lsnd/miniboone follow-up experiment with daedalus w.c. louis los alamos national laboratory august...
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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