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American Physical Society MultiDivisional Neutrino Study

DOE-OS Briefing January 7, 2005

Washington DC

Stuart FreedmanBoris Kayser

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Super KamiokANDE PMT Matrix

Part IWhy study neutrinos?

A view of the Sun from 1 Km underground

4

Ray Davis

Pioneering venture in Neutrino Physics

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E2 = m2c2

E1 = m1c2B. Pontecorvo

€

Ψe (t) = cos(θ)e−im1c

2th ν 1 + sin(θ)e

−im2c2t

h ν 2

Ψe (t) Ψe (0)2

=1− sin2(2θ)sin2((m2 −m1)c

2

2ht)

€

Pee =1−sin2(2θ )sin2(1.27(m2

2 −m12 )L

E)

Neutrino Ocillations

In the rest frame

Boosted to the lab frame

€

m22 −m1

2 = Δm2

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Atmospheric Neutrinos

π → μ +νμ

μ → e+νe +νμ

€

N(ν μ ) = 2N(ν e )

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The SuperKamiokande Light-Water Cherenkov Detector

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Solar Neutrino Experiments

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Neutrino Flavor Composition of 8B Flux

SNO

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Reactor Antineutrino Experiments

LMA: m2 = 5.5x10-5 eV2

sin2 2 = 0.833

KamLAND

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818 events if no oscillation56 events observed

MINOS (FNAL Soudan) 2005

Terrestrial Version of Atmospheric Neutrino Experiment

If no oscillation: 151 11

Observe: 108

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KamLANDIs the Neutrino Spectrum Distorted?

€

Pee =1− sin2(2θ)sin2(1.27(m2

2 −m12)L

E)

14

€

Ψe (t) Ψe (0)2

=1− sin2(2θ)sin2((m2 −m1)c

2

2ht)

Is there an oscillation effect

€

Pee =1− sin2(2θ)sin2(1.27(m2

2 −m12)L

E)

€

trestframe =tlabγ

=m

Etlab

€

L = c • tlab

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Observing the oscillations in the neutrino rest frame

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ν μ ν e?

ν ep→ e+n

μ+→ e+νeν μ

p→ π +

π+→ μ+νμ

LSND at Los Alamos

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Excerpts from the Charge

“…response to the remarkable recent series of discoveries in neutrino physics…”

“…build on the 2002 long range plans developed by NSAC and HEPAP.”

“…create a scientific roadmap for neutrino physics.”

“…examine the broad sweep of neutrino physics…”

“…move towards agreement on the next steps…”

The Study will lay scientific groundwork for the choices that must be made during the next few years.

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Neutrino Study Organization

Chairpersons

Solar and Atmospheric Neutrino ExperimentsReactor Neutrino Experiments

Superbeam Experiments and DevelopmentNeutrino Factory and Beta-Beam Experiments and Development

Neutrinoless Double Beta Decay and Direct Searches for Neutrino MassWhat Cosmology/Astrophysics and Neutrino Physics can Teach Each Other

Theory Discussion Group

Writing Committee

Organizing Committee

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APS Neutrino Study: Midcourse CorrectionApril 1-2, 2004Berkeley

UMNS =

Ue1 Ue2 Ue3

Uμ1 Uμ2 Uμ3

Uτ1 Uτ2 Uτ3

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

=

1

c23 s23

−s23 c23

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

c13 s13e−iδ

1

−s13eiδ c13

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

c12 s12

−s12 c12

1

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟

www.aps.org/neutrino

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US scientists participate in neutrino physics worldwide

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Present US Program in Neutrino Physics

NSF

NSF

DOE NP/HEP

DOE HEP

DOE NP/HEP

DOE NP

DOE HEP

NASA

DOE HEP

NSF NP

DOE HEP

NSF

DOE NP

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Many of the past experiments and many of the future experiments we feel are particularly important rely on suitable underground facilities. The availability of these facilities will be crucial to future neutrino research.

101

102

103

104

105

106

Muon Intensity, m

-2 y

-1

5 6 7 8 9

103

2 3 4 5 6 7 8 9

104

Depth, metres water equivalent

IMB

Soudan

Kamioka

Gran Sasso

HomestakeBaksan

Mont Blanc

Sudbury

Kolar

Muon flux vs overburden

Underground Facilities

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SNO

Part IIThe Story

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What Have We What Have We Learned?Learned?

What Do We What Do We NotNot Know? Know?

