y) = cos 2(φ i Ψ RP particles events b(fm) c v2 integral % % % % % % %

11 AuAu 10 GeV A LYZS events for each centrality class 0.6 < y < 2.6 all charges particles C 10-20% 1.2 Gθ(ir) θ = 0 1 c 10-20% b ( )fm c 20-30% b ( )fm 0.8 c 30-40% b ( 7.8-9)fm Integral eliptic flow is not zero c v2 Urqmd v2 LYZS/flow only 10-20% % ±0, % ±0, % ±0, % % % Nr. Events for LYZS should be higher 11

12 AuAu 30 GeV A LYZS Diferential eliptic flow v 2 (p T ) (Urqmd) 1.1 < y < 3.1 all charges particles Gθ(ir) 1.2 c % 1 c 20-30% c 30-40% Integral eliptic flow b(fm) c v2 Urqmd v2 LYZS/flow only % % ±0, % ±0, % ±0, % % %

13 Diferential eliptic flow 13

14 Conclusions 1. The aim of this presentation was to analyze the posibility of using multiparticles correlation method, Lee-Yang Zeroes, for the eliptic flow study as an alternative to Event Plan Method. Preliminary results on the feasibility of the LYZ applied on AuAu 10 and 30 GeV A are presented 2. The limitation of LYZ method is related to statistical fluctuations. Statistical fluctuations decrease like Necessary statistics v 2 θ > j 01 2M lnn ev 1 M N ev The method doesn t work very well in central and peripheral events. Small multiplicity R.S. Bhalerao, N. Borghini, J.Y. Ollitrault 3. Need for more simulations ( increase Nev ), testing LYZP, need comparations with other methods, need analysis for nonflow components, interaction with detectors ( CBMROOT simulations) 14