OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

1. From CS to Brick: first results from low density cosmic ray exposure at LNGS M. De Serio from Bari emulsion lab OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

2. 9 OPERA-like bricks (BAM bricks) with CS doublets were exposed to cosmic rays for a few minutes at LNGS ( ~100 tracks per brick) to study CS – brick connection in realistic conditions 8 bricks (without CS’s) were exposed to cosmic rays for additional 24 hours to collect tracks for film to film alignment Brick IDLab 521 Lyon 605 Bern 681 Bologna 973 Napoli 1025 Bari 1166 Salerno CS doublets were measured at LNGS scanning station predictions corresponding to selected CS track coincidences were provided to scanning labs OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

3. bottom layer top layer measured fog density (Chiara) : 9.0  0.2 grains / (10m)3 We observe an increase of fog density of a factor of ~ 2 ÷ 2.5 with respect to expectations ! Brick 1025 Clusters per image Clusters per image Micro-tracks per view Micro-tracks per view slope acceptance 0.4 OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

4. bottom layer top layer LNGS test exposure, June 2006 Tono refreshed emulsions exposed to cosmic rays (37 hours) slope acceptance 0.5 OPERA Scanning Meeting – LNGS, Oct. 9th, 2006

5. Brick 1025 scanned area in CS1-2:  4 x 4 cm2 CS track coincidences (set 1) 11 predictions pos  40 micron slope  0.025 Total # of grains (CS1+CS2)  40 OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

6. Prediction search: step 1 LNGS predictions were extrapolated to film 1 using angles and positions of measured base-tracks in CS2 and assuming a gap of 4800 micron Using the same set of X ray marks printed onto CS1-2 and film 1 and measured at LNGS, each track was searched for in film 1 in a 2 x 2 mm2 window around the extrapolated position ID NCAND Base-track selection cut: sigma  0.13*N – 1.7 (1.3) pos  1000m slope  0.03 pos  500m slope  0.03 pos  250m slope  0.02 confirmed by manual check 0 (1*) * slope  0.03 OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

7. Found tracks ID DPX DPY DSX DSY N MEAN RMS MEAN RMS OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

8. set 1 OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

9. Prediction search: step 2  Found tracks were used as predictions for DB-driven SB (X ray marks  optical marks)  Tracks were followed-back for 10 films SB results All tracks were confirmed OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

10. Film to film alignment (SB) 3 calibration zones: scanning area and distance from emulsion centre can be modified depending on cosmic ray track density and event position passing-through tracks are used to compute affine transformation parameters due to high background level, on-line tracking parameters and base-track selection cut were modified in order to keep the scanning time required for film inter-calibration below 30’ / film 3 calibration zones of ~ 0.5 mm2 WARNING 1: exposure to cosmic rays 24 hours only! 36 ÷ 48 hours required (as shown by Max’s work) WARNING 2: time required for inter-calibration to be reduced to the level of 5÷10’ / film OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

11. Tracks used for film to film inter-calibration x,y~ 6 ÷ 7 micron OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

12. Tracks used for film to film inter-calibration x,y~ 0.007 OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006

13. Conclusions A first attempt was made to locate CS predictions in OPERA bricks exposed to low density cosmic rays CS films were measured at LNGS scanning station Out of 11 predictions, 7(+1) tracks were successfully located in the brick; tracks were found in film 1 within 250micron, 0.02 (0.03) mrad w.r.t. to predictions; they were all confirmed by visual inspection and standard DB-driven procedure (10 films) OPERA Emulsion Workshop – Nagoya, 7-9 Dec. 2006