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Neutrino masses —There is some spectrum of 3 or more neutrino mass

eigenstates i:

(Mass)2

1

2

3

4

Mass () mi

From neutrino flavor change (oscillation) experiments, we have learned that —

Neutrinos have nonzero rest massesLeptons mix

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We do not know how many different neutrinos there are. Just 3, the partners of the 3 charged leptons??

If the Liquid Scintillator Neutrino Detector (LSND) experiment is confirmed, there are more than 3.

If LSND is not confirmed, nature may contain only 3 neutrinos.

Then, from the existing neutrino oscillation data, the neutrino spectrum looks like —

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(Mass)2

1

2

3

or

1

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}m2sol

m2atm

}m2sol

m2atm

m2sol = 8 x 10–5 eV2, m2

atm = 2.5 x 10–3 eV2~ ~

Normal Inverted

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Grand Unified Theories relate the Leptons to the Quarks.

is un-quark-like, and would probably involve a lepton symmetry with no quark analogue.

A grand goal of elementary particle physics is to unify all the forces of nature into a single force.

The Grand Unified Theories, which do this for all the forces of nature save gravity, favor —

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When W+ l+ + ,

the produced neutrino state |> is

| > = U*i |i> .

Neutrino of flavor Neutrino of definite mass mi

Unitary Leptonic Mixing Matrix

Flavor- fraction of i = |< |i>|2 = |Ui|2 .

le e, l , l

e, , or

i

Leptonic mixing —

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m2atm

e [|Uei|2] [|Ui|2] [|Ui|2]

(Mass)2

m2sol}

Bounded by reactor exps. with L ~ 1 km

From max. atm. mixing,

€

3 ≅ν μ +ν τ

2

From (Up) oscillate but (Down) don’t{{

{

In LMA–MSW, Psol(e e) = e fraction of 2

From max. atm. mixing, includes (–)/√2

From distortion of e(solar) and e(reactor) spectra

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The Mixing Matrix

€

U =

1 0 0

0 c23 s23

0 −s23 c23

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥×

c13 0 s13e−iδ

0 1 0

−s13eiδ 0 c13

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥×

c12 s12 0

−s12 c12 0

0 0 1

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥

×

eiα1 /2 0 0

0 eiα 2 /2 0

0 0 1

⎡

⎣

⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥

12 ≈ sol ≈ 32°, 23 ≈ atm ≈ 36-54°, 13 < 15°

would lead to P( ) ≠ P( ). CP

But note the crucial role of s13 sin 13.

cij cos ij

sij sin ij

Atmospheric Cross-Mixing Solar

Majorana CP phases~

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Are Neutrinos the Reason We Exist?The universe contains Matter, but essentially no antimatter.

Good thing for us:

This preponderance of Matter over antimatter could not have developed unless the two behave differently. (CP)

The observed difference between Quark and antiquark behavior, as described by the Standard Model, is inadequate.

Could the interactions of Matter and antimatter with neutrinos provide the crucial difference?

Matter AntimatterPoof!

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There is a natural way in which they could.

The most popular theory of why neutrinos are so light is the —

See-Saw Mechanism

NVery heavy neutrino

Familiar light neutrino

}

{

The heavy neutrinos N would have been made in the hot Big Bang.

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If Matter and antimatter interact differently with these heavy neutrinos N, then we can have —

Probability [ N e- + … ] ≠ Probability [ N e+ + … ]

Matter antimatter

in the early universe.

This phenomenon (leptogenesis) would have led to a universe containing unequal amounts of Matter and antimatter.

In time, they would have decayed into lighter particles.

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We cannot repeat the early universe.

But we can lend credibility to the hypothesis of leptogenesis by showing that Matter and antimatter interact differently with the light neutrinos .

Source Detector

e- -

Source Detector

e+ +

A neutrino flavor change involving Matter:

A neutrino flavor change involving antimatter:

If these two flavor changes have different probabilities, then quite likely so do —

N e- + … and N e+ + …

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If N decays led to the present preponderance of Matter over antimatter, then we are all descendants

of heavy neutrinos.

In Pursuit of 13

Both CP violation and our ability to tell whether the spectrum is normal or

inverted depend on 13.

How may 13 be measured?

If sin2213 < 0.01, a neutrino factory will be needed to study both of these issues.

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m2atm

(Mass)2

m2sol}

sin213 is the small e piece of 3.

3 is at one end of m2atm.

We need an experiment sensitive to m2atm,

and involving e.

sin213

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Complementary Approaches

Reactor e disappearance while traveling L ~ 1.5 km.

