# Presentation: 262518

## Sterile Neutrino Oscillations and CP-Violation Implications for MiniBooNE				NuFact’07Okayama, Japan

**Georgia Karagiorgi, Columbia University**
**August 10, 2007**

## Outline

- Sterile neutrino oscillation formalism
- Oscillation analysis
- Constraints from MiniBooNE result
- Preliminary oscillation analysis results
- CPV Implications and Future Studies at MiniBooNE

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Sterile Neutrino Oscillation Formalism

- νe
- νμ
- ντ
- νs

_***3 active + ***__***n***__*** sterile neutrinos:***_*** ***
***light**** *sterile neutrinos
-  they don’t interact thru standard weak couplings
-  they have very small active flavor content (*U**e4**,** **U**μ4**, ..., U**en**, U**μ**n*)
- 	 can participate in neutrino oscillations

-  ***For example, for 2 sterile neutrinos (3+2):***

***Oscillation:***
***Disappearance:***

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Oscillation Analysis

- be constrained by **short-baseline experiments** (sensitive to *high **Δ**m**2*)
- We are interested in:
**constraining the oscillation parameters** by a combined analysis of SBL data
- studying the **compatibility **of null SBL results with LSND and MiniBooNE results in a 3 active
- 	+ *n* sterile neutrino hypothesis

| 
Channel | 
Experiment | 

    Lowest  
Reach (90%CL) | 

    High | 

 Optimal |
| --- | --- | --- | --- | --- |
|  | LSNDKARMENNOMADMiniBooNE | 3x10-26x10-24x10-12.5x10-2 | > 2.5x10-3< 1.7x10-3< 1.4x10-3 | > 1.2x10-3< 1.0x10-3 < 1.0x10-3 |
|  | BugeyChooz | 1x10-2
7x10-4 | < 1.4x10-1< 1.0x10-1 | < 1.3x10-2 < 5x10-2 |
|  | CCFR84CDHS | 6x100
3x10-1 | nonenone | < 2x10-1 < 5.3x10-1 |

**          ****constraint (90%CL)**

**Oscillation Analysis**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Oscillation Analysis

**Using data from short baseline experiments:**
- Start with           *unoscillated* signal predictions from:
- Generate model parameters (importance sampling via *Markov chain*)
- For each set of parameters,
- get signal prediction after oscillation/disappearance for all experiments considered
- compare signal prediction to experimental data and calculate *   ,* goodness-of-fit for each experiment considered, and combined *   *, goodness-of-fit
- determine allowed regions by Gaussian approx.

_**Dataset:**_** LSND, KARMEN, NOMAD, MB, CCFR, CDHS, CHOOZ, BUGEY (+ atm constraint)**
- _# of bins:_     5            9             30           8      18        15          14           60               (1)

**appearance experiments**

**disappearance experiments**

*Model acceptance probability:*
* *

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Oscillation Analysis

- 	Approximation:* m**1** **≈** m**2** **≈** m**3** **≈** 0 *
*	**	**** **n *independent mass splittings*: *
*	**	**    **2n *moduli of mixing parameters*: U**e4**, U**μ**4**, ...*
*	**	**    **n-1 *Dirac CPV phases
*	**0.1eV**2** ≤       **     **≤ 100eV**2** *(motivated by LSND signal)
*	**                                                       *(imposed by atm and solar data)
*	*Atmospheric constraint:
- 		upper limit:
- 	CP violation option:* *
*	**        **Fix             , or allow to vary within  *

***3+n***** model parameter assumptions:**
**	****	**

**For example, for 3+2 oscillations:**
- 2 indep. mass splittings:** ***** ***
- 4 moduli:** ****      **
**1 CPV phase**:
***No CPV allowed for 3+1 models! ***

*[M. Maltoni, et al., hep-ph/0405172]*

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Constraints from MiniBooNE

**Recent MiniBooNE result** implies
- that MiniBooNE is **incompatible**
- with LSND within **2-neutrino**
**oscillation hypothesis**.
- 		*[see talk by C. Polly]*
***Calls for more complicated ***
***oscillation scenario ***
***(e.g., ******3+2, CPV******, ...)***
***in order to reconcile the ***
***two results.***
***Interested in “low-E excess” and ***
***implications for 3+******n****** ************ We consider ***
***the full energy range data ***
***(300 MeV < E < 3000 MeV) in ***
***our analysis. ***

*“**A Search for Electron Neutrino Appearance at the **Δ**m**2 **~ 1eV**2** Scale,” The MiniBooNE Collaboration [hep-ex/0704.1500].*

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## MiniBooNE Dataset

**    ****Allow both:****	*****            ******	*****	****(*****               *****oscillations) **
** **
**                ****and:****	***** ****** ******	*****	*****(******   ****** ******  disappearance) ***
***	******	******	******	******(******    ******  background disappearance)****** ***
- Use a** ratio **method:
- Compare: 	          **ratio** from **MC prediction** (first principles) after applying 		*             * oscillation,  *   * disappearance,  *    *disappearance
-             to:		***          ***** ratio** from **data **
**MC prediction** =
*  *
*n**bins**BooNE** = 8,           ndf**BooNE** = n**bins**BooNE** – 2n**sterile** –** **2n**sterile** ****– (n******sterile******-1)***

*intrinsic          ~0.5% of beam*

*full MiniBooNE error matrix (scaled to MC prediction)*
*	**	**[see talk by K. Mahn]*

*CPV case*

*         **with       energy spectrum*
*(full **ν**μ****ν**e** conversion;*
*takes into account different cross sections)*

**NEW!!!**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Preliminary Oscillation Results: 3+1

**Preliminary Oscillation Results: 3+1**

- 3+1 already excluded from previous studies (independent of MiniBooNE result)
- MiniBooNE ***         ***** ****    oscillation** upper limits in 3+1 scenario:

