# Presentation: 739561

## MiniBooNESteve BriceFermilab

- Oscillation Analysis
- Issues of the Past Year
- Normalization
- Optical Model
-  0 MisIDs
- Summary
- Future

## MiniBooNE Goal

- Search for e appearance in a  beam at the ~0.3% level
- L=540 m ~10x LSND
- E~500 MeV ~10x LSND

## Particle ID

- Identify electrons (and thus candidate  e events) from characteristic hit topology
- Non-neutrino background easily removed

## Particle ID

- To achieve good sensitivity the Particle ID must
- Eliminate ~99.9% of all  CC interactions
- Eliminate ~99% of all NC 0 producing interactions
- Maintain good (~30-60%) efficiency for e interactions
- It achieves these goals
- Exploring parallel, complementary approaches
- “Simple” cuts: easy to understand
- Boosted decision trees: maximize sensitivity

## Backgrounds

- Makeup of the backgrounds is different for the two particle ID approaches
- Different balance between intrinsic e and misIDed 
- Important check that backgrounds are understood
- Backgrounds are determined from our own data using
-   CCQE events for intrinsic e from +
- Single 0 events for 0 misID
- High energy e events for intrinsic e from K+

## Determining Backgrounds with MiniBooNE Data

- Osc e
- Example oscillation signal
-  m2 = 1 eV2
- SIN22 = 0.004
- Fit for excess as a function of reconstructed e energy

- Full data sample ~5.3 x 1020 POT

## Determining Backgrounds with MiniBooNE Data

- MisID 
- of these......
- ~83% 0
- Only ~1% of 0s are misIDed
- Determined by clean 0 measurement
- ~7%  decay
- Use clean 0 measurement to estimate  production
- ~10% other
- Use  CCQE rate to normalize and MC for shape

- Full data sample ~5.3 x 1020 POT

## Determining Backgrounds with MiniBooNE Data

- e from 
- Measured with  CCQE sample
- Same parent + kinematics
- Most important background
- Very highly constrained (a few percent)

- Full data sample ~5.3 x 1020 POT

## Determining Backgrounds with MiniBooNE Data

- e from K+
- Use High energy e and  to normalize
- Use kaon production data for shape
- Need to subtract off misIDs

- Full data sample ~5.3 x 1020 POT

## Determining Backgrounds with MiniBooNE Data

- High energy e data
- Events below ~1.5 GeV still in closed box (blind analysis)

- Full data sample ~5.3 x 1020 POT

## Issues Of the Past Year

- Most of the analysis effort over the last year has gone into
- Normalization
- Optical Model
-  0 MisIDs
- Each is a significant hurdle that has been overcome

## Issues of the Past Year: Normalization

- The MiniBooNE Run Plan reported we were seeing ~1.5 times as many events as the Monte Carlo predicted
- For an inclusive  event sample
- This normalization difference is now ~1.2
- Major changes in rate prediction since Run Plan (not complete list) ...
- -3.5%	from better  cross-section modeling
- +17.5%	from better modeling of incoming proton beam
- +5.2%	from CCQE cross-section tuning (MA extraction)
- -6.0%	from better modeling of secondary beam interactions
- +16.2%	from HARP + measurement + horn current + better    			modeling of primary proton interactions
- After a huge amount of cross-checking the agreement between data and MC  rates is now far less of an issue

## Issues of the Past Year: Optical Model

- Two Key features of MiniBooNE
- Trying to do very precise particle ID to identify a possible ~0.3% signal
- Several calibration sources, but none with the perfect properties (e.g. no 1 GeV electron gun)
- The approach must therefore be...
- Use the available calibration sources (Michel electrons, laser, etc)
- Have a very well tuned MC to extrapolate from what the calibration sources look like to what the signal and background look like
- Therefore...
- Need an “optical model” that matches data very well
- Optical Model = model for how light is created, propagated, and detected in MiniBooNE

