# Presentation: 303604

## MiniBooNE Oscillation Searches

- Steve Brice (Fermilab)
- for the MiniBooNE Collaboration
- Neutrino 2008

## Outline

- Electron Neutrino Appearance
- Oscillation Result
-  0 Rate Measurement
- Combining Analyses
- Compatibility of High m2 Measurements
- Low Energy Electron Candidate Excess
- Data from NuMI Beam
- Muon Neutrino Disappearance
- Anti-Electron Neutrino Appearance
- Summary

## The MiniBooNE Collaboration

- University of Alabama
- Bucknell University
- University of Cincinnati
- University of Colorado
- Columbia University
- Embry-Riddle Aeronautical University
- Fermi National Accerator Laboratory
- University of Florida

- Indiana University
- Los Alamos National Laboratory
- Louisiana State University
- University of Michigan
- Princeton University
- Saint Mary’s University of Minnesota
- Virginia Polytechnic Institute
- Yale University

## The MiniBooNE Strategy

- Keep L/E same,  change beam, energy, and systematic errors

- PesinsinmL

- Booster

*K**+*

- primary beam

- tertiary beam

- secondary beam

- (protons)

- (mesons)

- (neutrinos)

****

*******e*****

**Event rates:**

## The MiniBooNE Detector

- 541 meters downstream of target
- 3 meter overburden of dirt
- 12 meter diameter sphere
- Filled with 800 t of pure mineral oil
- 	(CH2--density 0.86, n=1.47)
- Fiducial volume: 450 t
- 1280 inner 8” phototubes-10% coverage,
- 240 veto phototubes
- (Less than 2% channels failed during run)

## Oscillation Analysis Results: April 2007

**track-based analysis:**
- Counting Experiment:    475<E<1250 MeV
- data:             380 events
- expectation: 358 19 (stat)  35 (sys)
- significance: 0.55 

**No evidence for ************→********e**** appearance **
**in the analysis region**

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

## Measuring NC 0 and Constraining e MisIDs

- Measuring NC 0 and Constraining e MisIDs

-  largest  NC 0 sample ever collected!

- arXiv: 0803.3423, accepted by Phys. Lett. B

- 28,600 0 events
- m ~ 20 MeV/c2

-  0 rate measured to a few percent
-  Critical input to oscillation result → without it, 0 background errors would be ~25%

## Oscillation Analysis Strategy

- Two algorithms were used:
- 	- “track-based likelihood”  (TBL)
- 		Uses direct reconstruction of particle types
- 		and likelihood ratios for particle-ID
- 	- “boosted decision trees”  (BDT)
- 		Set of low-level variables combined with
- 		BDT algorithm -> PID “score”
- - In the end, the TB analysis had slightly
- better sensitivity, so was used for primary results.

- (TB)

- (BDT)

## Combining eBDT + eTBL Samples

- Limits from fits to open data

- 10%-30% improvement in 90% C.L. limit below ~1eV2.

- The combination of the two e samples  gives an increase in coverage in the region m2<1 eV2.
- Differences in the details are due to the specific fluctuations in the data samples and the interplay with correlations among them.

- The combination yields
- a consistent result.

- paper at draft stage

**Preliminary**

## Global Data Analysis

- Combine results from several experiments --   LSND, MiniBooNE, Karmen and Bugey
- Compatibility
- How probable is it that all experimental results come from the same underlying 2- osc. hypothesis?
- Assessed by combining the 2 surface of each experiment
- Allowed regions
- Indicate where oscillation parameters would lie, at a given CL, assuming all expt. results can arise in a framework of 2- osc.
- The compatibility is the metric for the validity of this assumption.

