# Presentation: 661885

## A Discussion of the MiniBooNE Result

- Ray Stefanski
- Fermilab
- May 25, 2007
- XIX Recontres De Blois

## LSND gave clear evidence for oscillations;
A 3.8  signal at m2 ~ 0.6 eV2 ; sin2(2) ~0.001
Solar, atmospheric and reactor experiments have established at least two massive neutrino families
At least one sterile neutrino is required to accommodate LSND.
We use the nomenclature (3+N), N=no. sterile  
BBM & SSL set severe limits for N>0.

- LSND gave clear evidence for oscillations;
- A 3.8  signal at m2 ~ 0.6 eV2 ; sin2(2) ~0.001
- Solar, atmospheric and reactor experiments have established at least two massive neutrino families
- At least one sterile neutrino is required to accommodate LSND.
- We use the nomenclature (3+N), N=no. sterile 
- BBM & SSL set severe limits for N>0.

- Liquid Scintillator Neutrino Detector

- LSND; sterile neutrinos; Astrophysics and Cosmology.

- MiniBooNE

*Introductory remarks:*

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- Solar, atmospheric and reactor experiments establish the existence
- of neutrino oscillations and the neutrino mass.
- The 3 lepton families of the standard model fit the data very well:

- Unknowns:
-  Mass heirarchy
-  Absolute mass (KATRIN)
-     BBM; LSS; Weak Lensing
-  Dirac or Majorana
- 	(less2 decay)

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## LSND was an accurate measurement

- Similar in technique to Reines & Cowen
- A source of stopping  ‘s rather than a reactor
-  Energy spectrum of all decay products well known
- 2.2 MeV  from neutron capture rejects e

*Introductory remarks:*

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## Beam-related 

- Beam-related
- backgrounds

**Expectation for **
**oscillations **
**(********m****2****=0.24 eV****2****)**

- Excess after
- Beam-off
- subtraction

- It will be apparent that a confirming measurement is desirable.

*Introductory remarks:*

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## Short baseline (SBL) experiments set limits on (3+N) models.

*Introductory remarks:*

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##   (3+1) schemes cannot accommodate existing measurements. 

-   (3+2) schemes are still viable.
-   CPT non-conservation can apply to any (3+N) scheme.

- CPT conserved

- CPT conserved

**Also, inverted**
**hierarchy**

*Introductory remarks:*

- We can use (3+1) as an example:

- Sterile neutrinos

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## Implications for Cosmology

- (3+2) processes		Sorel, Conrad, & Shaevitz (hep-ph/0305255)
- (3+2) psudo- dirac  		Stephensen, Goldman, McKellar, & Garbutt (hep-ph/0404015)
- CPT Violation & (3+1) 	Barger, Marfatia, & Whisnant (hep-ph/0308299)
- Dark Matter		Hung (hep-ph/0010126)
- Dark Energy		Kaplan, Nelson, & Weiner (hep-ph/0401099)
- Mass Varying Nuetrinos	Falton, Nelson & Weiner; Astropart. Phys. 10 (2004) 005
- r-Process in Supernovae	Peres & Smirnov (hep-ph/0011454)
- E6 & baryon asymmetry	Ma & Raidal; 2002 *J. Phys. G: Nucl. Part. Phys.* **28** 95-101
- Leptogenesis		Chu & Cirelli Astro-ph/0608206
- Analysis that includes the MB result:
- (3+2) Sterile Neutrinos 	Maltoni & Schwertz [hep-ph] 0705.01076
- Analyses that predict a low-energy excess:
- Extra Dimensions & (3+1) 	Pas, Pakvasa, & Weiler (hep-ph/0504096)
- Sterile Neutrino Decay 	Palomares, Ruiz, Pascoli, & Schwetz (hep-ph/0505216)
- Lorentz Violation 		Katori, Kostelecky, Tayloe;  PRD 74, 105009 (2006)

*Implications for Cosmology*

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## Implications for Cosmology

- “Sterile neutrinos, lepton asymmetries, primordial elements:
- how much of each?”  YiZen Chu & Marco Cirelli Astro-ph/0608206

- Regions below and to the left
- of the thin lines are allowed
- by BBN because they
- correspond to an upper bound
- on 4He abundance Yp <0.258.