## Issues of the Past Year: Optical Model

- Stepwise approach to tuning the optical model

**External measurements &**
**laser calibration**

**First calibration**
**with michels**

**Calibration of scintillation**
**light with NC events**

**Final  calibration**
**with michels**

**Validation with **
**cosmic muons,**
********** ****events, and **
**NuMI ********e**** events**

## Issues of the Past Year: Optical Model

- Many variables are potentially useful in analyses
- Optical Model improvement measured by data/MC agreement in these  variables
- Huge gains in data/MC agreement

- Scintillation light
- from 1st gamma
- assuming a 0

- Nov05 MC
- May06 MC

## Issues of the Past Year: 0 MisIDs

- Issues of the Past Year: 0 MisIDs

- About 83% of all MisID background comes from single 0 events
- Use cleanly identified 0s to measure the 0 rate as a function of 0 momentum

- Need to get to high 0 momentum to enable measurement of high energy e background from K+
- Old  0 reconstruction could not do this
- Have developed a new 0 fitter that can go to high momentum and has better 0 efficiency and purity

## Issues of the Past Year: 0 MisIDs

- Issues of the Past Year: 0 MisIDs

- New 0 fitter can make 0 yield measurements up to the ~1.5 GeV level needed to get at the es from K+
- This is an ongoing analysis – not yet complete

## Summary

- Over the past year the major hurdles have been crossed
- Much more accurate prediction of rate – data/MC ~1.2
- Optical Model probably now good enough (more checks needed)
- Analysis for 0 misID measurement largely in place
- Still a lot of work to do – but the way forward is clear
- On track for a result as soon as this summer

## The Future

- Ran in anti-neutrino mode January 2006 to shutdown
- Will continue in anti-neutrino mode after shutdown
- First ever anti-neutrino measurements in this energy region
- SciBooNE experiment, at a near location in the beamline, will start in late 2006 (see SciBooNE talk)
- Possibility to build additional detectors closer or farther away (BooNE)
- MiniBooNE clone or new technology (e.g. LAr)
- MiniBooNE result will guide location
- ~2km detector for low m2
- ~0.2km detector for high m2

## Backups

## Neutrino Candidates

- DAQ triggered on beam from Booster
-   pulse through detector lasts 1.6 s
- By requiring tank activity and no veto activity the non-neutrino backgrounds become negligible

## proton->Be collisions at 8.9 GeV/c

- piplus cross section with full statistical plus systematic errors shown (except the 4% normalization error)

**0.75 < p******** < 6.5 GeV/c**
**30 < ************ < 210 mrad**

**Momentum and angular distribution of pions decaying to a ****neutrino that passes through the MB detector.**

**~76%**

## Low Q2 & MiniBooNE QE Model

-  perform shape fit to
-   MiniBooNE QE dN/dQ2
-    (~60,000 QE events after cuts)
-  fit for:
-    - Fermi Gas model pars (EB,pF)
-     - axial mass, MA
-     - and background fraction, BF
-  best shape fit yields
-   “effective parameters”:
-      - MA=1.24 GeV
-       - EB = 34 MeV
-       - pF = 246 MeV
-       - BF = 0.7

- (J. Monroe)

## Past  Data

-  not clear that past QE
-   neutrino data necessarily
-   rules out a larger value
-   for MA
-  example: BNL bubble
-   chamber data and d/dQ2
-   predictions with different
-   MA assumptions

## Checking Particle ID with NuMI Events

- Because of the off-axis angle, the beam at MiniBooNE from NuMI is significantly enhanced in es from K+
- Enables a powerful check on the Particle ID

## MiniBoonE results

- continued MB running:
- BNB-line data
- NuMI-line data

- SciBooNE
- information

- Improved MB signal:
- oscillation or decay?

- Follow-up Experiments

- BooNE (FNAL):
- LS and LAr
- detectors under
- consideration

- SNS
- (see APS
- Neutrino
- Study)

- JPARC
- (now
- under
- study)

- positive  result

- MiniBoonE 
- running
- (requires ~3+ years
- for CP Violation)

- signal in ?

- negative  result

- CP violation in...
- oscillation?
- decay?
- ... or something else?

- Follow-ups under
- consideration

- And in the
- future...