University of Chicago Reconstruction in Water Cherenkov: Using Timing Matt Wetstein Enrico Fermi Institute, University of Chicago Argonne National Laboratory on behalf of the LAPPD, LBNE collaborations, and the Fast-Timing Reconstruction Group: Z. Djurcic (ANL), G. Davies (Iowa State), H. Frisch (U Chicago) M. Sanchez (Iowa/ANL), M. Wetstein (U Chicago/ANL), T. Xin (Iowa State) Advances in Neutrino Technology - ANT 11 October 12, 2011 Wednesday, October 12, 2011
University of Chicago Reconstruction in Water Cherenkov: Using Correlated Timing and Spatial Information Matt Wetstein Enrico Fermi Institute, University of Chicago Argonne National Laboratory on behalf of the LAPPD, LBNE collaborations, and the Fast-Timing Reconstruction Group: Z. Djurcic (ANL), G. Davies (Iowa State), H. Frisch (U Chicago) M. Sanchez (Iowa/ANL), M. Wetstein (U Chicago/ANL), T. Xin (Iowa State) Advances in Neutrino Technology - ANT 11 October 12, 2011 Wednesday, October 12, 2011
Pi0s and e fg ects on long-baseline physics γ two forward gammas with angular separations typically π 0 π 0 smaller than 15º get mis-identified as a boost single electron shower γ γ π 0 π 0 after boost, the second low E gamma boost is too small to reconstruct Largest reducible background. In WC, in order to achieve a pure electron sample (~1% π 0 ), one needs harsh quality cuts that bring signal e ffj ciency down to 16% (28%) at 1 GeV (0.8 MeV). This loss of events explains the factor of 3-5 larger fiducial mass necessary to match the performance of an LAr There is still a room for significant improvement in the physics capabilities for a given mass of water. ANT 2011 3 Wednesday, October 12, 2011
Thinking about Full Track Reconstruction: WC as a Time Projection Chamber? 1. Signal per unit length ~20 photons/mm 2. Drift time ~225,000mm/microsecond 3. Topology drift distances depend on track parameters ANT 2011 4 Wednesday, October 12, 2011
Thinking about Full Track Reconstruction: WC as a Time Projection Chamber? 1. Signal per unit length Acceptance and coverage are important, especially at Low E. Is ~20 photons/mm there any way we can boost this number? Scintillation? 2. Drift time ~225,000mm/microsecond This necessitates fast photodetection. It also requires spatial resolution commensurate 3. Topology with the time resolution . drift distances depend This presents some on track parameters reconstruction challenges... ANT 2011 5 Wednesday, October 12, 2011
New Developments in Water-Based Detectors: Large Area, High Resolution MCP-PMTs LAPPD (Large-Area Picosecond Photodetector) Project: Make large-area MCPs with low-cost, bulk materials and batch industrial techniques &"#$%# • We’re attacking all aspects of this problem from the photocathode !"#$%# to the MCPs to vacuum sealing technology • Goal is not just proof of principle...It’s the KJ&.<& development of a commercializable product. IJ&.<& ANT 2011 6 Wednesday, October 12, 2011
New Developments in Water-Based Detectors: New Developments in Water-Based Detectors Large Area, High Resolution MCP-PMTs Data, 1.5 kV 1400000 Data 1.36 kV Simulation, 1.5 kV Simulation, 1.44 kV Simulation, 1.36 kV 1231250 1062500 893750 Transit Time Spread for MCP 100000 Transit Time Spread, MCP 72/78 at 2.6kV with 1kV across anode gap 72/78 at 2.6 k average gain 2500 10000 725000 0 100 200 300 400 1000 ALD-MCP 122 ALD-MCP 125-133 2000 Commercial MCP 100 10 1500 1 600 750 900 1050 1200 field-strength (Volts/mm) 300 V across the PC gap 1000 100 V across the PC gap 0.15 60 V across the PC gap 20 V across the PC gap voltage (Volts) 0.1 500 0.05 0 0 4 5 6 7 8 9 10 11 12 13 Arrival Time (seconds) � 9 � 0.05 arrival time (nanoseconds) x 10 6 6.5 7 7.5 8 8.5 time (seconds) � 9 x 10 Wetstein (U Chicago/ANL-HEP), B. Adams, M. Chollet(ANL-APS) ANT 2011 7 Wednesday, October 12, 2011
From SciBoone to....DanielBoone? ν D ANIEL B OONE First step: to demonstrate a working, small-scale neutrino detector Next Generation Water Cherenkov Experiment Concept and event rate calculation, courtesy of David Schmitz, FNAL courtesy of Zelimir Djurcic • expected rate of ~90k CC events and ~35k NC events per 1E20 POT, 10.6 ton fiducial volume • naively scale the event rate to oxygen using a factor 8/6, then you'd expect ~12.4k CC interactions/ton/1E20 and ~4.7k NC interactions/ ton/1E20 • Booster Neutrino Beam rate is ~0.5E19 POT per week on average • ~32.2k CC interactions/ton/year, ~11k NC interactions/ton/year in a water detector BEFORE accounting for the efficiencies of such a detector. ANT 2011 8 Wednesday, October 12, 2011
