Neutrino masses

Neutrino masses

Determination of absolute mass scale with beta decays:

single beta decays: energy spectra

search for neutrinoless double beta decays

The latter is extremely important in order to understand the Universe and sources of particle masses

2 0

1

Normal Inverted

(Mass)2

}

}

or

Neutrino (mass)2 spectrum

From neutrinos... DK&ER lecture11

2

3

1 3

1

2

2

sin2ϑ 13

sin2ϑ 13

δmsol2

δmsol2

Δmatm2

Δmatm2

δmsol2 ≅ 8g10−5 eV2

δmatm2 ≅ 2.5g10−3 eV2

e Uei

2 μ Uμi

2 τ Uτ i2

Various and complementary ways

to measure neutrino massCosmology Oscillation

Beta decay

Σ =m1 + m2 + m3 δmij2 = mi

2 − m j2

3From neutrinos... DK&ER lecture11

20

m = Uei2 mi

2

i=1

3

∑

Three roads to neutrino masses

4

Direct measurements of neutrino masses

32 2

1i i

i

m U m

3 3 - 2.2e: VH He+e ee em

+ 170k: eV mμμ μ μ

e: tritium decay

μ: decay

τ τ decay-: +5 18MeVmτ τ ττ


m = U i2mi

2

i=1

3

∑Information from the end of the energy spectrum.„Mass” of flavor α – combination of mass states.Very high precision of measurements needed.Up to now only limits.

Information from the end of the energy spectrum.„Mass” of flavor α – combination of mass states.Very high precision of measurements needed.Up to now only limits.

experimental observable is mexperimental observable is m22

Model independent neutrino mass from ß-decay kinematics

ß-source requirements :

- high ß-decay rate (short t1/2)

- low ß-endpoint energy E0

- superallowed ß-transition- few inelastic scatters of

ß‘s

ß-detection requirements :

- high resolution (ΔE< few eV)

- large solid angle - low background

EE00 = 18.6 keV = 18.6 keV

TT1/21/2 = 12.3 y = 12.3 y

3 3 -H He+e e

β-decay and neutrino mass

6 ΔΩ : 2π

History of tritium measurements


7

Electrostatic filter with magnetic adiabatic collimation


8

Status of previous tritium measurements


9

Troitsk Troitsk MainzMainz

windowless gaseous T2 source quench condensed solid T2 source

Mainz & Troitsk have reached their intrinsic limit of sensitivityMainz & Troitsk have reached their intrinsic limit of sensitivity

analysis 1994 to 1999, 2001 analysis 1998/99, 2001/02

both experiments now used for systematic investigationsboth experiments now used for systematic investigations

experimental observable in ß-decay is mν2

aim : improve m by one order of magnitude (2 eV 0.2 eV )

requires : improve m by two orders of magnitude (4 eV2 0.04 eV2 )

problem : count rate close to ß-end point drops very fast (~δE3)

• improve statistics :

- stronger tritium source (factor 80) (& large analysing plane, Ø=10m)

- longer measuring period (~100 days ~1000 days)

• improve energy resolution :

- large electrostatic spectrometer with ΔE=0.93 eV (factor 4 improvement)

- reduce systematic errors :

- better control of systematics, energy losses (reduce to less than 1/10)

2

Designing a next-generation experiment


10

L=23 m

KATRIN will reach a final sensitivity of 200 meV at 90\% C.L. on the absolute neutrino mass scale.


