1. Neutron Identification with ECAL  Sergey Kiselev, ITEP Moscow, for the ECAL group  Motivation  Input info  Signal parameters  Preshower – 1 GeV/c  Preshower – 4 GeV/c  Preshower – 8 GeV/c  ECAL – 1 GeV/c  ECAL – 4 GeV/c  ECAL – 8 GeV/c  Conclusion and next steps 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 1

2. Motivation  ~2400 particles enter to ECAL, ~1100 charged, ~1300 neutrals. ~25% of neutrals are neutrons. 70% of neutrals have p<1 GeV/c. Prim.Second.sum (,p<1 GeV/c) 401(220)628(600)1029(820) n(n,p<1 GeV/c)107(3)194(140)301(143)  Σ -  n π -, Σ +  n π +, Θ +  K + n 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 2

3. Input info  CbmRoot package (April 2005), Geant3  Realistic ECAL geometry (class CbmEcalV1). - Preshower: 1.5X0 Pb + 1cm scin. - ECAL: 25X0 Pb (140 0.1 cm layers) + scin. (140 0.1cm layers). - Transverse granularity: ~10 5 3x3 cm 2 cells. - Summing procedure of Eloss in a cell for a track. MCPoint parameters (x,…,px,…,time,…) correspond to the first entrance into the cell.  “Test” tracks n,  at θ =6 0, φ=45 0 with p=1, 4, 8 GeV/c were used as input 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 3

4. Signal parameters  Aim: to find signal parameters discriminate n/ at any momentum.  Signal -> 3x3 cluster: the cell with maximal E scin + 8 nearest cells.  Parameters of the 3x3 cluster: - number of “fired” cells, N - energy of these cells, E - cluster form: (central cell energy)/E - cluster time: (central cell time, t) – (light time to front of this cell, t 0 ) 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 4

5. Preshower - 1 GeV/c 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 5

6. Preshower - 4 GeV/c 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 6

7. Preshower - 8 GeV/c 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 7

8. ECAL - 1 GeV/c 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 8

9. ECAL - 4 GeV/c 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 9

10. ECAL - 8 GeV/c 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 10

11. Conclusion and next steps  Preshower/ECAL time is probably most effective variable to discriminate n/ .  Play with preshower: 2.0X0, 2.5X0 of Pb  UrQMD events: 1 central Au+Au event at 25 AGeV takes - ~ 6 min. of CPU (2 Mhz) - ~ 4 Mb output file _ 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 11

12. Preshower - p dependance pw%w% N cells in clust. E scin,MeV in clust. E max % E scin t-t 0, ns n1181.3±0.6 5±694±13 20±7 n4231.5±0.9 11±1590±173.6±2.5 n8322.0±1.5 18±2886±201.3±1.2  1711.4±0.8 9±694±120.1±0.1  4731.6±0.9 14±1194±100.1±0.2  8781.7±0.9 15±1394±100.2±0.2 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 12

13. ECAL - p dependance pw%w% N cells in clust. E scin,MeV in clust. E max % E scin t-t 0, ns n1 623.1±1.6 17±1376±20 18±3 n4 636.2±1.8113±4957±181.8±0.6 n8 667.8±1.6197±9646±150.9±0.4  11006.2±1.2 79±856±100.1±0.1  41008.2±0.8324±1550±80.1±0.1  81008.8±0.4654±2246±70.1±0.1 03.06.2005 CBM Simulation Meeting S.Kiselev ITEP 13