Partially Contained Atmospheric Neutrino Analysis

1. Partially Contained Atmospheric Neutrino Analysis Andy Blake + John Chapman Cambridge University January 2004

2. Two Categories of PC Event μ ν μ ν UPWARD-GOING MUONS DOWNWARD-GOING MUONS “direction” problem “containment” problem main background:stopping muons with mis-reconstructed direction main background: through-going muons that appear contained shield helps this analysis

3. Selecting PC Events (1) CONTAIN DIGITS (2) CONTAIN TRACKS Cambridge Demultiplexer Cambridge Track Reconstruction Combine digits in adjacent views + select events with non-contained hits beside 1 detector edge Select tracks with > 8 planes + 1 contained vertex top vertex contained bottom vertex contained Select events with hits < 0.5m from 1 detector edge upward-going candidate downward-going candidate

4. Event Rates September 2003 r18900-19800 (~0.12 kT-yr) 1,000,000 MC events 200,000 MC events stopping muons

5. Upward-Going PC Events

6. Upward-Going Muons – Aim Track Direction Track Topology Likelihood Analysis

7. Upward-Going Muons – Timing (1) (1) Timing • Fit S-CT with time slope ± 1 • Calculate RMS for each fit • Consider RMSup - RMSdown CT U view V view 1/β= +1 1/β= -1 Percentage success rate … S

8. Upward-Going Muons - Timing (2) • Can also make use of absolute values of RMS … Timing appears worse for data Resolution ~ 60cm ~ 2ns

9. Upward-Going Muons - Timing (3) RMSup / RANGE • RMS from fitting wrong time slope 0 fit track S

10. Upward-Going Muons - Timing Cuts PC digits / tracks 1st pass timing cuts • RMSup – RMSdown < 0.0 m 2nd pass timing cuts • RMSup – RMSdown < -0.2 m • RMSup < 2.0 m • RMSdown > 1.0 m • RMSup / RANGE < 0.5 • -1.4 < 1/β < -0.6 BKG / SIG ~ 1.0

11. Upward-going Candidates (1) data events: (1) run 19135, snarl 72302 CRATE 15 !

12. Upward-Going Candidates (2) data events: (2) run 18902, snarl 36351 NEUTRINO CANDIDATE

13. Upward-Going Candidates (3) MC events: (1) run 231, snarl 44685 Eμ = 6 GeV ? ? ? ? ? Large Angle Scattering ? ? ? ? ?

14. Upward-Going Candidates (4) MC events: (1) run 242, snarl 65409 Large Scattering Again !!!

15. Upward-Going Muons – Showers (1) (2) Vtx Showers • Mop up remaining hits in event • Calculate distance from each • track vertex to centre of hits: • ΔVTX = VTXshw - VTXtrk • Consider Δ VTXup - ΔVTXdown ΔVTXdown Percentage success rate … ΔVTXup for cosmics, showers are distributed roughly evenly between track vertices, but slightly more vertex showers are found at BOTTOM of track

16. Upward-Going Muons – Showers (2) Vertex Shower Reconstruction • showers reconstructed in two passes • 1st pass – dense“primary” showers ( ≥ 4 planes, ≥ 10 strips) • 2nd pass – diffuse“secondary” showers • select the dense showers • eliminates many “fake” muon showers … • … but some still found on steep tracks with multiple strips per plane

17. Upward-Going Muons - Showers (3) Quality Cuts shower density: shower vertex position: ρ ~ Nstrips / W3 Δ VTX = VTXshw - VTXtrk ΔVTXup W

18. Upward-Going Muons - Shower Cuts • shower planes > 4 • Δ VTXup < 0.7 m • density > 5.0 strips plane-3 BKG / SIG ~ 40.0

19. Upward-Going Candidates example data events neutrino

20. Downward-Going PC Events

21. Downward-Going Muons track containment • 0.5m containment cut on • top track vertex removes • 99% through-going muons • most remaining events are • steep muons that sneak • between the planes • remove clean background • using trace/direction cuts

22. Downward-Going Muons – Direction Cuts Py/P Pz/P py/p < 0.9 pz/p > 0.2

23. Downward-Going Muons –Trace Cuts extrapolate track to detector edge + calculate Z component TRACE Z Trace Z > 6 plns

24. Next Background Layer • Remaining background dominated by very steep muons: • muons travelling significant distances down a single plane • muons turning back on themselves

25. Downward-Going Muons –Very Steep Muons • Distances of digits from track vertex • Combine digits in adjacent • views around track vertex • Calculate distance between • track vertex and furthest digits • Charge around track vertex • Plane with maximum charge • close to track vertex ΔR < 1.1 m Q < 500 PE

26. Downward-Going Muons –Timing Quality Steep muon events have poor timing 0.5 < | 1/β | < 1.5

27. Downward-Going Muons -Containment Cuts • Py/P < 0.9 • Pz/P > 0.2 • Trace Z > 6 plns • Qmax < 500 PEs • ΔR < 1.1 m • 0.5 < 1/β < 1.5 • RMSdown < 2.0 m BKG / SIG ~ 10.0

28. Downward-Going Candidates • 6 MONTE CARLO EVENTS • 3 demux errors • 1 tracking error • 1 missing detector • 1 only just contained • 8 DATA EVENTS • 1 demux error • 2 tracking errors • 3 missing detector • 2 coil hole • … 0 neutrinos

29. Demultiplexing Errors these hits should be higher

30. Tracking Errors

31. Missing Detector swallowed by LI ?

32. Conclusion • Analysis is progressing … … but still need to peel away some more layers of background • Need detailed MC/data comparison e.g. high muon scattering MC timing resolution tracks/showers • Need another round of tagging/fixing reconstruction errors • … but it’s good that neutrinos can be extracted from the data!