Katrin

TLK

Karlsruhe Tritium Neutrino Experiment

at Forschungszentrum Karlsruhe

unique facility for closed T2 cycle:

Tritium Laboratory Karlsruhe

KATRIN experiment


12~ 75 m linear setup with 40 s.c. solenoids

Transport of KATRIN

Complicated transport of the spectrometer in Dec. 2006


sensitivity optimisation: LoI (2001) reference design (2004)

KATRIN sensitivity


14

improved sensitivity

discovery potentialdiscovery potentialm(m(νν) = 0.35 eV (5σ)) = 0.35 eV (5σ)

sensitivity (90% CL)sensitivity (90% CL)m(m(νν) < 0.2 eV) < 0.2 eV

-

• improved statistics: source luminosity, scanning • reduced systematics: ß-energy losses in source

Search for neutrinoless double beta decays

• Why so important?• What it would tell us (if seen)?Reminder:• Leptons are (mostly) left handed • Anti-leptons are (mostly) right

handed

• Contribution of states with „wrong helicity” is proportional to: for m=0 particle – no such contribution

2

2

v1

2

m

c E


2 0

Dirac neutrino vs Majorana neutrino

Dirac particles Majorana particles

Special case: particle is it’s own

anti-particle

R

L

R

L

R

L

C

P

T

C

P

T

Lorentz

Boost,

E, B

Spinor is fermion representation (in Dirac equation)For particles with m=0 reduces to 2 non-zero states

0

0

L

R

only neutral particles are candidates for beeing Majorana particle

Example of such is 0

Double beta decays


Double Beta Decay Candidates


Phenomenology of 0 and 2

• pairing interaction between nucleons (even-even nuclei more bound than the odd-odd nuclei)

• e.g. 136Xe and 136Ce are stable against decay, but unstable

against decay ( for 136Xe and for 136Ce)

19

odd-odd

even-even m(A,Z) > m(A,Z+2)

20

€

1

T1/ 22ν

=G2ν (Qββ11 ,Z) • M2ν

GT 2 1

T1/20 =G0 (Q

5 ,Z) • M0GT 2

• m

2

€

mββ ≡ m1Ue1

2+ m2Ue2

2e iα

*

+ m3Ue3

2e iβ

* −2iδ

Phase space(very well known)

Nuclear matrix element (NME)(challenging to calculate)

Phenomenology of 0 and 2

*, β * = linear combinations of Majorana phases α and β

1

i

i

e

e

MajoranaPhases

only 0

Neutrino mixing and oscillations

ij ij jj ii( cos , sin )sc

13 1312 12

12 12 23 23

13 13 23 23

c sc s

s c c s

s c

1

U 1

1 s c

δ

δ

i

i

e

e

AtmosphericAtmosphericReactor

Solar

3 mixing angles + 1 phase

wea

kei

gen

stat

es mass

eigen

states

νe e e eνμ μ μ μ

ντ τ τ τ

ν1 2 3 1ν1 2 3 2ν31 2 3

U U U

U U U

U U U

Pontecorvo – Maki – Nakagawa - Sakata (PMNS) matrix

ν21

48Ca→48Ti 4.271 0.18776Ge→76Se 2.040 7.882Se→82Kr 2.995 9.296Zr→96Mo 3.350 2.8100Mo→100Ru 3.034 9.6110Pd→110Cd 2.013 11.8116Cd→116Sn 2.802 7.5124Sn→124Te 2.228 5.64130Te→130Xe 2.533 34.5136Xe→136Ba 2.479 8.9150Nd→150Sm 3.367 5.6

Candidate Nuclei for Double Beta DecayQ (MeV) Abundance(%)


Electron spectrum from double decays

•Missing energy

•Energy resolution

•High rates capabilities


history 1935 - (2) rate first calculated by Maria Goeppert-Mayer 1937 - Majorana proposes his theory of two-component neutrino

1987 – Direct laboratory evidence for 2νββ: S. Elliot et al., Phys. Rev. Lett. 59, 2020, 1987

Direct evidence for two-neutrino double-beta decay in 82Se

Why it took so long? Background

τ1/2(U, Th) ~ 1010 years while signal: τ1/2(2νββ) ~ 1020 years

But next we want to look for a process with:

τ1/2(0νββ) ~ 1025-27 years24From neutrinos... DK&ER

lecture11

€

≡

history

2004 – controversial claim of observation of 0νββ:



Experiments with active targets


27


76Ge spectrum

76Ge spectrum with a possible 0νββ peak


30

Exposure(total):71.7 kg.y

76Ge

76Ge spectrum with a possible 0νββ peak

Clearly this needs to be verified...Clearly this needs to be verified...

