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CP Violation A. Pich – Benasque 2005
Antonio Pich , IFIC , Valencia
CP Violation A. Pich – Benasque 2005
Slight (~ 0.2 %) CP in K0 decays (1964)
Sizeable CP in B0 decays (2001)
CP : Symmetry of nearly all observed phenomena
C , P : Violated maximally in weak interactions
Huge Matter ─ Antimatter Asymmetryin our Universe Baryogenesis
Complex Phases
Interferences
Thus, CP requires:
CPT Theorem: T CP
CP Violation A. Pich – Benasque 2005
BosonsQuarks Leptons
muon
top beauty
photon
gluon
up down electron neutrino e
charm strange neutrino µ
Higgstau neutrino τ
e
µ
τ
ZZ00 WW ±±
CP Violation A. Pich – Benasque 2005
FERMION GENERATIONSFERMION GENERATIONSMassesMasses are are thethe onlyonly differencedifferenceGN 3= IdenticalIdentical CopiesCopies
0
1
Q
Q
=
= −
2 3
1 3
Q
Q
= +
= −j j
j j
v ul d′ ′⎛ ⎞
⎜ ⎟′ ′⎝ ⎠( )G1, , Nj = WHY ?WHY ?
( ) ( )( ) (0)† ( )
(0) ( )† (0)( ) ( ) ( ), , h.c.Y j j j jk R k R k RL L
jk
d u ljk jk jku d d u v l lc c c
φ φ φφ φ φ
+ +
+
⎧ ⎫⎡ ⎤⎪ ⎪′ ′ ′ ′⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟ ⎜ ⎟−⎝ ⎠ ⎝
′ ′ ′= + + +⎨ ⎬⎢ ⎥⎪ ⎪⎣ ⎦⎩ ⎭⎠ ⎝ ⎠
∑L
{ }1v
h.c.Y L R L R L Rud ld d u u l lH ′ ′ ′ ′⎛ ⎞ ′ ′ ′ ′ ′= − ⋅ ⋅ + ⋅ ⋅ + ⋅+⎜ ⎟ ⋅ +⎝ ⎠
M M ML
SSBSSB
ArbitraryArbitrary NonNon--Diagonal Diagonal ComplexComplex MassMass MatricesMatrices( ) ( ) ( ) v, ,
2, ,d u l
ud l jk jk jkjk c c c⎡ ⎤′ ′ ′ = −⎡ ⎤⎣ ⎦ ⎣ ⎦M M M
CP Violation A. Pich – Benasque 2005
DIAGONALIZATION OF MASS MATRICESDIAGONALIZATION OF MASS MATRICES
µ
†
†
†
Sd d d d d d d
u u u u u u u
l l l l l l l
′ = ⋅ = ⋅ ⋅ ⋅
′ = ⋅ = ⋅ ⋅ ⋅
′ = ⋅ = ⋅ ⋅ ⋅
M H U S S U
M H U S U
M H U S S U
M
M
M
†
† †
† †
f f
f f f f
f f f f
1
1
=
⋅ = ⋅ =
⋅ = ⋅ =
H H
U U U U
S S S S
( ) { }d d + u1 u +vY ud l lH l= − ⋅ ⋅ ⋅+ ⋅ ⋅ ⋅L M M M
diag ( , , ;) diag ( , , ) diag ( , , );u du c t s ed b lm m m m m m m m mµ τ= = =M M M
d d ; u u ;d d ; u u ;
L L L L L L
R R R R R R
ud l
u ud d l l
l ll l
′ ′ ′≡ ⋅ ≡ ⋅ ≡ ⋅
′ ′ ′≡ ⋅ ⋅ ≡ ⋅ ⋅ ≡ ⋅ ⋅
S S SS U S U S U
MassMass EigenstatesEigenstates
WeakWeak EigenstatesEigenstates≠
N C N C′ =L Lf f f f ; f f f fL L L L R R R R′ ′ ′ ′= =†u d u d ;L L L L u d′ ′ = ⋅ ⋅ ≡ ⋅S SV V CC CC′ ≠L L
QUARK MIXINGQUARK MIXING
CP Violation A. Pich – Benasque 2005
[ ]f f 5Nf
C f f2 sin cos
v aW W
Z Zeµ
µγθ θ
γ−= ∑L
FlavourFlavour ConservingConserving Neutral Neutral CurrentsCurrents
u c t
d s b
FlavourFlavour ChangingChanging ChargedCharged CurrentsCurrents
( ) ( )i5 5CC†
iji j
j1 1 h.c.
