Neutrino Oscillation

Neutrino Oscillation

Hitoshi Murayama (Berkeley)

PRC-US Meeting @ IHEPJune 12, 2006

Murayama, IHEP, June 12, 2006 2

Outline

• Past: Why Neutrinos?• Present: Era of Revolution• Future• Conclusion

Past

Why Neutrinos?


Interest in Neutrino Mass

• So much activity on neutrino mass already.

Why am I interested in this?Window to (way) high energy

scales beyond the Standard Model!• Two ways:

– Go to high energies– Study rare, tiny effects


Rare Effects from High-Energies

• Effects of physics beyond the SM as effective operators

• Can be classified systematically (Weinberg)


Unique Role of Neutrino Mass

• Lowest order effect of physics at short distances

• Tiny effect (m/E)2~(0.1eV/GeV)2=10–20!

• 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


Ubiquitous Neutrinos

They must have played some important role in the universe!

Present

Era of Revolution


The Data

Evidence for oscillation:

• “Indisputable”– Atmospheric– Solar– Reactor

• “strong”– Accelerator (K2K)

And we shouldn’t forget:

• “unconfirmed”– Accelerator (LSND)


SuperKamiokande Atmospheric disappear

Downwards ’s don’t disappear

1/2 of upwards ’s do disappear

2/dof=839.7/755 (18%)

m2=2.510-3 eV2

sin22=1


SNOSolar transform in

flavor

2/3 of e’s


KamLANDReactor neutrinos do

oscillate!

Proper time L0=180 km


What we learned

• Lepton Flavor is not conserved• Neutrinos have tiny mass, not very hierarchical

• Neutrinos mix a lotthe first evidence for

demise of the Minimal Standard Model

Very different from quarks


Typical Theorists’ View

ca. 1990

• Solar neutrino solution must be small angle MSW solution because it’s cute

• Natural scale for m223 ~ 10–100 eV2

because it is cosmologically interesting

• Angle 23 must be 23 ~ Vcb =0.04• Atmospheric neutrino anomaly must go away because it needs a large angle

Wrong!

Wrong!

Wrong!Wrong!


The Big Questions

• What is the origin of neutrino mass?• Did neutrinos play a role in our existence?

• Did neutrinos play a role in forming galaxies?

• Did neutrinos play a role in birth of the universe?

• Are neutrinos telling us something about unification of matter and/or forces?

• Will neutrinos give us more surprises?Big questions tough questions to answer


Immediate Questions

• Dirac or Majorana? • Absolute mass scale?

• How small is 13?• CP Violation?• Mass hierarchy?

• Is 23 maximal?• LSND? Sterile neutrino(s)? CPT violation?

Future


Immediate Questions





Immediate Questions





LSND doesn’t fit into the picture

• Sterile neutrino (3+1) barely consistent with short-baseline data

• Sterile neutrinos are strongly constrained by WMAP+SDSS: m<0.26 eV (95%CL)(Seljak, Slosar, McDonald)

• CPT violation without sterile neutrino excluded by SNO+KamLAND

HM, Pierce

WMAP3yr+SDSS


The hell breaks loose

• Mini-BooNE will open the box this summer

• If Mini-BooNE confirms LSND, it is hard to understand what is going on, because there is currently no simple way to accommodate LSND result with other neutrino data– Multiple sterile neutrinos? 3+2?– Sterile neutrino and CPT violation?– Mass varying neutrinos?– Something even more wild and wacky?


What it would take

• We will need neutrino “oscillation” experiments with multiple baselines, multiple modes– E~10 GeV, L~10km, looking for appearance– Redo CDHSW ( disappearance experiment with L=130 & 885m, E=19.2GeV)

– E~1 GeV, L~1 km, looking for oscillatory behavior and CP violation in e, or better, e

– Some in the air, some in the earth – Probably more– Muon source would help greatly


Immediate Questions





T2K (Tokai to Kamioka)


Immediate Questions





LMA confirmed by KamLAND

• Dream case for neutrino oscillation physics!

• m2solar within reach of long-baseline

expts• Even CP violation may be probable

• Possible only if:– m12

2, s12 large enough (LMA)

– 13 large enough€

P(ν μ → ν e ) − P(ν μ → ν e ) = −16s12c12s13c132 s23c23

sinδ sinΔm12

2

4EL

⎛

⎝ ⎜

⎞

⎠ ⎟sin

Δm132

4EL

⎛

⎝ ⎜

⎞

⎠ ⎟sin

Δm232

4EL

⎛

⎝ ⎜

⎞

⎠ ⎟


13 decides the future

• The value of 13 crucial for the future of neutrino oscillation physics

• Determines the required facility/parameters/baseline/energy– sin2213>0.01 conventional neutrino beam– sin2213<0.01 storage ring, beam

• Two paths to determine 13– Long-baseline accelerator: T2K, NOA– Reactor neutrino experiment: 2CHOOZ, Daya Bay


NOAFermilab to Minnesota

32-planeblock

Admirer

25ktMINOSNOA

L=810km


Daya BayNPP

Ling AoNPP

Ling Ao-ll NPP(under const.)