L/E ~ 500 km/GeV. This process depends on 13 alone.

Accelerator e while traveling L > Several hundred

km. L/E ~ 400 km/GeV. This process depends on 13 and

other neutrino properties, including whether the spectrum

is normal or inverted.

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How To Determine If The Spectrum Is Normal Or Inverted

In the experiments we will do with earth-born neutrinos, the neutrinos will travel through earth

matter.

Exploit the fact that, in matter, e – e interactions raise the effective mass of e.

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m2atm

e

(Mass)2

m2sol}

m2atm

m2sol}

vs.

sin213

sin213

If m2atm shrinks (grows) in matter, 13 grows (shrinks).

42

The effect of matter increases as the neutrino distance of travel within it, L, does.

Using larger L to determine whether the spectrum is normal or inverted could be a unique contribution of the U.S. program.

43

Does —

• i = i (Majorana neutrinos)

or• i ≠ i (Dirac neutrinos) ?

e+ ≠ e– since Charge(e+) = – Charge(e–).

But neutrinos may not carry any conserved charge-like quantum number.

A conserved Lepton Number L defined by—L() = L(l–) = –L() = –L(l+) = 1 may not exist.

If it does not, then i = i and we can have —

Are Neutrinos Their Own Antiparticles?

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Neutrinoless Double Beta Decay (0)

Observation would establish that —

• Lepton number L is not conserved

• Neutrinos are Majorana particles ( = )• The origin of neutrino mass is not the same as

the origin of the masses of charged leptons, quarks, nucleons, humans, the earth, galaxies

ii

W– W–

e– e–

Nuclear Process

Nucl Nucl’

Then neutrinos and their masses are very distinctive.

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The Quest for the Origin of Mass

Neutrino experiments and the search for the Higgs boson both probe the origin of mass.

The see-saw mechanism suggests that the physics behind neutrino mass resides at 1015 GeV, the extremely high energy where Grand Unified Theories say all the

forces of nature, save gravity, become one.

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The Open QuestionsThe Open Questions

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Neutrinos and the New Paradigm

• What are the masses of the neutrinos?

• What is the pattern of mixing among the different types of neutrinos?

• Are neutrinos their own antiparticles?

• Do neutrinos violate the symmetry CP?

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Neutrinos and the Unexpected

• Are there “sterile” neutrinos?

• Do neutrinos have unexpected or exotic properties?

• What can neutrinos tell us about the models of new physics beyond the Standard Model?

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Neutrinos and the Cosmos

• What is the role of neutrinos in shaping the universe?

• Is CP violation by neutrinos the key to understanding the matter – antimatter asymmetry of the universe?

• What can neutrinos reveal about the deep interior of the earth and sun, and about supernovae and other ultra high energy astrophysical phenomena?

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KamLAND

Part IIIRecommendations

for future experiments

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53

54

55

56

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KATRIN

’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11 ’12 ’13 ’14 ’15 ’16 ’17 ’18 ’19 ’20

Running

Running

Exi

stin

g P

rogr

am

Signal?

MINOS

RunningConstr. 7Be Solar

US Based

US Participation

KamLANDReactor

MiniBooNE

Super-K + K2K+T2K

HE Astro

SNO

Running

Running

Constr. RunningR&D

Construction Running

Construction Running

Green < $10M/yr Blue $10M - $40M/yrOrange $40M -$100M/yr Red > $100M/yr

New

Exp

erim

ents RunningConstructionR&D

Constr. Running

R&D Construction Running

R&D Constr. Running

R&D Construction Running

R&D No Signal?

1 ton

pp Solar

Reactor

Long Baseline

200 kg

Construction/RunningCross Sections

’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11 ’12 ’13 ’14 ’15 ’16 ’17 ’18 ’19 ’20

Green < $10M/yr Blue $10M - $40M/yrOrange $40M -$100M/yr Red > $100M/yr

New Experiments

Proton driver

R&D Construction Running

R&D R&D

Fac

ilit

ies

?01.02sin 132 ≥

R&D Construction Running

ConstructionR&D Multipurpose

Detector

UG Lab

Factory

Running

’04 ’05 ’06 ’07 ’08 ’09 ’10 ’11 ’12 ’13 ’14 ’15 ’16 ’17 ’18 ’19 ’20

Const.

Facilities

Green < $10M/yr Blue $10M - $40M/yrOrange $40M -$100M/yr Red > $100M/yr

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MiniBOONE