Pion production in n p collisions at 1.25 A GeV

1. A.Kurilkin, P.Kurilkin, V.Ladygin, A.Ierusalimov, T.Vasiliev, LHEP-JINR, Dubna, Russia For the HADES collaboration Pion production innpcollisions at 1.25AGeV

2. HADES experiment at SIS18, GSI • d+p reactions, May 2007: • LVL1 (MULT >2) && FW • Detector set-up: • LH2 target • 24 MDC • No Start detector • Forward Wall • Kinematics for np: • Kinetic Energy = 1.25 GeV • Momentum = 1.97 GeV/c • np selection by detecting Proton-spectator in FW 2

3. Introduction ? • Study of np reaction is important important to obtain the contribution of isoscalar(I=0)partial waves to the inelastic np collision. • Study of reactions with single and double pion production in the np collisions at different energies is important for the determination both of the energy dependences of the total np cross section and the contribution of inelastic channels to np interactions. np→ppπ- pp→ppπo HADES 1.97 V.V.Sarantsev et. All Eur. Phys.J. A 43, (2010) J.Bystricky et. all, J. Physique 48 (1987)

4. Experimental data for np→npπ+π- at 1.73 and 2.23 GeV/c The OPER model, developed in ITEP, was chosen to study the reaction mechanisms. [L.Ponomarev. Part. and Nucl., v.7(1), pp. 186-248, 1976,JINR, Dubna]. OPE – one pion exchange, OBE – one baryon exchange 4

5. Part I : Simulation of the np→npπ+π- reaction 1. Input : OPE+OBE model. (5M np→npπ+π- events) A.P. Jerusalimov 2. HGEANT + Hydra-8.21 3. PAT (W.Przygodahttp://hades-wiki.gsi.de/cgi-bin/viewauth/Homepages/PAT) http://relnp.jinr.ru/ishepp/presentations/Jerusalimov.pdf http://arxiv.org/abs/1102.1574 OPE+OBE The neutron momentum inside the deuteron is taken into account. 5

6. Predictions of OPE+OBE model if full phase spaceand contribution of OPE and OBE mechanisms to OPE+OBE. π- π+ In HADES acceptance In HADES acceptance 6

7. Part II :Experimental data analysis 1. Exp. dp@1.25GeV/u (MAY07) 2. DST gen2 with Hydra-8.21 3. PAT (selection the reaction channels) (W.Przygoda http://hades-wiki.gsi.de/cgi-bin/viewauth/Homepages/PAT)‏ 4. PostPAT analysis. Selection of np interactions from dp : LVL1 trigger (MULT >2) && FW Proton-spectator in the FW, 1.6GeV/c<Psp<2.6GeV/c ‏ 7

8. Part II :Event identification In order to perform particle identification following cuts are applied in the analysis: 1. PID cuts for single particle : p, π-, π+ beta vs momenta dE/dx in MDC(inner & outer) 2. Cut on momentum of Proton-spectator 1.6GeV/c<Psp<2.6GeV/c Analysis is performed using the PAT framework. Beta is reconstructed using particle hypotheses. (W.Przygoda http://hades-wiki.gsi.de/cgi-bin/viewauth/Homepages/PAT)‏ Post PAT analysis cuts. 8

9. Part II :Raw distributions Θlab(π+) Θlab(π+) M2miss Exp.data Simulation Θlab(π-) Θlab(π-) Minv(π+π-) Simulation TOF/TOFINO overlap 9

10. Part III :Efficiency and Acceptance corrections 1.Vertex reconstruction.(real data is used) 2. Pluto :White noise generation 3.HGEANT+Hydra-8.21 4. Analysis Sim. DST 5. Single track : Acceptance and Efficiency matrices. References: http://hades-wiki.gsi.de/cgi-bin/view/SimAna/Apr06TrackEmedding?rev=1.13 http://www.e12.physik.tu-muenchen.de/~lfabbi/analysis/effNov02/effNov02.html 10

11. Part III :Efficiency and Acceptance corrections Hydra-8.21: Input Pluto : Uniform single tracks (p,cos(Θlab),φ) (~350 MEvent for pions, ~700 MEvent for proton and deuteron ) Accepted: Hits inMDC1-4, TOF, TOFINO, SHOWER Reconstruction: RK (single track), RK+PID Correction matrices: Acceptance = Accepted/Input Efficiency = RK /Accepted Efficiency_with_PID = (RK+PID)/Accepted Binning : φ - 2o , (range : -180 o – 180 o) Θ – 1o, (range : 0 o – 90 o) p - 50 MeV(0 – 2 GeV for pions, 0 – 3 GeV for proton) 11

12. Part III: Acceptance and Efficiency matrices of π- (Slice - 50 MeV) Acceptance RK Efficiency (RK+PID) Efficiency 12

13. Part III: Acceptance and Efficiency matrices of π+ (Slice - 50 MeV) Acceptance RK Efficiency (RK+PID) Efficiency 13

14. Part III: Acceptance and Efficiency matrices of proton (Slice - 50 MeV) Acceptance RK Efficiency (RK+PID) Efficiency 14

15. Normalization: Scalling = 4 (LVL1) ; Part IV: Comparison of experimental data and OPER simulation pp pp http://hades-wiki.gsi.de/pub/SimAna/NormalizationForPpAndDp/pp_elastic260109.pdf 15

16. Part IV: Comparison of experimental and simulation data Preliminary Preliminary Preliminary Preliminary Efficiency corrected distributions : Eff = Eff. π+ * Eff. π- * Eff. p 16

17. Part IV: Comparison of experimental and simulation data m2n OpenAngle(π+π-) OpenAngle(pπ+) π+ p π- Preliminary Preliminary The same analysis procedure is used for sim. and exp.data 17

18. Summary • Single track Efficiency and Acceptence matrices for d, p, π+, π- are obtained. • The preliminary results for the np→npπ+π- reactions at 1.25 GeV corrected by the efficiency are obtained. • OPER model prediction for the np→npπ+π- reaction shows the reasonable agreement with experimental data.

19. Acknowlengements We would like to thank W.Przygoda,A.Rustamov, V.Pechenov, O.Pechenova, K.Lapidus, T.Galatyuk, G.Agakishiev and other people who helped us in our analysis!!! and thank you all for your attention!!!

20. Model : OPE + OBE (A.P.Ierusalimov)‏ diagrams OPE diagrams OBE 20

21. Experimental distributions for np→npπ+π- at p 1.73 GeV/c

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24. TOF and TOFINO detectors TOFINO 24 TOF

25. HADES setup 1 25

26. Exp. Data 26

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