Preliminary Ideas for a Near Detector at a Neutrino Factory

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Preliminary Ideas for a Near Detector at a
Neutrino Factory
Neutrino Factory Scoping Study Meeting 23
September 2005 Paul Soler University of
Glasgow/RAL
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Contents

• Near Detector Aims
• Flux normalization
• Cross-sections
• Parton Distribution Functions
• Charm production
• Sin2qw
• Possible near detector technologies
• 7.1 Silicon tracking detector
• 7.2 Liquid argon TPC or other technologies
• Conclusions

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1. Near detector aims

• Long baseline neutrino oscillation systematics
• Flux control and measurement for the long
  baseline search.
• Neutrino beam angle and divergence
• Beam energy and spread
• Control of muon polarization
• Near detector neutrino physics
• Cross-section measurements DIS, QES, RES
  scattering
• sin2?W - ?sin2?W 0.0001
• Parton Distribution Functions, nuclear shadowing
• ?S from xF3 - ??S0.003
• Charm production Vcd and Vcs, D0/ D0 mixing
• Polarised structure functions
• L polarization
• Beyond SM searches

General Purpose Detector(s)!!
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2. Flux normalisation (cont.)

• Neutrino beams from decay of muons

Polarisation dependence
Need to measure polarization!!
Pm1 gone!
Spectra at Production (e.g. 50 GeV)
Number CC interactions
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2. Flux normalisation (cont.)

• Rates
• Em 50 GeV
• L 100 m, d 30 m
• Muon decays per year 1020
• Divergence 0.1 mm/Em
• Radius R50 cm

E.g. at 25 GeV, number neutrino interactions per
year is 20 x 106 in 100 g per cm2 area.
High granularity in inner region that subtends
to far detector.
Yearly event rates
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2. Flux normalisation (cont.)

• Neutrino flux normalisation by measuring
• Signal low angle forward going muon with no
  recoil
• Calculable with high precision in SM
• Same type of detector needed for elastic
  scattering on electrons

E.g. CHARM II obtained value of sin2qW from
this
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3. Cross sections

• Measure of cross sections in DIS, QE and RES.
• Coherent p
• Different nuclear targets H2, D2
• Nuclear effects, nuclear shadowing, reinteractions

With modest size targets can obtain very large
statistics
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4. Parton Distribution Functions(s)

• Unpolarised and Polarised Structure functions
• ?S from xF3 - ??S0.003
• Sum rules e.g. Gross-Llewelyn Smith
• L polarization spin transfer from quarks to L
• NOMAD best data
• Neutrino factory 100 times more data

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5. Charm Production

• Charm production
• Measure of Vcd and strange quark content nucleon
• 6-7 of cross-section at 20 GeV?3 CC events
• about 3x107 charm states per year

McFarland

• mixing doubly Cabbibo
  suppressed?SM very small, new physics
• Babar Rmixlt4x10-3 (90 CL) hep-ex/0408066

Tagged sample
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6. sin2 qw

• Elastic scattering off electrons
• Deep inelastic scattering NC/CC

• ?sin2?W 0.0001

Good statistical accuracy on sin2?W (0.5x10-4)
but hadron uncertainties dominate
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7. Near detector technologies

• High granularity in inner region that subtends to
  far detector.
• Very good spatial resolution charm detection
• Low Z, large Xo
• Electron ID
• Does the detector have to be of same/similar
  technology as far detector?

• Possibilities
• silicon or fibre tracker in a magnet with
  calorimetry, electron and muon ID (eg.
  NOMAD-STAR??)
• Liquid argon calorimeter

• Does not need to be very big (eg. R50-100 cm)

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7.1 Vertex detector with spectrometer

• RD in NOMAD for short baseline nt detector based
  on silicon
• NOMAD-STAR

• Does not need to be very big (eg. R50-100 cm)

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7.1 Vertex detector with spectrometer

• Longest silicon microstrip detector ladders ever
  built 72cm, 12 detectors, 50 mm pitch, S/N161
• Vertex resolution 19 mm

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7.1 Vertex detector with spectrometer

• nm CC event

• Secondary vertex

• Primary vertex

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7.1 Vertex detector with spectrometer

• Vertex resolution 19 mm

• Impact parameter resolution 33 mm

• Used NOMAD-STAR to search for charm events
  marginal statistical accuracy, but was a good
  proof of principle

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7.1 Vertex detector with spectrometer

• Efficiency very low 3.5 for D0, D and 12.7
  for Ds detection because fiducial volume very
  small (72cmx36cmx15cm), only 5 layers and only
  one projection.
• From 200 million events, about 600,000 charm
  events, but efficiencies can be improved.

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7.2 Other technologies

• Liquid argon TPC in a magnetic field would be
  able to perform as a near detector as well
• Other possible technologies that have been used
  or are being proposed to be used as near
  detectors scintillating fibre tracker, standard
  gas TPC with target (T2K near detector)

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Conclusions

• The Near Detector(s) needs to meet two physics
  goals
• Flux control and measurement for the long
  baseline
• A dedicated near detector neutrino physics
  programme
• Silicon detectors could provide a solution for
  the near detector technology.
• Other options include liquid argon TPC, SciFi
  tracker, or gas TPC associated with a target.