Beyond DanielBoone...How do you scale this technology up? Building a large Water detector, based on LAPPDs is not simply a ~1m 3 ! matter of building a Super K type detector with MCPs • Di fg erent optimization of volume to length scale • Di fg erent balance of cost per surface area • Di fg erent physics capabilities for the same fiducial mass Cost isn’t just number of PMTs ~20 ton ! excavation costs, magnetic shielding (not necessary for MCPs), more or better use fiducial volume, competition in the PMT market Lower costs are important, but physics reach should be the focus In particular, lower costs and more e ffj cient use of target mass means ~100 ktons ! leaves room for departure from conventional WC design in ways that could enhance analysis • possibility of segmentation? Less losses, scattering, dispersion... • applied magnetic fields? Disclaimer: This is not targeted at LBNE stage I: possible upgrade path or second detector....Or something beyond... ANT 2011 9 Wednesday, October 12, 2011
HiRes Water Group Z. Djurcic (ANL), G. Davies (Iowa State), H. Frisch (U Chicago) M. Sanchez (Iowa/ANL), M. Wetstein (U Chicago/ANL), trackresidualdist trackresidualdist T. Xin (Iowa State) Entries Entries 29230 29230 Mean Mean 3.184 3.184 200 RMS RMS 3.601 3.601 � � 2 2 / ndf / ndf 597.4 / 417 597.4 / 417 Rising edge 180 These new capabilities and new possible driven by Constant Constant 1096 1096 ! ! 9.7 9.7 • 160 chromatic 1.278 1.278 0.009 0.009 MPV MPV ! ! optimizations necessitate a strong simulation and dispersion Sigma Sigma 0.6612 0.6612 ! ! 0.0048 0.0048 140 reconstruction program. 120 100 Collaboration among the hi-res WCh working • 80 Tail driven by scattered light group has produced a new platform for testing 60 algorithms on WCh detectors with interactively 40 modifiable photodetector properties. 20 0 -10 -5 0 5 10 15 20 25 These e fg orts have already identified promising • features in observables, such as timing residuals, that could potentially be used to improve track reconstruction and better identify pi0 0.0025 backgrounds. 0.002 GEANT-based studies are ongoing...there is much • 0.0015 work ahead. Plans for new post-docs and students to be starting soon. 0.001 0.0005 These e fg orts are well integrated into the WC • algorithms development e fg orts for LBNE. Many 0 of the tools will be useful for the nominal LBNE -5 0 5 10 timing residual (ns) design. ANT 2011 10 Wednesday, October 12, 2011
Isochrons Can we use slices in constant time to fully reconstruct tracks? pi0 electron ANT 2011 11 Wednesday, October 12, 2011
Track Reconstruction Using an “Isochron Transform” The isochron method is a Hough Transform in 4- space, that builds tracks from a pattern of hits in time and space. d s 2 α θ c Δ t ≈ s 1 /c + s 2 n/c s 1 Connect each hit to the vertex, through a two segment path, one segment representing the path of the charged particle, the other path representing the emitted light. There are two unknowns: s 1 and α but there are two constraints: s 1 + s 1 = d and Δ tmeasured = s 1 /c + s 2 n/c ANT 2011 12 Wednesday, October 12, 2011
Track Reconstruction Using an “Isochron Transform” Trajectories of Constant Transit Time 1000 900 800 700 600 500 400 300 200 100 0 0 200 400 600 800 1000 And of course, there are a degenerate number of track directions, from which a photon emitted at the Cherenkov angle can hit ANT 2011 13 Wednesday, October 12, 2011
Track Reconstruction Using an “Isochron Transform” However multiple hits from the same point of emission, will maximally intersect along the point of emission...This is similar to the Hough transform. ANT 2011 14 Wednesday, October 12, 2011
Track Reconstruction Using an “Isochron Transform” Results of a toy Monte Carlo with perfect resolution Color scale shows the likelihood that light on the Cherenkov ring came from a particular point in space. Concentration of red and yellow pixels cluster around likely tracks sohp sohp 2400 1800 2200 600 1600 400 2000 1400 1800 400 200 1600 1200 1400 200 1000 1200 0 8000 1000 0 8000 6000 -200 -200 6000 4000 4000 -400 2000 -400 2000 0 0 0 200 400 600 800 1000 0 200 400 600 800 1000 Two tracks displaced from a Single track common vertex ANT 2011 15 Wednesday, October 12, 2011
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