Upload
gyda
View
49
Download
1
Tags:
Embed Size (px)
DESCRIPTION
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. }. or. (Mass) 2. }. - PowerPoint PPT Presentation
Citation preview
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
5From neutrinos... DK&ER lecture11
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
From neutrinos... DK&ER lecture11
7
Electrostatic filter with magnetic adiabatic collimation
From neutrinos... DK&ER lecture11
8
Status of previous tritium measurements
From neutrinos... DK&ER lecture11
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
From neutrinos... DK&ER lecture11
10
L=23 m
KATRIN will reach a final sensitivity of 200 meV at 90\% C.L. on the absolute neutrino mass scale.
11From neutrinos... DK&ER lecture11
Katrin
TLK
Karlsruhe Tritium Neutrino Experiment
at Forschungszentrum Karlsruhe
unique facility for closed T2 cycle:
Tritium Laboratory Karlsruhe
KATRIN experiment
From neutrinos... DK&ER lecture11
12~ 75 m linear setup with 40 s.c. solenoids
Transport of KATRIN
Complicated transport of the spectrometer in Dec. 2006
13From neutrinos... DK&ER lecture11
sensitivity optimisation: LoI (2001) reference design (2004)
KATRIN sensitivity
From neutrinos... DK&ER lecture11
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
15From neutrinos... DK&ER lecture11
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
17From neutrinos... DK&ER lecture11
Double Beta Decay Candidates
18From neutrinos... DK&ER lecture11
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(%)
22From neutrinos... DK&ER lecture11
Electron spectrum from double decays
•Missing energy
•Energy resolution
•High rates capabilities
23From neutrinos... DK&ER lecture11
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:
25From neutrinos... DK&ER lecture11
26From neutrinos... DK&ER lecture11
Experiments with active targets
From neutrinos... DK&ER lecture11
27
28From neutrinos... DK&ER lecture11
76Ge spectrum
76Ge spectrum with a possible 0νββ peak
29From neutrinos... DK&ER lecture11
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
From neutrinos... DK&ER lecture11
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
From neutrinos... DK&ER lecture11
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
43From neutrinos... DK&ER lecture11
From Elliot and Vogel, hep-ph/0202264
Neutrinoless ββ-decay limits
44From neutrinos... DK&ER lecture11
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
48From neutrinos... DK&ER lecture11