NuMuBars Caius Howcroft and Jeff Hartnell MINOS Collaboration Meeting MarchApril 2006

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NuMuBarsCaius Howcroft and Jeff HartnellMINOS
Collaboration MeetingMarch/April 2006
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Outline

• Multiple physics motivations for studying
  NuMuBars
• NuMuBar appearance searches in FD (NuMu-gtNuMuBar
  transitions)
• Constraining the Nue flux of the beam
• Measurement of dm2Bar (and sin2thBar)
• Cross-section measurements in ND
• Understanding hadron production issues
• Many Common Issues
• Understand charge separation
• Understand the beam
• Understand reconstruction effects
• Ideas for the future (special runs)
• A lot of work in the last few months this is a
  whirlwind tour!
• Apologies if I miss anyone...

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A Search for NuMu-gtNuMuBar Transitions

• Work from many people over the last few months
  (Rustem, David Jaffe, PedroCaius, JustinGiles,
  JJH)
• See DocDB 1571, 1583, 1647, 1663 and more
• It's an important test of
• lepton number conservation
• helicity conservation
• The experimental question that MINOS can answer
  is very simple
• do neutrinos stay as neutrinos 2.5 ms after
  production (as a function of energy)
• but...

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How to present our data is not straightforward

• Lack of physically motivated models
• Normal oscillations and different xsections
  complicate matters
• Several ideas put forward, lots of bouncing of
  ideas around between people, highlights (and
  possible champions) are
• Exotic oscillations (PedroCaius...)
• Decay oscillations (?)
• Double ratio (David J., Rustem...)
• Fractional Appearance (JJH, Giles, Justin...)

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Exotic Oscillations(PedroCaius)
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Double-ratio(Rustem, David Jaffe)
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Fractional Appearance(JJH, Justin, Giles,...)

• Model Independent technique
• Takes advantage of varying sensitivity with
  energy
• Try to present data in a way that conveys maximum
  information and plays on the strengths of the
  experiment
• (NuMuBar_Obs NuMuBar_Bkg) / NuMu_Expected (vs.
  E)
• where NuMuBar_Obs observed spectrum in FD
• and NuMuBar_Bkg mis-id NuMu NC beam
  NuMuBar assuming oscillations
• and NuMu_Expected prediced NuMu spectrum in FD
  assuming

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A quick look at our model-independent
sensitivity toNuMu -gt NuMuBar transitions

• Plot this
• (NuMuBar_Obs NuMuBar_Bkg) / NuMu_Expected vs.
  Energy
• use FD MC (R1.18.2)
• Use dm2 and sin2th from CC analysis for MC
  expectation
• Assume
• equal cross-sections (actually a factor of 2-3
  typically)
• 100 efficiency
• 100 purity
• Zero systematics
• Gaussian errors
• Very idealised, but I hope it gets the concept
  across and gives a rough guide to our sensitivity
• Very preliminary!

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(Very Rough) Sensitivity for 1e20 POT

• (NuMuBar_Obs NuMuBar_Bkg) /
  NuMu_Expected
• Expect very few NuMuBars
• Sensitivity is dominated by number of NuMus
  available to make the transition (oscillations
  make this worse)
• Energy dependence is clear
• Best in the peak of the oscillated NuMu spectrum
• Worst in the high energy tail where NuMu
  statistics are poor
• The usual 1/Sqrt(N) scaling

Rough Guide Only!
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Measuring Beam Nue flux using NuMuBar(David
Jaffe, Pedro, Miland...)

• See Pedro David's talk in nue plennary session
  and NuMuBar parallel session
• Nues at low energy mostly come from Mu decay
• gives a Nue NuMuBar (electron)
• Measure NuMuBar from Mu decay and you have a
  measurement of your Nue contamination for the
  theta13 analysis
• Intrinsic background is NuMuBar from pi-
• Can estimate using horn-off data since Mu come
  predominantly from focused pi

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dm2Bar sin2thBar(Pedro Caius)

• Test of CPT conservation
• Do neutrinos and anti-neutrinos have different
  mass splittings and hence different masses?
• Do they mix differently?
• Requires anti-neutrino running
• Take a factor of 3 hit in event rate
• different cross-sections
• different hadron production yields (pi / pi-)
• BUT can take advantage of neutrino running to
  accumulate events in the high energy tail!
• Only need a small amount of reversed horn current
  running...

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Dm2Bar Plots
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Charge Separation

• Many people working on improving efficiencies and
  purities many good ideas!
• Majority Curvature (JustinGiles)
• Directional PID (RustemKarol)
• NuMuBar-ID (Pedro)
• Cuts (JJH)

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Majority Curvature(Justin Giles)

• Break the track up into smaller segments
• Look at the curvature of each segment
• See which way the majority of the segments bend
• That should weight the consistent B-field
  curvature above the single scattering curve

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The Problem

• Negative muon
• Scatters at z 5.7m
• Gets reconstructed with wrong charge sign

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Directional PID(Rustem Karol)

• Don't have to do a fit
• Look at spatial differences

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Cross-sections in the ND(Donna, Debdatta,
Minsuk,...)

• See ND working group talks
• Share many of the same issues
• Understanding charge sign separation in data and
  MC
• level of agreement of B-field between data and MC
• Understanding acceptances, efficiencies,
  purities...
• effect of tracking, shower assignment, etc
• differences between data and MC

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Ideas for the future

• Runs with reversed magnetic field in the Near
  detector
• focus Mu rather than Mu-
• rather different acceptance and backgrounds
• important test of how well we understand our data
• good for understanding NuMu as well
• study in MC first
• Anti-neutrino running (reversed horn current)
• With a month or two of data should make a 20 (?)
  measurement of dm2Bar
• High energy running good for us too!

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Organisation

• Lots of work needed and exciting physics to be
  done!
• We have had two small, informal phone meetings so
  far to get started
• Productive focus to some important problems
• We will advertise more widely in the future

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Conclusions

• Much work and progress in the last few months on
  NuMuBar analyses
• charge sign separation
• assessing agreement between data and MC
• for detector quantities
• for beam quantities
• Much exciting physics to be done
• NuMuBar appearance searches in FD (NuMu-gtNuMuBar
  transitions)
• Constraining the Nue flux of the beam
• Measurement of dm2Bar (and sin2thBar)
• Cross-section measurements in ND
• Understanding hadron production issues