New experiment with Ge: GERDATo check the questionable result – new experiment with Ge is prepared GERDA (with contribution from Jagiellonian Uniw.), the background reduction will be better …

31

Experimental techniques

32

Background, isotope choice

Tracking and calorimeterSource ≠ detector

TPC (Xe)

Efficiency, Mass

CalorimeterSource=detector

Resolution, efficiency

0

Main features:High energy resolutionModest background rejection

Main features:High background rejectionModest energy resolution

0

33

F. T. Avignone, G. S. King and Yu. G. Zdesenko,``Next generation double-beta decay experiments:

Metrics for their evaluation,’’ New J. Phys. 7, 6 (2005).

from S. Elliott and P. Vogel

E1 + E2 (normalized to Q)

2 spectrum(normalized to 1)

0 spectrum(5% FWHM)(normalized to 10-6)

0 spectrum(5% FWHM)(normalized to 10-2)

Separation of 0 from 2

Energy resolution is essentialEnergy resolution is essential

3 m

4 m

B (25 G)

20 sectors Source: 10 kg of ββ isotopic foils area = 20 m2, thickness ~ 60 mg/cm2

Tracking detector: drift wire chamber operating (9 layers) in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O

Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs

Magnetic field: 25 GaussGamma shield: pure iron (d = 18cm)Neutron shield: 30 cm water (ext. wall)

40 cm wood (top and bottom) (since March 2004: water boron)

Fréjus Underground Laboratory : 4800 m.w.e.NEMO-3 detector

34Particle ID: e, e, γ and

Source: 10 kg of isotopic foils area = 20 m2, thickness ~ 60 mg/cm2

Tracking detector: drift wire chamber operating (9 layers) in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O

Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs

Magnetic field: 25 GaussGamma shield: pure iron (d = 18cm)Neutron shield: 30 cm water (ext. wall)

40 cm wood (top and bottom) (since March 2004:

water boron)

Fréjus Underground Laboratory : 4800 m.w.e.NEMO-3 detector

35

100Mo 6.914 kg Q = 3034 keV

decay isotopes NEMO-3

82Se 0.932 kg Q = 2995 keV

116Cd 405 g Q = 2805 keV96Zr 9.4 g Q = 3350 keV150Nd 37.0 g Q = 3367 keV

Cu 621 g

48Ca 7.0 g Q = 4272 keV

natTe 491 g

130Te 454 g Q = 2529 keV

2 measurement

External bkg measurement

0 search(All enriched isotopes produced in Russia)

36

isotope foils

scintillators

PMTs

Calibration tube

Cathod rings Wire chamber

37

Typical 2 event observed from 100Mo

Top view

Side view

ββ events in NEMO-3 experiment


38

During installation AUGUST 2001 39

Built for τaup experiment (proton decay) in 1981-1982

Laboratoire Souterrain de Modane

COMMISSARIAT À L’ÉNERGIE ATOMIQUE

DIRECTION DES SCIENCES DE LA MATIÈRE

FRANCE ITALIE

AltitudesDistances

1228 m 1298 m1263 m0 m 6210 m 12 868 m

4700 m.w.e

40

(Data Feb. 2003 – Dec. 2004)

T1/2 = 7.11 0.02 (stat) 0.54 (syst) 1018 y7.37 kg.y

Cos(ϑ)

Angular Distribution

219 000 events6914 g

389 daysS/B = 40

NEMO-3

100Mo

E1 + E2 (keV)

Sum Energy Spectrum

219 000 events6914 g

389 daysS/B = 40

NEMO-3

100Mo

Background subtracted

• Dataββ2ν Monte Carlo

• Dataββ2ν Monte CarloBackground subtracted

100Mo ββ2ν results


41

E1 + E2 (MeV)