- arXiv:0805.1764 [hep-ex], submitted to Phys. Rev. D

## Global Fits to Experiments

| LSND | KARMEN2 |  | MB | Bugey | Max. Compat % | m2 | Sin22 |
| --- | --- | --- | --- | --- | --- | --- | --- |
| X | X |  | X |  | 25.36 | 0.072 | 0.256 |
| X | X |  | X | X | 3.94 | 0.242 | 0.023 |
|  |  |  |  |  |  |  |  |
| X |  | X |  |  | 16.00 | 0.072 | 0.256 |
| X |  | X |  | X | 2.14 | 0.253 | 0.023 |
|  |  |  |  |  |  |  |  |
|  | X | X |  |  | 73.44 | 0.052 | 0.147 |
|  | X | X |  | X | 27.37 | 0.221 | 0.012 |

## Global Fit Results-2D Fits

- LSND, KARMEN2 & MiniBooNE
- 25.36% compatibility at m2 = 0.072 eV2, sin22 = 0.256
- LSND, KARMEN2, MiniBooNE & Bugey
- 3.94% compatibility at m2 = 0.242 eV2, sin22 = 0.023

## Low Energy e CandidateExcess

-                              _ __reconstructed neutrino energy bin (MeV)_
- _                               __200-300           300-475       475-1250       _
- _Data                       375±19           369±19            380±19_
- total background    284±25           274±21            358±35
- eintrinsic                   26                   67                  229
-  induced                258                 207                 129_         _

-  No significant excess at higher E, wheree bkgd dominates.
-  Largest backgrounds at lower E are -induced, in particular:
- NC 0
- NC →N
- Dirt

**Preliminary**

- Low Energy e CandidateExcess

## Updates to Low Energy e Prediction

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

## Updates to Low Energy e Prediction

- Included photonuclear effect

- Arrows indicate whether effect is to increase or decrease the low energy data excess
- The effects have different magnitudes despite the arrows all being the same size

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

- Photonuclear absorption removes one of the gammas from a -induced NC 0  
- Photonuclear absorption was missing from our GEANT3 detector Monte Carlo
- Reduces size of excess

- Effect of photonuclear interactions

## Updates to Low Energy e Prediction

- Included photonuclear effect
- Absent from GEANT3 – creates background from 0s
- More comprehensive hadronic errors
- e.g. uncertainties in final state following photonuclear interaction

- Arrows indicate whether effect is to increase or decrease the low energy data excess
- The effects have different magnitudes despite the arrows all being the same size

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

## Updates to Low Energy e Prediction

- Included photonuclear effect
- Absent from GEANT3 – creates background from 0s
- More comprehensive hadronic errors
- e.g. uncertainties in final state following photonuclear interaction
- Better handling of beam + production uncertainties
- Errors propagated in model-independent way

- Arrows indicate whether effect is to increase or decrease the low energy data excess
- The effects have different magnitudes despite the arrows all being the same size

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

## Updates to Low Energy e Prediction

- Included photonuclear effect
- Absent from GEANT3 – creates background from 0s
- More comprehensive hadronic errors
- e.g. uncertainties in final state following photonuclear interaction
- Better handling of beam + production uncertainties
- Errors propagated in model-independent way
- Improved measurement of  induced 0s
- e.g. finer momentum binning

- Arrows indicate whether effect is to increase or decrease the low energy data excess
- The effects have different magnitudes despite the arrows all being the same size

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

## Updates to Low Energy e Prediction

- Included photonuclear effect
- Absent from GEANT3 – creates background from 0s
- More comprehensive hadronic errors
- e.g. uncertainties in final state following photonuclear interaction
- Better handling of beam + production uncertainties
- Errors propagated in model-independent way
- Improved measurement of  induced 0s
- e.g. finer momentum binning
- Incorporation of MiniBooNE 0 coherent/resonant measurement
- No longer need to rely on more uncertain past results

- Arrows indicate whether effect is to increase or decrease the low energy data excess
- The effects have different magnitudes despite the arrows all being the same size

