Transcript Slide 1

LSND/MiniBooNE Follow-up Experiment
with DAEdALUS
W.C. Louis
Los Alamos National Laboratory
August 6, 2010
Outline

LSND & MiniBooNE nm -> ne Oscillation Results

3+1 Fit to World Antineutrino Data

Testing the LSND/MiniBooNE Signals with DAEdALUS

Conclusions
2
LSND Signal





LSND experiment
Stopped pion beam
p+ -> m+ nm
m+ -> e+ nm ne
Excess of ne in nm beam
ne signature: Cherenkov light
from e+ with delayed g from
n-capture
Excess=87.9 ± 22.4 ± 6 (3.8s)
3
LSND Signal
Can't reconcile LSND result with
atmospheric and solar neutrino using
only 3 Standard Model neutrinos –
only two independent mass splitings
mass

Assuming two neutrino oscillations
2

4
Sterile Neutrinos
n5

3+N models

N>1 allows CP violation
Dm452 ~ 0.1 – 100 eV2
mass
2
n4
Dm342 ~ 0.1 – 100 eV2
n3
n2
n1

nm -> ne ≠ nm -> ne
5
MiniBooNE Neutrino Result
PRL 102, 101802 (2009)



6.5e20 POT
No excess of events in signal
region (E>475 MeV)
Ruled out simple 2n oscillations
as LSND explanation (assuming
no CP or CPT violation)
SIGNAL REGION
Phys. Rev. Lett. 98, 231801 (2007)
6
MiniBooNE Neutrino Result
PRL 102, 101802 (2009)
• Excess of events observed
at low energy:
128.8 ± 20.4 ± 38.3 (3.0σ)
• Shape not consistent with
simple 2n 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
7
MiniBooNE Antineutrino Result

5.66e20 POT

arXiv:1007.1150
8
MiniBooNE Antineutrino Null Probability


Absolute c2 probability of null point (background only) model independent
Frequentist approach
475-1250 MeV
chi2/NDF
probability
nm -> ne
6.1/6
40%
nm -> ne
18.5/6
0.5%
9
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 (sin22q, Dm2) = (0.9584, 0.064 eV2)
c2/ND = 16.4/12.6; Prob. = 20.5%
c2/ND = 8.0/4; Prob. = 8.7% (475-1250 MeV)
10
E>475 MeV
MiniBooNE
nm->ne oscillation
results appear to
confirm the LSND
evidence for
antineutrino
oscillations,
although more data
are needed
11
LSND/MiniBooNE Data Compared to 3+N Global Fits
(fits from Karagiorgi et al.)
3+1
3+2
3+1 Global Fit to World Antineutrino Data
(with old MiniBooNE data set)
G. Karagiorgi et al.,
PRD80, 073001 (2009)
Best 3+1 Fit:
Dm412 = 0.915 eV2
sin22qme = 0.0043
c2 = 87.9/103 DOF
Prob. = 86%
Predicts nm & ne
disappearance of
sin22qmm ~ 35% and
sin22qee ~ 4.3%
3+N Models Requires Large nm Disappearance!
In general, P(nm -> ne) < ¼ P(nm -> nx) P(ne -> nx)
Reactor Experiments: P(ne -> nx) < 5%
LSND/MiniBooNE: P(nm -> ne) ~ 0.25%
Therefore: P(nm -> nx) > 20%
MiniBooNE Neutrino & Antineutrino
Disappearance Limits
A.A. Aguilar-Arevalo et al., PRL 103, 061802 (2009)
Global best fit
*
*
Improved results soon from MiniBooNE/SciBooNE Joint Analysis!
Future Experiments


MicroBooNE

CD1 approved

Address MB low energy n 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!
17
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 n flux; (2) x100 lower cosmic-muon rate; (3) negligible
DIF background; (4) run 12 months per year (instead of 3); (5)
larger distance for Dm2<1 eV2 implies lower n backgrounds;
18
MiniDAEdALUS
For OscSNS
& not
MiniDAEdALUS
nm -> ne D(L/E) ~ 3% ; ne p -> e+ n (2.2 MeV g)
nm -> ne D(L/E) < 1% ; Monoenergetic nm !; ne C -> e- Ngs (17.3 MeV e+)
nm -> ns D(L/E) < 1% ; Monoenergetic nm !; nm C -> nm C* (15.11 MeV g)
nm -> ns ; nm C -> nm C* (15.11 MeV g)
MiniDaedalus would be capable of making precision measurements
of ne appearance & nm disappearance and proving, for example, the
existence of sterile neutrinos! (see Phys. Rev. D72, 092001 (2005)).
Search for Sterile Neutrinos with MiniDAEdALUS
(or WC) Via Measurement of NC Reaction:
nm C -> nm C*(15.11)
Garvey et al., Phys. Rev. D72 (2005) 092001
MiniDAEdALUS

ne appearance (left) and nm disappearance
sensitivity (right) for 1 year of running (for 60m!)
LSND Best Fit
LSND Best Fit
21
Conclusions
• The MiniBooNE data are consistent with nm -> ne oscillations at
Dm2 ~ 1 eV2 and consistent with the evidence for antineutrino
oscillations from LSND.
• The MiniBooNE nm -> ne oscillation allowed region appears to be
different from the nm -> ne oscillation allowed region.
• The world antineutrino data fit well to a 3+1 oscillation model with
Dm2 ~ 1 eV2. All 3+N models predict large nm disappearance!
• A MiniBooNE-like detector (MiniDAEdALUS) located ~300’ below the
DAEdALUS cyclotron could measure neutrino oscillations with high
significance (>>5s) and prove that sterile neutrinos exist!
22
Backup
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 (sin22q, Dm2) = (0.0066, 4.42 eV2)
c2/NDF = 20.4/15.3; Prob.=17.1%
24
E>200MeV



Subtract excess produced by neutrinos in n mode
(11.6 events)
E<475MeV:

Large background

Not relevant for LSND type osc.

Big systematics
Null c2=32.8; p=1.7%
Best fit (sin22q, Dm2) = (0.0061, 4.42 eV2)
c2/NDF = 21.6/15.3; Prob.=13.7%
25
Future sensitivity
E>475MeV fit


MiniBooNE approved for
a total of 1e21 POT
Potential exclusion of null
point assuming best fit
signal
26
Protons on Target
BooNE
6.5e20 Far + 1e20 Near POT





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
Near/Far 4 s sensitivity
similar to single detector
90% CL
Sensitivity
(Neutrino mode)
Study L/E dependence
Gain statistics quickly,
already have far detector data
27
BooNE

Better sensitivity to nm (nm) disappearance

Look for CPT violation (nm  nm  nm nm)
6.5e20 Far/1e20 Near POT
1e21 Far/1e20 Near POT
28
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
29
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
1250
475
333
Energy in MB [MeV]
30
E>475 MeV

1 sigma contour
includes
0.003<sin22q<1
31
Initial MINOS nm Disappearance Results
Expect nm disappearance above
10 GeV for LSND neutrino oscillations.
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
33