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

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 521Lyon 605Bern 681Bologna 973Napoli 1025Bari 1166Salerno 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

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

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

ID DPX DPY DSX DSY GTOT SLOPE scanned area in CS1-2:  4 x 4 cm 2 CS track coincidences (set 1) OPERA Emulsion Workshop – Nagoya, 7-9 Dec  pos  40 micron  slope  Total # of grains (CS1+CS2)  40 Brick predictions

OPERA Emulsion Workshop – Nagoya, 7-9 Dec 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 mm 2 window around the extrapolated position ID NCAND  pos  1000  m  slope  0.03  pos  500  m  slope  0.03  pos  250  m  slope  0.02 *  slope  (1 * ) confirmed by manual check Base-track selection cut: sigma  0.13*N – 1.7 (1.3)

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

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

OPERA Emulsion Workshop – Nagoya, 7-9 Dec 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 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 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 3 calibration zones of ~ 0.5 mm 2

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

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

OPERA Emulsion Workshop – Nagoya, 7-9 Dec 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)