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

## Updates to Low Energy e Prediction

- Included photonuclear effect
- Absent from GEANT3 – creates background from 0s
- More comprehensive hadronic errors
- e.g. uncertainties in final state following photonuclear interaction
- Better handling of beam + production uncertainties
- Errors propagated in model-independent way
- Improved measurement of  induced 0s
- e.g. finer momentum binning
- Incorporation of MiniBooNE 0 coherent/resonant measurement
- No longer need to rely on more uncertain past results
- Better handling of the radiative decay of the  resonance
- Comprehensive review of how the 0,+ radiative decay rate is inferred from the measured 0 rate

- Arrows indicate whether effect is to increase or decrease the low energy data excess
- The effects have different magnitudes despite the arrows all being the same size

- Nearing the end of a comprehensive review of the e appearance backgrounds and their uncertainties
- 	→ Not Quite Ready for Release Yet

## Updates to Low Energy e Cuts

- Add a new cut on “Distance to Wall backward” to reduce these.

- In low energy region there is a
- significant background from neutrino
- interactions in the dirt outside the tank

- Updates to Low Energy e Cuts

- Removing dirt events

## Removing Dirt Events

**MC upgrades and new cuts have no appreciable effect above 475 MeV**

- “Distance to Wall Backwards”
-  cut:-
-  Reduces dirt events by ~80%
-  Reduces  e  events by ~20%

- Plot has no dirt removal cuts

## NuMI Events in MiniBooNE

********: 81%   ******e**: 5%  ********: 13%  ******e**: 1%

- The beam at MiniBooNE from NuMI is significantly enhanced in e from K decay because of the 110 mrad off-axis position.
- MiniBooNE is 745m from NuMI target

**Work in collaboration with MINOS**

**MiniBooNE**

## 

- PRELIMINARY

- Good agreement between data and Monte Carlo:the MC is tuned well.

- Very different backgrounds
- compared to MB (Kaons vs Pions)
- Ongoing effort to reduce ******e** CCQE sample systematics
- 1.26 excess < 900 MeV

- PRELIMINARY

**NuMI ************ and ********e**** Data**

************
**CCQE**
**sample**

**********e**
**CCQE**
**sample**

- paper at draft stage

## MiniBooNE  Disappearance Sensitivity

- MiniBooNE  Disappearance Sensitivity

- MiniBooNE data 90% CL sensitivity (_NOT_ limit from data)
- CDHS   CCFR  90% CL
- Combined analysis with SciBooNE data will significantly improve this sensitivity

- Preliminary

## MiniBooNE Present and Future

- Taken ~6.6 x 1020 POT in neutrino mode
- Making suite of cross-section measurements
- Searching for various neutrino oscillations
- Publications coming out
- Taken ~2.5 x 1020 POT in anti-neutrino mode
- Making suite of cross-section measurements
- Searching for anti-neutrino disappearance
- In Nov 2007 request granted for extra running for an anti-nue appearance search
- LSND result was an indication of anti-nue appearance
- Extra ~2.5 x 1020 POT (making grand total of ~5 x 1020 POT)
- Should take FY2008 and FY2009 running

## Anti-nue Appearance Sensitivity

- Region allowed at 90% C.L.
- by joint analysis of
- LSND and KARMEN

**Only anti-neutrinos allowed to oscillate**

**Preliminary**

## Summary

- Electron Neutrino Appearance
- Combining Analyses
- Sets a tighter limit
- Compatibility of High m2 Measurements
- High m2 experiments compatible with 2v osc. at only 3.94% level
- Low Energy Electron Candidate Excess
- Full update coming this summer
- Data from NuMI Beam
- Sample complementary to MB flux, only small significance LE excess seen with current uncertainties
- Muon Neutrino Disappearance
- Result this summer
- Anti-Electron Neutrino Appearance
- Doubling current POT for result

## Backups

## CC +
2 papers expected 
CC 0
Reconstruction challenges overcome
1 paper expected
NC 0
1 paper submitted PLB
Coherent/resonant in nu and anti-nu modes
Flux averaged cross-section measurement
2 further papers expected
NC Elastic
Flux averaged cross-section measurement
1 paper expected
 -e Elastic
Nu mag. Mom
1 paper expected. 

