# Presentation: 303603

## MiniBooNE Update andExtension Request

- Richard Van de Water and Steve Brice
- for the MiniBooNE Collaboration
- Nov 2, 2007

## Overview

- Brief reminder of oscillation result
- Update on low energy excess
- Sampling of other analyses
- Run request for an electron anti-neutrino appearance search

***“******MiniBooNE requests an additional 3.0 x 10******20****** POT in anti-neutrino mode to give the experiment a total of ~5.0 x 10******20****** POT in this configuration and enable a powerful check of the LSND result in anti-neutrinos. The experiment further requests that these POT be delivered in FY2008 and FY2009.”***

## oscillation analysis: 

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

- oscillation analysis:
- Results in April 2007

- No evidence for e appearance
- in the analysis region

- However, at low energy

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

## Status of Low Energy e Candidate Analysis Since Oscillation Publication

- Have observed a ~4 sigma excess down to 200 MeV (including systematic errors).
- Confirmed excess is electromagnetic (electron or gamma-ray), i.e. particle ID is working at low energy. MiniBooNE has no ability to distinguish gammas from electrons
- Events have normal reconstruction, e.g. Visible energy, radius, x,y,z, beam angle, etc.
- Major sources of backgrounds all look well modelled, e.g. dirt, radiative delta decay, mis-ID pions and muons.
- Working on possible new sources of single gamma-rays.
- Currently analyzing neutrinos from NuMI source, horn-off, and anti-neutrino data sets.

## Examination of backgrounds

- _Examination of backgrounds_

-                              _ __reconstructed neutrino energy bin (MeV)_
- _                               __200-300           300-475       475-1250       _
- total background    284±25            274±21            358±35
- eintrinsic                   26                    67                  229
- _____ __induced                258                  207                 129         _
-       NC 0                                   115                   76                    62
-       NC →N20                   51                    20
-       Dirt                         99                   50                    17
- _      __other                      24                   30                    30   _
- _data                           375__±__19           369__±__19            380__±__19   _

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

- New 200-300 MeV bin

**Preliminary**

## Checking Known e Backgrounds 

- Measure 0 production rate as a function of 0 momentum and compare to MC prediction to calculate a correction factor. Correct NC  mis-ID rate using this measured correction factor
- (Also can be used to correct the  N +  radiative background)
- Dirt background is due to  interactions  outside detector creating neutrals that enter tank
- Measured in “dirt-enhanced” samples:
- Before box-opening meas/pred =  1.00±0.15
- After box opening (bigger sample)  meas/pred = 1.080.12
- Backgrounds with a muon measured using events with cleanly time separated electron from muon decay
- Includes any background from muon internal bremsstrahlung
- Paper on this work: arXiv:0710.3897  [hep-ex] Submitted to PRD

**visible energy (GeV)**

**dist to tank wall along track (cm)**

## Possible Sources of Additional Single Gamma Backgrounds

**Possible Sources of Additional Single Gamma Backgrounds**

- Processes that remove/absorb one of the gammas from a -induced NC 0  
- Photonuclear absorption was missing from our GEANT3 detector Monte Carlo
- But tends to give extra final state particles.
- Reduces size of excess
- Systematics being calculated
- No effect above 475 MeV

-  processes that produce a final state single gamma
- Example: “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 to check prediction.(Harvey, Hill, and Hill, arXiv:0708.1281[hep-ph])

***    ***Since MiniBooNE cannot tell an electron from a single gamma, any process that leads to a single gamma in the final state can be a background

**200<En<300 Photonuc adds ~27% of excess**
**300<En<475 Photonuc adds ~13% of excess**

**Stat error only**

**Preliminary**

## NuMI Events in MiniBooNE

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

**D**e**cay Pipe**

**Beam Absorber**

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

****

**MINOS near**

**NuMI Events in MiniBooNE**

- MiniBooNE

**Work in collaboration with MINOS**

## NuMI  and e Samples

-   **Charged Current Quasi Elastic Sample**

-  e **Charged Current Quasi Elastic Sample**

- Results to be presented at an
- Upcoming Wine and Cheese seminar

## CC +
2 papers expected 
CC 0
Reconstruction challenges overcome
1 paper expected
NC 0
1 paper about to be submitted to PRD
Coherent/resonant in nu and anti-nu modes
Flux averaged cross-section measurement
2 further papers expected
NC Elastic
About to graduate
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 about to be submitted to PRD
- Coherent/resonant in nu and anti-nu modes
- Flux averaged cross-section measurement
- 2 further papers expected
- NC Elastic
- About to graduate
- 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 paper submitted to PRL
- 2 further papers expected

