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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?