1. OPERA Physics Coordination, CERN, 03/05/2006 Effect of  and  radiation on the on-line emulsion scanning M. Cozzi for the Bologna group

2. OPERA Physics Coordination, CERN, 03/05/2006 First test: Electron exposure @ LNF 500 MeV 3 stacks of 6 consecutive emulsions »Bologna – Salerno and Napoli Density: – 45 e/mm 2  ~ 50 mrad – 30 e/mm 2  ~ 300 mrad Area of the spot ~ 27 cm 2 –defocused using 4 cm glass plate in front of the emulsion stacks  larger spot but electron energy degraded…

3. OPERA Physics Coordination, CERN, 03/05/2006 The  and  exposure in the Bologna stack #1 #2 #3 #4 #5 #6     1 234576     V 3 5 4 1 6 7 2 Zone 1: (100  + 250  )/view Zone 2: (200  + 500  )/view Zone 3: 100  /view Zone 4: 200  /view Zone 5: 400  /view Zone 6: 250  /view Zone 7: 500  /view 1 View EES = 310 x 390  m 2

4. OPERA Physics Coordination, CERN, 03/05/2006 Micro-track density pl4 TOP BOTTOM Huge FOG density not related to the alpha and beta exposure  not uniform background density, changing from one plate to another.

5. OPERA Physics Coordination, CERN, 03/05/2006 Base-track density Quality cut:  2 <2.5

6. OPERA Physics Coordination, CERN, 03/05/2006  500 mrad && out of beam && quality cut

7. OPERA Physics Coordination, CERN, 03/05/2006 Efficiency computation Only 5 plates have been used. Track selection: pl1+pl2 && pl5+pl6 Then we search in plate 4 a match within 25 mrad and 10  m. Efficiency on plate 4 was defined as and was evaluated in each zone.

8. OPERA Physics Coordination, CERN, 03/05/2006 Reference zone Zone 1: (100 a + 250 b)/view Zone 2: (200 a + 500 b)/view Zone 3: 100 a/view Zone 4: 200 a/view Zone 5: 400 a/view Zone 6: 250 b/view Zone 7: 500 b/view

9. OPERA Physics Coordination, CERN, 03/05/2006 zone ID exposures densities (particles/view) Quality Cut B.T./mm 2 (out of beam) Volume Tracks (on beam) Eff. ±1 % stat err 1    17.7124473 2    23.4134775 3  19.6112573 4  16.5130877 5  16.1133372 6  20.0136772 7  20.2145071 Ref0 17.5182175 RESULTS:

10. OPERA Physics Coordination, CERN, 03/05/2006 Conclusions Not uniform fog density, difficult to compute the background related to alpha and beta tracks. Efficiencies are lower than expected, however not dependent on alpha and beta doses.

11. OPERA Physics Coordination, CERN, 03/05/2006 Further investigation on the efficiency with a simulation ORFEO simulation of the LNF exposure The low momentum electron tracks can be reconstructed with the same efficiency I applied in the simulation

12. OPERA Physics Coordination, CERN, 03/05/2006 Second test: Pion exposure @ KEK 1GeV 18 consecutive emulsions (Bologna, Salerno and Naples) Three beam angles (  x,  y ): –(0.15, 0.0) –(0.3, 0.0) –(-0.3, 0.0) density of ~2÷2.5 x 10 3 /cm 2 in the whole emulsion surface

13. OPERA Physics Coordination, CERN, 03/05/2006 Data analysis Zone1 Zone2 Zone3 Zone4 General scan on each plate ACQ: 25000  100000 x 15000  35000 y On line cut on the micro-track pulse height of 7/17 “active” layers plzone1zon2zone3zone4 E1517min  and  23.8  /(100  m) 2 17min  E1617min  17min 

14. OPERA Physics Coordination, CERN, 03/05/2006 Micro-track density Each bin is 1mm 2 3 time larger2 time larger

15. OPERA Physics Coordination, CERN, 03/05/2006 Micro-track angular distributions

16. OPERA Physics Coordination, CERN, 03/05/2006 Micro-track density NOT exposed

17. OPERA Physics Coordination, CERN, 03/05/2006 Base-tracks Quality Cut:

18. OPERA Physics Coordination, CERN, 03/05/2006 Base-track density |θ|<400 mrad && Quality Cut 2 time larger1.5 time larger

19. OPERA Physics Coordination, CERN, 03/05/2006 Base-track density (Out of Beam directions) Quality Cut applyed  < 500 mrad Not pion angular directions

20. OPERA Physics Coordination, CERN, 03/05/2006 The18 OPERA films in vacuum pack were not perfectly flat during the exposure

21. OPERA Physics Coordination, CERN, 03/05/2006 Considering only a more central region: s.eY<25000 the angular peaks have a gaussian distribution.

22. OPERA Physics Coordination, CERN, 03/05/2006 Volume-tracks We cut an area of 2 cm 2 around the exposed zone and one at the center (the reference zone). In each zone the alignment is quite good and volume tracks have been connected through the 6 plates.

23. OPERA Physics Coordination, CERN, 03/05/2006 Efficiency computation N5+N4N4 1-N4/(N4+N5) Ref Zone 1501859480(74 ± 1) % -300569176(70 ± 2) % 300532135(75 ± 2) % Zone4  1501622447(72 ± 1) % -300449139(70 ± 2) % 300429113(74 ± 2) % Zone3  1501571413(74 ± 2) % -300525182(65 ± 2) % 300417130(69 ± 2) %

24. OPERA Physics Coordination, CERN, 03/05/2006 Conclusions The micro-tracks density increases in the  and  exposed zones up to a factor 3. The base-track density increase up a factor 2 after the quality cut is applied. Manual check have to be done to investigate the source of background. Volume-tracks density is lower than expected (it needs angle corrections?) Base-track efficiencies evaluated in different zones are comparable within 5%.