Application of the Beta-ray alignment for the OPERA CSDs Seigo Miyamoto

Beta-ray alignment New alignment method by using beta- ray from environmental radioactive isotopes. Coincidence at contacted emulsion layers. Effective to correct the distortion( is essential for good position resolusion) of film by development or drying.

Detection of position displacement peak of beta-ray -Take all combination of dx in ~+-100um - Angle allowance is FREE. 2.1um 1.8um

If the tightness of packing is enough, Position displacement of high energy tracks from beta-ray alignment peak (um)

Application for the OPERA CSD Alignment accuracy is less than 1um. Effective to reject BG tracks very much. Samples : Cosmic run events CSDs Neutrino events CSDs

At first, division of area (5mm x 5mm)

Procedure Taking all combinations of MicroTracks in contacted layers, And Detection of beta-ray alignment peaks in each unit areas. Position displacement distribution from the X-ray alignment

40 um 20um in delta position space Plot vector as the center of peak in each unit area on the film map -> Relative Distortion map.

Some Samples

Estimation of successful area Continuity check is suitable which beta-ray alignment is success or not because distortion should be continual. -Check the difference of vector between adjacent area. -For example, d(dX)(a,b)=dX b -dX a - if d(dX) =2 adjacent areas, “a” is defined as continual(successful). b a c d e

beta-ray alignment summary

Continual area ratio of CSDs sucessful

The reason of below 90% Not enough beta-rays to align Peak is detected, but double Large Gap exists

Examples, Double Peak

Examples, Large Gap is Detected.

Summary Beta-ray alignment was applied to real OPERA Experiment. The number of beta-ray for alignment is enough. We estimated mechanical tightness. 26/32 CSDs is aligned successfully. 5/32 CSDs have Double Peaks, these are recoverable by detection both (We have 2 alignments, BG Doublet tracks become twice). 1/32 CSD has large (more than 100um) gap, we can detect it. We continue the study of these 6 events.