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

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

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. V.V.Sarantsev et. All Eur. Phys.J. A 43, (2010) J.Bystricky et. all, J. Physique 48 (1987) ? 1.97 np→pp π - pp→pp π o HADES

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

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 PAT ( W.Przygoda ) The neutron momentum inside the deuteron is taken into account. OPE+OBE

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

7 Part II : Experimental data analysis 1. Exp. 2. DST gen2 with Hydra PAT (selection the reaction channels) (W.Przygoda )‏ 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 ‏

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 )‏ Post PAT analysis cuts.

9 Part II : Raw distributions Θ lab (π + ) Θ lab (π - ) M inv (π + π - ) M 2 mis s TOF/TOFINO overlap Exp.dataSimulation Θ lab (π + ) Θ lab (π - )

10 Part III : Efficiency and Acceptance corrections 1. Vertex reconstruction. (real data is used) 2. Pluto : White noise generation 3. HGEANT+Hydra Analysis Sim. DST 5. Single track : Acceptance and Efficiency matrices. References:

11 Part III : Efficiency and Acceptance corrections Hydra-8.21: Input Pluto : Uniform single tracks (p,cos(Θ lab ),φ) (~350 MEvent for pions, ~700 MEvent for proton and deuteron ) Accepted: Hits in MDC1-4, 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 - 2 o, (range : -180 o – 180 o ) Θ – 1 o, (range : 0 o – 90 o ) p - 50 MeV(0 – 2 GeV for pions, 0 – 3 GeV for proton)

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

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

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

15 Normalization: Scalling = 4 (LVL1) ; pp NormalizationForPpAndDp/pp_elastic pdf Part IV: Comparison of experimental data and OPER simulation

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

17 Part IV: Comparison of experimental and simulation data The same analysis procedure is used for sim. and exp.data Preliminary m2nm2n OpenAngle(π + π - ) π-π- π+π+ p Preliminary OpenAngle(pπ + )

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

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

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TOF and TOFINO detectors TOFINO TOF 24

HADES setup 1 25

Exp. Data 26

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