LSND/MiniBooNE Follow-up Experiment with DAEdALUS

W.C. Louis

Los Alamos National Laboratory

August 6, 2010

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Outline

LSND & MiniBooNE e Oscillation Results

3+1 Fit to World Antineutrino Data Testing the LSND/MiniBooNE Signals with DAEdALUS Conclusions

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LSND Signal

LSND experiment Stopped pion beam

+ e+ e

Excess of e in beam

e signature: Cherenkov light

from e+ with delayed from n-capture

Excess=87.9 ± 22.4 ± 6 (3.8)

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LSND Signal

Assuming two neutrino oscillations

Can't reconcile LSND result with atmospheric and solar neutrino using only 3 Standard Model neutrinos – only two independent mass splitings

2mass

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Sterile Neutrinos

3+N models

N>1 allows CP violation

e

≠ e

2mass

m34

2 ~ 0.1 – 100 eV2

m45

2 ~ 0.1 – 100 eV2

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MiniBooNE Neutrino ResultPRL 102, 101802 (2009)

6.5e20 POT

No excess of events in signal region (E>475 MeV)

Ruled out simple 2 oscillations as LSND explanation (assuming no CP or CPT violation)

SIGNAL REGION

Phys. Rev. Lett. 98, 231801 (2007)

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MiniBooNE Neutrino ResultPRL 102, 101802 (2009)

• Excess of events observed at low energy:128.8 ± 20.4 ± 38.3 (3.0σ)

• Shape not consistent with simple 2 oscillations

• Magnitude consistent with LSND

• Anomaly Mediated Neutrino-Photon Interactions at Finite Baryon Density: Jeffrey A. Harvey, Christopher T. Hill, & Richard J. Hill, arXiv:0708.1281

• CP-Violation 3+2 Model: Maltoni & Schwetz, arXiv:0705.0107; T. Goldman, G. J. Stephenson Jr., B. H. J. McKellar, Phys. Rev. D75 (2007) 091301.

• Extra Dimensions 3+1 Model: Pas, Pakvasa, & Weiler, Phys. Rev. D72 (2005) 095017

• Lorentz Violation: Katori, Kostelecky, & Tayloe, Phys. Rev. D74 (2006) 105009

• CPT Violation 3+1 Model: Barger, Marfatia, & Whisnant, Phys. Lett. B576 (2003) 303

• New Gauge Boson with Sterile Neutrinos: Ann E. Nelson & Jonathan Walsh, arXiv:0711.1363

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MiniBooNE Antineutrino Result

5.66e20 POT arXiv:1007.1150

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MiniBooNE Antineutrino Null Probability

Absolute 2 probability of null point (background only) - model independent

Frequentist approach

475-1250 MeV chi2/NDF probability

e 6.1/6 40%

e 18.5/6 0.5%

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MiniBooNE Oscillation Fit E>475

5.66E20 POT

E>475 is signal region for LSND type osc.

Oscillations favored over background only hypotheses at 99.4% CL (model dependent)

Best fit (sin22, m2) = (0.9584, 0.064 eV2) 2/ND = 16.4/12.6; Prob. = 20.5%2/ND = 8.0/4; Prob. = 8.7% (475-1250 MeV)

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MiniBooNE

e oscillation results appear to confirm the LSND evidence for antineutrino oscillations, although more data are needed

E>475 MeV

LSND/MiniBooNE Data Compared to 3+N Global Fits (fits from Karagiorgi et al.)

3+1

3+2

G. Karagiorgi et al.,PRD80, 073001 (2009)

Best 3+1 Fit:m41

2 = 0.915 eV2

sin22e = 0.0043 = 87.9/103 DOFProb. = 86%

Predicts e

disappearance of sin22~ 35% andsin22ee ~ 4.3%

3+1 Global Fit to World Antineutrino Data(with old MiniBooNE data set)

3+N Models Requires Large Disappearance!

In general, P(e) < ¼ P(x) P(e x)

Reactor Experiments: P(e x) < 5%

LSND/MiniBooNE: P(e) ~ 0.25%

Therefore: P(x) > 20%

MiniBooNE Neutrino & Antineutrino Disappearance Limits

Improved results soon from MiniBooNE/SciBooNE Joint Analysis!

A.A. Aguilar-Arevalo et al., PRL 103, 061802 (2009)

*

*

Global best fit

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Future Experiments

MicroBooNE CD1 approved Address MB low energy excess Statistics too low for antineutrinos

Few ideas under consideration: Move or build a MiniBooNE like detector at 200m

(LOI arXiv:0910.2698) A new search for anomalous neutrino oscillations at the

CERN-PS (arxiv:0909.0355v3) Redoing a stopped pion source at ORNL (OscSNS -

http://physics.calumet.purdue.edu/~oscsns/) or DAEdALUS!

