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Brief review of CC energy analysis work. D.A. Petyt Jan ‘03. CC energy analysis: a c 2 fit of the reconstructed energy distribution of identified CC-like events in the far detector.
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Brief review of CC energy analysis work D.A. Petyt Jan ‘03 • CC energy analysis: a c2 fit of the reconstructed energy distribution of identified CC-like events in the far detector. • CC events identified by placing cuts on simple quantities such as event length, mean pulse height per plane, Hough transform ‘track-like’ estimator. • No reconstruction – identified CC events are smeared by nominal MINOS energy resolution functions. • Systematics – a guesstimate of beam and reconstruction uncertainties. Should be looked at in more detail. • NC contamination accounted for. • Comparison of statistical techniques – c2 versus Feldman-Cousins. • Use of CC energy analysis to discriminate between oscillations and exotic models (neutrino decay, extra dimensions). First look in NuMI-L-701.
Selecting CC events j nm CC NC CC-like cuts evlength > 38 .or. (h.t.rms < 10 .and planeocc > 0.8 .and ph/plane < 2.5 mips .and ph/plane < 1.5 mips .and evlength > 4) Fraction of mis-identified NC
Efficiencies as a function of En and y NC events passing the event length cut
Reconstructed energy distributions • Smearing functions applied: • NC contamination included (see over)
Ph2le True CC True NC Ph2me Neutral current contamination • Effect of NC contamination:- • Ratio in lowest energy bin is always ~1. • Oscillation ‘dip’ is shallower. • Slightly larger parameter measurement errors
Parameter measurement errors • Perform a c2 fit between oscillated far detector spectrum with parameters (Dm2,sin22q)and unoscillated far spectrum. • Assume the following systematic errors: • 2% overall flux uncertainty • 2% bin-to-bin flux uncertainty (1 GeV bins) • 2% overall CC efficiency uncertainty + (2-En)*1.5% below 2 GeV • 90% C.L. allowed region is defined by c2min+4.61
Parameter measurement errors contd. • Assumes 10 kt. yr. exposure with nominal proton intensity. • Predicts ~10% parameter measurement errors for S-K best-fit point • Out-of-date analysis, should be re-done: • Uses older, less efficient CC selection algorithm • Beam systematics are 4% rather than 2% • Sin22q=0.9 rather than 1.0
90% C.L. limits from CC energy test • Systematic errors chosen for this analysis have more effect at high Dm2 • Oscillation pattern smeared out by energy resolution – CC energy analysis becomes a rate test.
Feldman-Cousins: Dc2904.61 • Calculate Dc290 at each point in parameter space by: • Generating large no. of experiments at (Dm20,sin22q0) and fit to find global c2 minimum • Plot Dc2=c2min-c2(Dm20,sin22q0) and find value of Dc2 that includes 90% of the experiments. This is Dc290. • Correctly accounts for acceptance effects at the physical boundary and sensitivity variations within the physical region. Distribution of Dc29010 Dm2=0.003, sin22q=0.8 Cumulative distribution 800 experiments Dc290 Dc290=4.3
Comparison of F/C and c2+4.61 allowed regions Dm2=0.003, sin22q=0.8 • Not much difference for these parameter values. This is because: • Large oscillation effect. c2surface is parabolic around minimum. • Allowed region does not intersect physical boundary where differences are generally the largest. • I have observed an effect for sin22q=1 and low Dm2 • F/C allowed regions are slightly smaller than c2+4.61 • Concept of sensitivity important in F/C • 90% C.L. region for data should be accompanied by ‘average 90% C.L. contour’ calculated from an ensemble of MC experiments generated at data best fit point c2+4.61 Feldman-Cousins
Exotics 1: Neutrino decay • S-K data fits well to nmnt oscillation hypothesis, but other models, which have a different L/E dependence can also fit the data. • Can MINOS rule out these other models using the CC energy test? n decay prob: (high Dm2) No osc. (low Dm2) Osc. Dm2=0.003 n decay Generate1000 expts assuming nu decay. Plot c2 difference between best fit to standard osc. and nu decay hypothesis
No osc. Osc. Dm2=0.003 n decay Exotics 2: Extra dimensions Extra dimensions prob: • Oscillation fit can provide acceptable c2 in some cases, spurious signals tend to occur at large values of Dm2 and low values of sin22q (see bottom left plot) Location of false minima in osc. parameter space
References CC energy analysis notes: • D.A. Petyt D.Phil thesis, Chapters 4 and 5 – the original CC energy analysis. Contains some early attempts to evaluate the effect of systematics. Very out-of-date. http://www.physics.ox.ac.uk/Neutrino/Petyt/Petyt.htm • NuMI-L-612: “Physics potential of the three Ph2 beam designs” – contains a section on CC energy sensitivities. Slightly out-of-date. • http://www.david.petyt.ukgateway.net/osiris.ppt - talk on F-C vs c2 differences. • NuMI-L-482: “Simulation of CC energy analysis” – c2analysis (I use the same error matrix method for including systematic errors). • NuMI-L-486: “CC Limits and Measurements”– F-C analysis. • NuMI-L-701: “Effect of the Hadron Hose on MINOS physics” – includes nu decay and extra dimensions analysis. Also includes a discussion of beam systematics and their effect on the CC energy test. • Blessed plot site: contains the most recent CC energy analysis results. Z-test (unbinned CC energy analysis): • NuMI-L-106: The analysis in detail.