**Broad Range of Analyses**

**  ****Collaboration spent last 2 years sole focused on**** ********e**** ****appearance analysis**
**  ****Collaboration retasked over last 5 months to broad range of analyses**
**  ****No organizational separation between neutrino and anti-neutrino mode**
**  ****15 PhD Students + 4 graduated**

## CCQE Events

-  Excellent description of CCQE reaction has been obtained after adjustment of 2 Fermi-gas-model parameters:
-  From Q2 (4-mom. transfer) fits to  CCQE data:
- 	MAeff -- Effective axial mass
-   -- Pauli blocking param
-  Paper on this work: arXiv:0706.0926 [hep-ex], submitted to PRL

-  CCQE Q2  distribution

-  CCQE E  distribution

**CCQE Events**

## Wrong Sign Extraction

- Critical to extract neutrino flux in anti-neutrino mode from data and not rely entirely on MC
- Use angular distribution of muons from CCQE interaction
- All anti-nu analyses depend on this work

- Neutrino Mode
- MC Prediction:
- WS-QE:	~2%
- RS-QE:	~75%
- Non-QE:	~23%

- Anti-Neutrino Mode
- MC Prediction:
- WS-QE:	~20%
- RS-QE:	~50%
- Non-QE:	~30%

**Stat errors only**

## NC 0 in Anti-Neutrino Mode 

- Coherent contribution evident

**E********(1-COS************) (MeV)**

**M******** (MeV)**

**Statistical errors only**
**No fit, just out-of-the-box Monte Carlo**

**This is the worlds only anti-neutrino NC ********0**** sample below 2 GeV**

## MiniBooNE Present and Future

- Taken 5.58 x 1020 POT in neutrino mode
- Making suite of cross-section measurements
- Also searching for neutrino disappearance
- Publications already coming out
- No need to request more neutrino mode running
- Taken 2.33 x 1020 POT in anti-neutrino mode
- Making suite of cross-section measurements
- Searching for anti-neutrino disappearance
- PAC request for extra running for an anti-nue appearance search
- LSND result was an indication of anti-nue appearance
- CP violating models (e.g. “3+N”) predict no MB signal in neutrino mode, but LSND style signal in anti-neutrino mode
- Extra 3 x 1020 POT (making grand total of ~5 x 1020 POT)
- Should take FY2008 and FY2009 running

## Calculating anti-e Appearance Sensitivity

- Two key features of neutrino mode oscillation result:
- Backgrounds measured or constrained by MiniBooNE data
- Systematics estimated by assessing uncertainty in all relevant low level quantities (e.g. pion production, detector optical model, etc) and propagating these to an error matrix on the final histogram.
- This approach carries over directly to an anti-e measurement
- i.e. the vast majority of the work has already been done
- Just need to turn the crank on the anti-neutrino MC and propagate error matrices to produce complete anti-e sensitivity
- Full set of low level systematics has already been assessed
- The major differences from neutrino mode analysis are handled automatically
- For example: larger wrong sign background in e and  samples

## Anti-nue Appearance Sensitivity

**Anti-nue Appearance Sensitivity**

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

**Only anti-neutrinos allowed to oscillate**

## Conclusion and Request

- MiniBooNE is bringing out a wide range of important results in neutrino and anti-neutrino oscillation and cross-section physics.
*“**MiniBooNE requests an additional 3.0 x 10**20** POT in anti-neutrino mode to give the experiment a total of ~5.0 x 10**20** POT in this configuration and enable a powerful check of the LSND result in anti-neutrinos. The experiment further requests that these POT be delivered in FY2008 and FY2009.”*

