1. Preliminary results of  separation from data tracks 1.Outline 2.Comparison of cosmics in both bricks  and  tracks 4.Separation with NN 5.Conclusion, TBD OPERA Collab. Meeting GS May 2005 Thomas Waelchli LHEP Uni Bern

2. Data from 2 nd PSI-TB June 2004 Pion beam: 202MeV/c, (  contamination <1%) Muon beam: 120MeV/c, (e contamination <5%) 2 bricks (  30 cells,  : 50 cells) Goal: –Follow tracks until they stop –Develop simple method for identification based on ‘normal scanning’ (16 layers/emulsion) –Fill NN with MCS angles, scattering coord., (dE/dx) 2x5cm 2 (  ), 3x3cm 2 (  ) scanned, outside beam-spot Tracks reconstructed with FEDRA –Using 200MeV/c for Kalman filter –Standard instrumental precision 1. OUTLINE T. Waelchli, OPERA Collab. Meeting GS May 2005

3. FINDING COSMICS… CUTS: {((nseg>10 && n0 (N-3)) && t.eFlag>=0 && track starts in 1 st or 2 nd emulsion &&  (nseg-10) < 0.6} N: number of cells in brick  t.eP  t.eP > 0.7

4. 2. COSMICS IN BOTH BRICKS T. Waelchli, OPERA Collab. Meeting GS May 2005 seg i seg i+1 ii XiXi Pb beam ii Average MCS angle:  av =   i *cos(  i )/nseg) Average MCS coordinate:  X av =   X i *cos(  i )/nseg)  X av  X av same in  and  brick Instrumental precision ca. 3  m muon brick pion brick

5. 00 muon brick pion brick  av muon brick pion brick T. Waelchli, OPERA Collab. Meeting GS May 2005 2. COSMICS IN BOTH BRICKS  -brick is shorter  larger angle of incidence  0 possible  av ca. 2mrad smaller in  -brick  possible thru …. But  av   identical  No bias  av /  0 muon brick pion brick

6. 3.  AND  TRACKS  707  227 T. Waelchli, OPERA Collab. Meeting GS May 2005 CUTS: {nseg>=10 && n0 =0 && t.eP<0.3 && track starts in 1 st or 2 nd emulsion &&  (nseg-10) < 0.6} N: number of cells in brick  

7. T. Waelchli, OPERA Collab. Meeting GS May 2005 3.  AND  TRACKS  av muons pions  X av muons pions  av and  X av only average defined number of cells before the end of a track. -Good separation already ‘from eye’ -bla

8. T. Waelchli, OPERA Collab. Meeting GS May 2005 3.  AND  TRACKS s.eVolume av muons pions muons cosm.  pions cosm.  cosm. (  ) cosm. ....

9. NN with 2 (3) input neurons INPUT LAYER : 2 (3) neurons filled with  av,  X av and (eVol av ) H IDDEN LAYER with 2 (3) neurons OUTPUT LAYER with 1 neuron: “0” for muon “1” for pion typical NN output T. Waelchli, OPERA Collab. Meeting GS May 2005  X av INHIDOUT  or   av eVol av () Many different configurations tested: Varying number of cells Omitting cells at end of a track Best efficiency is 85% using 9 cells, omitting the last.

10. Conclusion and TBD Separation capability of data tracks up to 85% with less than 10 available segments TO BE DONE: Improve / fine-tune simulation (include dE/dx into NN) Check mixing/ambiguities of FEDRA reconstructed tracks as function of density with simulation T. Waelchli, OPERA Collab. Meeting GS May 2005