***90% CL excluded regions***
***Single-sided raster scan, 2 dof***

- 1

- 1

- 1

*[See, e.g.: M. Sorel, et al., hep-ph/0305255*
*and talk by T. Schwetz] *

**P r e l i m i n a r y**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Preliminary Oscillation Results: 3+1

**Preliminary Oscillation Results: 3+1**

- 3+1 already excluded from previous studies (independent of MiniBooNE result)
- MiniBooNE ***             ***** ****oscillation** upper limits in 3+1 scenario:

***90% CL excluded regions***
***Single-sided raster scan, 2 dof***

*[See, e.g.: M. Sorel, et al., hep-ph/0305255*
*and talk by T. Schwetz] *

**P r e l i m i n a r y**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Preliminary Oscillation Results: 3+1

**Preliminary Oscillation Results: 3+1**

- 3+1 already excluded from previous studies (independent of MiniBooNE result)
- MiniBooNE ***    ***** ****disappearance** upper limits in 3+1 scenario:

***90% CL excluded regions***
***Single-sided raster scan, 2 dof***

- 1

- 1

- 0

- 0

*[See, e.g.: M. Sorel, et al., hep-ph/0305255] *

**P r e l i m i n a r y**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Preliminary Oscillation Results: 3+1

**Preliminary Oscillation Results: 3+1**

- 3+1 already excluded from previous studies (independent of MiniBooNE result)
- MiniBooNE ***    ***** ****disappearance** upper limits in 3+1 scenario:

***90% CL excluded regions***
***Single-sided raster scan, 2 dof***

- 0

- 0

- 1

*[See, e.g.: M. Sorel, et al., hep-ph/0305255] *

**P r e l i m i n a r y**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Preliminary Oscillation Results: 3+2

- For comparison, we show 2 analyses:
- MiniBooNE data with ***             *****oscillations only**
- MiniBooNE data with *          *   oscillations **and** ***   ***** ****and **
**	****disappearance**
- In both cases we show results from fits with:
- 	Appearance only experiments
- 	All experiments combined

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Preliminary Oscillation Results: 3+2 Allowing Only                Oscillations in MiniBooNE Data

**Preliminary Oscillation Results: 3+2**** **Allowing Only**                Oscillations **in MiniBooNE Data

**Appearance-only** experiments: KARMEN, MB, LSND, NOMAD
- CPC
- CPV

**90%CL ****99%CL**

**P r e l i m i n a r y**

**P r e l i m i n a r y**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Appearance-only experiments: KARMEN, MB, LSND, NOMAD
CPC

CPV

- CPC
- CPV

**90%CL ****99%CL**

**Preliminary Oscillation Results: 3+2**Allowing  **      and     **** ****  Disappearance Also**

**P r e l i m i n a r y**

**P r e l i m i n a r y**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Combined analysis: all experiments
CPC

CPV

**Combined **analysis: all experiments
- CPC
- CPV

**90%CL ****99%CL**

**P r e l i m i n a r y**

**P r e l i m i n a r y**

**Preliminary Oscillation Results: 3+2**** **Allowing Only**                Oscillations **in MiniBooNE Data

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Combined analysis: all experiments
CPC

CPV

- CPC
- CPV

**90%CL ****99%CL**

**P r e l i m i n a r y**

**P r e l i m i n a r y**

**Preliminary Oscillation Results: 3+2**Allowing  **      and     **** ****  Disappearance Also**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## There are allowed 3+2 regions

Allowing       and       disappearance along with               oscillations to describe MiniBooNE data does not seem to either favor or disfavor combined fits, compared to only allowing    

There is no preference for CPC vs. CPV scheme
Best fit models:
CPC combined analysis:

CPV combined analysis:

- Allowing *  *    and *   *   disappearance along with *           *   oscillations to describe MiniBooNE data does not seem to either favor or disfavor combined fits, compared to only allowing *   *
- There is no preference for CPC vs. CPV scheme
- Best fit models:
- CPC combined analysis:
- CPV combined analysis:

**General Remarks for 3+2**

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## CP-Violation: Implications for MiniBooNE

**90%CL ****99%CL**

- Allowed MiniBooNE **oscillation probability asymmetry **within 3+2 oscillation scenario:

- Allowed region obtained using
- constraints from null SBL
- + LSND experiments only

- MC predicted
- MiniBooNE
- full-osc rates

*[G. K. et al., hep-ph/0609177].*

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## CP-Violation: Implications for MiniBooNE

**90%CL ****99%CL**

- MiniBooNE asymmetry predicted based on
- 3+2 best fit model
- for CPV combined
- analysis:

**Asymmetry significance ~ 1**
*assuming 6x10**20** POT** **in *
*both neutrino and antineutrino*
*running mode*
*(data collected as of now: *
* **neutrino** ** mode: **7.0**x10**20 **POT*
* **antineutrino mode: 2.**4**x10**20** POT)*

- Georgia Karagiorgi, Columbia U.

- NuFact'07

## Conclusions

- Both CPC and CPV 3+2 oscillation scenarios are allowed by a combined analysis of SBL data, including LSND and MiniBooNE
- MiniBooNE provides strong limits on *          *    oscillations and limits on *   * and *    * disappearance within a 3+1 hypothesis
- MiniBooNE data: important in addressing the viability of sterile neutrino models
- Leptonic CP-violation possibility opened up in the 3+2 sterile neutrino hypothesis could have measurable effects at MiniBooNE
- A longer running in anti-neutrino mode would allow more detailed studies of CPV scenario and more confident determination of a possible CPV phase

- Georgia Karagiorgi, Columbia U.

- NuFact'07