1. Neutrino Event Reconstruction Andy Blake Cambridge University September 2003

2. Introduction Reconstruction software development ongoing at Cambridge. New version of AtNuReco now in CVS. AtNuReco is a track/shower reconstruction package developed for use in atmos neutrino analysis. General principles: (1) track/shower reconstruction should provide first order event separation. (2) concurrent track/shower reconstruction. This talk reviews status of track/shower reconstruction and introduces work on energy reconstruction.

3. AtNuReco Algorithm Clusters Track SegmentsShower Segments TracksShowers 2D Showers2D Tracks 3D 3D Tracks3D Showers 3D CandTracksCandShowers Strips

4. Monte Carlo Studies 100,000 atmos neutrino events (~250 kT-yrs) 120,000 beam neutrino events (~200 kT-yrs) Study track/shower reconstruction + energy reconstruction. DetSim Cambridge Demultiplexer Cambridge Reconstruction Standard Reconstruction Analysis

5. Atmos Nu Track Efficiency/Purity

6. Beam Nu Track Efficiency/Purity efficiencypurity

7. Track Reconstruction Quality atmos nu eventsbeam nu events

8. Shower Finding in Transition … Separate into ‘dense’ (EM-like) and ‘diffuse’ (NC-like) showers. Reconstruct using ‘expanding’ clustering window. Not complete – only dense showers so far... atmos nu eventsbeam nu events shower multiplicity diffuse showers high multiplicity – not physical..?

9. Atmos Nu Shower Efficiency v e CC eventsNC events

10. Energy Reconstruction For ν μ CC events … neutrino energy = muon energy + vertex shower energy Consider muon kinematics in beam events … scattering of muon …energy transferred to muon … … so it’s important to measure the vertex shower as well as the muon.

11. Measuring Muon Energy muon angular resolution: skewed high energy tails (reco efficiency + fake tracks) ΔE=5% muon energy resolution:

12. Measuring Shower Energy shower angular resolution: ΔE=30% suppressed low energy tails (reco efficiency) shower energy resolution: but ΔP z not symmetric bad scale!

13. Measuring Total Energy (1) Try simple addition: all eventsevents with no vertex shower

14. Kinematic Constraints (1) We can constrain reconstruction of beam neutrino energy … ν μ Neutrinos arrive from Fermilab know about neutrino interactions measure shower energy + direction know resolution measure muon energy + direction know resolution powerful constraint for beam neutrinos … try to implement these constraints and improve energy resolution.

15. Kinematic Constraints (2) Maximize likelihood: X i = measured quantities kinematic quantities ( W = mass of hadronic system Y = momentum transfer to hadronic system Ω = rotation angle ) resolution functions (energy, angle) e.g. neutrino energy vs. hadronic mass e.g. probability vs. overall energy E ν = 3.7GeV E fit = 3.8GeV example event:

16. Measuring Total Energy (2) all eventsevents with no vertex shower Kinematic fit centres the distributions on zero … … but overall resolution still dominated by track/shower resolution.

17. Conclusion Reconstruction development ongoing at Cambridge. (i) tracks – lower efficiency but better purity. (ii) showers – in active development. Now looking at reconstruction of kinematic quantities too. (i) constrain ν direction for beam nu analysis. (ii) form p(L/E) for atmos nu analysis. Reconstruction has come a long way … … but still lots to do!