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MiniDAEdALUS

Build MiniBooNE-like detector ~300’ (~90m) below cyclotron; (or use large WC detector filled with Gd!)

Copy MiniBooNE detector design except for higher PMT coverage (10%->20%) and addition of ~0.031 g/l of b-PBD; cost ~$10-15M

Poor cyclotron duty factor compensated by 300’ overburden (cosmic muon rate reduced by factor of ~100)

Assume ~ 1 year of data at ~1MW

Well understood neutrino fluxes and cross sections

Many advantages over LSND: (1) x5 larger detector; (2) x4 higher flux; (2) x100 lower cosmic-muon rate; (3) negligible DIF background; (4) run 12 months per year (instead of 3); (5) larger distance for m2<1 eV2 implies lower backgrounds;

MiniDAEdALUS

-> e (L/E) ~ 3% ;

e p -> e+ n (2.2 MeV )

-> e (L/E) < 1% ; Monoenergetic !; e

C -> e- Ngs (17.3 MeV e+)

-> s (L/E) < 1% ; Monoenergetic !; C -> C* (15.11 MeV )

-> s ; C -> C* (15.11 MeV )

MiniDaedalus would be capable of making precision measurements of

e appearance & disappearance and proving, for example, the

existence of sterile neutrinos! (see Phys. Rev. D72, 092001 (2005)).

For OscSNS& notMiniDAEdALUS

Search for Sterile Neutrinos with MiniDAEdALUS (or WC) Via Measurement of NC Reaction: C -> C*(15.11)

Garvey et al., Phys. Rev. D72 (2005) 092001

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MiniDAEdALUS

e appearance (left) and disappearance

sensitivity (right) for 1 year of running (for 60m!)

LSND Best Fit LSND Best Fit

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Conclusions

• The MiniBooNE data are consistent with e oscillations at m2 ~ 1 eV2 and consistent with the evidence for antineutrino oscillations from LSND.

• The MiniBooNE e oscillation allowed region appears to be different from the e oscillation allowed region.

• The world antineutrino data fit well to a 3+1 oscillation model with m2 ~ 1 eV2. All 3+N models predict large disappearance!

• A MiniBooNE-like detector (MiniDAEdALUS) located ~300’ below the DAEdALUS cyclotron could measure neutrino oscillations with high significance (>>5) and prove that sterile neutrinos exist!

Backup

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E>200MeV 5.66E20 POT

Oscillations favored over background only hypotheses at 99.6% CL (model dependent)

No assumption made about low energy excess

Best fit (sin22, m2) = (0.0066, 4.42 eV2)2/NDF = 20.4/15.3; Prob.=17.1%

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E>200MeV Subtract excess produced by neutrinos in mode

(11.6 events)

E<475MeV:

Large background

Not relevant for LSND type osc.

Big systematics

Null 2=32.8; p=1.7%

Best fit (sin22, m2) = (0.0061, 4.42 eV2)2/NDF = 21.6/15.3; Prob.=13.7%

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Future sensitivity

MiniBooNE approved for a total of 1e21 POT

Potential exclusion of null point assuming best fit signal

E>475MeV fit

Protons on Target

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BooNE

MiniBooNE like detector at 200m

Flux, cross section and optical model errors cancel in 200m/500m ratio analysis

Present neutrino low energy excess is 6 sigma statistical; 3 sigma when include systematics

Study L/E dependence Gain statistics quickly,

already have far detector data

Near/Far 4 sensitivity similar to single detector90% CL

6.5e20 Far + 1e20 Near POT

Sensitivity(Neutrino mode)

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BooNE Better sensitivity to disappearance

Look for CPT violation ≠

6.5e20 Far/1e20 Near POT 1e21 Far/1e20 Near POT

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Reminders of some analysis choices

Data bins chosen to be variable width to minimize N bins without sacrificing shape information

Technical limitation on N bins used in building syst error covariance matrices with limited statistics MC

First step in unblinding revealed a poor chi2 for oscillation fits extending below 475 MeV

Region below 475 MeV not important for LSND-like signal -> chose to cut it out and proceed

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Reminders of some pre-unblinding choices

Why is the 300-475 MeV region unimportant?

Large backgrounds from mis-ids reduce S/B

Many systematics grow at lower energies

Most importantly, small S/B so not a good L/E region to look for LSND type oscillations

Energy in MB [MeV]1250 475 333

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E>475 MeV

1 sigma contour includes 0.003<sin22<1

Initial MINOS Disappearance Results

Expect disappearance above10 GeV for LSND neutrino oscillations.

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OscSNS Spallation neutron source at ORNL

1GeV protons on Hg target (1.4MW)

Free source of neutrinos

Well understood flux of neutrinos

Physics reach would be similar with DARDaedalus