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, GSIHADES 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→ppπ-

pp→ppπoHADES

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. 186-248, 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-8.213. PAT (W.Przygoda http://hades-wiki.gsi.de/cgi-bin/viewauth/Homepages/PAT )

The neutron momentum inside the deuteron is taken into account.

http://relnp.jinr.ru/ishepp/presentations/Jerusalimov.pdfhttp://arxiv.org/abs/1102.1574

OPE+OBE

6

Predictions of OPE+OBE model if full phase space

and contribution of OPE and OBE mechanisms to OPE+OBE.

π- π+

In HADES acceptance In HADES acceptance

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

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.

9

Part II : Raw distributions

Θlab(π+)

Θlab(π-)Minv(π+π-)

M2miss

TOF/TOFINO overlap

Exp.data Simulation

Simulation

Θlab(π+)

Θlab(π-)

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.5. Single track : Acceptance and Efficiency matrices.

References: http://hades-wiki.gsi.de/cgi-bin/view/SimAna/Apr06TrackEmedding?rev=1.13http://www.e12.physik.tu-muenchen.de/~lfabbi/analysis/effNov02/effNov02.html

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 in MDC1-4, TOF, TOFINO, SHOWER

Reconstruction: RK (single track), RK+PIDCorrection matrices: Acceptance = Accepted/InputEfficiency = RK /AcceptedEfficiency_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)

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) ;

eventsmbN pp

pp 910)25.085.3(

0

0**

NdM

dNScalling

dM

d

inv

pp

pp

http://hades-wiki.gsi.de/pub/SimAna/ NormalizationForPpAndDp/pp_elastic260109.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

Preliminary

Preliminary

Preliminary

17

Part IV: Comparison of experimental and simulation data

The same analysis procedure is used for sim. and exp.data

Preliminary

m2n

OpenAngle(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

22

23

TOF and TOFINO detectors

TOFINOTOF 24

HADES setup

1

25

Exp. Data

26

27