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What is the case for nufact?. Hitoshi Murayama (UC Berkeley) Intl Scoping Study Meeting of Nufact and Superbeam Boston University, March 8, 2006. The Question. Neutrino physics has been full of surprises We’ve learned a lot in the last ~8 years We want to learn more

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what is the case for nufact

What is the case for nufact?

Hitoshi Murayama (UC Berkeley)

Intl Scoping Study Meeting of

Nufact and Superbeam

Boston University, March 8, 2006

the question
The Question
  • Neutrino physics has been full of surprises
  • We’ve learned a lot in the last ~8 years
  • We want to learn more
  • New projects are more and more expensive
  • Is it really worth it?
  • Especially worth ~B$, B€, 100B¥?

ISS Physics WS Boston

elevator pitch
Elevator Pitch
  • If you happen to be on an elevator with a powerful senator, can you explain why you want to spend ~B$ on your project in 30 seconds?

ISS Physics WS Boston

what will not work
What will NOT work

For politicians and taxpayers, these arguments wouldn’t be convincing and/or interesting enough

  • Measurements as precisely as we can
  • Push limits on 13 as much as we can
  • Verify the three-generation framework of neutrino oscillation
  • Distinguish different flavor modles
  • Field needs another machine to sustain itself

ISS Physics WS Boston

quantum universe report
Quantum Universe Report

What are neutrinos telling us?

  • Of all the known particles, neutrinos are the most mysterious. They played an essential role in the evolution of the universe, and their tiny nonzero mass may signal new physics at very high energies.

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quantum universe report1
Quantum Universe Report
  • Einstein’s Dream of Unified Forces
    • Are there undiscovered principles of nature: new symmetries, new physical laws?
    • How can we solve the mystery of dark energy?
    • Are there extra dimensions of space
    • Do all the forces become one?
  • The Particle World
    • Why are there so many kinds of particles?
    • What is dark matter? How can we make it in the laboratory?
    • What are neutrinos telling us?
  • The Birth of the Universe
    • How did the universe come to be?
    • What happened to the antimatter?

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outline
Outline
  • Why Neutrinos?
  • A few scenarios
    • sin2 213≪ 0.01
    • sin2 213 > 0.01
    • Mini-BooNE confirms LSND
    • LHC discovers new physics < TeV
  • The Big Questions
    • Scenario to “establish” seesaw/leptogenesis
  • Conclusion

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interest in neutrino mass
Interest in Neutrino Mass
  • So much activity on neutrino mass already.

Why are we doing this?

Window to (way) high energy scales beyond the Standard Model!

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why beyond the standard model
Why Beyond the Standard Model
  • Standard Model is sooooo successful. But none of us are satisfied with the SM. Why?
  • Because it leaves so many great questions unanswered

 Drive to go beyond the Standard Model

  • Two ways:
    • Go to high energies
    • Study rare, tiny effects

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rare effects from high energies
Rare Effects from High-Energies
  • Effects of physics beyond the SM as effective operators
  • Can be classified systematically (Weinberg)

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unique role of neutrino mass
Unique Role of Neutrino Mass
  • Lowest order effect of physics at short distances
  • Tiny effect (mn/En)2~(0.1eV/GeV)2=10–20!
  • Inteferometry (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

ISS Physics WS Boston

ubiquitous neutrinos
Ubiquitous Neutrinos

They must have played some

important role in the universe!

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the data
The Data

de Gouvêa’s classification:

  • “Indisputable”
    • Atmospheric
    • Solar
    • Reactor
  • “strong”
    • Accelerator (K2K)

And we shouldn’t forget:

  • “unconfirmed”
    • Accelerator (LSND)

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historic era in neutrino physics
Historic Era in Neutrino Physics

We learned:

  • Atmospheric nms are lost. P=4.2 10–26(SK) (1998)
  • converted most likely to nt (2000)
  • Solar ne is converted to either nm or nt(SNO) (2002)
  • Only the LMA solution left for solar neutrinos (Homestake+Gallium+SK+SNO) (2002)
  • Reactor anti-ne disappear (2002) and reappear (KamLAND) (2004)

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neutrinos do oscillate
Neutrinos do oscillate!