Empty detectors: moved to underground halls through access tunnel.Filled detectors: swapped between underground halls via horizontal tunnels.

Total tunnel length: ~2700 m

230 m290 m

730 m

570 m

910 m

Daya Bay Near360 m from Daya BayOverburden: 97 m

Ling Ao Near500 m from Ling AoOverburden: 98 m

Far site1600 m from Ling Ao2000 m from DayaOverburden: 350 m

Mid site~1000 m from DayaOverburden: 208 m

Entrance portal

Daya Bay


3 sensitivity on sin2

213


T2K vs NOA

• LBL e appearance

• Combination of– sin2213– Matter effect– CP phase 95%CL resolution

of mass hierarchy


Accelerator vs Reactor

90% CL

Reactor w 100t (3 yrs) + Nova Nova only (3yr + 3yr) Reactor w 10t (3yrs) + Nova

90% CL

McConnel & Shaevitz, hep-ex/0409028

90% CL

Reactor w 100t (3 yrs) +T2K T2K (5yr,-only) Reactor w 10t (3 yrs)+T2K Reactor experiments can

help in Resolving the 23 degeneracy

(Example: sin2223 = 0.95 ± 0.01)


My prejudice

• Let’s not write a complicated theory

• The only natural measure for mixing angles is the group-theoretical invariant Haar measure

• Kolmogorov–Smirnov test: 64%

• sin2 213>0.04 (2)• sin2 213>0.01 (99%CL)

231213


Immediate Questions





What about the Big Questions?

• What is the origin of neutrino mass?• Did neutrinos play a role in our existence?

• Did neutrinos play a role in forming galaxies?

• Did neutrinos play a role in birth of the universe?

• Are neutrinos telling us something about unification of matter and/or forces?

• Will neutrinos give us more surprises?Big questions tough questions to answer


Seesaw Mechanism

• Why is neutrino mass so small?

• Need right-handed neutrinos to generate neutrino massνL νR( )

mD

mD

⎛

⎝ ⎜

⎞

⎠ ⎟ νLνR

⎛

⎝ ⎜

⎞

⎠ ⎟ νL νR( )

mD

mD M

⎛

⎝ ⎜

⎞

⎠ ⎟ νLνR

⎛

⎝ ⎜

⎞

⎠ ⎟ mν =

mD2

M<<mD

To obtain m3~(m2atm)1/2, mD~mt, M3~1014–

1014GeV

, but R SM neutral

37

Leptogenesis

• You generate Lepton Asymmetry first. (Fukugita, Yanagida)

• Generate L from the direct CP violation in right-handed neutrino decay

• L gets converted to B via EW anomaly More matter than anti-matter We have survived “The Great Annihilation”

• Despite detailed information on neutrino masses, it still works (e.g., Bari, Buchmüller, Plümacher)

Γ(N1→ νiH)−Γ(N1 → νiH)∝ Im(h1jh1khlk*hlj

*)


Origin of Universe

• Maybe an even bigger role: inflation

• Need a spinless field that – slowly rolls down the

potential– oscillates around it minimum– decays to produce a thermal

bath• The superpartner of right-

handed neutrino fits the bill• When it decays, it produces

the lepton asymmetry at the same time (HM, Suzuki, Yanagida, Yokoyama)

• Decay products: supersymmetry and hence dark matter

Neutrino is mother of the Universe?

QuickTime™ and aCinepak decompressor

are needed to see this picture.





~

ampl

itud

esi

ze o

f th

e un

iver

se

R


LHC/ILC may help

• LHC finds SUSY• ILC measures masses

precisely

• If both gaugino and sfermion masses unify, there can’t be new particles < 1014GeV except for gauge-singlets


Plausible scenario

• 0 found• LHC discovers SUSY• ILC shows unification of gaugino and scalar masses

• Dark matter concordance between collider, cosmology, direct detection

• CP in -oscillation found

• Lepton flavor violation limits (e, e conversion, etc) improve

• Tevatron and EDM (e and n) exclude Electroweak Baryogenesis

• CMB B-mode polarization gives tensor mode r=0.16If this happens, we will be led to believe

seesaw+leptogenesis (Buckley, HM)


Conclusions

• Neutrino oscillation a unique tool to probe (very) high-energy world

• Era of revolution• sin2 213 decides the future• My prejudice: 13 is “large”• Reactor & accelerator LBL expts complementary

• To understand “big questions” we need a diverse set of experiments


The Ivisibles


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Neutrino Oscillation