2 2 ll
g u d vW lµµ µγ γ γ γ
⎡ ⎤= − + − +⎢ ⎥
⎣ ⎦∑ ∑VL
CP Violation A. Pich – Benasque 2005
MeasurementsMeasurements ofof VVijij
W
jdiu
e−
eν
ijV
j i
2
ij( )ed u e ν−Γ → ∝ V
We measure decays of hadrons (no free quarks)
Important QCD Uncertainties
CP Violation A. Pich – Benasque 2005
i jV0.9740 0.00050.9729 0.0012
0.2220 0.00250.2208 0.00340.2219 0.0
0.9739
025
Nuclear decay
decays/ , Latti
0.0005
0.2217 0.00250.224 0.012
0.
ce
974 0.00.97 0.1
h1
ad13
ud
us
cd
cs
e
e
n p e v
K e v
K
v d c X
W c s
V
V
VW
V
β
πτ
π µν
−
−
+
+
±
±
±
±
→
→
→
→
→
±
±
±→
±±
±
0.160.1
*
2
,
0.0414 0.00210.0410 0.0015
0.0033 0.00060.00
0.0411 0.0015
0.0037 0.00050.97
,
47 0.00 9
,
/
0
u j cd c
cb
l
l
l
ub
b
l
V V
B D l vb c l v
B l vb u l v
t bW
V
V
qW
ρ
+−
±±
±±±
→
→→
→
±→
( ) (LEP)∑2 2
uj cjj
V + V = 1.999 ± 0.025
CKM entry Value Source
2
q t qtb VV ∑
2 2 2ud us ubV + V + V = 0.9976 ± 0.0021
CP Violation A. Pich – Benasque 2005
i jV0.9740 0.0005
0.2220 0.0
Nuclear decay
decays/
0.2, Lattice
217 0.00250.224 0.012
0.974 0.
0250.2208 0.00340.2219 0.0025
0.9013
0.1ha
7d
1
ud
us
cd
cs
e
e
V
V
V
V
n p e v
K e v
K
v d c X
W c sW
β
πτ
π µν
−
−
+
+
±
±
→
→
→±
→
→±
±±
→
±
±
0.9744 ± 0.00.9769 ± 0. 13
0000
5
0.160.1
*
2
,
0.0414 0.00210.0410 0.0015
0.0033 0.00060.00
0.0411 0.0015
0.0037 0.00050.97
,
47 0.00 9
,
/
0
u j cd c
cb
l
l
l
ub
b
l
V V
B D l vb c l v
B l vb u l v
t bW
V
V
qW
ρ
+−
±±
±±±
→
→→
→
±→
( ) (LEP)∑2 2
uj cjj
V + V = 1.999 ± 0.025
CKM entry Value Source
2
q t qtb VV ∑
Serebrov et al
2 2 2ud us ubV + V + V = 0.9986 ± 0.0021
CP Violation A. Pich – Benasque 2005
QUARK MIXING MATRIXQUARK MIXING MATRIX2GNUnitaryUnitary MatrixMatrix::G GN N× parametersparameters
† †⋅ = ⋅ =V V V V 1
arbitraryarbitrary phasesphases::G2 1N −
jii i j j;e eiiu u d dθφ→ → j i )
ij j(
iei θ φ−→V V
ijV
( )G G1 12
N N −
PhysicalPhysical ParametersParameters::
ModuliModuli ;; phasesphasesG G1 ( 1) ( 2)2
N N− −
CP Violation A. Pich – Benasque 2005
● Nf = 2 : 1 angle, 0 phases (Cabibbo)
No CPC C
C C
cos sinsin cos
θ θθ θ
⎡ ⎤= ⎢ ⎥−⎣ ⎦
V
ij ij ij ijcos ; sinc sθ θ≡ ≡● Nf = 3 : 3 angles, 1 phase (CKM)
( )
13
