# Presentation: 793781

## Status Report on T2K Oscillation SensitivityJessica Dunmore, Dave Casper, Chris Regis (UCI)27 February 2005

## Oscillation Sensitivity Studies

- Goal is a realistic sensitivity study including
- Reconstructed observables
- Far and near detectors
- Statistical errors
- Systematic errors

- Systematic effects to include are:
**energy scale**
**fiducial volume**
**cross sections**
**incident flux**
- detector efficiency
- backgrounds

**Notes:**
At UCI, we have been developing a more sophisticated approach to study the effects of various systematic uncertainties on the sensitivity of the T2k experiment.

## Technique

- We have started with the simpler  disappearance experiment.
- Extension to appearance experiment should be straight-forward
- We use the SK/Fogli linearized “pull2” technique to include systematic errors
- G.L. Fogli *et al.*, Phys. Rev. **D 66**, 053010 (2002)
- Use the reconstructed E spectrum for1-ring, -like events in SK and 2km to fitfor (sin2 223, m223)
- Use GCALOR fluxes (JNUBEAM 40 GeV, 5-years)

## n is the number of observables (near + far)
k is the number of correlated systematic effects

*G. Fogli, et al., Phys. Rev D66, 053010 (2002)

*n* is the number of observables (near + far)
*k* is the number of correlated systematic effects
- *G. Fogli, *et al*., Phys. Rev D66, 053010 (2002)

**Notes:**
Extra xi term added for normalization.

## Comments on Pull Approach 2

- The *c**k**n* represent the change in the expected event rate of bin *n* due to a 1 change in the *k*th systematic.
- There is one *k* for each systematic *k*.  This assumes:
- each may be treated independently
- linearly varying effect on predicted rate in each bin
- Determine *k*’s by solving set of *k* linear equations.
- The 2 is then minimized over *R**n**pred*(m2, sin22,CP)

## Comments on Pull Approach 2

- The *c**k**n* represent the change in the expected event rate of bin *n* due to a 1 change in the *k*th systematic.
- There is one *k* for each systematic *k*.
- Determine *k*’s by solving set of *k* linear equations.
- The 2 is then minimized over *R**n**pred*(m2, sin22,CP)

## MC Samples

- Analysis requires predicting the reconstructed energy spectrum for:
- All points in oscillation parameter space
- All possible values of systematic parameters
- Use reconstructed 100-year SK atmospheric samples (from NUANCE) to extract:
- Ereconstructed vs. E transfer matrices
- Efficiencies for signal and background reactions
- Signal and background cross-sections per kton H2O

## Reconstructed Muon Energy Spectra

- Simulated reconstructed muon energy spectrum at SK
-  5 years of data,
-  22.5 kton fiducial volume
- 	no oscillation
- 	after oscillation
- 	    sin223=1.0
- 	    m223=0.0024
- 	with systematic errors
- 	     -3% energy	     -20% CCQE
- 	    +30% NC

- Reconstructed Energy (GeV)

## Results of pull 2 fit

- Fit:
- 2km near detector included
- (0.952, 2.37 x 10-3)
- 2=61.3 / 78
- CCQE = 0.49
- NC = 1.05

- Reconstructed Energy (GeV)

- (0.95, 2.4 x 10-3),

- For 200 experiments:

## Results of pull x2 fit

- m2

- sin22

## Dependence of Oscillation Sensitivity on Neutrino Cross Sections

- Only cross section uncertainty included

- NC uncertainty is double CC

## Outstanding Issues

- Include flux uncertainties
- Add other near detectors
- 280m detector has not yet been included
- Need to make assumptions about performance
- Perform appearance experiment

## Conclusions

- The technique appears to work, but it is crucial to include the uncertainty on the flux.
- Still working on finding a good way to do this.
- Cannot make conclusions about how uncertainties on the neutrino cross sections affect the oscillation sensitivity without flux uncertainty included.

## Correlated Systematic Uncertainties

## Reconstructed Energy

- Event rate,
- bin *n*
- detector *i*

- “Transfer” matrix:
- E, true  E, recon

- Cross-section of
- interaction *j*,
- energy bin *m*

- Efficiency of detector *i* for
- interaction *j*,
- energy bin *m*

- Neutrino flux in
- detector *i*,
- interaction *j*,
- energy bin *m*

- Mass of detector *i*

- Sum over interaction types

## A Simple Example

-  disappearance with 3% energy scale shift at SK
- just one of many uncertainties
- Fit the data using
- no systematic correction term
- varying energy scale allowed in the fit

- (After 5 yrs. data)

- Number of events / 50 MeV

- Reconstructed  Energy (GeV)

## Results of 2 Fit

-   2.58
- x10-3
- 2.54
- 2.50
- 2.46

-   2.58
- x10-3
- 2.54
- 2.50
- 2.46

- 0.99                   0.995                  1.0

- 0.99                   0.995                  1.0

- No systematic uncertainties included.

- “True” value

- Energy scale systematic included in 2 minimization.

- 1.5% bias

- 99% 95%  90% CL

- 99% 95%  90% CL

- Very Preliminary

- Very Preliminary

## Effect of Cross Section Uncertainties on Oscillation Parameter Errors

**    ****0      4       8     12    16    20    24    28    32**

- Uncertainty on NC (%)

- There is no uncertainty on the flux included.