Sampling Detectors for ne Detection and Identification

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Sampling Detectors for ne Detection and
Identification

• Interest de jour what is sin22q13 ?
• oscillations nm -gt ne
• superbeams

• Current generation of experiments
• How can we do better
• Sampling detectors for ne detection

• Adam Para, Fermilab
• NuFact02
• Imperial College

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Different baselines where the oscillation peaks
are ?
L(km)/n 1 2 3
300 0.73 GeV 0.24 GeV 0.15 GeV
750 1.82 GeV 0.60 GeV 0.36 GeV
1500 3.64 GeV 1.21 GeV 0.73 GeV
En lt 1 GeV (KEK/JHF to SuperK, CERN to Frejus
0.3 lt En lt 3 GeV (NuMI)
0.5lt En lt 6 GeV (CERN to Taranto, BNL to ?)
Flux/rates drop
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Neutrino Cross Sections
Many particles
Nlepton
Nlp
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What will MINOS do?
Two functionally identical neutrino detectors

Det. 1
Det. 2
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ne Interactions in MINOS?

• NC interactions
• Energy distributed over large volume

ne CC, Etot 3 GeV
NC, Eobs 3 GeV

• ne CC interactions (low y)
• Electromagnetic shower
• Short
• Narrow
• Most of the energy in a narrow cluster

• Detector Granularity
• Longitudinal 1.5X0
• Transverse RM

energy
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Needle in a Haystack ? NC Background
n spectrum
NC (visible energy), no rejection
Spectrum mismatch These neutrinos contribute to
background, but no signal
ne (Ue32 0.001)

• ne background

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MINOS Limits on nm to ne Oscillations
10 kton-yr exposure, Dm20.003 eV2,
Ue320.01 Signal (e 25) - 8.5 ev ne
background - 5.6 ev Other (NC,CC,nt)
34.1 ev M. Diwan,M. Mesier, B. Viren, L. Wai,
NuMI-L-714 90 CL Ue32lt 0.01 Limit
comparable to a far superior detector (ICARUS) in
CNGS beam

Sample of ne candidates defined using
topological cuts
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Receipe for a Better Experiment

• More neutrinos in a signal region
• Less background
• Better detector (improved efficiency, improved
  rejection against background)
• Bigger detector

• Lucky coincidences
• distance to Soudan 735 km, Dm20.025-0.035 eV2
• Below the tau threshold! (BR(t-gte)17)

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Two body decay kinematics
At this angle, 15 mrad, energy of produced
neutrinos is 1.5-2 GeV for all pion energies ?
very intense, narrow band beam

• On axis En0.43Ep

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Off-axis magic ( D.Beavis at al. BNL Proposal
E-889)
1-3 GeV intense beams with well defined energy in
a cone around the nominal beam direction
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NC/ ne /p0 detectors
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CHARM II (nme scattering)

• Challenges
• Identify electrons
• Small cross section, large background from NC
  interactions

• Solution
• Low Z, fine grained calorimeter

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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

• 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 detector an example
Cheap low z absorber recycled plastic
pellets Cheapest detector glass RPC (?)
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Constructing the detector wall

• Containment issue need very large detector
• Engineering/assembly/practical issues

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On the Importance of the Energy Resolution
Cut around the expected signal region too improve
signal/background ratio

• M. Messier, Harvard U.

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Energy resolution vis-à-vis oscillation pattern

• First oscillation minimum energy resolution/beam
  spectrum 20 well matched to the width of the
  structure
• Second maximum 20 beam width broader than the
  oscillation minimum, need energy resolution lt10.
  Tails??

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Energy Resolution of Digital Sampling Calorimeter

• Digital sampling calorimeter
• 1/3 X0 longitudinal
• 3 cm transverse
• Energy Cx( of hits)
• DE 15 _at_ 2 GeV
• DE 10 4-10 GeV
• 15 non-linearity _at_ 8 GeV, no significant
  non-gaussian tails

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Improve energy resolution?

• Total Absorption Calorimeter HPWF

Energy resolution limited by fluctuations of the
undetected energy nuclear binding energy,
neutrinos and not by sampling fluctuations Crude
sampling calorimeter (CITFR), 10 cm steel,
better energy resolution than total absorption
one (HPWF)
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Neutrino energy, Quasi-elastics ?
m
nm n ? m p
(Em , pm)
n
p
m events
En(reconstruct)
s80MeV
En(reconstruct) En (True) (MeV)
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2 GeV CC ne / NC interactions
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2 GeV nm CC interaction
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7 GeV CC ne / NC interactions
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CC ne vs NC events example

• Electron candidate
• Long track
• showering I.e. multiple hits in a road around
  the track
• Large fraction of the event energy
• Small angle w.r.t. beam
• NC background sample reduced to 0.3 of the final
  electron neutrino sample (for 100 oscillation
  probability)
• 35 efficiency for detection/identification of
  electron neutrinos

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Detector questions/issues

• What is the optimal absorber material (mostly an
  engineering/cost question, if DX0 kept constant)
• What longitudinal sampling (DX0)?
• What is the desired density of the detector?
  (containment/engineering/transverse segmentation)
• Containment issues fiducial volume vs total
  volume, engineering issues what is the practical
  detector size?
• What is the detector technology (engineering/cost
  issue if transverse segmentation kept constant)
• What is the optimal transverse segmentation
  (e/p0, saturation,)
• Can a detector cope with cosmic ray background?
  What is the necessary timing resolution?