13 13
13 13
12 13 12 13 13
12 23 12 23 13 12 23 12 23 13 23 13
12 23 12 23 13 1
2 3
2 2
3 2
2 23 12 23 13 23 13
41 /2 ( )
1 /2(1 ) 1
i
i i
i i
c c s c s
s c c s s c c s s s s c
s s c c s c s s c s
e
e
c c
e
e e
i
i
AA
A A
δ
δ δ
δ δ
λ λ λ ρλ λ λ
λ ρ λ
η
ηλ
−⎡ ⎤⎢
⎡ ⎤− −⎢ ⎥− −⎢ ⎥⎢ ⎥− − −
⎥⎢ ⎥− − −⎢ ⎥
− − −⎢ ⎥⎣ ⎦
⎣ ⎦
≈ +
=V
O
13 0)0 (ηδ ≠≠ CP2 2Csin 0.222 ; 0.84 ; 0.41Aλ θ ρ η≈ ≈ ≈ + ≈
CP Violation A. Pich – Benasque 2005
Standard Standard ModelModel : : 33 fermionfermion familiesfamilies neededneededCP
2 2 2 2 2 22( ( ) () ) ( )t c c u t uu m m m m m mM − − −≡H
2 2 2 2 2 22( ( ) )) ( ) (s sb d b dd m m m m m mM − − −≡H
CP 2 2( ) ( ) 0u dM M⋅ ⋅ ≠H H J
212 13 23 12 13 23 13
2 6 410sinc c c s s As λ ηδ −<= =J
•• LowLow--EnergyEnergy PhenomenaPhenomena
•• SmallSmall EffectsEffects ~ ~ JJ
•• BigBig AsymmetriesAsymmetries SuppressedSuppressed DecaysDecays
•• B B DecaysDecays are are anan optimaloptimal place place forfor signalssignalsCP
CP Violation A. Pich – Benasque 2005
DIRECT DIRECT CP ( ) ( )P f P f| | | |→ ≠ →T T
( ) 1 1 221 2P f T Ti ii ie ee eδ δφ φ
→ = +T
( ) { }1 21 2*P 1 2fP f T Ti ii iee eeφ δφδη η − −
→ = +T
CP
0dB
( ) ( )( ) ( )
2 12 1
2 11 2
1 22 2
1 2 1 2
si sP f P f 2 T TT T 2 T TP f P f
in( )cos(
n( )cos( ))
δφ φφ φ
δδ δ
Γ → − Γ → −=
+ +Γ → + Γ → −−
−−
OneOne needsneeds::
2 Interfering Amplitudes
2 Different Weak Phases
2 Different FSI Phases 2 1sin( ) 0δ δ⎡ ⎤− ≠⎣ ⎦
2 1sin( ) 0φ φ⎡ ⎤− ≠⎣ ⎦
CP Violation A. Pich – Benasque 2005
INDIRECT INDIRECT : : KK00 ── KK00 MIXINGMIXING¯̄CP0 0
2( , )i
i j ijij
j SS r rK K Oηλ λ ∆ =
⎧ ⎫⎨ ⎬⎩ ⎭∑H ∼
2 2* ( , ); ,i i si i Wd ir m i uV V cM tλ =≡≡
( )( )2/9 0 0 2 22
4( ) ˆ3L L L L K KS Ks BK s d s d K MO fα
αα µ γ γ−∆ =
⎛ ⎞= ≡ ⎜ ⎟⎝ ⎠
0 0 0LK Kp Kq+∼ ( ) ( )1 1K Kq p ε ε≡ − +
0 0( ) ( );l ls u s uK l K lπ ν π ν− + + −→ →→ →
( ) ( )( ) ( )
( )0 0
0 0
2
2 2 2
2 2 Re1 |
| | | || |
(0.327 0| |
. )%|
012K
K
L Ll l
L Ll l
p qK l K l
K l K ql pπ ν π ν
π ν π ενε− + + −
− + + −
Γ → − Γ →=
−= = ±
Γ → + Γ → ++
ReRe ((εεKK) = (1.64 ) = (1.64 ±± 0.06) 0.06) ·· 1010--33¯
CP Violation A. Pich – Benasque 2005
( )( ) K
L
S
T KT K
