Low Z Detector Simulations

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Low Z Detector Simulations
Off-Axis Detector Workshop

• Stanley Wojcicki
• Stanford University
• January 24, 2003
• Stanford, Ca

( Work done in collaboration with Tingjun Yang )
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Outline

• Introductory Comments
• Parameters/Issues
• Few Typical Events
• Methodology and Initial Results
• Plans for the Future

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Experimental Challenge
(visible E)
5 times below CHOOZ limit
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NuMI Off-axis Detector

• Different detector possibilities are currently
  being studied
• The goal is an eventual gt20 kt fiducial volume
  detector
• The possibilities are
• Low Z target with RPCs, drift tubes or
  scintillator
• Liquid Argon (a large version of ICARUS)
• Water Cherenkov counter
• One can do relatively generic simulations for the
  first category of detectors

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Detector(s) Challenge

• Surface (or light overburden)
• High rate of cosmic ms
• Cosmic-induced neutrons
• But
• Duty cycle 0.5x10-5
• Known direction
• Observed energy gt 1 GeV

LoDen RD project

• Principal focus electron neutrinos
  identification
• Good sampling (in terms of radiation/Moliere
  length)
• Large mass
• maximize mass/radiation length
• cheap

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A possible low Z detector
The absorber medium can be cheap recycled
plastic pellets The active detector in this
version are RPC chambers
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Relative electron/muon (pion)
appearance
Clean track muon (pion)
Fuzzy track electron
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No of hits/plane for m and e
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Examples of Backgrounds

NC - p0 - irreducible (PH?)
NC - p0 - initial gap
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Backgrounds (ctd)
NC - p0 - 2 tracks
nm CC - with p0 - muon
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Aims of the studies

• Understand ne detection efficiency that is
  possible
• Understand background contributions
• Devise optimum algorithms
• Understand detector optimization
• Strip width
• Possible gain from pulse height
• Benefits of 2D readout

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Electron Criteria

• FH Hits in road/planes hit is high (gt1.4)
• FH also high on each half (gt1.15)
• No gap between vertex and 1st hit on track
• No gaps early in the track
• Minimum track length (gt8 planes)
• Not accompanied by a muon
• No converted gamma in vicinity

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Muon and gamma definitions

• What is a muon?
• FH is low (lt1.2)
• Curvature is small
• Minimum track length
• What is a converted gamma in vicinity?
• FH is high (gt1.4)
• Some distance from vertex
• Gap(s) early in the track
• Makes a relatively small angle wrt primary track

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Overall Event Criteria

• Total energy in the event (as measured by total
  number of hits) within some limits
• Overall asymmetry of the event wrt beam direction
  is low

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Energy Resolution

• ne CC events
• passing all cuts
• 1 lt En lt 3 GeV
• s 15.1

Oscillated ne spectrum at 715 km, 9 km
for Dm2 3 x 10-3 s 15.9
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Initial practice analysis

• Toy beam - gaussian distribution, centered at 2
  GeV with a width of 0.4 GeV and truncated at 1
  and 3 GeV
• Relatively monolithic detector, mean density
  somewhat smaller than what is currently proposed
• Early version of the analysis algorithms based on
  using the longest track only
• Standard NuMI neutrino interaction generator is
  used is it correct for the tails?

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Initial Results (4 cm strips)

• Assumed same number of oscillated nes
• Assumed same ratio of beam to oscillated nes
• Figure-of-merit (FOM) defined as
  signal/sqrt(backround)

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Issue of Rates

• At 9 km and 715 km, medium energy NuMI beam, 3.7
  x 1020 p/yr, produce in 5 yrs, 20 kt detector,
  400 oscillated ne evts (CHOOZ limit, Posc0.05,
  Ue320.025)
• For 37.5 detection efficiency, Ue32.0025, we
  get 15 events in that time
• The beam ne background should be comparable or
  smaller than that

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Relative Effectiveness of Cuts (an
example)
1st cuts gaps in front, hits/50 of planes
(gt1.06,1.29) 2nd cuts hits/all planes (gt1.42),
no of planes(gt9)
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Track Length Distributions
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Plans for the Future

• Make simulation more realistic
• Use NuMI offaxis beam (9 and 11 km)
• Make detector geometry more realistic
• Use full fledged analysis programs
• Optimize reconstruction/event selection
  algorithms
• Roads around the tracks
• Values of cuts used
• Maximum likelihood or neural network

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Plans for the Future (ctd)

• Optimize the design of the detector
• Determine strip width tradeoffs
• Determine possible gain from pulse height
  information
• Determine loss of sensitivity from 1D readout
• Understand fiducial volume issues
• Understand impact of beam parameters
• Dependence on transverse distance
• Possible gain from shorter decay pipe
• Dependence on target position and (?) location of
  2nd horn
• Understand ND -gt FD extrapolation (nm CC issue)

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Conclusions

• The initial studies show that a low Z
  calorimeter, with fine granularity, can
  accomplish desired aims
• The efficiency/background rejection should be
  competitive or maybe better than that of
  JHF/SuperK
• The realistic quantitative studies are just
  beginning