1. Mark Dorman Separation Of Charged Current And Neutral Current Events In The MINOS Far Detector Using The Hough Transform Mark Dorman 16/12/04

2. Mark Dorman The Problem ● Low energy (<3GeV) events are not always well reconstructed by the offline analysis software...

3. Mark Dorman The Problem (cont.) At low energies : ● Short muon tracks can look like part of an EM shower ● Hard to tell... Neutral Current Event Charged Current Event ● Must look in more detail at event topology...

4. Mark Dorman The Hough Transform ● A mathematical technique to detect lines in images. ● Here 'image' means a set of points in some 2D space that correspond to hits in the far detector. ● Formally the Hough transform can be represented: ● Where the delta is a Hough indicator...

5. Mark Dorman The Hough Transform ● A set of points (x,y) is mapped to a set of points (m,c). ● The Hough indicator is incremented by one if the contents of the bracket are zero... ● The highest Hough count corresponds to the most probable line (i.e. track) in real space.

6. Mark Dorman Using The Transform 1. A pair of coordinates (x,y) is chosen 2. A value of the gradient is chosen and the corresponding intercept is found 3. The corresponding bin in Hough space is incremented 4. Steps 2-3 are repeated for all gradients 5. Steps 1-4 are repeated for all coordinates ● To work with the transform Hough space must be binned with a set number of sample gradients...

7. Mark Dorman Real Space ● 6 hits on y=0.731x+1.428 (and 17 hits of random noise)

8. Mark Dorman Hough Space ● Hough space is binned 80x80 with 40 sample gradients

9. Mark Dorman Results ● The most probable line is then drawn:

10. Mark Dorman Results ● The most probable line is then drawn: The program finds: Gradient - 0.7375 (0.731) Intercept - 1.45 (1.428)

11. Mark Dorman Discriminating Power ● The HT provides a way of investigating the geometry of an event: ● A charged current event would be characterised by a well defined peak in Hough space. ● A neutral current event would have a 'ridge' corresponding to the set of lines in a jet with different gradients.

12. Mark Dorman Further Work ● Extend the program to search for multiple lines (peak localisation and rms values) ● Consider cuts to aid to the transform (possible weighting with energy) ● Integrate the code into the MINOS offline software using real MINOS variables as the input points (mock data challenge data)

13. Mark Dorman The End... Thanks for listening.