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(tau neutrino magnetic moment) Reinhard Schwienhorst University of Minnesota Donut analysis Talk at Nagoya University, 6/9/99

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Outline Introduction Physics –magnetic moment interaction –Expected event yield Spectrometer analysis: –Monte Carlo Analysis –Cuts Preliminary Physics result Conclusions All of the numbers in this presentation are preliminary

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Introduction Standard Model – =0 current experimental limit: – e : <1.8 10 -10 B – : <7.4 10 -10 B – : <5.4 10 -7 B (all obtained in neutrino-electron scattering experiments)

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Magnetic moment interaction ee ee

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Magnetic moment interaction example (MC)

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Physics reminder Neutrino-electron scattering –no hadronic activity in the event –small forward angle magnetic moment interaction –cross section : neutrino magnetic moment E : neutrino energy T: electron kinetic energy

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Electron energy and angle Production angle and energy for the electron in a magnetic moment interaction

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Expected event yield If =5.4 10 -7 B (the current limit): –with an electron energy cutoff at 5GeV current cat3 neutrino event sample expect 10 magnetic moment interactions (compared to 40 CC interaction) –with an electron energy cutoff at 0.5GeV.nustrip files expect 30 magnetic moment interactions –with an electron energy cutoff at 10MeV emulsion analysis expect 80 magnetic moment interactions we must scan at least 1/3 of the emulsion to improve the sensitivity

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Emulsion-only analysis Scan a large volume of the emulsion Search for single electron tracks in the direction of the beam –challenges: identify electrons down to very low energies many straight tracks in the emulsion Advantage: independent of the spectrometer, time, trigger disadvantages: –must scan a large volume –background from pair production

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Spectrometer analysis outline Optimize cuts for magnetic moment events –cross-check with CC events (data and MC) easy to find ® determine efficiency apply to neutrino candidate events –apply first to MC events, determine expected # of events –blind analysis apply to nustrip files – find (almost) all candidate events – not quite a blind analysis at the end, scan emulsion for confirmation –identify hadrons, decays, secondary interactions, nuclear breakup

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Monte Carlo analysis So far only periods 3 and 4 Trigger efficiency =65% for magnetic moment interactions with T>0.5GeV Tune each cut to remove no more than ~5% of the magnetic moment interactions

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4GeV that E EMCAL

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Cuts II SF system: –require small # of SF hits (< 12000) –remove events with: hadrons: highly ionizing tracks (large fiber pulseheight) tracks not coming from the emulsion (muons interacting in the shielding) tracks that go straight through a module (electrons are required to shower) –require at least one straight SF line in each view (<0.1rad) put the vertex at the origin of this line –require the vertex to be in the emulsion volume

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Cuts III Trigger counters: –remove backward trigger O O O O O O O O T1 O O X X O O O O O T2 O O X O O O O O T3 –require a trigger panel hit on a straight line behind the vertex VDC: –require VDC hits on a straight line behind the vertex

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Cut efficiency: electronic analysis Percentage of events removed in periods 3+4

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Cuts IV Refit and find the vertex remove events “by hand” if: –a straight muon is in the SF –the event has only a single track with P>0 –there are slow hadrons in the SF apply all of the previous cuts again output: 3 cat3 events, 14 nustrip events –periods 3 and 4 –MC efficiency for these cuts 100%

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Cuts V Careful visual inspection of each event –Can it be scanned? –Check E EMCAL /P for each track –Check track straightness (angle <0.1rad in X and Y) –check trigger timing Output: 0 cat3 events, 1 nustrip event –if current limit: expect 6 cat3 events, 11 nustrip events

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Candidate event

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Preliminary Physics result Data analysis: –0 events for T>5GeV –1 events for T>0.5GeV –systematic error: not determined yet, assume 0.5events preliminary 90% confidence limit for the magnetic moment:

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Conclusions The magnetic moment analysis is still in progress Searching for event candidates in the nustrip files will give the best limit Emulsion information for candidate events is very important An emulsion-only analysis is only useful if we scan a considerable fraction of the emulsion volume

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