133 eventsS/B 6.76

948 days7g

48Ca

150Nd925 days S/B 1.019.41g

932 g,389 days

2750 eventsS/B = 4

82SeNEMO-3 454 g,

534 days 109 events

S/B = 0.25130Te

NEMO-3

96Zr

2.8 ± 0.1 (stat) ± 0.3 (sys) 1019 y

E1 + E2 (MeV)

7.6 ± 1.5 (stat) ± 0.8 (sys) 1020 y

2.3 ± 0.2 (stat) ± 0.3 (sys) 1019 y9.11 +0.25-0.22(stat) ± 0.63 (sys) 1018 y 4.4 +0.5

-0.4 (stat)± 0.4 (sys) 1019 y

9.6 ± 0.3 (stat) ± 1.0 (sys) 1019 y

Other results from NEMO-3: 2

42

Results for 20 searches

Isotope Experiment48Ca HEP Beijing >1.1x102

2*23-50

76Ge Heidelberg-Moscow >5.7x102

52-8

IGEX >0.8x102

5

82Se Irvine >2.7x102

24-14

NEMO 2 >9.5x102

1

96Zr NEMO 2 >1.3x102

1

100Mo LBL >2.2x102

2*3-111

UCI >2.6x102

1

Osaka 5.5x1022 2

NEMO2 >5x1021

130Te Milano >1.4x102

32-5

136Xe Caltech/PSI/Neuchatel >4.4x102

32-5

150Nd UCI >1.2x102

15-6

01/ 2 ( )T yr ( )

ULm eV

Germ

an

ium

dio

de c

al.

Te0

2 c

ryo

calo

rim

.X

e

TPC

Upper limits


From Elliot and Vogel, hep-ph/0202264

Neutrinoless ββ-decay limits


Neutrino mass and mass ordering

45

€

Δmsol2 ≈ 7.7 ×10−5eV 2

€

Δmatm2 ≈ 2.4 ×10−5eV 2

€

}€

}

€

m12

€

m22

€

m32

€

0?

€

m12

€

m22

€

m32

?

Normal Inverted

m(“e”) < 2.2 eVMainz-Troitsk 3H decay

m(“μ”) < 190 keVm(“τ”) < 18.2 MeV

Σm < 0.14 - 1.3 eV

Cosmological models

? >> Δmatm2

What is the scale of neutrino masses?

46

A. Strumia and F. Vissani, ``Neutrino masses and mixings.’’ arXiv:hep-ph/0606054.

F. Feruglio, C. Hagedorn, Y. Lin and L. Merlo, ``Theory of the Neutrino Mass,’’ arXiv:0808.0812 [hep-ph].

€

mββ ≡ (0.70-0.04+0.02)m1 + (0.30−0.02

+0.04 )m2eiα *

+ (≤ 0.05)m3eiβ * −2iδ

mββ may be very tiny in case of cancellations due to phases mββ may be very tiny in case of cancellations due to phases

HM ClaimNEMO 3

CUORICINO, EXO-200

GERDA(PII)SuperNEMO

CUORE,EXO

>2020, 1t experiments ( ≥ 2)

>>2020, >10t experiment

47C

osm

olo

gic

ally

dis

favou

red

regio

n

(WM

AP)

Projections – ββ0ν

47

Summary

Direct neutrino mass measurements – sensitivity good enough only for νe - may be successful in case of inverted hierarchy

Search for 0νββ – extremely important because: It may answer the following basic questions:

Is the total lepton number conserved? Essential for understanding the matter-antimatter asymmetry in Universe

What is nature of neutrinos: Dirac or Majorana ( 0ββ possible only for Majorana neutrinos) - essential for understanding the source of particle masses


Date post:	07-Jan-2016
Category:	Documents
Upload:	gyda
View:	35 times
Download:	1 times

Neutrino masses

Documents