ππ
επηπ
+ −
+− + −→
≡ ≈→
0 0
00 0 0( )( )
L
SK
T KT K
π πηπ π
ε→≡ ≈
→
3(2.271 0.017) 10 iK e εφε −= ± ⋅
(43.5 0.5)εφ = ±( ) 2 20.22 .1 0 43ˆ 1KBA Aη ρ⎡ ⎤+ =⎣ ⎦−
Buras et al
DIRECT in K DIRECT in K →→ ππ ππCP
Kε ′+ 2 Kε ′−
( ) 00 42
1Re / 1 (17.2 1.8) 106K K
ηε εη+−
−⎧ ⎫⎪ ⎪′ ≈ − = ± ⋅⎨ ⎬⎪ ⎪⎩ ⎭
NA48, NA31
KTeV, E731
Short-distance OPECiuchini et al, Buras et al
Long-distance χPTPallante-Pich-ScimemiCirigliano-Ecker-Neufeld-Pich
( ) ( )11 49ThRe / 19 10K Kε ε + −
−′ = ⋅
CP Violation A. Pich – Benasque 2005
BB00 ── BB00 MIXINGMIXING¯̄3
ud ub cd cb td tbV V V V V V Aλ∗ ∗ ∗∼ ∼ ∼
20 220 4( , )H ˆ3 Bt B BttdB B V S fr r M B⎛ ⎞
⎜ ⎟⎝ ⎠
∼
01(0.502 0.006) ps
dBM −∆ = ± tdV
0114.5 ps (95% C.L.)
sBM −∆ >22
ts tdV V
0 02 2/ / 1tbB BM m m∆Γ ∆ ∼
2 2/1 c tmq p m− ∼
0 0/ 0.770 0.011d dB BM∆ Γ = ±
( )0Re 0.0007 0.0017dBε = − ±
CP very small
010.19(0.47 0.01) ps0 C4 F.2 D
sB−+∆Γ = ±−
CP Violation A. Pich – Benasque 2005
BB00 ── BB00 MIXING AND DIRECT MIXING AND DIRECT ¯̄ CP0 0
f f f f f0 0
f f f f f
T T[ f ] ; T T[ f ] ; T / T
T T[ f ] ; T T[ f ] ; T / T
B B
B B
ρ
ρ
→ → → − → ≡
→ → → − → ≡
0B
0B
f
0 0 ; f fB B= − =CP CP
( ) ( )
( ) ( )
0 2 2 2f f f f
0 2 2 2f f f f
cos( ) sin( )
cos( ) sin( )
1[ ( ) f ] | T | 1 | | 1 | | 2 Im2
1[ ( ) f ] | T | 1 | | 1 | | 2 Im2
t
t
M t MqB t ep
pB t eq
t
M t M t
ρ ρ ρ
ρ ρ ρ
−Γ
−Γ
⎧ ⎫⎛ ⎞Γ → + + − −⎨ ⎬⎜ ⎟
⎝ ⎠⎩ ⎭
⎧ ⎫⎛ ⎞Γ
∆ ∆
∆ ∆→ + + − −⎨ ⎬⎜ ⎟⎝ ⎠⎩ ⎭
∼
∼
2f2 ff f
2 2 2 2f
f f ff f f
f
2 Im 2 Im1 | |1 | | ; ; ;
1 | | 1 | | 1 | | 1 | |C S C
q pp S q
ρ ρρρ
ρ ρ ρ ρ
⎛ ⎞ ⎛ ⎞−⎜ ⎟ ⎜ ⎟−− ⎝ ⎠ ⎝ ⎠≡ ≡ ≡ − ≡
+ + + +
( )( )
0
0
*2
* 0; M
d
s
Mtqtb
tqtb
i B
B
qp
e φ βφ− ≈≈ =
⎧⎨⎩
V VV V
M∆Γ ∆
CP Violation A. Pich – Benasque 2005
BB00 ── BB00 MIXING AND DIRECT MIXING AND DIRECT ¯̄ CPCP self-conjugate: ff fη=0B
0B
f
( )( )
0
0
*2
* 0; M
d
s
Mtqtb
tqtb
i B
B
qp
e φ βφ− ≈≈ =
⎧⎨⎩
V VV V
Assumption: Only 1 decay amplitude
*
*2A
ADqqb qqq qb
qqqb
i
b qqq
e φ′→ ′
′→ ′
−= =V VV V
( ) ( )( ) ( )
0 0
f0 0 sin(f f
sin(f
2 ) ;f
) M D
B BM t
B Bφ φ φ φη
Γ → − Γ →= ∆
→=
+ Γ+
Γ →
DirectDirect informationinformation onon thethe CKM CKM matrixmatrix
CP Violation A. Pich – Benasque 2005