Proper time 

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what we learned
What we learned
  • Lepton Flavor is not conserved
  • Neutrinos have tiny mass, not very hierarchical
  • Neutrinos mix a lot

the first evidence for

incompleteness of Minimal Standard Model

Very different from quarks

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typical theorists view ca 1990
Typical Theorists’ View ca. 1990
  • Solar neutrino solution must be small angle MSW solution because it’s cute
  • Natural scale for Dm223 ~ 10–100 eV2 because it is cosmologically interesting
  • Angle q23 must be ~ Vcb =0.04
  • Atmospheric neutrino anomaly must go away because it needs a large angle

Wrong!

Wrong!

Wrong!

Wrong!

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slide19

The Ivisibles

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the big questions
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

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immediate questions
Immediate Questions
  • Dirac or Majorana?
  • Absolute mass scale?
  • How small is q13?
  • CP Violation?
  • Mass hierarchy?
  • Is q13 maximal?
  • LSND? Sterile neutrino(s)? CPT violation?

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tools
Tools
  • Available tools now:
    • SuperK, SNO, KamLAND, Borexino, Mini-BooNE, MINOS, Cuoricino, NEMO, SDSS, …
  • Available soon (?):
    • Opera, Double-Chooz, T2K, MINERA, SciBooNE, NOA, reactor 13 expts, KATRIN, PLANCK, new photometric surveys, more 0 expts, …

Do we really need more?

What do we need?

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do we really need more what do we need
Do we really need more?What do we need?
  • The answer depends on what we will find in the near future
  • Talk about a few scenarios
    • sin2 213≪ 0.01
    • sin2 213 > 0.01
    • Mini-BooNE confirms LSND
    • LHC discovers new physics < TeV

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obvious case
Obvious case?
  • Superbeams will not address 13, mass hierarchy, or CP violation
  • A clear case for neutrino factory and/or -beam
  • de Gouvêa: Will we get the funds to get a neutrino factory even if all previous investments end up “unsuccessful”?

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sin 2 2 13 0 012
sin2 213>0.01
  • Reactor/T2K/NOA finds sin2 213

This is my prejudice

  • Upgrades (4MW J-PARC to HyperK, Proton Driver+NOA 2nd detector, etc)
    • Measures sin2 213 precisely
    • Determines mass hierarchy
    • Discovers CP violation

What’s left then?

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the source of cp violation
The source of CP violation
  • Having seen does not tell us what is causing it (in particular in the presence of “matter effect background”)
  • Is it due to the Dirac phase in the MNS matrix?
  • Exactly the same question being addressed by B-factories
    • i.e., K can be explained by the KM phase, but is it?
    • Cross check in a different system, e.g., B  Yes!
    • Is there new interaction (e.g. SUSY loop)?  future

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testing mns hypothesis
Testing MNS hypothesis
  • One way I know is to use tau modes
  • Consequence of CPT and three flavors
  • Can they be studied at neutrino factory?
    • I know it is tough even for a neutrino factory, but other facilities will clearly not do it

ISS Physics WS Boston

testing mns hypothesis1

()

()

(e)

(e)

Testing MNS hypothesis
  • A simulation like this will make the case

w/o new neutrino interaction

with new neutrino interaction

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the hell breaks loose
The hell breaks loose
  • In this case, 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?
    • Sterile neutrino and CPT violation?
    • Mass varying neutrinos?
    • Something even more wild and wacky?

ISS Physics WS Boston

what it takes
What it takes
  • 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

ISS Physics WS Boston

tev new physics
TeV new physics
  • Whatever it is,
    • SUSY, large extra dimensions, warped extra dimension, technicolor, Higgsless, little Higgs

it is hard to avoid the TeV-scale physics to contribute to flavor-changing effects in general

  • Renewed strong case for, e.g., super-B
  • Very strong case for lepton flavor violation, g2
    • Hence, for a muon storage ring
  • Obvious competition with ILC and beyond

ISS Physics WS Boston

for example susy
For example, SUSY
  • High-energy data (LHC/ILC) will provide masses of superparticles
    • But most likely not their mixings
  • Low-energy LFV experiments (e.g., e, AeA) provide rates (T-odd asymmetry if lucky)
    • Combination of virtual particles in the loop and their mixing
  • Put them together
    • Resolve the mixing
    • Constrain models of flavor

ISS Physics WS Boston

what about the big 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

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neutrinos must be massless
Neutrinos must be Massless
  • All neutrinos left-handed  massless
  • If they have mass, can’t go at speed of light.
  • Now neutrino right-handed??

 contradiction  can’t be massive

ISS Physics WS Boston

two ways to go
(1) Dirac Neutrinos:

There are new particles, right-handed neutrinos, after all

Why haven’t we seen them?

