Neutrino physics: The future

Gabriela Barenboim

TAU04

We know that neutrinos are massive and oscillate !

e

Pure e source

Evidence for flavor change

Solar neutrinos: Compelling evidence

e + +

e

= 13

Reactor neutrinos: very strong evidence

One pair of parameters fits both solar and reactor data

produced

surviving

reactor

detector180 km

e 0.6 e

Atmospheric neutrinos: Compelling evidence

detector

Earth

(up)

(down)

The hypothesis with one pair of parameters fits both the atmospheric and accelerator data

Expect 106 events

in far detector Observe 72

events

Accelerator neutrinos: interesting evidence

LSND: unconfirmed evidence

We do not know how many neutrino mass eigenstates

there are.

Assuming CPT, confirmation of LSND by MiniBooNE

would imply there are more than 3

What have we already learnt ?

Neutrinos Required m2

solar - reactor 10-(4-5)

atmos.- accelerator 10-3

LSND 1

eV2

solar - reactor 10-(4-5) atmos.- accelerator 10-3

LSND 1

For only three neutrinos

m2=(m32-m2

2) + (m22-m1

2) +

(m12-m3

2) =0

How many neutrino species are there ?

Do sterile neutrinos exist ?

How many neutrino species are there ?

Do sterile neutrinos exist ?

Let´s assume there are only three neutrinos

The neutrino mixing matrix

The unknown oscillation parameters

What is the size of sin2(213) ?

Is there CP violation ?

What is the mass hierarchy ?

What is the sign of m213 ?

We determined that m(KL) > m(KS) by

Passing kaons through matter (regenerator)

Beating the unknown sign[m(KL) –m(KS)] against the known sign[reg. ampl.]

We determined that m(KL) > m(KS) by

Passing kaons through matter (regenerator)

Beating the unknown sign[m(KL) –m(KS)] against the known sign[reg. ampl.]

We will determine the sign(m213) by

Passing neutrinos through matter (Earth)

Beating the unknown sign(m213) against the

known sign[forward e e e e ampl]

How we are going to do it ?

Method 1: accelerator experiments

Appearance experiment e

Measurement of e and e yields 13 and

Matter effects present, baselines of O(100-1000 km)

The off axis idea

By going off axis, the beam energy is reduced

and the spectrum becomes very sharp.

Allows an experiments to pick an energy for the maximum oscillation

length.

.Minakata and Nunokawa

What will we get ?

.Minakata and Nunokawa

What will we get ?

Method 2: reactor experiments

Disappearance experiment e x

Clean measurement of 13

No matter effects, baselines O(1 km)

Reactor experiments : the future

Reactor experiments : the future

detector 1

detector 2

R. McKeown

What is the absolute mass scale ?

mass(heavy)

What is the absolute mass scale ?

.04 eV < mass(heavy)

m2atm

What is the absolute mass scale ?

.04 eV < mass(heavy) < .23 eV

m2atm

WMAP + 2dFRS + other data

mi < .71 eV

B

c

h

m

xe

….

M.Tegmark

M.Tegmark

.04 eV < mass(heavy) < .40 eV

m2atm

If the primordial power spectrum

does not have the usually assumed

shape, mi < 1.2 eV

What is the absolute mass scale ?

phase space determines energy spectrumtransition energy E0 = Ee + En (+ recoil corrections)

experimental observable

– decay kinematics

-3 -2 -1 0 Ee-E0 [eV]

1

0.8

0.6

0.4

0.2

0

rel.

rate

[a.u

.]

theoretical spectrum near endpoint

m = 0eV

m = 1eV

dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – m2 ]1/2

phase space determines energy spectrumtransition energy E0 = Ee + En (+ recoil corrections)

experimental observable

– decay kinematics

-3 -2 -1 0 Ee-E0 [eV]

1

0.8

0.6

0.4

0.2

0

rel.

rate

[a.u

.]

theoretical spectrum near endpoint

m = 0eV

m = 1eV

dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – m2 ]1/2

NOT me

m Uei2mi2

i1

3

5

KATRIN sensitivity & discovery potential

m < 0.2eV (90%CL)

m = 0.35eV (5)

m = 0.3eV (3)

sensitivity

discovery potential

expectation:

after 3 full beam years syst ~ stat

What kind of particle is the neutrino ?

What kind of particle is the neutrino ?

Is the neutrino a truly neutral particle ?

Why not add a Dirac mass term ?

m L R

Why not add a Dirac mass term ?

m L R

This requires R. Then no (SM) principle prevents the occurrence

of

M CR

R

cLL L Lm

Majorana mass

Dirac mass LR L Rm (conserves L)

cRR R RM

from Yukawa couplings

(violates L)

CP conjugate of left-handed

neutrino

Right-handed neutrinos

Complete See-Saw Mechanism

1I I TLL LL LR RR LRm m m M m

cLL L Lm

I I cLL LR Lc

L R TRLR RR

m m

m M

Dirac matrix

Heavy Majorana matrix

Light Majorana matrix

Diagonalise to give effective mass

Type II contribution

Type I see-saw mechanism Type II see-saw mechanism

R

LL

2

I I c uLL L L

vm Y

M

Types of see-saw mechanism

L L

Heavy triplet

cRR R RM

1I TLL LR RR LRm m M m

Y

Naturalness may be over rated …

Do this look natural ??

How we can find out ?

x

p

p

n

n

e

e

SM double weak process

4 body decay: continuos spectrum for the e energy sum

How we can find out ?

x

p

p

n

n

e

e

SM double weak process

4 body decay: continuos spectrum for the e energy sum

x

p

p

n

n

e

e

Only allowed for Majorana

2 body decay: e energy sum is a delta

i is emitted ( RH + O(mi/E) LH )

Amp[i contribution] mi

Amp[0] | mi Uei2|

x

p

n

n

e

e

i is emitted ( RH + O(mi/E) LH )

Amp[i contribution] mi

Amp[0] | mi Uei2|

x

p

n

n

e

e

effective neutrino mass

m=| mi Uei2|

Cosmology

Beta decay

Oscillations

Double-beta decaym Uei

2mi

i1

3

i

mij2 m j

2 mi2

m Uei2mi2

i1

3

m1 m2 m3

“Unexpected” properties

Finite lifetime

Lorentz non-invariance

Magnetic moment

CPT non-invariance

SummaryWe have learned that neutrinos have masses.

But we do not know

How many species there are

How much the neutrinos weigh

Whether =

We have discovered that two mixing angles are large.

But we do not know

The size of the crucial third angle

Whether oscillations violate CP

The spectral pattern

Do not miss the neutrino talk at

TAU09 !!!