- 2 papers expected
- CC 0
- Reconstruction challenges overcome
- 1 paper expected
- NC 0
- 1 paper submitted PLB
- Coherent/resonant in nu and anti-nu modes
- Flux averaged cross-section measurement
- 2 further papers expected
- NC Elastic
- Flux averaged cross-section measurement
- 1 paper expected
-  -e Elastic
- Nu mag. Mom
- 1 paper expected.

- Oscillation
- Refined Nue appearance
- Nuebar appearance
- Numu and numubar disappearance
- 1 PRL, ~3 further papers expected
- Low Energy Excess
- Big effort
- 2+ papers expected
- Alternative Oscillations
- Phenomenology
- CP violation, Lorentz violation, ...
- 3+ papers expected
- NuMI Events
- Large event rate from NuMI beam
- Check on osc. and Low E
- 1 paper being written
- CCQE
- 1 PRL, 2 further papers expected

- Broad Range of Analyses

**  ****No organizational separation between neutrino and anti-neutrino mode**
**  ****12 PhD Students + 6 graduated**

##  NC Elastic

- NC EL

- Results (from 10% nu sample):
-     - NC elastic diff. cross section
-      (per nucleon, n+p averaged, flux averaged)
-     - Flux Integrated Cross-Section
- 	= 8.8 ±0.6(stat) ±2.0(syst) x10-40 cm2
-     - Measured axial mass (NC)
- 	= 1.34 +0.38–0.25 GeV
- - work of Chris Cox, Indiana U., Ph.D. 2008
- - further analysis on full nu data set and with goal of
-   reducing systematic errors in progress
-   (D. Perevalov, Alabama)
- - eventual analysis goal:
-    NC/CCQE ratio measurement and antinu data

## Global Data Analysis

- Data provided as points on 2-D              m2 - sin22 grid
- Each pt = agreement between data & 2- hypothesis at that point
- Data in ln(L), ln (L), 2 grids
- Not able to obtain absolute 2 (goodness  of fit) from all experiments!
- Must use 2 grids in this analysis

## Two Methods

- Create 2 grids in 2 ways
- 2-D grid uses global best fit point to calculate the 2 at each point
- Prob to observe all expt results if nature has 2- osc in this entire m2 region
- 1-D (Raster Scan) uses local best fit point at each m2 to produce 2
- Compat at each m2, if nature truly had   2- osc at that specific m2

## Compatibility Calculation

- Construct a 2 grid for each expt.
- each pt = local value - best fit value
- Sum individual 2 grids
- Compatibility = 2 prob. of minimum of summed grid, using a reduced NDF
- (indep. ) - (# indep  estimated from data)
- ex : MB + LSND = 4 - 2 = 2 NDF

- Maltoni, Schwetz, Phys. Rev. D. 68, 033020 (2003)

## Allowed Region

- Each expt’s 2 grid converted into 2 prob grid using standard NDF (2, 1)
- Multiply 2 prob grids together, produce x
- Allowed regions = closed contours in space
- Exclusion bands = non-closed contours
- Values to R are excluded at a given CL

- Roe, Probability and Statistics in Experimental Physics, (2001)

## LSND, MB, Bugey,  KAR2

- 2.14% vs 3.94%!
- Best fit point = 0.242 eV2 , 0.023 sin22
- Including KARMEN2 increases the NDF used to calculate prob, but provides no increase in sensitivity!

**Notes:**
Allowed regions and compat with 3 expts, with 4 expts (25% vs 3%)

## Anomaly Mediated Background

- “Anomaly mediated neutrino-photon interactions at finite baryon density.”
- Standard Model process
-      Under active investigation, prediction of
-      ~140 (g/10)4 events, where  gis 10 to 30.
- Can use photon energy and angle to check prediction.(Harvey, Hill, and Hill, arXiv:0708.1281[hep-ph])