1. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 Dr. Quasi-Elastic (or... How I learned to stop worrying and love the Hough transform) Mark Dorman ● Update on Hough transform methodology ● Searching for QE events at low energies

2. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 Brief Review Of Methodology ● The Hough transform provides a way of quantifying the 'trackiness' or 'showeriness' of an event. ● Have used (z,tpos) from the SR ntpStrip objects as the 2D input space for the transform. ● Am using RMS75 variables to characterise the localisation of a peak in Hough space; localised peak = CC, 'ridge' structure = NC.

3. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 RMS75 Variables For CC/NC Separation In A Low Energy Sample ● Am using MDC FD files; ~135k events. After a standard FD fiducial cut and removing events with (reco_emu+reco_eshw)<3GeV this leaves ~11k. ● If this were taken to be the CC sample then it would have a purity of ~66%. ● Can improve purity with RMS75 variables: ● A cut at <15 for CC gives efficiency=~80%, purity=~80%.

4. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 QE Selection – Event Substructure ● Want to use the Hough transform to identify some structure in a CC event beyond the muon track.

5. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 Methodology ● Want to remove the hits that correspond to the peak in Hough space for the original transform:

6. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 Performing a Second Hough Transform ● Also add a z-position cut to the event of 1.5m from the event vertex to remove any hits that would not belong to the short track. This leaves;

7. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 Performing a Second Hough Transform ● Also add a z-position cut to the event of 1.5m from the event vertex to remove any hits that would not belong to the short track. This leaves; ● Then perform second transform over a wider range of gradients to try to identify the remaning short track; ● The second transform identifies the track. Although this was an easy case...

8. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 QE Selection ● I take the RMS75 variables and Hough peak height from the second transform into PAN. Idea is to use knowledge about the event substructure to identify QE, resonance and DIS events – i.e. find protons, pions etc. ● The RMS75 variables descibe the 'trackiness' of the remaining hits in the event and the Hough peak height represents the length of the track found. ● For the following plots I have taken the cut on my original Hough transform RMS75 variables at <10 for inclusion into the CC sample giving: ● Of this CC sample the QE purity before any further cuts is ~35%. ● CC sample efficiency = ~73% ● CC sample purity = ~86%

9. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 RMS75 for Event Process Separation ● The following plot shows the RMS75 values from the second transform (i.e. relating to the short tracks) by process;

10. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 RMS75 for Event Process Separation ● The following plot shows the RMS75 values from the second transform (i.e. relating to the short tracks) by process; No clear separation powers

11. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 RMS75 for Event Process Separation ● The following plot shows the efficiency and purity of a QE sample if i make a cut on the RMS75 variable from the previous slide; ● It is hard to get above ~35% efficiency without taking a huge fall in efficiency.

12. Mark Dorman UCL/RAL MINOS ANL Meeting March 05 RMS75 for Event Process Separation ● The following plot shows the efficiency and purity of a QE sample if i make a cut on the RMS75 variable from the previous slide; ● It is hard to get above ~35% efficiency without taking a huge fall in efficiency. ● Maybe the Hough peak height can help with separation...