Right-handed neutrino must be very very weakly coupled

Why?

Two ways to go

ISS Physics WS Boston

extra dimensions
Extra Dimensions
  • All charged particles are on a 3-brane
  • Right-handed neutrinos SM gauge singlet

 Can propagate in the “bulk”

  • Makes neutrino mass small

mn ~ 1/R if one extra dim  R~10mm

  • An infinite tower of sterile neutrinos
  • Or anomaly mediated SUSY breaking

ISS Physics WS Boston

two ways to go1
(2) Majorana Neutrinos:

There are no new light particles

Why if I pass a neutrino and look back?

Must be right-handed anti-neutrinos

No fundamental distinction between neutrinos and anti-neutrinos!

Two ways to go

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seesaw mechanism
Seesaw Mechanism
  • Why is neutrino mass so small?
  • Need right-handed neutrinos to generate neutrino mass

, but nR SM neutral

To obtain m3~(Dm2atm)1/2, mD~mt, M3~1015GeV (GUT!)

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grand unification
electromagnetic, weak, and strong forces have very different strengths

But their strengths become the same at 1016 GeV if supersymmetry

To obtain

m3~(Dm2atm)1/2, mD~mt

 M3~1015GeV!

Grand Unification

M3

Neutrino mass may be probing unification:

Einstein’s dream

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leptogenesis
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)

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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?

~

R

Origin of Universe

amplitude

size of the universe

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origin of the universe
Origin of the Universe
  • Right-handed scalar neutrino: V=m2f2
  • ns=0.96
  • r=0.16
  • Detection possible in the near future

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can we prove it experimentally
Can we prove it experimentally?
  • Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data
  • But: we will probably believe it if the following scenario happens

Archeological evidences

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a scenario to establish seesaw
A scenario to “establish” seesaw
  • We find CP violation in neutrino oscillation
    • At least proves that CP is violated in the lepton sector
  • Ue3 is not too small
    • At least makes it plausible that CP asymmetry in right-handed neutrino decay is not unnaturally suppressed
  • But this is not all

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a scenario to establish seesaw1
A scenario to “establish” seesaw
  • LHC finds SUSY, LC establishes SUSY
  • no more particles beyond the MSSM at TeV scale
  • Gaugino masses unify (two more coincidences)
  • Scalar masses unify for 1st, 2nd generations (two for 10, one for 5*, times two)

 strong hint that there are no additional particles beyond the MSSM below MGUT except for gauge singlets.

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gaugino and scalars
Gaugino masses test unification itself independent of intermediate scales and extra complete SU(5) multiplets

Scalar masses test beta functions at all scales, depend on the particle content

Gaugino and scalars

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a scenario to establish seesaw2
A scenario to “establish” seesaw
  • Next generation experiments discover neutrinoless double beta decay
  • Say, mee~0.1eV (quasi-degenerate)
  • There must be new physics below ~1014GeV that generates the Majorana neutrino mass

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a scenario to establish seesaw3
A scenario to “establish” seesaw
  • It leaves the possibility for R-parity violation
  • Consistency between cosmology, dark matter detection, and LHC/ILC will remove the concern

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high precision even for ilc
High precision even for ILC

Preliminary

Matt Buckley

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a scenario to establish seesaw4
A scenario to “establish” seesaw
  • B-mode fluctuation in CMB is detected, with a reasonable inflationary scale

 strong hint that the cosmology has been ‘normal’ since inflation (no extra D etc)

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a scenario to establish seesaw5
A scenario to “establish” seesaw

Possible additional archeological evidence, e.g.,:

  • lepton-flavor violation (e conversion, ) seen at the “reasonable” level expected in SUSY seesaw (even though I don’t believe mSUGRA)
  • BdKS shows deviation from the SM consistent with large bR-sR mixing above MGUT
  • Isocurvature fluctuation seen suggestive of N1 coherent oscillation, avoiding the gravitino problem

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conclusions
Conclusions
  • Revolutions in neutrino physics
  • Neutrino mass probes rare/subtle/high-energy physics
  • There is a very good chance for further big progress
  • Most likely, we will need superbeam, and also neutrino factory and/or beta beam
  • Neutrino physics is within the context of particle physics, astrophysics and cosmology
  • Big questions can be answered only based on collection of experiments, not oscillation alone

What’s the elevator pitch?

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