- Regions below and to the left
- of the thick lines are allowed
- by LSS because they correspond
- to a bound on neutrino mass
- represented by h2< 0.8X10-2,
- where is the mass-energy density
- attributed to neutrinos, and
-  h = H0/(100 km/s Mpc).

- (3+1) excluded region
- From results of SBL and
- atmospheric experiments.
- Strumia: hep-ph/0201134

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## Supernova, sterile neutrinos and the r-process.

*Implications for Cosmology*

- mass eigenstates

- flavor states

- s – e resonance

-                           Level crossing diagram for the
-                           (3+1) scheme with normal mass
-                           hierarchy in supernova

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## MiniBooNE compared to LSND

*MiniBooNE*

**MiniBooNE compared to LSND**

| Estimated Signal 0.26 oscillation: |  |
| --- | --- |
| > en >e- +p                             ~ 163 |  |
| Estimated Backgrounds |  |
| Mis-identified interactions | 110 |
| e like from surrounding material | 20 |
| Beam intrinsic e | 225 |
| Total estimated background | 355 |

- Cherenkov light generated by a  and the
- subsequent decayed e provide a signature
- for  _CCQE_ events.

**p**

****

**n**

**(Scintillation)**

- Cherenkov **1**

- 12C

- Cherenkov **2**

**e**

**p**

**(Scintillation)**

- Cherenkov **1**

- 12C

**n**

**e**

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## The analysis was blind. 2 independent analyses were performed:Track Based Analysis (TBA); Boosted Decision Tree (BDT)Prior to box-opening, the collaboration decided to present TBA .BDT confirms TBA with somewhat larger systematics.

- MB300

- MB475

- The excess over predicted background for
- EQE <475 MeV cannot be explained as an oscillation signal. It’s origin is not understood,
- and is undergoing additional analysis by the collaboration.

- The analysis was blind. 2 independent analyses were performed:Track Based Analysis (TBA); Boosted Decision Tree (BDT)Prior to box-opening, the collaboration decided to present TBA .BDT confirms TBA with somewhat larger systematics.

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## Result

-  The MiniBooNE exclusion region compared
- 	to Bugey, KARMEN2, and LSND.
-  Bugey also defines an exclusion region.
-  KARMEN2 & LSND show inclusive  regions.
-  KARMEN2 has a 64% compatibility with LSND.
-  MiniBooNE has a 2% compatibility with LSND.

*MiniBooNE*

**Result**

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*Implications for Cosmology*

- “Sterile neutrino oscillations after first MiniBooNE results” Michele Maltoni and Thomas Schwertz [hep-ph] 0705.01076 May 1, 2007. Sent to the archive ~2 weeks after the MB result.

- Allowed regions for SBL
- appearance data in (3+2)
- schemes at 90, 95, 99,
- 99.73% CL (2dof).
- According to these authors
- there is 85% consistency
- between MB300 and SBL
- experiments with help of a tiny amount CP violation.

- However, there is a 3 to 4  disagreement between fits to appearance and disappearance data: “The main improvement in the (3+2)
- schemes is to reconcile LSND and MB, whereas it is not possible to evade efficiently the constraints from disappearance data. A possible source of this different result might be the inclusion of atmospheric neutrino data in the fit, which is important to constrain sterile oscillations in the  sector.”

- Allowed regions in (3+1) schemes.

- Allowed regions in (3+2) schemes.

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## Theoretical signals 

- It is possible to construct the global model for neutrino
- oscillation including Lorentz and CPT violation

- Effective Hamiltonian:
- Only three parameters are required in the model. (a, c, E)

- Theoretical signals
- (no experimental smearing)

- This simple model is consistent with all existing neutrino oscillation data, including solar, atmospheric, reactor, and LSND.
- It predicts a signal at low E region for MiniBooNE.

- “Global 3-parameter model for neutrino oscillations using Lorentz
- violation”  Katori, Kostelecky, Tayloe;  PRD 74, 105009 (2006)

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## Pas, Pakvasa and Weiler

- Phys Rev D **72, **095017 (2005)

- Sterile-active neutrino oscillations and
- shortcuts in the extra dimension

*Implications for Cosmology*

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## Conclusions

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## Slide 18