# Presentation: 002156

## Impact of Neutrino OscillationMeasurements on Theory

- Hitoshi Murayama
- NuFact 03
- June 10, 2003

## Past

## Rare Effects from High-Energies

*Rare Effects from High-Energies*

- Effects of physics beyond the SM as effective operators
- Can be classified systematically (Weinberg)

- NuFact03 Hitoshi Murayama

## Unique Role of Neutrino Mass

- Lowest order effect of physics at short distances
- Tiny effect (*m***/*E***)2~(eV/GeV)2=10–18!
- Interferometry (*i.e.*, Michaelson-Morley)!
- Need coherent source
- Need interference (*i.e.*, large mixing angles)
- Need long baseline
*Nature was kind to provide all of them!*
- “neutrino interferometry” (a.k.a. neutrino oscillation) a unique tool to study physics at very high scales

- NuFact03 Hitoshi Murayama

## Grand Unification

*Grand Unification*

- electromagnetic, weak, and strong forces have very different strengths
- But their strengths become the same at 1016 GeV if supersymmetry
- A natural candidate energy scale ~1016GeV
- 	  *m*~0.003eV
*m*~(*m*2atm)1/2~0.03eV
*m*~(*m*2LMA)1/2~0.007eV

- Neutrino mass may be probing unification:
*Einstein’s dream*

- NuFact03 Hitoshi Murayama

## Present

## Progress in 2002 on the Solar Neutrino Problem

- April 2002 with SNO

- Dec 2002
- with KamLAND

*Progress in 2002 **on the Solar Neutrino Problem*

- NuFact03 Hitoshi Murayama

## Typical Theorists’ View ca. 1990

- Solar neutrino solution *must* be small angle MSW solution because it’s cute
- Natural scale for *m*223 ~ 10–100 eV2 because it is cosmologically interesting
- Angle **23 must be of the order of *V**cb*
- Atmospheric neutrino anomaly must go away because it needs a large angle

*Wrong!*

*Wrong!*

*Wrong!*

*Wrong!*

- NuFact03 Hitoshi Murayama

## Surprises

- Prejudice from quarks, charged leptons:
- Mixing angles are small
- Masses are hierarchical
- In LMA, all mixing except *U**e*3 large
- Two mass splittings not *very* different
- Atmospheric mixing *maximal*
- Any new symmetry or structure behind it?

- NuFact03 Hitoshi Murayama

## Question of Flavor

- What distinguishes different generations?
- Same gauge quantum numbers, yet different
- Hierarchy with small mixings:
- 		 Need some ordered structure
- Probably a hidden *flavor quantum number *
- 		 Need flavor symmetry
- Flavor symmetry must allow top Yukawa
- Other Yukawas forbidden
- Small symmetry breaking generates small Yukawas
- Try to find underlying symmetries from data (bottom-up)
- Repeat Heisenberg, Gell-Mann–Okubo

- NuFact03 Hitoshi Murayama

## Different Flavor Symmetries

- Altarelli-Feruglio-Masina hep-ph/0210342

- Hall, HM, Weiner

- Sato, Yanagida

- Barbieri et al

- NuFact03 Hitoshi Murayama

## Lack of symmetry explains data

- Suppose there is no symmetry behind the neutrino masses and mixings (“anarchy”)
- Random 3 by 3 matrix
- MNS matrix distributed to the group invariant measure (Haba, HM)

- Kolmogorov–Smirnov test
- (de Gouvêa, HM)

- NuFact03 Hitoshi Murayama

## Future

## Critical Measurements

- sin2 2**23=1.000.01?
- Determines a need for a new symmetry to *enforce* the maximal mixing
- sin2 2**13<0.01?
- Determines if the flavor quantum number of electron is different from mu, tau
- Normal or inverted hierarchy?
- Most symmetries predict the normal hierarchy
- CP Violation?
- Plausibility test of leptogenesis

- NuFact03 Hitoshi Murayama

## Dynamics behind flavor symmetry?

- Once flavor symmetry structure identified (e.g., Gell-Man–Okubo), what is dynamics? (e.g., QCD)

-    Supersymmetry:
- Anomalous U(1) gauge symmetry with Green-Schwarz mechanism
-    Large Extra Dimensions:
- Fat brane with physically separated left- and right-handed particles
-    Technicolor:
- New broken gauge symmetries at 100TeV scale

- NuFact03 Hitoshi Murayama

## LSND3.3 Signal

- Excess positron events over calculated BG

- NuFact03 Hitoshi Murayama

## CPT Violation?“A desperate remedy...”

- LSND evidence:
- 		*anti-neutrinos*
- Solar evidence:
- 		*neutrinos*
- If neutrinos and anti-neutrinos have different mass spectra, atmospheric, solar, LSND accommodated without a sterile neutrino
- 	(HM, Yanagida)
*Best fit to data* < 2002
- (Strumia)

- NuFact03 Hitoshi Murayama

## KamLAND impact

- However, now there is an evidence for “solar” oscillation in anti-neutrinos from KamLAND
- Barenboim, Borissov, Lykken: evidence for atmospheric neutrino oscillation is dominantly for neutrinos.  Anti-neutrinos suppressed by a factor of 3.

- New CPT violation:

- NuFact03 Hitoshi Murayama

## CPT Theorem

- Based on three assumptions:
- Locality
- Lorentz invariance
- Hermiticity of Hamiltonian
- Violation of any one of them:
- 		*big impact on fundamental physics*
- Neutrino mass: tiny effect from high-scale physics
- Non-local Hamiltonian? (HM, Yanagida)
- Brane world? (Barenboim, Borissov, Lykken, Smirnov)
- Homeotic theory? (Barenboim, Lykken)

- NuFact03 Hitoshi Murayama

## Conclusion

- Still a lot to learn from neutrino oscillation
-  **23, **13, normal or inverted hierarchy, CP violation
- Determine the underlying symmetry behind flavor (masses and mixing)
- In conjunction with data from *energy frontier*, we hope to understand dynamics behind the flavor symmetry
- Maybe even more surprises
- CPT violation? Sterile neutrinos?

- NuFact03 Hitoshi Murayama