0dB π π+ −→0 0/ SdB J K→ Ψ 0 0 0
SsB Kρ→
2cscbV V Aλ∗ ∼
2tstbV V Aλ∗ −∼
( )3ub udV V A iλ ρ η∗ −∼
( )3 1tb tdV V A iλ ρ η∗ − +∼
( )3ub udV V A iλ ρ η∗ −∼
( )3 1tb tdV V A iλ ρ η∗ − +∼
φ β φ β γ π α+ = − φ γ≠
*** ***** ** BADBAD
CP Violation A. Pich – Benasque 2005
0 0
0 0
( / ) ( / )0
( / ) ( / )S S
S S
B J K B J KB J K B J K
ψ ψψ ψ
Γ → − Γ →≠
Γ → + Γ →
BABAR
SignalCP
sin(2β) = 0.726 ± 0.037,/ , (2 ) , ,c cS L S S SJ K S K K Kψ ψ χ η
[BABAR, BELLE, ALEPH, CDF, OPAL]
CP Violation A. Pich – Benasque 2005
UNITARITYUNITARITYTRIANGLES TRIANGLES
* * * ( )0ui uj ci cj ti tj i jV V V V V V ≠+ + =
( )2 3
2 2
3 2
41 /2 ( )
1 /2(1 ) 1
AA
A
i
i A
η
η
λ λ λ ρλ λ λ
λ ρ λλ
⎡ ⎤− −⎢ ⎥− −⎢ ⎥⎢ ⎥− − −⎣ ⎦
≈ +V O
CP Violation A. Pich – Benasque 2005
* * * 0ud ub cd cb td tbV V V V V V+ + =
* *ud ub cd cbV V V V * *
td tb cd cbV V V V
2
2
0.347 0.025
0
112112
.196 0.045
η
ρ
η λ
ρ λ
= ±
=
⎛ ⎞≡ −⎜
±
⎟⎝ ⎠⎛ ⎞≡ −⎜ ⎟⎝ ⎠
96.1 7.0 ; 23.4 1.5 ; 60.3 6.8α β γ= ± ° = ± ° = ± °
UTUTfitfit
CP Violation A. Pich – Benasque 2005
{ }f f0 cos( ) sin) 1 ([ ( f ] )MC t M tSB t ∆→ + ∆Γ −∼
Cππ Sππ
BABAR - 0.09 ± 0.15 ± 0.04 - 0.30 ± 0.17 ± 0.03
BELLE - 0.56 ± 0.12 ± 0.06 - 0.67 ± 0.16 ± 0.06
0dB π π+ −→
0dB
φ β γ π α+ = − ??
Direct , Penguins2
f2f
f
1 | |1 | |
0C ρρ
−≡ ≠
+ CP
IsospinIsospin RelationsRelations (Gronau – London)
01
2( )T B π π+ −→
0 0 0( )T B π π→
0 0( ) ( )TT B Bπ ππ π+ −+ −= →→
01
2( )T B π π+ −→
0 0 0( )T B π π→
• Significant penguin pollution
P / T = 0.3 ± 0.1 (Buras et al)
• FSI phases (ambiguities)
• EW penguins
• B → π ρ , ρρ , a1 π
CP Violation A. Pich – Benasque 2005
MEASURING HADRONIC CONTAMINATIONSMEASURING HADRONIC CONTAMINATIONS
Time Evolution
Transversity Analysis: B → V V
Isospin Relations (Gronau-London)
Mixing (Gronau-Wyler, Atwood-Dunietz-Soni)
Dalitz Analysis
SU(3) Relations: B → πK , π π , ...
…
0 0D -D0 0 0
0 0 0 0
2 T( ) T( ) T( )
2 T( ) T( ) T( )S S Sd
B D K B D K B D K
B D K B D K B D K
+ + + + + ++
+ ++
→ = → + →
→ = → + →
CP Violation A. Pich – Benasque 2005
DIRECT DIRECT CP 5.9 5.9 σ σ signalsignal
0 00
0 0
Br( ) Br( )( )
Br( ) Br(0.113 0.