## BackUp Slides

## Anti-Neutrino Low Energy Excess Scenarios

- Predictions for the excess of nue(bar) candidate events in anti-neutrino mode under 3 scenarios:-
- The excess is due to nue CC interactions
- The excess is due to a mis-estimation of the numu NC D rate
- The excess is due to some other NC process whose cross-section is the same for neutrinos and anti-neutrinos
- With 5.0 x 10 20  POT in anti-neutrino mode the excesses in these scenarios are not significantly different from each other
- Alternatively if one naively scales the neutrino mode excess down by the ratio of anti-neutrino mode to neutrino mode backgrounds then one predicts an excess of 67±16.7(sys)±16.4(stat) for 5.0 x 1020 POT.

## CP Violating Models

- Adding two (or more) sterile neutrinos brings a CP violating phase (45) into the mixing matrix
- Fits of such models to world data allow the possibility for MiniBooNE to see no signal in neutrino mode, but a visible signal in anti-neutrino mode

## Particle Identification  

- No major discrepancy in Particle Identification

## NC 0 and Radiative N Backgroundsare Constrained by Identified NC 0 Events

- Using PID variables isolate a very pure sample 0 events from  N   N + 0 (mainly from  N + 0 )
- Purity ~90% or greater
- Measure 0 production rate as a function of 0 momentum and compare to MC prediction to calculate a correction factor.
- Correct NC  mis-ID rate using this measured correction factor(Also can be used to correct the  N +  radiative background)

- M Mass Distribution for Various p0 Momentum Bins

## “Dirt” background

- - Dirt background is due to  interactions
-   outside detector creating neutrals that enter tank
- - **Measured** in “dirt-enhanced” samples:
- 	- before box-opening, fit predicted:  1.00±0.15
- 	- in different (open) sample, a fit says that meas/pred is 1.080.12.
- - Shape of visible E and distance-to-wall  distributions   are well-described by MC

- results from dirt-enhanced fits

**visible energy (GeV)**

**dist to tank wall along track (cm)**

- 76% 0  

## Muon Misidentification(including muon internal bremsstrahlung) 

**Muon Misidentification****(including muon internal bremsstrahlung) **

- Data-MC excess, but note the scale!

- Apply reconstruction and particle
- identification to clean sample muon
- CCQE events (muon decay visible).
- Then scale normalization to account for
- how often the second subevent is missing
- What results is a direct measurement and MC
- prediction for almost all the rate at which events
- with a final state muon enter the e background

- -Misidentified Muons not a problem.

- Paper on this work:
- arXiv:0710.3897  [hep-ex]
- Submitted to PRD

## Detector Anomalies or Reconstruction Problems

**Detector Anomalies or Reconstruction Problems**

- No Detector anomalies found
- - Example: rate of electron candidate events is
-   constant (within errors) over course of run

- No Reconstruction problems found
- - All low-E electron candidate events have   been examined via event displays,   consistent with 1-ring events

***Signal candidate events are consistent with single-ring neutrino interactions******        ************  But could be either electrons or photons***

## energy/angle distributions in E bins

- 200< E<300 MeV

- 300 <E<475 MeV

- 475 <E<3000 MeV

- 200< E<300 MeV

- 300< E<475 MeV

- 475< E<3000 MeV

- At higher energy, data are well-described by
- predicted background

- Excess distributed among visible E, cos bins

- visible energy distributions:

- cos distributions:

## Other DistributionsUZ, Radius, RtoWall, etc.

- => Events distributed throughout tank, no indication of edge effects.

## Logistics

- Survey of collaborating institutions on ability to staff shifts in new two years
- Recent past: 54 FTE
- FY2008: 44 FTE
- FY2009: 37 FTE
- FY2008 shared with SciBooNE so filling shifts should not be an issue
- FY2009 will need to increase people’s shift quota and perhaps take measures like pager shifts for overnight

## Sensitivity Over LSND Only Regions

- Regions allowed at 90% C.L.
- And 95% C.L. by LSND alone

## Effect of Statistics and Systematics

**Effect of Statistics and Systematics**

- Regions allowed at 90% C.L.
- And 95% C.L. by LSND alone