# Presentation: 704314

## MiniBooNE Low Energy Analysis 

**H. Ray**
*Los Alamos National Laboratory*

## Oscillation Fit Reporting

- The final fit for  e oscillations was performed using 2 different analyses
- Track Based : EQE 475 MeV to 3 GeV
- Boosting : EQE 300 MeV to 3 GeV
- Increased from 300 MeV due to 2 fit of 1% in Evis variable during 1st step of  unblinding process

- H. Ray

## Oscillation Fit Reporting

- We felt that we had checked everything to our full ability, and to our best knowledge could not further constrain processes in the low E region
- MC studies of potential LSND oscillation signals  indicated we could tighten the E requirement with a negligible loss in sensitivity
- Prior to unblinding, we agreed to also examine events with EQE > 300 MeV in the Track Based analysis

- H. Ray

**Notes:**
We stand behind our systematic error estimates
Say in words : WE USE OUR OWN DATA TO UNDERSTAND WHATs GOING ON
while we were looking at this we DID NOT KNOW IF THERE WAS AN EXCESS OR DEFICIT

## Observed Event Distribution

- H. Ray

## Observed Event Distribution

- Counting Expt :
- 300 MeV < EQE< 1.250 GeV
- 749 observed evts
- 631 ± 25 ± 45 expected events
**Excess over background : ****2.3******

**Background-subtracted**

**475 MeV to 3 GeV**

- H. Ray

## Observed Event Distribution

**Background-subtracted**

**475 MeV to 3 GeV**

- H. Ray

## Observed Event Distribution

**Background-subtracted**

- Best Fit (sin22, m2) = (1.0, 0.03 eV2)

**300 MeV to 3 GeV**

- Only 4% Compatible w/LSND

- 2 Probability: 18%, Null Hypothesis= 3%

- H. Ray

## What are the Low-E Events?

- These low Energy events could be _*many *_things
- We saw these events for the first time on Monday, March 26th (2007)
- The following presents our very preliminary investigations to date

- H. Ray

## Fit Energy Event Composition

- Boost Analysis
- 300 MeV  to 3 GeV

- Likelihood Analysis
- 475 MeV  to 3 GeV

- intrinsic e
-  mis-id

- H. Ray

**Notes:**
Put in color box rosetta stone

Boost vs likelihood 
Dirt + ccqe + other numu = 578 + 492 + 126 vs + 17 + 24 + 15
Pi0 = 1096 vs 84
Delta = 135 vs 19
Kp = 334 vs 121
K0 = 86 vs 28
Mup  = 413 vs 160
Pip = other nue = 12 vs 5

## Low Energy Event Composition

- Boost Analysis
- 300 MeV  to 475 MeV

- Likelihood Analysis
- 300 MeV  to 475 MeV

- intrinsic e
-  mis-id

- H. Ray

**Notes:**
Need good words - why is this interesting?
Add rosetta stones
84% dirt in Boost other
Boost vs likelihood 
Dirt + ccqe + other numu = 61 + 9 + 3 vs + 50 + 12 + 4 + 13
Pi0 = 72 vs 76
Delta = 50  vs 51
Kp = 19  vs 14
K0 = 5 vs 4
Mup  = 52 vs 48
Pip = other nue = 0 vs 1 

## Fundamental Information

**Shutdowns**

- Low E events show no bias in
- event time

**369 events **

**369 events **

- Not normalized to POT

- H. Ray

## Cosmic Rays

**Measured from our strobe data**

- Cosmic events populate
- upper region of tank

- Low E events show no bias in
- Y (vertical) position

**2 expected evts in osc. analysis**

**369 events **

- H. Ray

## Radiative Delta and NC0

**Constrain our NC********0 ****production rate using data from our detector**
- Reduces error on mis-id 0 (<2%!)

- This also constrains the radiative  resonance rate, thus constraining rate of  N 

- H. Ray

**Notes:**
Say radiative delta to match more closely to what Eric says
Spend less time on this - just reference Eric

## What we know so far

- Low E events pass EM Particle ID
- Gamma or electron
- The evts do not appear to be biased in run range or event time
- The evts do not appear to be due to cosmic ray background
- Radiative Delta : unlikely = need x3 increase
- NC0 : unlikely = measure very well with our data

- H. Ray

## Summary

- A two-neutrino appearance only model systematically disagrees with the shape of the excess as a function of E
- Need to investigate non-oscillation explanations of the low E excess
- Investigation of these low E events is underway

- H. Ray

## Final Results

- Any conclusions drawn about the low E events will have no effect on our oscillation result

- H. Ray