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Latest CC analysis developments
• New selection efficiencies:– Based on C++ reco + PDFs rather than old
(Fortran+reco_minos) cuts– Attempt to optimise PID cut
• 5 year plan:– Sensitivities calculated year by year
• Discrimination between osc. models– Standard oscillations vs nu decoherence
D. A. Petyt May ‘03
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PDF-based CC/NC separation• Idea is to replace old cut-based efficiencies with more modern/realistic values
• New selection uses likelihood method described at South Carolina
• Currently using simplest implementation – 3 1D pdfs.
CC
NC
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PID results (from SC)
CC
NC
Cut on the PID parameter to distinguish between CC/NC – the precise value of this cut will be a trade-off between purity and efficiency
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Sample ‘CC-like’ distributions
Visible energy (0-30 GeV)
PID>-0.5
PID>0.1PID>-0.1
PID>-0.3
Key
Perfect ID
CC
NC
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Optimising the PID cut
• Many possible ways to do this. The method I chose attempts to optimise the oscillation signal by examining– Overall significance of the effect (units of – Size of the dip at oscillation maximum (units of – Evidence for a rise at low energy (units of
• Optimisation will depend on how well NC background is understood. – I assume that I can make a full subtraction of the mis-identified
NC events, but assign an additional error that is proportional to the number of NC events in each bin of Evis
• Optimisation will be dependent on m2. – The plots I show here are for m2=0.0025 eV2
– Have looked at m2=0.0016 eV2. Optimum cut seems similar but statistical errors are large
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PID cut =-0.5, m2=0.0025
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Finding the optimum
• Define a quality factor that is the product of these three quantities.
• Optimum selection between –0.1<PID<0.1
• Optimium PID cut increases with increasing uncertainty on NC background
• I chose PID>–0.1 – try to maximise CC efficiency
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CC selection efficiencies as a fn. of true E and y
True neutrino energy (0-30 GeV)
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NC inefficiencies
Factor of 3 lower than previous cuts
True neutrino energy (0-30 GeV)
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Comparison of old and new efficiencies
Unoscillated CC spectra – No NC background
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5 year plan• I have taken the numbers for the
‘default’ 5 year plan that was sent around several weeks ago and have calculated year-by-year sensitivities with the following inputs:– le and semi-me,he beams from
NuMI-L-783– Efficiencies based on PID cut– Assume “VLE=LE”– Ignore anti-neutrino running (don’t
know fluxes)– Statistical errors only –
recommendations for beam (and other) systematics?
• This is a literal interpretation of 5 yr plan:– Do we want more generic N1020
p.o.t plots instead/as well? Some of these were shown at SC.
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Discriminating against exotic models• Several exotic models of neutrino mixing exist which can provide a
reasonable fit to the SK -like data.• Nu decay is ruled out by SK due to the non-observation of sterile. Nu
decoherence, which does not involve activesterile transitions, is still a possibility.
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Oscillations vs decoherence
• This analysis motivated by hep-ph/0303064, which shows how well SK+K2K data can discriminate against the decoherence hypothesis
• General survival probability (osc+decoherence):
– Comments:• Pure oscillations: • Pure decoherence: m2• In pure decoherence scenario: P
• I have performed a fit to these 3 parameters, assuming standard oscillations with m2=0.0025 eV2 and compared the results to those obtained for SK/K2K in hep-ph/0303064
E
LmeP E
L
2cos1
2
2sin1
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2 2
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Fit result – 5 year plan, year 1
Shown are the three 2D projections of the 3-dimensional allowed volume
SK allows m20 at 99% C.L. MINOS does not
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Fit result – 5 year plan, year 5
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Constraint on decoherence parameter
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Plots for 5yr plan/response to PAC questions• Two basic questions:
– What plots are required?
– What inputs (beams, systematics…)
• 5 year plan plots:– Specific run plans and/or generic sensitivity vs POT plots?
– Low m2 scenario (using VLE beam, if available)?
• PAC questions:– Q1 – ‘5 sigma dip’: precise definition? Easy to do but implies low p.o.t. even for
low m2
– Q2,3 – ‘95% exclusion of nu decay/3 preference of osc. over decay’: between best-fit osc and best-fit decay? Probably also implies low p.o.t. (see decoherence results)
• Inputs:– More up-to-date spectra (esp. le) available?
– Recommended systematic uncertainties on beam flux?
– Treatment of mis-identified NC: assume perfect subtraction or full subtraction with some error. What error?