)019d d
dd d
B K B KA B K
B K B K
π ππ
π π
− + + −±
− + + −
→ − →→
→±≡ =
+ →∓
0BABAR0.133 0.030 0.009
0.1 BE01 0.025 0.00 L E5( )
LdA B Kπ ±→
± ±
± ±=
⎧⎪⎨⎪⎩
∓
•• B B →→ ππππ datadata
•• SU(3) SU(3) symmetrysymmetry
•• NeglectNeglect ““penguinpenguin”” andand““exchangeexchange”” topologiestopologies
0th
0.1410.143 0.08( ) 3dA B Kπ ±
−→ +=∓
Buras et al
CP Violation A. Pich – Benasque 2005
K K →→ ππ νν νν̄̄( ) ( )* 2 2, /i s i W L L L LidF V V m s KM dµ µν γ ν π γT ∼
Buchalla – BurasIsidori , Misiak – UrbanFalk et alMarciano - Parsa
( )
( )
11
0 1
4
21
2 2
4
Br (7.7 1.1) 10
Br (2.6 0.
(1.4 )
5) 10L
K
K
A
A
η ρπ ν ν
π ν ν η
+ + −
−
⎡ ⎤+ −⎣→ = ± ⎦×
→ = ± ×
∼
∼
Long-distance contributions are negligible
CP( )0 0LK π ν ν→ ≠T
BNL: BNL: few events!
KTEV:KTEV:
( ) 10Br 10K π ν ν+ + −→ ∼
( )0 7Br 5.9 10 (90% C.L.)LK π ν ν −→ < ×
NewNew ExperimentsExperiments NeededNeeded
CP Violation A. Pich – Benasque 2005
SUMMARY SUMMARY remains a major pending question
Related to Flavour Structure
Related to SSB Scalar Sector (Higgs)
Important cosmological implications (Baryogenesis)
Sensitive to New Physics
Highly constrained in the SM: 1 phase only
Many interesting signals within experimental reach
Better control of QCD effects urgently needed
CP
CP
CP Violation A. Pich – Benasque 2005
ComplexComplex phasesphases in in YukawaYukawa couplingscouplings onlyonly::
( ) ( )jk j
( ) (0)†
j j L k R k R(0) ( )†j k
k( , ) h.c.Yd uL d d uc cu
φ φφ φ
+
+
⎡ ⎤⎛ ⎞ ⎛ ⎞′ ′ ′ ′= + +⎢ ⎥⎜ ⎟ ⎜ ⎟−⎝ ⎠ ⎝ ⎠⎣ ⎦
∑
(0) v / 2φ⎡ ⎤=⎣ ⎦SSBSSB
{ }( )jL k R j
( )jk jL Rk k h.c.
2v1
vYd uc dL d cu uH ′ ′⎛ ⎞+⎜ ′ ′= − + +⎟
⎝ ⎠
( )jkqc diagonalization
{ }jj
C
jL jR jL jR
†iC ij5 j
i j
h.c.
(1 ) h.c.
1v
2 2
Y udL
L
d d u u
g W d
m
u
mH
µµ γ γ
= − ⎛ ⎞+⎜ + +
= − +
⎟⎝ ⎠
∑ V
TheThe CKM CKM matrixmatrix VVijij isis thethe onlyonly sourcesource ofof CPCP
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005The Standard Model A. Pich - CERN Summer Lectures 2004
CP Violation A. Pich – Benasque 2005
( )i 5 j
i
( )CC
jij
† (1 ) h.c.2 2
ll Wg lL µµ ν γ γ= − +∑ V
SeparateSeparate LeptonLepton NumberNumber ConservationConservation R( )νMinimal SM without
i( )ijj
llν ν≡ V
( ) †5CC (1 ) h.c.
2 2l
ll
lgL W µµ ν γ γ− += ∑IFIF i
m 0ν =
( Co, n, served )eeL L L LL L µµ ττ + +
IFIF i
iR exist and m 0νν ≠
BUTBUT 11 7Br ( ) 1.2 10 Br ( ) 3.1 10eµ γ τ µ γ− −→ < × → < ×;(90 % CL)